Dynamically controlling vertical speed and flight path angle during different flight phases

Abstract

A method of controlling an aircraft includes receiving a pilot input command and determining which one of a plurality of aircraft flight parameters to hold constant. The aircraft flight parameters include an altitude of the aircraft, a vertical speed of the aircraft, and a flight path angle of the aircraft. The determination of which one of a plurality of aircraft flight parameters to hold constant is based on both a speed of the aircraft and the determination of whether the pilot input command is commanding an ascent or descent of the aircraft. The method of controlling ascent of an aircraft includes controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant.

Description

Agent Ref 16499-0038-00304DYNAMICALLY CONTROLLING VERTICAL SPEED AND FLIGHT PATH ANGLE DURING DIFFERENT FLIGHT PHASESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims priority to and the benefit of U.S. Provisional Application No. 63 / 701,199, filed September 30, 2024, titled “DYNAMICALLY CONTROLLING VERTICAL SPEED AND FLIGHT PATH ANGLE DURING DIFFERENT FLIGHT PHASES” (Attorney Docket No. 16499.6019-00000), the contents of which is incorporated herein in its entirety and for all purposes.TECHNICAL FIELD

[0002] This disclosure relates generally to the field of powered aerial vehicles. More particularly, and without limitation, the present disclosure relates to innovations in aircraft control. Certain aspects of the present disclosure generally relate to controlling an aircraft to reduce pilot workload.BACKGROUND

[0003] The present disclosure relates generally to controlling certain aspects of flight during ascent and descent. Some aircrafts, such as an eVTOL aircraft, may be capable of operating in multiple different flight phases and transitioning between phases during flight. Without sufficient support from a flight control system, there could be significant pilot workload making it more difficult for them to safely and effectively control the aircraft.SUMMARY

[0004] The present disclosure generally relates to a flight control system that controls certain aspects of flight to minimize pilot workload during an aircraft’s ascent and descent. The inventors here have recognized several problems that may be associated with flying an aircraft, including an aircraft that uses electric or hybrid-electric propulsion units (hereinafter referred to as electric propulsion units or “EPUs”). For example, during ascent it may be desirable to fly at a high vertical speed to maximize the gain in altitude early. However, it can be difficult for a pilot to control the aircraft at the desired vertical speed while also controlling other aspects of flight (e.g., heading, forward speed etc.) During descent, it may be desirable to fly at a fixed flight path angle (FPA) to navigate the aircraft to a specific point in space, such as a landing area or hover location. It can be similarly difficult to manage the flight path angle while also controlling other aspects of flight (e.g., heading, forward speed etc.). Further, in some states of flight it may be desirable to hold an altitude of the aircraft soAgent Ref: 16499-0038-00304 a pilot can focus on manual control of other aspects. Therefore, there is a need for a flight control system that can automatically control the vertical speed, altitude, and / or flight path angle depending on an aircraft’s flight conditions to reduce a pilot’s workload. This automatic control may improve the safety of an aircraft in flight (e.g., reduce workload so a pilot may detect and address an emergency situation), as well as its efficiency of energy use, such as by reducing pilot overcorrections. In some embodiments, the automatic control may operate based on frequent, repeated, and / or continuous calculations, which would be grossly impractical and unsafe, if not impossible, for a pilot to perform during flight.

[0005] One aspect of the present disclosure is directed to a method of controlling an aircraft, comprising: receiving a pilot input command, determining whether the pilot input command is commanding an ascent or descent of the aircraft, and determining which one of a plurality of aircraft flight parameters to hold constant, the aircraft flight parameters comprising an altitude of the aircraft, a vertical speed of the aircraft, and a flight path angle of the aircraft. The method further comprises wherein the determination of which one of a plurality of aircraft flight parameters to hold constant is based on both a speed of the aircraft and the determination of whether the pilot input command is commanding an ascent or descent of the aircraft and controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figures 1 and 2 illustrate an aircraft, consistent with disclosed embodiments.

[0007] Figures 3A, 3B, 3C, 3D, 3E, and 3F illustrate exemplary top plan views of aircraft, consistent with disclosed embodiments.

[0008] Figure 4 illustrates a diagram for aircraft control, consistent with disclosed embodiments.

[0009] Figures 5A and 5B detail how the vertical speed hold or flight path angle hold may vary based on flight conditions of the aircraft, consistent with disclosed embodiments.

[0010] Figures 6A and 6B detail the relationship between flight path angle and vertical speed, and algorithms that allow for smooth transition between flight path angle hold and vertical speed hold, consistent with disclosed embodiments.

[0011] Figures 7A and 7B detail the effect of a pilot input when received as a stick command and a beep command, consistent with disclosed embodiments.

[0012] Figure 8 illustrates a flowchart of an exemplary process for controlling an aircraft, consistent with disclosed embodiments.Agent Ref: 16499-0038-00304

[0013] Figure 9 illustrates a functional block diagram of an exemplary control system of an electric VTOL aircraft, consistent with disclosed embodiments.DETAILED DESCRIPTION

[0014] The present disclosure addresses a system to reduce a pilot workload. The aircraft may be an electric or hybrid-electric aircraft. The aircraft may be an aircraft with a human pilot, an aircraft without a human pilot (e.g., an unmanned aerial vehicle, or UAV), a drone, a helicopter, and / or an airplane. As used herein, “pilot” may refer to a human pilot in the aircraft, a human pilot outside of the aircraft (e.g., a remote operator), an autopilot, or any combination thereof. The aircraft includes a physical body and one or more components (e.g., a wing, a tail, a propeller) configured to allow the aircraft to fly. In some embodiments, the aircraft is driven by one or more electric propulsion units (hereinafter referred to as electric propulsion units or “EPUs”), which may include at least one engine, at least one partial motor, at least one rotor, at least one propeller, a nacelle, a housing, or any combination thereof. The aircraft also includes at least one source of energy, which may provide energy to the one or more EPUs. The aircraft may be fully electric, hybrid, or hydrocarbon fuel powered. For example, in some embodiments, the aircraft is a tilt-rotor aircraft configured for frequent (e.g., over 50 flights per work day), short-duration flights (e.g., less than 100 miles per flight) over, into, and out of densely populated regions.

[0015] The disclosed embodiments reduce pilot workload by controlling the aircraft according to a set vertical speed, altitude, or flight path angle (FPA) based on flight conditions of the aircraft. “Flight conditions” may refer to pilot input, forward speed (e.g., airspeed or groundspeed), and / or ascent or descent (e.g., pilot commanded or sensed) of the aircraft. The disclosed embodiments may include transmitting information about a vertical speed, altitude, or FPA held constant. In some embodiments, the transmitted information about a held parameter may be delivered to a pilot, an operator of the aircraft, one or more processors or memories on-board the aircraft, one or more processors or memories off-board the aircraft, a non-operator of the aircraft (e.g., a command center, air traffic control, an instructor for training purposes or training safety). Additionally, in some embodiments, the transmitted information about a held parameter (e.g., a set vertical speed, altitude, or FPA) may include information transmitted via a visual display or indicator (e.g., display, waming / caution light, color-coded indicator, symbolic indicator), an auditory indicator (e.g., alarms, tones, synthesized voice messages), a haptic indicator (i.e., tactile or force feedback) (e.g., inceptor shaker, inceptor pusher, control force feedback, vibrating pilot seat or throttle).Agent Ref 16499-0038-00304The disclosed embodiments may include a display, user interface, or any other device capable of transmitting information to a pilot of the aircraft. The transmitted information may include flight conditions, the set vertical speed, the set altitude, the set FPA, or any other information pertaining to pilot workload.

[0016] In some embodiments, an aircraft of any of the disclosed embodiments may be simulated. For example, the aircraft may be simulated in a simulation environment, such as in a simulator (e.g., a simulator for flight training), a testing simulation environment, or a virtual environment in a video game. Additionally or alternatively, in some embodiments, at least one device of an aircraft may be simulated. For example, the at least one device (e.g., EPU, display wing, effector, and / or actuator, etc.) may be simulated in a simulation environment, such as in a simulator (e.g., a simulator for flight training), a simulated testing environment, or a virtual environment in a video game. A representation of the simulated display may be displayed on at least one display device (e.g., monitor, tablet, smartphone, computer screen, or any other display device) operatively connected to at least one processor configured to execute software code stored in a storage medium for performing flight controls operations, such as those further detailed below with reference to Fig. 4 and those further detailed below with reference to Fig. 9. These flight controls operations consistent with the disclosed embodiments may be implemented as a process further detailed below with reference to Fig. 8, which may be a computer-implemented process.

[0017] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the disclosure. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the subject matter recited in the appended claims.

[0018] While the majority of the herein disclosed embodiments apply an altitude hold threshold range, it is to be appreciated that the herein disclosed methods may be adapted for use with any threshold range associated with an aircraft parameter, and such alternatives fall within the scope of the present disclosure. A threshold range may include a plurality of values. A threshold range may refer to a band, interval, set, or range of values associated with a system determining whether to initiate, maintain, or terminate a particular control state. Such a threshold range may include positive, negative, or zero values, where these values may correspond to a parameter relevant to the system making a control state determination.Agent Ref: 16499-0038-00304The values of the threshold range may correspond to commanded inputs, sensed conditions, or derived states associated with the system making a control state determination.

[0019] As an example, a threshold range may be used in the context of altitude control of an aircraft and may be referred to as an altitude hold threshold range, which may be a type of threshold range that defines a set of values associated with determining to hold an altitude of the aircraft. Further, an altitude hold threshold range may be used to control an aircraft to hold at a constant value of altitude. An altitude hold threshold range is illustrated and described further throughout the detailed description (e.g., in reference to FIG. 5A and in ffl0067]-

[0071] ).

[0020] Fig. 1 is an illustration of a perspective view of an exemplary Vertical Take-Off and Landing (VTOL) aircraft, consistent with disclosed embodiments. Fig. 2 is another illustration of a perspective view of an exemplary VTOL aircraft in an alternative configuration, consistent with embodiments of the present disclosure. Figs. 1 and 2 illustrate a VTOL aircraft 100, 200 in a cruise configuration and a vertical take-off, landing and hover configuration (also referred to herein as a “lift” configuration), respectively, consistent with embodiments of the present disclosure. Elements corresponding to Figs. 1 and 2 may possess like numerals and refer to similar elements of aircrafts 100, 200. Aircraft 100, 200 may include a fuselage 102, 202, wings 104, 204 mounted to fuselage 102, 202 and one or more rear stabilizers 106, 206 mounted to the rear of the fuselage 102, 202. A plurality of lift propellers 112, 212 may be mounted to wings 104, 204 and may be configured to provide lift for vertical take-off, landing and hover. A plurality of tilt propellers 114, 214 may be mounted to wings 104, 204 and may be tiltable (e.g., configured to tilt or alter orientation) between the lift configuration in which they provide a portion of the lift required for vertical take-off, landing and hovering, as shown in Fig. 2, and the cruise configuration in which they provide forward thrust to aircraft 100 for forward flight, as shown in Fig. 1. As used herein, a tilt propeller lift configuration refers to any tilt propeller orientation in which the tilt propeller thrust is providing primarily lift to the aircraft and tilt propeller cruise configuration refers to any tilt propeller orientation in which the tilt propeller thrust is providing primarily forward thrust to the aircraft.

[0021] In some embodiments, a “phase of flight” or “flight phase,” (e.g., hover, cruise, forward flight / wing-bome flight, takeoff, landing, transition) may be defined by a combination of flight conditions (e.g., a combination of flight conditions within particular ranges), which may include one or more of a speed, airspeed, groundspeed, altitude, pitch angle (e.g., of the aircraft), tilt angle (e.g., of one or more propellers), roll angle, rotationAgent Ref: 16499-0038-00304 speed (e.g., of one or more propellers), torque value, pilot command, or any other value indicating a current or requested (e.g., commanded) state of at least part of the aircraft. A “flight state” may include a flight phase and / or forces or environmental factors experience by the aircraft, such as at least one of weather conditions, air density, natural wind movements, humidity, a proximity of at least one component to a vortex ring state, etc.

[0022] “Vertical flight” or a “hover” phase of flight may be considered any phase of flight where lift for an aircraft is provided predominantly by engines (e.g., EPUs), rather than one or more wings. “Horizontal flight, a “cruise” phase of flight, or a wing-borne phase of flight may be considered any phase of flight where lift for an aircraft is provided predominantly by one or more wings, rather than by any engine (e.g., EPU). “Transition” may be considered any phase of flight where an aircraft is shifting from vertical flight to horizonal flight, or vice versa.

[0023] In some embodiments, lift propellers 112, 212 may be configured for providing lift only, with all horizontal propulsion being provided by the tilt propellers. For example, lift propellers 112, 212 may be configured with fixed positions and may only generate thrust during take-off, landing and hover phases of flight. Meanwhile, tilt propellers 114, 214 may be tilted upward into a lift configuration in which thrust from propellers 114, 214 is directed downward to provide additional lift.

[0024] For forward flight, tilt propellers 114, 214 may tilt from their lift configurations to their cruise configurations. In other words, the orientation of tilt propellers 114, 214 may be varied from an orientation in which the tilt propeller thrust is directed downward (to provide lift during vertical take-off, landing and hover) to an orientation in which the tilt propeller thrust is directed rearward (to provide forward thrust to aircraft 100, 200). The tilt propellers assembly for a particular electric engine may tilt about an axis of rotation defined by a mounting point connecting the boom and the electric engine. When aircraft 100, 200 is in full forward flight, lift may be provided entirely by wings 104, 204. Meanwhile, in the cruise configuration, lift propellers 112, 212 may be shut off. Blades 120, 220 of lift propellers 112, 212 may be held in low-drag positions for aircraft cruising. In some embodiments, lift propellers 112, 212 may each have two blades 120, 220 that may be locked, for example while the aircraft is cruising, in minimum drag positions in which one blade is directly in front of the other blade as illustrated in Fig. 1. In some embodiments, lift propellers 112, 212 have more than two blades, such as four blades. In some embodiments, tilt propellers 114, 214 may include more blades 116, 216 than lift propellers 112, 212. For example, as illustrated in Figs. 1 and 2, lift propellers 112, 212 may each include, e.g., two blades,Agent Ref 16499-0038-00304 whereas tilt propellers 114, 214 may each include more blades, such as the five blades shown. In some embodiments, each of tilt propellers 114, 214 may have 2 to 5 blades, and possibly more depending on the design considerations and requirements of the aircraft.

[0025] In some embodiments, the aircraft may include a single wing 104, 204 on each side of fuselage 102, 202 (or a single wing that extends across the entire aircraft). At least a portion of lift propellers 112, 212 may be located rearward of wings 104, 204 (e.g., rotation point of propeller is behind a wing from a bird’s eye view) and at least a portion of tilt propellers 114, 214 may be located forward of wings 104, 204 (e.g., rotation point of propeller is in front of a wing from a bird’s eye view). In some embodiments, all of lift propellers 112, 212 may be located rearward of wings 104, 204 and all of tilt propellers 114, 214 may be located forward of wings 104, 204. According to some embodiments, all lift propellers 112, 212 and tilt propellers 114, 214 may be mounted to the wings — e.g., no lift propellers or tilt propellers may be mounted to the fuselage. In some embodiments, lift propellers 112, 212 may be all located rearwardly of wings 104, 204 and tilt propellers 114, 214 may be all located forward of wings 104, 204. According to some embodiments, all lift propellers 112, 212 and tilt propellers 114, 214 may be positioned inwardly of the ends of wing 104, 204.

[0026] In some embodiments, lift propellers 112, 212 and tilt propellers 114, 214 may be mounted to wings 104, 204 by booms 122, 222. Booms 122, 222 may be mounted beneath wings 104, 204, on top of the wings, and / or may be integrated into the wing profile. In some embodiments, lift propellers 112, 212 and tilt propellers 114, 214 may be mounted directly to wings 104, 204. In some embodiments, one lift propeller 112, 212 and one tilt propeller 114, 214 may be mounted to each boom 122, 222. Lift propeller 112, 212 may be mounted at a rear end of boom 122, 222 and tilt propeller 114, 214 may be mounted at a front end of boom 122, 222. In some embodiments, lift propeller 112, 212 may be mounted in a fixed position on boom 122, 222. In some embodiments, tilt propeller 114, 214 may mounted to a front end of boom 122, 222 via a hinge. Tilt propeller 114, 214 may be mounted to boom 122, 222 such that tilt propeller 114, 214 is aligned with the body of boom 122, 222 when in its cruise configuration, forming a continuous extension of the front end of boom 122, 222 that minimizes drag for forward flight.

[0027] In some embodiments, aircraft 100, 200 may include, e.g., one wing on each side of fuselage 102, 202 or a single wing that extends across the aircraft. According to some embodiments, the at least one wing 104, 204 is a high wing mounted to an upper side of fuselage 102, 202. According to some embodiments, the wings include control surfaces, such as flaps such as flaps, ailerons, spoilers, and / or flaperons (e.g., configured to performAgent Ref: 16499-0038-00304 functions of both flaps and ailerons). According to some embodiments, wings 104, 204 may have a profile that reduces drag during forward flight. In some embodiments, the wing tip profile may be curved and / or tapered to minimize drag.

[0028] In some embodiments, rear stabilizers 106, 206 include control surfaces, such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wing(s) may have any suitable design for providing lift, directionality, stability, and / or any other characteristic beneficial for aircraft. In some embodiments, the wings have a tapering leading edge.

[0029] In some embodiments, lift propellers 112, 212 or tilt propellers 114, 214 may be canted relative to at least one other lift propeller 112, 212 or tilt propeller 114, 214, where canting refers to a relative orientation of the rotational axis of the lift propeller / tilt propeller about a line that is parallel to the forward-rearward direction, analogous to the roll degree of freedom of the aircraft.

[0030] In some embodiments, one or more lift propellers 112, 212 and / or tilt propellers 114, 214 may be canted relative to a cabin of the aircraft, such that the rotational axis of the propeller in a lift configuration is angled away from an axis perpendicular to the top surface of the aircraft. For example, in some embodiments, the aircraft is a flying wing aircraft as shown in Fig. 3F below, and some or all of the propellers are canted away from the cabin.

[0031] Figs. 3A-3F are illustrations of a top plan view of exemplary VTOL aircrafts, consistent with embodiments of the present disclosure. There may be a number of design considerations (cost, weight, size, performance capability, etc.) that may influence the number and / or combination of tilt and lift propellers in a VTOL aircraft. As further described below the number and orientation of propellers (and other effectors or actuators) may affect how forces are created. Therefore, the flight control system may adjust aircraft effectors or actuators in certain ways (e.g., those discussed in disclosed embodiments) to control the aircraft in a manner that reduces pilot workload.

[0032] Fig. 3A illustrates an arrangement of electric propulsion systems 265-276, consistent with embodiments of the present disclosure. Referring to Fig. 3A, the aircraft shown in the figure is a top plan view of an exemplary aircraft 350. Aircraft 350 may include twelve electric propulsion systems (265-276) distributed across the aircraft. In some embodiments, a distribution of electric propulsion systems may include six forward electric propulsion systems (265, 266, 267, 268, 269, and 270) and six aft electric propulsion systems (271, 272, 273, 274, 275, and 276). In some embodiments, the six forward electric propulsion systems (265, 266, 267, 268, 269, and 270) may be tiltable along at least one axis and may beAgent Ref: 16499-0038-00304 operatively connected to propellers and the six aft electric propulsion systems (271, 272, 273, 274, 275, and 276) may not be tiltable along at least one axis (e.g., all axes) and may be operatively connected to propellers. In other embodiments, the six forward electric propulsion systems (265, 266, 267, 268, 269, and 270) and a number of aft electric propulsion systems (271, 272, 273, 274, 275, and 276) may be tiltable along at least one axis and the remaining aft electric propulsion systems (271, 272, 273, 274, 275, and 276) may not be tiltable along at least one axis (e.g., all axes). In other embodiments, all forward electric propulsion systems (265, 266, 267, 268, 269, and 270) and aft electric propulsion systems (271, 272, 273, 274, 275, and 276) may be tiltable along at least one axis. The propellers of an electric propulsion system (EPS) (e.g., propellers described in Figs. 3A-3F) may be tiltable (e.g., the propeller blades may have collective blade tilt), whether or not the EPU itself can tilt. In some embodiments, the tilt of an EPS may be linked with the tilt of propeller blades of the EPU, either through a physical connection or a software command, such that a change in tilt of one causes a change of tilt in the other.

[0033] Fig. 3B illustrates an alternate arrangement of electric propulsion systems 277-284, consistent with embodiments of the present disclosure. Referring to Fig. 3B, the aircraft shown in the figures is a top plan view of an exemplary aircraft 351. Aircraft 351 may include eight electric propulsion systems 277-284 distributed across the aircraft. In some embodiments, a distribution of electric propulsion systems may include four forward electric propulsion systems (277, 278, 279, and 280) and four aft electric propulsion systems (281, 282, 283, and 284). In some embodiments, the four forward electric propulsion systems (277, 278, 279, and 280) may be tiltable along at least one axis and may be operatively connected to propellers and the four aft electric propulsion systems (281, 282, 283, and 284) may not be tiltable along at least one axis (e.g., all axes) and may be operatively connected to propellers. In other embodiments, the four forward electric propulsion systems (277, 278, 279, and 280) and a number of aft electric propulsion systems (281, 282, 283, and 284) may be tiltable along at least one axis and may be operatively connected to propellers and the remaining aft electric propulsion systems (281, 282, 283, and 284) may not be tiltable along at least one axis (e.g., all axes) and may be operatively connected to propellers. In other embodiments, all forward and aft electric propulsion systems (277-284) may be tiltable along at least one axis and may be operatively coupled to propellers.

[0034] Fig. 3C illustrates an alternate arrangement of electric propulsion system 261-264, consistent with the embodiments of the present disclosure. Fig. 3C is a top plan view of an exemplary aircraft 352. In some embodiments, electric propulsion systems 261-264 may beAgent Ref: 16499-0038-00304 or include ducted fans that are operably connected to the electric propulsion systems (e.g., electric engines or motors). In some embodiments, the aircraft may include one or more banks of ducted fans on each wing of the aircraft (e.g., electric propulsion systems 261, 262, 263, and 264) on each wing (e.g., 261w, 262w, 263w, and 264w) and each bank of ducted fans may be connected to tilt together (e.g., between lift and forward thrust configuration). In some embodiments aircraft 352 includes a left front wing 26 Iw and right front wing 263 w and a left rear wing 262w and right rear wing 264w. In some embodiments, each wing (26 Iw. 262w, 263w. and 264w) of the aircraft includes a bank of connected ducted fans (e.g., electric propulsion systems 261, 262, 263, and 264). In some embodiments, each bank of connected ducted fans is tiltable (e.g., between lift and forward thrust), while in other embodiments only the bank of fans on the front wing(s) (26 Iw and 263 w) are tiltable.

[0035] Fig. 3D illustrates an alternate arrangement of electric propulsion systems, consistent with embodiments of the present disclosure. Referring to Fig. 3D, the aircraft shown in the figure is a top plan view of exemplary aircraft 353. Aircraft 353 may include six electric propulsion systems (285, 286, 287, 288, 289, and 290) distributed across the aircraft. In some embodiments, a distribution of electric propulsion systems may include a first set of four electric propulsion systems 285, 286, 287, and 288 coplanar in a first plane and a second set of two electric propulsion systems 289 and 290 coplanar in a second plane. In some embodiments, the first set of electric propulsion systems 285, 286, 287, and 288 may be tiltable along at least one axis and may be operatively connected to propellers and a second set of electric propulsion systems 289 and 290 may not be tiltable along at least one axis (e.g., all axes) and may be operatively connected to propellers. In other embodiments, the first set of electric propulsion systems 285, 286, 287, and 288 and the second set of aft electric propulsion systems 289 and 290 may all be operatively connected to propellers.

[0036] Fig. 3E illustrates an alternate arrangement of electric propulsion systems, consistent with embodiments of the present disclosure. Referring to Fig. 3E, the aircraft shown in the figure is a top plan view of an exemplary aircraft 354. Aircraft 354 may include four electric propulsion systems distributed across the aircraft. In some embodiments, a distribution of electric propulsion systems may include four coplanar electric propulsion systems 291, 292, 293, and 294. In some embodiments, all of the electric propulsion systems (291, 292, 293, and 294) may be tiltable along at least one axis and operatively connected to propellers.

[0037] Fig. 3F illustrates an alternate arrangement of electric propulsion systems, consistent with embodiments of the present disclosure. Referring to Fig. 3F, the aircraft shown in the figure is a top plan view of an exemplary aircraft 355. Aircraft 355 may include six electricAgent Ref: 16499-0038-00304 propulsion systems 295, 296, 297, 298, 299, and 264 distributed across the aircraft. For example, in some embodiments, aircraft 355 may include four forward electric propulsion systems 295, 296, 297, and 298, which may be tiltable along at least one axis and operatively connected to propellers, and the two aft electric propulsion systems 299 and 264, which may not be tiltable along at least one axis (e.g., all axes) and may be operatively connected to propellers. In some embodiments (not shown), aircraft 355 may include ten electric propulsion systems distributed across the aircraft. For example, in some embodiments, the aircraft may include six forward electric propulsion systems, which may be tiltable along at least one axis and operatively connected to propellers, and the four aft electric propulsion systems, which may not be tiltable along at least one axis (e.g., all axes) and may be operatively connected to propellers. In some embodiments, some or all of the aft electric propulsion systems may be operatively connected to tilt propellers.

[0038] As shown in Fig. 3F, in some embodiments, aircraft 355 may have a flying wing configuration, such as a tailless fixed-wing aircraft with no definite fuselage. In some embodiments, aircraft 355 may have a flight wing configuration with the fuselage integrated into the wing. In some embodiments, the tilt propellers may rotate in a plane above the body of the aircraft when the tilt propellers operate in a lift configuration.

[0039] As disclosed herein, the forward electric propulsion units (EPUs) and aft EPUs may be of a clockwise (CW) type or counterclockwise (CCW) type. Some embodiments may include various forward EPUs possessing a mixture of both CW and CCW types. In some embodiments, the aft EPUs may possess a mixture of CW and CCW type systems among the aft EPUs. In some embodiments, each EPU may be fixed as clockwise (CW) type or counterclockwise (CCW) type, while in other embodiments, one or more EPUs may vary between clockwise (CW) and counterclockwise (CCW) rotation.

[0040] Figure 4 illustrates a diagram for aircraft control, consistent with the disclosed embodiments. Flight Control System (FCS) 401 may be implemented by at least one processor (e.g., at least one microprocessor-based controller) configured to execute software code stored in a storage medium (e.g., a computer-readable medium, a non-transitory computer-readable medium) to implement any combination of the functions described herein. FCS 401 may also be implemented in hardware, or a combination of hardware and software and may be configured to perform a single step or sequence repeatedly until a desired or commanded outcome is achieved.

[0041] For instance, in some embodiments, one or more of control commands 404, control allocation 405, vehicle dynamics 406, or flight parameter hold 408 may be implemented inAgent Ref: 16499-0038-00304 software, hardware, or a combination of both software and hardware. Further, one or more of pilot input 403 or vehicle sensing 407 may be implemented in software, hardware, or in a combination of both software and hardware. As an example, one or more of pilot input 403, control commands 404, control allocation 405, vehicle dynamics 406, vehicle sensing 407, or flight parameter hold 408 may include software modules, functions, or programs.

[0042] In some embodiments, Flight Control System (FCS) 401 may include one or more flight control computers (FCC) to perform the associated functions and memory device(s) may store a set of algorithms, models, and / or rules configured to govern a behavior of an aircraft (e.g., control or influence one or more aircraft flight elements, such as electric engines and / or flight control surfaces of the aircraft) in response to one or more pilot inputs and external factors (e.g., as sensed by one or more sensors). FCS 401 and / or the one or more FCCs may be physically mounted within the aircraft and / or communicably connected to one or more components (e.g., effectors, inceptors) of the aircraft. In some embodiments, the flight control system may store flight control laws configured to achieve at least one of desired flight characteristics, stability, and / or performance. For example, flight control laws may be configured to improve stability and controllability of an aircraft by controlling how the aircraft responds to at least one of one or more pilot inputs, vehicle dynamics (e.g., disturbances, such as turbulence, gusts, etc.), or changes in flight conditions (e.g., altitude, speed, forward speed, airspeed, groundspeed, vertical speed, angle of attack). Consistent with disclosed embodiments, the aircraft may be controlled by commands (e.g., commands from control allocation 405) transmitted from a device (e.g., FCS 401) to one or more effectors of the aircraft, which may change, control, manage, or otherwise influence one or more of a speed, a speed component, an altitude, a force, a thrust, a torque, or any flight characteristic associated with the aircraft or one of its components. An effector may include a control surface, an actuator, a motor, an EPU, or any other movable aircraft structure configured to influence aircraft behavior, consistent with disclosed embodiments. The commands may be generated based on at least one pilot input (e.g., to an inceptor), at least one automatic computer computation (e.g., to control, vertical speed, altitude, or flight path angle, as described further below), or a combination of both. In some embodiments, an FCC may be configured to transmit information to other processing systems of the aircraft, including a display, user interface, or any other processing system that may deliver information from the FCC to a pilot of the aircraft or ground systems.

[0043] Pilot Input 403 represents input from a pilot input device indicating a commanded aircraft state. The pilot input device is configured to receive pilot input and generate orAgent Ref: 16499-0038-00304 influence a signal. The pilot input device may include button(s), switch(es), knob(s), slider(s), inceptor(s) (e.g., pilot stick), any combination thereof, or any other device configured to generate or influence a signal based on a physical action from a pilot, whether the pilot is located onboard the aircraft or at a remote location in communication with the aircraft.

[0044] Pilot input 403 may include or be associated with one or more parameters. One or more parameters of pilot input 403 may include quantities or values, such as measurable quantities, reference values, or control objectives that may represent a pilot’s intent for aircraft maneuvers or performance. For example, these parameters may be expressed as absolute targets (e.g., an incremental value of a beep command, a commanded altitude, a commanded flight path angle of 0.7 degrees), as rates of change (e.g., rate of altitude change, decrease altitude by —0.5 m / s, increase forward speed at a rate of 1 1 m / s2, roll rate, yaw rate), or any other quantifiable parameter associated with a pilot input command or pilot input device.

[0045] In some embodiments, pilot input 403 may include or be associated with a commanded rate of change of altitude of the aircraft, where the commanded rate of change of altitude of the aircraft may correspond to vertical speed (h) (e.g., later described in reference to Fig. 6A and 6B). Further, pilot input 403 may be configured to indicate a commanded rate of change of altitude of the aircraft, instruct the aircraft to change altitude with a pilot- specified rate, or cause the aircraft to change altitude with a pilot-specified rate. Additionally, in some embodiments, pilot input 403 may include or be associated with a commanded flight path angle (FPA), where the commanded flight path angle may correspond to flight path angle (y or ycmd) (e.g., later described in reference to FIG. 6A and FIG. 6B). Further, pilot input 403 may be configured to indicate a commanded FPA, instruct the aircraft to change altitude with a pilot-specified FPA, or cause the aircraft to change altitude with a pilot- specified FPA. For example, pilot input 403 may be an inceptor movement (e.g., longitudinal or lateral movement of a pilot stick or pilot yoke), where inceptor displacement may determine or be used to determine a commanded rate of change of altitude of the aircraft or an FPA. In another example, pilot input 403 may be a beep command, where the pilot input may provide commands in set increments, which may include a commanded altitude or flight path angle change, where the commanded change may occur over a pre-determined or commanded amount of time or a system-determined amount of time based on flight conditions. As an example, the signal corresponding to pilot input 403 may include data (e.g., input processed by pilot input device before transmitting data to FCS 401, a mappingAgent Ref: 16499-0038-00304 between input and flight controls which may be stored locally at pilot input device) that includes the commanded rate of change of altitude of the aircraft or the FP A. As another example, a signal corresponding to pilot input 403 may be processed by FCS 401 to derive or determine the commanded rate of change of altitude of the aircraft or the FPA based on the data included in the signal. As a further example, FCS 401 may include a mapping of pilot input 403 to control commands 404 may include determining a commanded rate of change of altitude of the aircraft or an FPA based on a pilot input command.

[0046] In some embodiments, pilot input 403 may include or be associated with a commanded change in altitude, where the commanded change in altitude may be a requested or directed adjustment of the aircraft’s altitude. Further, a commanded change in altitude may include a pilot input command that may cause the aircraft to initiate an ascent or descent toward a different altitude (e.g., for a non-zero commanded change in altitude, where a positive commanded change in altitude may correspond to an ascent of the aircraft and a negative commanded change in altitude may correspond to a descent of the aircraft). A commanded change in altitude may be based on (e.g., requested or directed) by a pilot input command (e.g., a pilot input command from a pilot input device, pilot input 403), such as an inceptor command or a beep command.

[0047] In some embodiments, pilot input 403 may include a commanded rate of altitude change of the aircraft, and the commanded rate of altitude change of the aircraft may be associated with a change in altitude. In some embodiments, the change in altitude may be a commanded change in altitude due to a pilot input command (e.g., pilot input 403).

[0048] In some embodiments, as described below in reference to Fig. 9, pilot input 403 can include pilot input from Right Inceptor L / R 902a, Autopilot bank command 902b, Left Inceptor L / R 902c, Autopilot climb command 902d, Right inceptor F / A 902d, Left inceptor switch 902f, and / or Left inceptor F / A 902g. For example, a pilot input device may include one or more of right inceptor(s) (right stick) (e.g., moving right inceptor left / right and / or right inceptor forward / aft), left inceptor(s) (left stick) (e.g., moving left inceptor left / right and / or left inceptor forward / aft), and / or an inceptor switch.

[0049] In some embodiments, as described below with respect to Figs. 7A-7B, pilot input 403 may include inceptor (stick) commands and beep commands. In some embodiments, a pilot input device may include an interface (e.g., display screen(s), switch(es), button(s), lever(s), and / or other interface(s)). The interface may include or be communicably connected to an autopilot system. The interface may enable the display or transmission of information concerning one or more aircraft flight parameters, which may include information about anAgent Ref: 16499-0038-00304 aircraft flight parameter that is held constant, consistent with disclosed embodiments. In some embodiments, the transmitted information may include an alert about a plurality of flight parameters or a flight parameter that is held constant. As used throughout, the term “constant” may refer to exact constancy or near constancy, such as remaining constant within a threshold tolerance. It is also appreciated that while an aircraft parameter may be held constant, such as by a processing system, the aircraft degree of freedom corresponding to that aircraft parameter may in reality have some variance, such as due to wind effects on the aircraft. It is also appreciated that while some embodiments may refer to holding a thing constant without referring to a parameter (e.g., flight path angle, altitude, speed), those embodiments may apply equally to the corresponding parameter (e.g., flight path angle, altitude, speed).

[0050] In some embodiments, a pilot input device may be present within an aircraft. In other embodiments, a pilot input device may be external to the aircraft (e.g., for remote control). In yet other embodiments, at least one pilot input device may be present in the aircraft and at least one pilot input device may be external to the aircraft.

[0051] Control commands 404 represent one or more executable processes to provide commands (e.g., moment commands to control allocation 405) to control the aircraft. The processes may include modeling a commanded aircraft response (e.g., determining a shape of an ideal aircraft response), feedback and feedforward processes (e.g., determining corresponding forces to accomplish a desired change in the aircraft), outer loop processes (e.g., determining a corresponding yaw, roll, command, pitch, and / or thrust), and / or one or more inner loop control law processes (e.g., determining moment commands). Each of these processes may include one or more control laws, rules, functions, models, and / or algorithms (e.g., stored in a memory) and may dynamically adjust their outputs based on inputs (e.g., from pilot input 403, flight parameter hold 408, and vehicle sensing 407). In some embodiments, control commands 404 may be determined based on a commanded rate of altitude change of the aircraft.

[0052] In some embodiments, as described below in reference to Fig. 9, control commands 404 may include executable processes to provide commands to control the aircraft, such as Automatic transition function 903, Turn-rate command model 904, Lateral speed command model 906, Climb command model 908, Forward speed command model 910, Feedback 912, Feed forward 914, Feedback 916, Feedback 918, Feed forward 920, and / or Feedback 922.

[0053] Control allocation 405 may control the aircraft’s flight elements (e.g., effectors) based on input from control commands 404 and / or vehicle sensing 407. For example, controlAgent Ref: 16499-0038-00304 allocation 405 may control (e.g., transmit one or more commands to) one or more EPUs of the aircraft (e.g., electric engines, propellers, actuators, rotors, etc.). Control allocation 405 may further control one or more control surface(s) of the aircraft, including flaperon(s), ruddervator(s), aileron(s), spoiler(s), rudder(s), and / or elevator(s).

[0054] Control allocation 405 may include one or more models or functions (e.g., an optimizer function) to control commands to EPUs, control surfaces, and / or other effectors that meet a commanded aircraft state while also meeting one or more hard and / or soft constraints. For example, control allocation 405 may weight different priorities such as maintaining a lift and / or forward thrust (e.g., for aircraft stability or controllability), meeting a battery requirement (e.g., a de-rated battery state, such as a state of charge, a state of power, a state of health, etc.), maintaining flight within a flight envelope, and / or avoiding propeller speeds corresponding with vibration over a threshold, etc. In some embodiments, control allocation 405 may determine multiple control solutions to meet the commanded aircraft state and select the solution that best meets (e.g., maximizes the results of) the priorities (e.g., according to relative weights between the priorities).

[0055] In some embodiments, as described below in reference to Fig. 9, control allocation 405 may include one or more models or functions, such as Lateral / Directional Outer Loop Allocation 924, Longitudinal Outer Loop Allocation 926, Inner loop control laws 928, and / or Control Allocation 929.

[0056] Vehicle dynamics 406 represents the controlled flight elements (e.g., electric propulsion system(s) and / or control surfaces) and aircraft dynamics (e.g., how the aircraft responds to flight element control (aircraft orientation, movement etc.)). In some embodiments, as described below in reference to Fig. 9, vehicle dynamics 406 may include Vehicle Dynamics Control 930.

[0057] Vehicle sensing 407 may detect flight conditions of the aircraft, such as vehicle dynamics using a combination of sensors, processors, and / or memory devices. Vehicle sensing 407 may include one or more sensors configured to detect vehicle dynamics and / or an aircraft state, such as acceleration and / or pitch orientation sensors (e.g., accelerometer(s), 3-axis accelerometer(s), gyroscope(s), and / or 3-axis gyroscope(s)), airspeed sensors (e.g., pitot tube sensors), and / or ground speed sensors. Vehicle sensing 407 may further include one or more inertial measurement units (IMUs) to determine a position of the aircraft (e.g., a yaw angle, roll angle, pitch angle, and / or any other orientation across one or two axes) and / or aircraft component (e.g., angle of an actuator), velocity of the aircraft, angular rate of the aircraft (e.g., roll, pitch, and / or yaw rate), and / or an acceleration of the aircraft (e.g.,Agent Ref: 16499-0038-00304 longitudinal, lateral and / or vertical acceleration), or any physical characteristic of the aircraft or one of its components.

[0058] Vehicle Sensing 407 may include an air data system and / or airspeed sensors (e.g., pitot tubes), groundspeed sensors, Global Positioning System (GPS) sensors, propeller speed sensors (e.g., hall effect sensors and / or optical sensors), propeller tilt angle sensors, (e.g., magnetic sensors, position displacement sensors, linear displacement sensors etc. to measure a nacelle tilt angle), inertial sensors, range sensors (RADAR, LIDAR, and / or camera sensors), pressure sensors (e.g., to determine altitude), accelerometers, and / or gyroscopes to determine flight conditions.

[0059] Vehicle Sensing 407 may be configured to measure a change of altitude of the aircraft or a rate of change of altitude of the aircraft. In some embodiments, the measured change of altitude or rate of change of altitude of the aircraft may be used for determining which one of a plurality of aircraft flight parameters to hold constant. Further, in some embodiments, the measured change of altitude or rate of change of altitude may be associated with a pilot input command (e.g., pilot input 403), such that vehicle sensing 407 or pilot input 403 may be used (e.g., as part of a process disclosed herein, such as process 800) to determine which one of a plurality of aircraft flight parameters to hold constant. In some embodiments, one or more aircraft flight parameters may be held constant. In some embodiments, two or more aircraft flight parameters may be held constant. In some embodiments, three or more aircraft flight parameters may be held constant.

[0060] In some embodiments, vehicle sensing 407 and / or another control component (e.g., flight parameter hold 408) may categorize a flight condition based on comparing one or more sensor measurements and / or pilot input(s) to one or more pre-stored thresholds. For example, vehicle sensing 407 and / or another control component may categorize a flight condition into one of the groups illustrated in Figs. 5A-5B to control certain aspects of flight based on the categorization. Further, in some embodiments, vehicle sensing 407 and / or another control component may categorize a flight condition to determine how a pilot input will be mapped as illustrated in Figs. 6A, 6B, 7A, and 7B. Flight condition categorization may be based on forward speed (e.g., airspeed or groundspeed), torque (e.g., commanded), propeller speed(s), aircraft orientation (e.g., pitch angle), propeller tilt angle, one or more pilot commands, and / or any other flight condition(s). In some embodiments, flight condition categorization may be based on aircraft speed (e.g., forward speed, vertical speed, airspeed, groundspeed, horizontal component of forward speed, vertical component of forward speed) and pilot inputAgent Ref: 16499-0038-00304(e.g., whether descent or ascent is commanded). In some embodiments, as described below in reference to Fig. 9, vehicle sensing 407 may include Vehicle Dynamics Sensing 931.

[0061] Flight parameter hold 408 may detect flight conditions of the aircraft and hold constant at least one flight parameter, such as an altitude, vertical speed, or flight path angle (FPA) based on the detected flight conditions. Holding a flight parameter constant may refer to maintaining a specific value of the flight parameter (e.g., a chosen flight parameter, a determined flight parameter), while allowing other flight parameters to vary. A flight parameter hold (e.g., flight parameter hold 408) may include maintaining a specific value of a flight parameter without requiring manual input from a pilot of the aircraft. A flight parameter hold (e.g., flight parameter hold 408) or holding a flight parameter constant may include monitoring the flight parameter and adjusting control surfaces, thrust, or other elements of Vehicle Dynamics 406 to maintain a specific value of the flight parameter. For example, based on the detected flight conditions of the aircraft, flight parameter hold 408 will maintain an existing and / or commanded altitude, vertical speed, or FPA when no active pilot input is received at one or more input devices, such as when the pilot lets go of pilot input device(s) configured to direct aircraft ascent or descent. Flight parameter hold 408 may detect a forward speed (e.g., airspeed or groundspeed) and whether the aircraft is ascending or descending (e.g., based on commanded pilot input and / or sensed aircraft conditions). Based on these conditions, flight parameter hold 408 may hold an altitude, vertical speed, or FPA (e.g., as detailed in Fig. 5A). In some embodiments, flight parameter hold 408 may be configured to hold at least one flight parameter, which may include an altitude, vertical speed, or FPA. The control commands 404 may determine (e.g., generate and / or transmit) moment and / or thrust commands to maintain the vertical speed, FPA , or altitude using one or more control laws, rules, functions, models, and / or algorithms (e.g., stored in a memory). For example, control commands 404 may determine a pitch command, thrust command (e.g., vertical thrust command), elevator command, cyclic command, collective command, and / or attitude command required to maintain an altitude, speed, or FPA (e.g., based on commanded state(s) and feedback from vehicle sensing 407). As discussed above, commands from control commands 404 may be sent to control allocation 405 which may control one or more effectors, such as EPUs and / or control surfaces of the aircraft, according to the commands. In other embodiments, control commands 404 may directly control one or more effectors of the aircraft.

[0062] In some embodiments, a method (e.g., computer-implemented method and / or method executed by at least one processor) may include determining which one of a plurality ofAgent Ref: 16499-0038-00304 aircraft flight parameters to hold constant. The aircraft flight parameters may comprise at least one of (e.g., all three of) an altitude of the aircraft, a vertical speed of the aircraft, or an FPA of the aircraft. In different holds (e.g., flight parameter hold regions) one of these flight parameters may be held constant (e.g., as part of the method, by at least one processor implementing the method, etc.), as illustrated in Fig. 5A. In some embodiments, the determination of which one of a plurality of aircraft flight parameters to hold constant is based on both a speed (e.g., forward speed, vertical speed, airspeed, groundspeed, horizontal component of forward speed, vertical component of forward speed) of the aircraft and the determination (e.g., by the method) of whether a pilot input command (e.g., current command or most recent command) is commanding an ascent or descent of the aircraft. In some embodiments, one or more of a plurality of aircraft flight parameters may be held constant based on both a speed of the aircraft and the determination of whether a pilot input command is commanding an ascent or descent of the aircraft. While the terminology “is commanding” is used herein, it is appreciated that this may refer to either a present command or a past command, such as a most recently received or processed pilot command. Determining whether a pilot input command is commanding an ascent or descent may include determining a vertical speed component (e.g., over a threshold) is precipitated by one or more commands (e.g., from pilot input), determining whether a current trajectory of the aircraft is ascending or descending, determining an aircraft trajectory based on one or more commands, and / or measuring one or more values related to a state of the aircraft (e.g., using sensors to determine motion of the aircraft). In some embodiments, the determination of which one of a plurality of aircraft flight parameters to hold constant may be based only on an airspeed of the aircraft. For example, if the method determines that the airspeed is below a threshold, it may further determine to hold an altitude of the aircraft constant, with no determination of whether the pilot command is commanding an ascent or descent. By way of further example, the method may determine whether the pilot command is commanding an ascent or descent after (e.g., based on) determining that the airspeed is above the threshold. After determining which one of a plurality of aircraft flight parameters to hold constant, the method may control the aircraft based on a pilot input command, while holding the determined aircraft flight parameter constant. As discussed further below, a speed, ascent, or descent may be determined based on a pilot input command, at least one sensed condition (e.g., speed, rate of climb, trajectory, or vertical speed component, etc.), or a combination of both.

[0063] For example, controlling the aircraft may include, at speeds below a first predetermined threshold (e.g., a first speed threshold), holding an altitude of the aircraftAgent Ref: 16499-0038-00304 based on a lack of pilot input (e.g., when a pilot releases a vertical speed command, when no direct pilot input is being received, when no change in pilot input is received). Additionally or alternatively, controlling the aircraft may include, at speeds above the first predetermined threshold (e.g., a first speed threshold) when an ascent is commanded (e.g., has been commanded or where the current aircraft trajectory is ascending), holding a vertical speed of the aircraft at a constant value while allowing an FPA of the aircraft to vary. Additionally or alternatively, controlling the aircraft may include, at speeds above a second predetermined threshold (e.g., a second speed threshold) when an ascent is commanded (e.g., has been commanded or where the current aircraft trajectory is ascending), holding the FPA at a constant value while allowing the vertical speed to vary. Additionally or alternatively, controlling the aircraft may include, at speeds above the first predetermined threshold (e.g., a first speed threshold) when a descent is commanded (e.g., has been commanded or where the current aircraft trajectory is ascending), holding the FPA at a constant value while allowing the vertical speed to vary.

[0064] Figs. 5A and 5B illustrate how the vertical speed hold or FPA hold may vary based on flight conditions (e.g., commanded and sensed) of the aircraft. Fig. 5A illustrates the transitions between altitude hold, vertical speed hold, and FPA hold relative to flight conditions (e.g., climb vs. descent and a speed of the aircraft). In some embodiments, consistent with those described above, the holds (e.g., holding an aircraft parameter constant) may be performed when the aircraft is not receiving a pilot input commanding a change in an aircraft’s trajectory (e.g., change in ascent or descent). The hold regions depicted in Figs. 5A and 5B may be implemented (e.g., through automatic control of one or more effectors) by at least one processor (e.g., an FCC), for example, based on received (e.g., commanded and / or sensed) flight conditions.

[0065] As shown by altitude hold 501, at low aircraft speed (e.g., total airspeed or groundspeed), an altitude of the aircraft may be held constant. For example, at an airspeed below a threshold in the range of 1 kts - 15kts (e.g., 5kts), altitude may be held constant. Similarly, when an aircraft is at a low ascent or descent (e.g., previously commanded or sensed) and the pilot stops providing an input to change a trajectory (e.g., a change an ascent or descent) an altitude may be held constant. For example, an altitude may be held constant when an ascent (e.g., previously commanded or sensed) is lower than a first threshold (e.g., an FPA threshold in the range of 0 to 1 degrees) and higher than a second threshold (e.g., an FPA threshold in the range of 0 to -1 degrees). For example, an altitude may be held constant when an ascent is lower than a first threshold (e.g., a vertical speed in a range of 0 to 0.75Agent Ref: 16499-0038-00304 meters per second (m / s)) and higher than a second range (e.g., vertical speed in a range of 0 to 0.5 (m / s)). In some embodiments, the first and second thresholds may have the same absolute value, while in other embodiments they may vary. In some embodiments, based on a pilot input commanding a either a vertical speed or an FPA within the established respective ranges, the altitude may be held constant regardless of the aircraft’s speed (e.g., forward speed, vertical speed, airspeed, groundspeed, horizontal component of forward speed, vertical component of forward speed).

[0066] Further, a low ascent or descent may refer to a rate of altitude change (e.g., commanded rate of altitude change, sensed rate of altitude change) that is within a predetermined threshold range or with an absolute value is below a predetermined threshold. A low ascent or descent may be determined based on a commanded rate of altitude change. A commanded rate of altitude change may be determined from or associated with a pilot input command. For instance, a commanded rate of altitude change may be determined based on the initial position and current position at a pilot input device. As an example, for an inceptor command, displacement of a pilot input device less than or equal to a threshold (e.g., at or below a certain longitudinal displacement, lateral displacement, displacement angle, or displacement distance of the pilot input device) may correspond to a low ascent or descent command, which may result in an altitude hold (e.g., altitude hold 501). A displacement of a pilot input device (e.g., corresponding to an inceptor command) may be mapped to a commanded vertical speed (h) or FPA (y or ycmd) of the aircraft, from which the commanded rate of altitude change may be determined or with which the commanded rate of altitude change may be associated.

[0067] As shown by vertical speed hold 502, at intermediate aircraft speed (e.g., airspeed or groundspeed above a threshold indicated by the left vertical line of vertical speed hold 502) and an ascent above the altitude hold threshold range (e.g., shown by, corresponding to, or associated with altitude hold 501), a vertical speed may be held constant. For example, in a speed range above an altitude hold threshold range and below a second speed threshold (e.g., an airspeed threshold in the range of 20-85 kts, where the range may be inclusive of 20 kts and 85 kts) and ascent above the altitude hold threshold range, a vertical speed may be held constant.

[0068] As shown by flight path angle (FPA) hold 503, at a higher aircraft speed (e.g., airspeed or groundspeed) and ascent above the altitude hold threshold range, an FPA may be held constant. For example, in a speed range above a vertical speed hold threshold and ascentAgent Ref: 16499-0038-00304 above an altitude hold threshold range, an FPA may be held constant. Further, when the aircraft is in a descent below the altitude hold threshold range and a vertical speed above the altitude hold threshold range, FPA may be held constant. In some embodiments, vertical speed may not be automatically held when the aircraft is descending (as depicted in Fig. 5A). In other embodiments, vertical speed may be automatically held in certain flight conditions during descent (not shown in Fig. 5A). While terms such as “range” are used to describe certain thresholds, it is appreciated that single values (fixed or variable), statistical values, dynamic values, equations, functions, limits, or other representations may be used.

[0069] An altitude hold threshold range may be a type of threshold range (e.g., as described in UH[OO 18]-

[0019] ). An altitude hold threshold range may refer to a plurality of values corresponding to conditions under which a system determines to hold an aircraft’s altitude or controls the aircraft to maintain an altitude. An altitude hold threshold range may refer to a set of values lying between a lower limit and an upper limit (e.g., inclusive). The plurality of values of an altitude hold threshold range may include positive, negative, or zero values. For example, an altitude hold threshold range may be illustrated in FIG. 5A with the region corresponding to altitude hold 501 along the horizontal axis.

[0070] The plurality of values of an altitude hold threshold range may correspond to a condition of the aircraft (e.g., measured condition, predicted condition, commanded condition, or combination thereof). For instance, an altitude hold threshold range may include a plurality of values corresponding to a commanded or sensed flight parameter. For instance, a commanded or sensed flight parameter may include a rate of altitude change of the aircraft, a vertical speed of the aircraft, or a flight path angle (FPA) of the aircraft, for example, as illustrated in FIG. 5 A and FIG. 5B. A commanded or sensed flight parameter may further include or be associated with a commanded or sensed change in altitude.

[0071] In some embodiments, an altitude hold threshold range may include or represent a range of ascents, a range of positive commanded rates of altitude change, or a range of positive flight path angles (FPA) (e.g., the +y axis of FIG. 5A). Further, an ascent, positive rate of altitude change, or positive FPA may include or be associated with a positive altitude change. In some embodiments, an altitude hold threshold range may include a range of descents, a range of negative rates of altitude change, or a range of negative flight path angles (FPA) (e.g., the -y axis of FIG. 5A). Further, a descent, negative rate of altitude change or negative FPA may include or be associated with a negative altitude change. In some embodiments, an altitude hold threshold range may include a rate of altitude change or an FPA of zero (or near zero, such as within a predetermined range including zero), which mayAgent Ref: 16499-0038-00304 be commanding neither an ascent or descent. For example, an altitude hold threshold range may include positive, negative, and zero values of commanded rate of altitude change or commanded altitude change (e.g., as illustrated in FIG. 5A).

[0072] Fig. 5B illustrates example ranges that may establish the boundaries of altitude hold, vertical speed hold, and FPA hold. While airspeed is used as an example threshold to establish transitions between altitude hold, vertical speed hold, and FPA hold, in other embodiments groundspeed or a horizontal component of airspeed may establish these transitions. Similarly, while FPA and vertical speed (e.g., detected via pilot input commands) is used to establish transitions between altitude hold, vertical speed hold, and FPA hold, in other embodiments thresholds for ascent and / or descent may correspond to sensed aircraft conditions, such as GPS measurements, air data measurements, inertial measurements, range measurements (e.g., RADAR, LIDAR, or camera measurements taken with respect to the ground), or a combination of sensed measurements.

[0073] Figs. 6A-6B detail the relationship between flight path angle (FPA) and vertical speed and algorithms that allow for a smooth transition between vertical speed hold and FPA hold. As shown at depiction 601, the relationship between FPA (y), airspeed (total speed of the* h aircraft) (V), and vertical speed ( i) is: sin(y) = - . The relationship between FPA rate (y) and normal acceleration (nz) is y = nz. The relationship between vertical acceleration and normal acceleration (nz) is h=nzgsin(y). In some embodiments, at least one processor may determine a flight parameter (e.g., for automatic control, such as controlling vertical speed) based on one or more of these relationships.

[0074] In some embodiments, pilot input (e.g., a longitudinal or lateral stick movement or beep input) may be mapped to different commands based on flight conditions of the aircraft. For example, as shown in process 602, in a low speed range (e.g., a speed range corresponding to an altitude hold) a pilot input is mapped to a vertical speed command h (e.g., using a gain and filter component). In some embodiments, when no pilot input is received, pilot input may be mapped to a command to hold altitude. For example, a vertical speed may be set to zero or a change in vertical speed may be set to zero. In some embodiments, feedback indicating a change in altitude from the held position may drive aircraft control and the aircraft may be controlled to eliminate the change. For example, feedback may include GPS measurements, pressure measurements, inertial measurements, and / or range measurements (e.g., RADAR, LIDAR, camera) indicating a change in altitude. In some embodiments, process 602 may be carried out (e.g., executed) by at least oneAgent Ref: 16499-0038-00304 processor (e.g., FCC) multiple times (e.g., repeatedly, periodically, continually) while the aircraft is in flight.

[0075] As shown in process 603, in other speed ranges (e.g., a speed range above altitude hold) a pilot input is mapped to a normal acceleration nz(e.g., using a gain and filter). When no pilot input is received and the aircraft is in FPA hold range (e.g., range shown by, corresponding to, or associated with FPA hold 503 in Fig. 5A), an FPA corresponding to the normal acceleration command is determined using is y = nzand integrating for y. The FPA (y) is held constant while vertical speed (h) is adjusted to accommodate changes in airspeed using h = sin(y) * V.

[0076] When no pilot input is received and the aircraft is in vertical speed hold range (e.g., range shown by, corresponding to, or associated with vertical speed hold 502 in Fig. 5A), a vertical speed corresponding to the normal acceleration command is determined using h=n7gsin(y) and integrating for (h). The vertical speed (h) is held constant while the FPA (y) is adjusted to accommodate changes in airspeed using y = asin (h / V).

[0077] When no pilot input is received and the aircraft is in an altitude hold region (e.g., Fig. 5A range shown by, corresponding to, or associated with altitude hold 501), the aircraft may be controlled to maintain the altitude, as described above with reference to process 602. In some embodiments, process 603 may be carried out (e.g., executed) by at least one processor (e.g., FCC) multiple times (e.g., repeatedly, periodically, continually) while the aircraft is in flight.

[0078] Fig. 6B illustrates a smooth switching process, according to embodiments of the present disclosure. As shown, the pilot input may be a result of a “pilot stick command” or a “beep command”, as further detailed below with respect to Fig. 7A. A “pilot stick command” may refer to an input on (e.g., obtained or received from) a pilot input device (e.g., stick, lever, throttle etc.) that provides commands along a continuous spectrum. A “beep command” may refer to input on a pilot input device (e.g., button, switch, trim switch, stick, lever, throttle etc.) that provides commands in set increments (e.g., discrete inputs). In some embodiments, a pilot input device for a “beep command” may be configured such that a single discrete movement (e.g., a press, push, flick etc.) is needed to change the increment. Each command may be associated with their respective gains, may be filtered, and may be mapped to a normal acceleration command nz.Agent Ref: 16499-0038-00304

[0079] As shown, based on the normal acceleration command nz, a pseudo flight path angle (FPA) rate, Ypseudo, is determined using Ypseud0=nz ~^~ ■ In the vertical speed hold region, VRef is the maximum of V and Vthsid, VRef = max(V, Vthsid), where Vthsid is the maximum airspeed for vertical speed hold 502 prior to transitioning to FPA hold 503, as shown in Fig. 5A (e.g., 85 kts). Therefore, in the vertical speed hold region, vertical speed h will be constant and FPA Ycmd will vary as a function of V, Ycmd = asin Q VRefsln . Inthe FPA hold region, VRef = V. Therefore, in the FPA hold region, vertical speed h will vary as a function of airspeed, h = sinV and FPA, Ycmd, will be held constant (as the terms cancel out). Therefore, the aircraft may seamlessly switch between the vertical speed hold region and the FPA hold region using a pilot input command (e.g., the same pilot stick command).

[0080] Fig. 7A further details the effect of a pilot input when received as a stick command or a beep command. As shown, a stick command may be mapped to a change in vertical speed when in a low speed or hover region (e.g., a speed threshold below an altitude hold threshold range). At a speed above low speed, a stick command may be mapped to a change in load factor (e.g., normal acceleration nz). As shown, a “beep command” may command an incremental change in altitude (e.g., an altitude change in a range of ,5ft - 10ft, 2-15ft, 1 -20ft) at low speed. At a speed above low speed, a “beep command” may command an incremental change in flight path angle (FPA) (e.g., an FPA change in a range of 0.1 deg - 1 deg FPA). In some embodiments, in low speed, the beep command may be mapped to a vertical speed command over a set time increment (e.g., discrete time increment, such as 1 second, 2 seconds, etc.) to achieve the incremental change in altitude. In some embodiments, above low speed, the beep command may be mapped to a change in load factor to achieve the incremental change in FPA.

[0081] In some embodiments, as shown in Fig. 7B, both the stick command and beep command may be received on the same pilot input device. Therefore, a pilot can easily switch between the two commands. For example, a pilot can rotate an input device (e.g., a thumbstick) about an axis to provide a stick command and input a discrete movement (e.g., a press, flick push) on the input device (e.g., at the top) to provide a beep command.

[0082] Fig. 8 illustrates a flowchart for example process 800 of controlling an aircraft, consistent with the disclosed embodiments. In some embodiments, process 800 may be a computer-implemented method of controlling an aircraft. In some embodiments, process 800Agent Ref: 16499-0038-00304 may be performed with at least one processor (e.g., at least one processor connected to a computer-readable medium, an FCS, etc.) to perform operations or functions described herein. In some embodiments, process 800 may be implemented in a system including a pilot input device and at least one processor configured to carry out process 800. In some embodiments, process 800 may be implemented as software (e.g., program codes, instructions) that is stored in a memory or a non-transitory computer readable medium. In some embodiments, some aspects of process 800 may be implemented as hardware (e.g., a specific-purpose circuit). In some embodiments, process 800 may be implemented as a combination of software and hardware.

[0083] Referring to Fig. 8, process 800 may include a step 802 of receiving a pilot input command. For example, step 802 may include FCS 401 receiving pilot input 403, where the pilot input command may be a pilot stick command (e.g., an inceptor command), a beep command, or no input, consistent with disclosed embodiments. For example, step 802 may include FCS 401 receiving pilot input 403, where the pilot input command is commanding a climb or descent of the aircraft, consistent with disclosed embodiments (e.g., as discussed above with respect to Fig. 5A, Fig. 5B, Fig. 6A, and Fig. 6B, such as in 1ffi

[0064] -

[0079] ). For example, step 802 may include a pilot input command that is the last pilot input 403 received by FCS 401, consistent with disclosed embodiments. For example, step 802 may include FCS 401 receiving pilot input 403, where pilot input 403 is a no input command.

[0084] Receiving a pilot input command may include receiving a pilot input command that includes one or more parameters. These one or more parameters may include a commanded flight path angle (FPA), a commanded rate of altitude change, a commanded vertical speed, or a speed from which commanded vertical speed can be derived. Receiving a pilot input command may include a pilot input command that is associated with a commanded rate of change of altitude of the aircraft. For example, a stick command (e.g., an inceptor command) may include a degree of deflection of the stick, which may correspond to a commanded rate of change of altitude of the aircraft. For example, a beep command may include a pilot selection of a rate of change of altitude of the aircraft.

[0085] Process 800 may include a step 804 of determining whether the pilot input command is commanding an ascent or descent of the aircraft. For example, step 804 may include FCS 401 determining control commands 404 based on a received pilot input 403, where the determination of control commands 404 may include determining whether the pilot input command is commanding an ascent or descent of the aircraft, consistent with disclosed embodiments.Agent Ref: 16499-0038-00304

[0086] In some embodiments, step 804 may include determining whether the pilot input command is commanding an ascent or descent of the aircraft based on a sensed aircraft condition. Step 804 may further include determining whether the pilot input command is commanding an ascent or descent of the aircraft based on both a pilot input command and a sensed condition. In some embodiments, determining whether the pilot input command is commanding an ascent or descent of the aircraft may include comparing a sensed aircraft condition to an aircraft condition threshold. For example, step 804 may include FCS 401 determining control commands 404 based on a received pilot input 403 and vehicle sensing 407, where the determination of control commands 404 may include determining whether the pilot input command is commanding an ascent or descent of the aircraft, consistent with disclosed embodiments.

[0087] In some embodiments, step 804 may include determining an amount (e.g., magnitude, rate) of an ascent or descent of the aircraft (e.g., to be compared to a threshold, consistent with disclosed embodiments). Determining whether the pilot input command is commanding an ascent or descent of the aircraft may include determining whether one or more parameters included in the pilot input command, such as a commanded flight path angle (FPA) or a commanded rate of altitude change, indicate an ascent or descent (e.g., commanded ascent or descent) of the aircraft. For instance, a positive FPA or commanded rate of altitude change may correspond to an ascent (e.g., a commanded ascent) of the aircraft. Further, a negative FPA or commanded rate of altitude change may correspond to a descent (e.g., commanded descent) of the aircraft.

[0088] Determining whether the pilot input command is commanding an ascent or descent of the aircraft (e.g., step 804) may include determining a commanded rate of altitude change of the aircraft. Determining whether the pilot input command is commanding an ascent or descent of the aircraft (e.g., step 804) may include determining a commanded rate of altitude change associated with the received pilot input (e.g., receiving a pilot input command as described in reference to step 802). For example, a commanded ascent may correspond to a positive commanded rate of altitude change of the aircraft. As another example, a commanded descent may correspond to a negative commanded rate of altitude change of the aircraft. One or more parameters of a pilot input command may be compared to a threshold to determine that an aircraft is in an ascent or descent state. For instance, for a threshold of 0 degrees for a commanded FPA, a positive value of commanded FPA may indicate an ascent, and a negative value of commanded FPA may indicate a descent (e.g., a value of 0 degrees may be an altitude hold condition). Additionally, for a threshold of ±0.3 degrees forAgent Ref: 16499-0038-00304 commanded FPA, a commanded FPA above 0.3 degrees may be an ascent, a commanded FPA below -0.3 degrees may be a descent, and a commanded FPA on [—0.3, 0.3] may be an altitude hold condition.

[0089]

[0090] In some disclosed embodiments, determining whether the pilot input command is commanding an ascent or descent of the aircraft may include comparing a sensed aircraft condition to an aircraft condition threshold. Comparing a sensed aircraft condition to an aircraft condition threshold may refer to the process by which a control system evaluates a measured state of the aircraft against a predefined limit, tolerance, or band of acceptable values. The sensed aircraft condition may be determined through the use of on-board sensors or derived data from systems of the aircraft. The comparison of a sensed aircraft condition to an aircraft condition threshold may be used to determine an ascent, a descent, or holding altitude (e.g., no altitude change). For instance, the aircraft may determine a sensed condition, such as altitude, rate of altitude change, vertical speed, or flight path angle. One or more of these sensed conditions may be compared to a threshold to determine that an aircraft is in an ascent or descent state. For instance, for a threshold of 0 degrees for a sensed FPA, a positive value of sensed FPA may indicate an ascent, and a negative value of sensed FPA may indicate a descent (e.g., a value of 0 degrees may be an altitude hold condition). Additionally, for a threshold of ±0.3 degrees for a sensed FPA, a sensed FPA above 0.3 degrees may be an ascent, a sensed FPA below -0.3 degrees may be a descent, and a sensed FPA on [—0.3, 0.3] may be an altitude hold condition.

[0091] Process 800 may include a step 806 of determining which one of a plurality of aircraft flight parameters to hold constant. Some disclosed embodiments may include determining which one of a plurality of aircraft flight parameters to hold constant, consistent with disclosed embodiments (e.g., as discussed above with respect to Fig. 5A, Fig. 5B, Fig. 6A, and Fig. 6B, such as in paragraphs

[0052] -

[0067] ). In some embodiments, the plurality of aircraft flight parameters may include an altitude of the aircraft, a vertical speed of the aircraft, and a flight path angle (FPA) of the aircraft. In some disclosed embodiments, the determination of which one of a plurality of aircraft flight parameters to hold constant is based on a speed of the aircraft. In some disclosed embodiments, the determination of which one of a plurality of aircraft flight parameters to hold constant is based on the determination of whether the pilot input command is commanding an ascent or descent of the aircraft. In some disclosed embodiments, the determination of which one of a plurality of aircraft flightAgent Ref: 16499-0038-00304 parameters to hold constant is based on both a speed of the aircraft and the determination of whether the pilot input command is commanding an ascent or descent of the aircraft.

[0092] Determining which one of a plurality of aircraft flight parameters to hold constant may include determining whether one or more parameters of the pilot input command are within a threshold range. For instance, a pilot input command may include or be associated with one or more parameters, which may include a commanded flight path angle (FPA) or a commanded rate of altitude change.

[0093] As an example, to determine which one of a plurality of aircraft flight parameters to hold constant, the commanded flight path angle (FPA) of the one or more parameters may be compared to a threshold range to determine whether the FPA is above, within, or below the threshold range, where the within condition may include the minimum and maximum values of the threshold range. Based on this comparison, the aircraft flight parameter held constant may differ based on whether the FPA is above, within, or below the threshold range. Additionally, the aircraft flight parameter held constant may depend on the speed of the aircraft. Additionally, in some embodiments, the threshold range may be an altitude hold threshold range.

[0094] As an example, for a determination that the FPA is within the threshold range, the one parameter held constant may be the altitude of the aircraft (e.g., altitude hold 501 of FIG. 5A). As an additional example, for a determination that the FPA is below the threshold range, for speeds above a first speed threshold, the FPA may be the aircraft flight parameter held constant (e.g., FPA Hold 503 of FIG. 5A). As a further example, for a determination that the FPA is above the threshold range, for speeds above the first speed threshold and below a second speed threshold, the vertical speed of the aircraft may be the aircraft flight parameter held constant (e.g., Vertical Speed Hold 502 of FIG. 5A). Additionally, for speeds above the second speed threshold, the FPA may be the aircraft flight parameter held constant (e.g., FPA Hold 503 of FIG. 5A). In these examples, the threshold range may be an altitude hold threshold range.

[0095] As an example, to determine which one of a plurality of aircraft flight parameters to hold constant, the commanded rate of altitude change of the one or more parameters of the pilot input command may be compared to a threshold range to determine whether the rate of altitude change is above, within, or below the threshold range, where the within condition may include the minimum and maximum values of the threshold range. Based on this comparison, the aircraft flight parameter held constant may differ based on whether the commanded rate of altitude change is above, within, or below the threshold range.Agent Ref: 16499-0038-00304Additionally, the aircraft flight parameter held constant may depend on the speed of the aircraft. Additionally, in some embodiments, the threshold range may be an altitude threshold range.

[0096] As an example, for a determination that the rate of altitude change is within the threshold range, the one parameter held constant may be the altitude of the aircraft (e.g., altitude hold 501 of FIG. 5A). As an additional example, for a determination that the rate of altitude change is below the threshold range, for speeds above a first speed threshold, the FPA may be the aircraft flight parameter held constant (e.g., FPA Hold 503 of FIG. 5A). As a further example, for a determination that the rate of altitude change is above the threshold range, for speeds above the first speed threshold and below a second speed threshold, the vertical speed of the aircraft may be the aircraft flight parameter held constant (e.g., Vertical Speed Hold 502 of FIG. 5A). Additionally, for speeds above the second speed threshold, the FPA may be the aircraft flight parameter held constant (e.g., FPA Hold 503 of FIG. 5A). In these examples, the threshold range may be an altitude hold threshold range.

[0097] Determining which one of a plurality of aircraft flight parameters to hold constant may include the determination of a commanded rate of altitude change of the aircraft. For example, a commanded descent may correspond to a negative commanded rate of altitude change of the aircraft, which may include a commanded negative vertical speed of the aircraft (h) or a commanded negative FPA (y or ycmd) as described in reference to Fig. 6A and 6B. Additionally, a commanded ascent may correspond to a positive commanded rate of altitude change of the aircraft or a positive vertical speed of the aircraft (h) as described in reference to Fig. 6A and 6B. Further, a commanded rate of altitude change of the aircraft may be equal to zero. For example, a commanded rate of altitude change of the aircraft within a threshold range (e.g., an altitude hold threshold range, vertical speed (h) within an inclusive range of - 0.25 meters per second (m / s) and 0.25 meters per second (m / s), FPA (y or ycmd) within an inclusive range of -0.3 degrees and 0.3 degrees) may result in determining to hold the altitude of the aircraft constant. Further, in some embodiments, the threshold range for holding the altitude of the aircraft constant may include a commanded rate of altitude change of the aircraft that is zero. As another example, a commanded rate of altitude change of the aircraft outside a threshold range (e.g., an altitude hold threshold range, vertical speed (h) within an inclusive range of -0.25 meters per second (m / s) and 0.25 meters per second (m / s), FPA (y or ycmd) within an inclusive range of -0.3 degrees and 0.3 degrees) may result inAgent Ref: 16499-0038-00304 determining to hold one of the plurality of aircraft flight parameters constant based on the speed of the aircraft.

[0098] In some embodiments, step 806 may include determining to hold the altitude of the aircraft constant (e.g., altitude hold 501 of FIG. 5A or FIG. 5B, flight parameter hold 408 of FIG. 4 is an altitude hold). For example, determining which one of a plurality of aircraft flight parameters to hold constant may include determining to hold the altitude of the aircraft constant when a speed of the aircraft is below a threshold (e.g., first speed threshold, altitude hold 501 as described in reference to FIG. 5A).

[0099] In some embodiments, a determined commanded rate of altitude change may be used to determine which one of a plurality of aircraft flight parameters to hold constant. In some embodiments, a commanded change in altitude of the aircraft may be determined. In some embodiments, a determined commanded rate of altitude change may be associated with a commanded change in altitude of the aircraft. For example, determining which one of a plurality of aircraft flight parameters to hold constant may include determining to hold the altitude of the aircraft constant (e.g., altitude hold 501 of FIG. 5A and FIG. 5B) when the determined commanded rate of altitude change is associated with a change in altitude that is within an altitude hold threshold range (e.g., a value included in an inclusive range).

[0100] In some embodiments, step 806 may include determining to hold the flight path angle of the aircraft constant (e.g., FPA hold 503 of FIG. 5A, flight parameter hold 408 of FIG. 4). For example, determining which one of a plurality of aircraft flight parameters to hold constant may include determining to hold a flight path angle of the aircraft constant when the speed of the aircraft is above a threshold (e.g., second speed threshold, speed above VS / FPA transition as illustrated in FIG. 5B (i.e., VS / FPA transition illustrated in FIG. 5A as vertical line between Vertical Speed Hold 502 and FPA Hold 503)) and the determined commanded rate of altitude change is associated with a change in altitude greater than an altitude hold threshold range. In some embodiments, a commanded or determined change in altitude greater than an altitude hold threshold range may be an ascent (e.g., as illustrated in FIG.5A).

[0101] As another example, determining which one of a plurality of aircraft flight parameters to hold constant may include determining to hold a flight path angle of the aircraft constant when the speed of the aircraft is greater than or equal to a threshold (e.g., first speed threshold, FPA Hold 503 as described in reference to FIG. 5A) and the determined commanded rate of altitude change is associated with a change in altitude less than an altitudeAgent Ref: 16499-0038-00304 hold threshold range. In some embodiments, a commanded or determined change in altitude less than an altitude threshold range may be a descent (e.g., as illustrated in FIG. 5A).

[0102] In some embodiments, step 806 may include determining to hold the vertical speed of the aircraft constant (e.g., Vertical Speed Hold 502 of FIG. 5A, flight parameter hold 408 of FIG. 4 is a vertical speed hold). For example, determining which one of a plurality of aircraft flight parameters to hold constant may include determining to hold a vertical speed of the aircraft constant when the speed of the aircraft is greater than or equal to a first threshold and less than or equal to a second threshold (e.g., Speed below VS / FPA transition as described in reference to FIG. 5B (i.e., VS / FPA transition illustrated in FIG. 5A as vertical line between Vertical Speed Hold 502 and FPA Hold 503)) and the determined commanded rate of altitude change is associated with a change in altitude greater than an altitude hold threshold range. In some embodiments, a change in altitude less than an altitude hold threshold range may be an ascent (e.g., as illustrated in FIG. 5A).

[0103] In some disclosed embodiments, the determination of an aircraft flight parameter to hold constant includes determining one or more of a plurality of aircraft flight parameters to hold constant. In some disclosed embodiments, the determination of an aircraft flight parameter to hold constant includes determining two or more of a plurality of aircraft flight parameters to hold constant. In some disclosed embodiments, the determination of an aircraft flight parameter to hold constant includes determining three or more of a plurality of aircraft flight parameters to hold constant.

[0104] In some embodiments, step 806 may include determining control commands 404 based on received pilot input 403, where the determination of control commands 404 may include determining which one of a plurality of aircraft flight parameters to hold constant. The plurality of aircraft flight parameters may include an altitude of the aircraft, a vertical speed of the aircraft, and an FPA of the aircraft. In the case of a pilot input command within an altitude hold threshold range, control commands 404 may be determined based on the received pilot input 403, and the determined control commands 404 may include a command for flight parameter hold 408, where flight parameter hold may include a command for altitude hold 501.

[0105] In some embodiments, step 806 may include determining control commands 404 based on vehicle sensing 407, where the determination of control commands 404 may include determining which one of a plurality of aircraft flight parameters to hold constant. The plurality of aircraft flight parameters may include an altitude of the aircraft, a vertical speed of the aircraft, and an FPA of the aircraft. In the case of an aircraft speed below a speedAgent Ref: 16499-0038-00304 threshold, control commands 404 may be determined based on vehicle sensing 407, which may include a sensed speed of the aircraft. The determined control commands 404 may include a command for flight parameter hold 408, where flight parameter hold 408 may include a command for altitude hold 501.

[0106] In some embodiments, step 806 may include determining control commands 404 based on received pilot input 403 and vehicle sensing 407, where the determination of control commands 404 may include determining which one of a plurality of aircraft flight parameters to hold constant. The plurality of aircraft flight parameters may include an altitude of the aircraft, a vertical speed of the aircraft, and an FPA of the aircraft. Vehicle sensing 407 may include sensing a speed of the aircraft and transmitting information about the sensed speed of the aircraft to FCS 401, such that FCS 401 may determine control commands 404 based on the sensed speed of the aircraft. Determining control commands 404 may include determining one or more commands to implement a flight parameter hold 408.

[0107] As an additional example, FCS 401 may determine control commands 404 based on the received pilot input 403 and / or vehicle sensing 407, and the determined control commands 404 may include a command for flight parameter hold 408. The determined control commands 404 and vehicle sensing 407 may be input to control allocation 405 to control vehicle dynamics 406. Vehicle sensing 407 may include a feedback signal that is input to control allocation 405, such that the aircraft flight parameter may be held constant. The aircraft flight parameter may include an altitude of the aircraft, a vertical speed of the aircraft, and an FPA of the aircraft. The flight parameter hold 408 may be implemented through the FCS 401 by control commands 404, control allocation 405, vehicle dynamics 406, and vehicle sensing 407. Implementing flight parameter hold 408 may include implementing altitude hold 501, vertical speed hold 502, or FPA hold 503. The implemented flight parameter hold 408 may be determined based on received pilot input 403 and / or vehicle sensing 407. In some embodiments, flight parameter hold 408 may be configured to hold one or more of a plurality of aircraft flight parameters constant.

[0108] Further, in some embodiments, flight parameter hold 408 may be configured to hold two or more of a plurality of aircraft flight parameters constant. For instance, flight parameter hold 408 may be configured to hold two or more of a plurality of aircraft flight parameters constant (e.g., vertical speed and flight path angle, altitude and flight path angle, vertical speed and altitude). Additionally, in some embodiments, flight parameter hold 408 may be configured to hold three or more of a plurality of aircraft flight parameters constant. As another example, flight parameter hold 408 may be configured to hold three or more of aAgent Ref: 16499-0038-00304 plurality of aircraft flight parameters constant (e.g., vertical speed, altitude, and flight path angle).

[0109] Process 800 may include a step 808 of controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant, consistent with disclosed embodiments (e.g., as discussed above with respect to Fig. 5A, Fig. 5B, Fig. 6A, and Fig. 6B, such as in paragraphs

[0052] -

[0067] ). For example, FCS 401 may determine control commands 404 based on the received pilot input 403 and / or vehicle sensing 407, and the determined control commands 404 may include a command for flight parameter hold 408. The determined control commands 404 may be input to control allocation 405 to control vehicle dynamics 406, such that the aircraft flight parameter may be held constant. The aircraft flight parameter may include an altitude of the aircraft, a vertical speed of the aircraft, and an FPA of the aircraft. The flight parameter hold 408 may be implemented through the FCS 401 by control commands 404, control allocation 405, vehicle dynamics 406, and vehicle sensing 407. Implementing flight parameter hold 408 may include implementing altitude hold 501, vertical speed hold 502, or FPA hold 503. The implemented flight parameter hold 408 may be determined based on received pilot input 403 and / or vehicle sensing 407.

[0110] In some embodiments, step 808 may include controlling the aircraft based on the pilot input command while holding the altitude of the aircraft constant (e.g., altitude hold 501 of FIG. 5A or FIG. 5B, implementing flight parameter hold 408 where flight parameter hold 408 is an altitude hold). For example, controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant may be configured to hold the altitude of the aircraft at a constant value, when a speed of the aircraft is below a threshold (e.g., first speed threshold, altitude hold 501 along vertical axis of FIG. 5A). As another example, controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant may be configured to hold the altitude of the aircraft at a constant value, when a parameter of the one or more parameters of the pilot input command (e.g., commanded FPA, commanded rate of altitude change) is within a threshold range (e.g., altitude hold threshold range) (e.g., altitude hold 501 along horizontal axis of FIG. 5A and described in reference to FIG. 5B).

[0111] In some embodiments, step 808 may include controlling the aircraft based on the pilot input command while holding the vertical speed of the aircraft constant (e.g., vertical speed hold 502 of FIG. 5A or FIG. 5B, implementing flight parameter hold 408 where flight parameter hold 408 is an altitude hold). For example, controlling the aircraft based on theAgent Ref: 16499-0038-00304 pilot input command while holding the determined aircraft flight parameter constant may be configured to hold the vertical speed of the aircraft at a constant value, when a speed of the aircraft that is greater than or equal to a first threshold (e.g., first speed threshold) and less than or equal to a second threshold (e.g., second speed threshold) (e.g., speed below VS / FPA transition as described in reference to FIG. 5B), and where a parameter of the one or more parameters of the pilot input command (e.g., commanded FPA, commanded rate of altitude change) are greater than a threshold range (e.g., an altitude hold threshold range). In some embodiments, a commanded rate of altitude change or a commanded FPA that is greater than an altitude hold threshold range may be an ascent (e.g., as illustrated in FIG. 5A). In some embodiments, while holding a vertical speed of the aircraft at a constant value, the FPA of the aircraft may be allowed or configured to vary.

[0112] In some embodiments, step 808 may include controlling the aircraft based on the pilot input command while holding the flight path angle of the aircraft constant (e.g., FPA hold 503 of FIG. 5A or FIG. 5B, implementing flight parameter hold 408 where flight parameter hold 408 is an FPA hold). For example, controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant may be configured to hold the FPA of the aircraft at a constant value, when a speed of the aircraft is above a threshold (e.g., second speed threshold, speed above VS / FPA threshold as illustrated in FIG. 5B), and where a parameter of the one or more parameters of the pilot input command (e.g., commanded FPA, commanded rate of altitude change) is greater than a threshold range (e.g., an altitude hold threshold range). In some embodiments, a commanded rate of altitude change or a commanded FPA that is greater than an altitude hold threshold range may be an ascent (e.g., as illustrated in FIG. 5A). In some embodiments, while holding an FPA of the aircraft at a constant value, the vertical speed of the aircraft may be allowed or configured to vary.

[0113] As another example, controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant may be configured to hold the FPA of the aircraft at a constant value, when the speed of the aircraft is above a threshold (e.g., first speed threshold), and where a parameter of the one or more parameter of the pilot input command (e.g., commanded FPA, commanded rate of altitude change) is less than a threshold range (e.g., an altitude hold threshold range). In some embodiments, a commanded rate of altitude change or a commanded FPA that is less than a threshold range may be a descent (e.g., an altitude hold threshold range as illustrated in FIG. 5A). In some embodiments, while holding an FPA of the aircraft at a constant value, the vertical speed of the aircraft may be allowed or configured to vary.Agent Ref: 16499-0038-00304

[0114] In some embodiments, step 808 may include controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant, where the determined flight parameter may be held constant until another pilot input (e.g., pilot input command) is received (e.g., received at a pilot input device, received by FCS 401 of FIG. 4).

[0115] In some embodiments, the implemented flight parameter hold 408 may be configured to hold one or more of a plurality of aircraft flight parameters constant. In some embodiments, the implemented flight parameter hold 408 may be configured to hold two or more of a plurality of aircraft flight parameters constant. In some embodiments, the implemented flight parameter hold 408 may be configured to hold one or more of a plurality of aircraft flight parameters constant.

[0116] In some embodiments, process 800 or step 808 may further include displaying an indication of the determined aircraft flight parameter held constant, where the displayed indication may be displayed to a pilot or other operator of the aircraft.

[0117] In some embodiments, process 800 or step 808 may further include transmitting an alert indicating the determined aircraft flight parameter held constant.

[0118] In some embodiments, process 800 or step 808 may further include transmitting information about a vertical speed of the aircraft held constant or a flight path angle held constant. This transmitted information may be displayed at a user interface of the aircraft.

[0119] In some embodiments, process 800 or step 808 may further include transmitting information associated with an aircraft flight parameter held constant.

[0120] Fig. 9 illustrates a functional block diagram of an exemplary control system 900 of an aircraft, consistent with disclosed embodiments. System 900 may be implemented by at least one processor (e.g., at least one a microprocessor-based controller) configured to execute software code stored in a storage medium (e.g., a computer-readable medium, a non- transitory computer-readable medium) to implement the functions described herein. System 900 may also be implemented in hardware, or a combination of hardware and software. System 900 may be implemented as part of a flight control system of the aircraft (e.g., part of FCS 401 in Fig. 4) and may be configured to perform a single step or sequence repeatedly until a desired or commanded outcome is achieved. It is to be understood that many conventional functions of the control system are not shown in Fig. 9 for ease of description. System 900 further includes one or more storage mediums storing model(s), function(s), table(s), and / or any information for executing the disclosed processes. As further described below, any or each box indicating a command model (e.g., 904, 906, 908, and 99), feedback (912, 916, 918, and 922), feed forward (914, 920), Outer Loop Allocation (924, 926), innerAgent Ref: 16499-0038-00304 loop control laws 928, and control allocation 929 may represent or include module(s), script(s), function(s), application(s), and / or program(s) that are executed by processor(s) and / or microprocessor(s) of system 900. It is appreciated that the complexity and interconnectedness of the functional block diagram of Fig. 9 would be impossible, or at least impractical, to effectively implement by a human user, especially when considering that these functionalities are implemented while the aircraft is flying (including taking off or landing).

[0121] In some embodiments, control system 900 may be configured based on one or more flight control laws. Flight control law may comprise a set of algorithms, models, and / or rules configured to govern a behavior of an aircraft (e.g., control or influence one or more effectors of the aircraft) in response to one or more pilot inputs and external factors. In some embodiments, flight control laws may be configured to achieve at least one of desired flight characteristics, stability, or performance. For example, flight control laws may be configured to ensure stability and controllability of an aircraft by controlling how the aircraft responds to at least one of one or more pilot inputs, vehicle dynamics (e.g., disturbances, such as turbulence, gusts, etc.), or changes in flight conditions (e.g., altitude, forward speed, vertical speed, airspeed, groundspeed, horizontal component of forward speed, vertical component of forward speed, angle of attack).

[0122] System 900 may detect one or more inputs, such as from a pilot input device configured to receive at least one pilot input and generate or influence a signal. A pilot input may be generated by and / or received from an input device or mechanism of the aircraft, such as a button, a switch, a knob, a stick, a slider, an inceptor, any combination thereof, or any other device configured to generate or influence a signal based on a physical action from a pilot. For example, a pilot input device may include one or more of right inceptor(s) (e.g., moving right inceptor left / right 902a and / or right inceptor forward / aft 902e), left inceptor(s) (e.g., moving left inceptor left / right 902c and / or left inceptor forward / aft 902g), and / or left inceptor switch 902f. In some embodiments, a pilot input device may include an interface with an autopilot system (e.g., display screen(s), switch(es), button(s), lever(s), and / or other interface(s)). Optionally, system 900 may further detect inputs from an autopilot system, such as autopilot roll command 902b, autopilot climb command 902d, and / or other command(s) to control the aircraft.

[0123] In some embodiments, the one or more inputs may include at least one of a position and / or rate of a right inceptor and / or a left inceptor, signals received (e.g., response type change commands, trim inputs, reference inputs, backup control inputs, etc.) from switches on the inceptors, measurements of aircraft state and environmental conditions (e.g., measuredAgent Ref: 16499-0038-00304 load factor, forward speed, vertical speed, airspeed, groundspeed, horizontal component of forward speed, vertical component of forward speed, roll angle, pitch angle, actuator states, battery states, aerodynamic parameters, temperature, gusts, etc.) based on data received from one or more sensors of the aircraft, obstacles (e.g., presence or absence of other aircraft and / or debris), and an aircraft mode (e.g., taxiing on the ground, takeoff, in-air). For example, right inceptor L / R 902a may comprise a lateral position and / or rate of a right inceptor (e.g., an inceptor positioned to the right of another inceptor and / or an inceptor positioned on the right side of a pilot area), autopilot roll command 902b may comprise a roll signal received in autopilot mode, left inceptor L / R 902c may comprise a lateral position and / or rate of a left inceptor (e.g., an inceptor positioned to the left of another inceptor and / or an inceptor positioned on the left side of a pilot area), autopilot climb command 902d may comprise a climb signal received in autopilot mode, right inceptor F / A 902e may comprise a longitudinal position and / or rate of the right inceptor, left inceptor switch 902f may comprise a signal from a switch for enabling or disabling automatic transition function 903, and left inceptor F / A 902g may comprise a longitudinal position and / or rate of the left inceptor.

[0124] Each input may include data as listed above (e.g., signals from switches, measurements of aircraft state, aircraft mode, etc.). Actuator states may include actuator hardware limits, such as travel limits, speed limits, response time limits, etc., and can include actuator health indicators that may indicate deteriorations in actuator performance that may limit a given actuator’s ability to satisfy actuator commands. Actuator states may be used to determine the bounds (e.g., minimum / maximum values) for individual actuator commands. Battery states may correspond to remaining energy of the battery packs of the aircraft, which may be monitored when control allocation 929 considers balancing battery pack energy states. Aerodynamic parameters may be parameters derived from aerodynamic and acoustic modeling and can be based on the actuator Jacobian matrices and actuator states. Each input received from an inceptor may indicate a corresponding adjustment to an aircraft’s heading or power output.

[0125] In some embodiments, FCS 401 of Fig. 4 may receive or obtain a pilot input command from pilot input devices such as: Right Inceptor L / R 902a, Autopilot bank command 902b, Left Inceptor L / R 902c, Autopilot climb command 902d, Right inceptor F / A 902e, Left inceptor switch 902f, or Left inceptor F / A 902g. In some embodiments, pilot input 403 of Fig. 4 may include input from pilot input devices such as: Right Inceptor L / R 902a, Autopilot bank command 902b, Left Inceptor L / R 902c, Autopilot climb command 902d, Right inceptor F / A 902e, Left inceptor switch 902f, or Left inceptor F / A 902g.Agent Ref 16499-0038-00304

[0126] Command models 904, 906, 908 and 910 may be configured to determine a shape (e.g., aggressiveness, slew rate, damping, overshoot, etc.) of an ideal aircraft response. For example, each command model of command models 904, 906, 908 and 910 may be configured to receive and interpret at least one of inputs 902a, 902b, 902c, 902d, 902e, 902f and 902g and, in response, compute a corresponding change to an aircraft’s orientation, heading, and propulsion, or a combination thereof using an integrator (not pictured). In some embodiments, right inceptor L / R 902a and autopilot roll command 902b may be fed into turnrate command model 904, left inceptor L / R 902c may be fed into lateral speed command model 906, autopilot climb command 902d and right inceptor F / A 902e may be fed into climb command model 908, and left inceptor F / A 902g may be fed into forward speed command model 910. In some embodiments, an output from automatic transition function 903 may be fed into at least one of climb command model 908 or forward speed command model 910. For example, based on receiving an enable signal from left inceptor switch 902f, automatic transition function 903 may automatically determine at least one of a climb signal or a forward speed signal for transmission to at least one of climb command model 908 or forward speed command model 910.

[0127] Turn-rate command model 904 may be configured to output a desired position and / or turn-rate command and may also be configured to compute a desired heading of the aircraft to be assumed when the inceptor is brought back to a centered position (e.g., in detent). Lateral speed command model 906 may be configured to output a desired position and / or lateral speed command. Climb command model 908 may be configured to output at least one of a desired altitude, vertical speed, or vertical acceleration command. Forward speed command model 910 may be configured to output at least one of a desired position, longitudinal speed, or longitudinal acceleration command. In some embodiments, one or more of the command models may be configured to output an acceleration generated in response to changes in speed command. For example, climb command model 908 may be configured to output a vertical acceleration generated in response to a change in vertical speed command.

[0128] Feed forward 914 and 920 may each receive as input one or more desired changes (e.g., desired position, speed and / or acceleration) from corresponding command models 904, 906, 908 and / or 910 as well as data received from the one or more aircraft sensors (e.g., airspeed, groundspeed, vehicle orientation, vehicle load factor, measured acceleration, vehicle mass and inertia, air density, altitude, aircraft mode, etc.) and may be configured to output, for each desired change, a corresponding force to accomplish the desired change. InAgent Ref: 16499-0038-00304 some embodiments, feed forward 914 and 920 may be configured to determine the corresponding force using simplified models of aircraft dynamics. For example, based on a known (e.g., a stored value of) or determined mass of the aircraft, feed forward 914 and 920 may be configured to determine a force to cause the aircraft to follow a desired acceleration command. In some embodiments, feed forward 914 and 920 may be configured to use a model predicting an amount of drag on the vehicle produced as a function of speed in order to determine a force required to follow a desired speed command signal.

[0129] Feedback 912, 916, 918, and 922 may each receive as input the one or more desired changes (e.g., desired position, speed and / or acceleration) from command models 904, 906, 908 and / or 910 as well as data received from Vehicle Sensing 931 indicative of Vehicle Dynamics 930. For example, sensed Vehicle Dynamics 930 may comprise the physics and / or natural dynamics of the aircraft, and Vehicle Sensing 931 sensor measurements may capture how the aircraft moves in response to pilot inputs, propulsion system outputs or ambient conditions. In some embodiments, Vehicle Dynamics 930 may represent the control of different flight elements (e.g., electric propulsion system(s) and / or control surfaces) and the corresponding effect on the flight elements and aircraft dynamics.

[0130] In some embodiments, FCS 401 of Fig. 4 may control flight elements based on Vehicle Dynamics Control 930. In some embodiments, Vehicle Dynamics 406 of Fig. 4 may include Vehicle Dynamics Control 930.

[0131] Additionally or alternatively, data received from Vehicle Sensing 931 may include error signals generated, by one or more processors, based on exogenous disturbances (e.g., gust causing speed disturbance). In some embodiments, feedback 912, 916, 918 and 922 may be configured to generate feedback forces (e.g., at an actuator) based on the received error signals. For example, feedback 912, 916, 918 and 922 may generate feedback forces with the intent of counteracting the effect(s) of external disturbances. Additionally or alternatively, feedback 912, 916, 918 and 922 may be configured to generate feedback forces based on modeling errors. For example, if an incorrect aircraft mass is input into either feed forward 914 or 920, the aircraft may accelerate faster or slower than the desired change. Based on determining a difference between the desired acceleration and the measured acceleration, one or more processors may generate an error signal (e.g., included in Vehicle Sensing 931) which may be looped into feedback 912, 916, 918 or 922 to determine an additional force needed to correct the error.

[0132] In some embodiments, feedback 912, 916, 918 or 922 may be disabled. For example, in response to losing position and / or ground speed feedback due to disruption of globalAgent Ref 16499-0038-00304 position system (GPS) communication, system 900 may be configured to operate without feedback 912, 916, 918 or 922 until GPS communication is reconnected.

[0133] In some embodiments, feedback 912, 916, 918 or 922 may receive as input a plurality of measurements as well as a trust value for each measurement indicating whether the measurement is valid. For example, one or more processors of system 900 may assign a Boolean (true / false) value for each measurement used in system 900 to indicate that the measurement is trustworthy (e.g., yes) or that the measurement may be invalid (e.g., no). Based on one or more processors identifying a measurement as invalid, feedback 912, 916, 918 or 922 may omit that measurement for further processing. For example, in response to one or more processors identifying a heading measurement as invalid, feedback 912, 916, 918 or 922 may omit subsequent heading measurements in determining feedback force(s).

[0134] In some embodiments, feedback 912, 916, 918 or 922 may determine one or more feedback forces based on actuator state information received from one or more sensors (e.g., included in Vehicle Sensing 931). For example, in response to actuator state information indicating that there is a failure of an actuator, one or more processors of system 900 may update one or more processes of System 900 and determine an alternative command to achieve the desired change. For example, one or more processors of system 900 may adjust one or more model(s), function(s), algorithm(s), table(s), input(s), parameter(s), threshold(s), and / or constraint(s) based on (e.g., in response to) a change in state (e.g., failure) of an actuator (or other aircraft component, such as an engine or battery, for other examples). Alternative command(s) (e.g., yaw, pitch, roll, thrust, or torque) may be determined based on the adjustment(s). Additionally or alternatively, in response to actuator state information indicating that one or more actuators are at a maximum value, one or more processors of system 900 may update one or more processes of system 900 (e.g., as described above) and determine an alternative command to achieve the desired change.

[0135] Total desired forces may be calculated based on outputs of feedback 912, 916, 918 and 922 and feed forward 914 and 920. For example, one or more processors of system 900 may calculate a desired turn -rate force by summing the outputs of feedback 912 and feed forward 914. Additionally or alternatively, one or more processors of system 900 may calculate a desired lateral force by summing the outputs of feedback 916 and feed forward 914. Additionally or alternatively, one or more processors of system 900 may calculate a desired vertical force by summing the outputs of feedback 918 and feed forward 920. Additionally or alternatively, one or more processors of system 900 may calculate a desired longitudinal force by summing the outputs of feedback 922 and feed forward 920.Agent Ref: 16499-0038-00304

[0136] In some embodiments, FCS 401 of Fig. 4 may include a function, model, feed forward, or feedback, such as: Automatic transition function 903, Turn-rate command model 904, Lateral speed command model 906, Climb command model 908, Forward speed command model 910, Feedback 912, Feed forward 914, Feedback 916, Feedback 918, Feed forward 920, and / or Feedback 922. In some embodiments, control commands 404 of Fig. 4 may be based on Automatic transition function 903, Turn-rate command model 904, Lateral speed command model 906, Climb command model 908, Forward speed command model 910, Feedback 912, Feed forward 914, Feedback 916, Feedback 918, Feed forward 920, and / or Feedback 922.

[0137] Lateral / Directional Outer Loop Allocation 924 and Longitudinal Outer Loop Allocation 926 may each be configured to receive as input one or more desired forces and data received from Vehicle Sensing 931 (e.g., airspeed, groundspeed, vehicle orientation, vehicle load factor, measured acceleration, vehicle mass and inertia, indications of working / failed actuators, air density, altitude, aircraft mode, whether the aircraft is in the air or on the ground, weight on wheels, etc.). Based on the inputs, Outer Loop Allocation 924 and 926 may be configured to command roll, command yaw, command pitch, demand thrust, or output a combination of different commands / demands in order to achieve the one or more desired forces.

[0138] Lateral / Directional Outer Loop Allocation 924 may receive as input a desired turnrate force and / or a desired lateral force and may command roll or command yaw. In some embodiments, Lateral / Directional Outer Loop Allocation 924 may determine output based on a determined flight mode. A flight mode may be determined using pilot inputs (e.g., a selected mode on an inceptor) and / or sensed aircraft information (e.g., a forward speed, vertical speed, an airspeed, a groundspeed, a horizontal component of a forward speed, vertical component of forward speed). For example, Lateral / Directional Outer Loop Allocation 924 may determine a flight mode of the aircraft using at least one of a determined (e.g., sensed or measured) airspeed or an input received at a pilot inceptor button (e.g., an input instructing the aircraft to fly according to a particular flight mode). In some embodiments, Lateral / Directional Outer Loop Allocation 924 may be configured to prioritize a pilot inceptor button input over measured airspeed in determining the flight mode (e.g., the pilot inceptor button is associated with a stronger weight or higher priority than a measured airspeed). In some embodiments, Lateral / Directional Outer Loop Allocation 924 may be configured to blend (e.g., using weighted summation) the determined airspeed and pilot inceptor button input to determine the flight mode of the aircraft. In a hover flight mode,Agent Ref: 16499-0038-00304Lateral / Directional Outer Loop Allocation 924 may achieve the desired lateral force with a roll command (e.g., roll angle, roll rate) and may achieve the desired turn-rate force with a yaw command. In some embodiments, such as in hover flight mode, the aircraft may be configured to not be able to accelerate outside a predetermined hover envelope (e.g., hover speed range). In a forward-flight mode (e.g., horizontal flight), Lateral / Directional Outer Loop Allocation 924 may achieve the desired lateral force with a yaw command and may achieve the desired turn-rate force with a roll command. In forward flight mode, Lateral / Directional Outer Loop Allocation 924 may be configured to determine output based on sensed airspeed. In a transition between hover flight mode and forward flight mode, Lateral / Directional Outer Loop Allocation 924 may achieve desired forces using a combination of a roll command and a yaw command.

[0139] Longitudinal Outer Loop Allocation 926 may receive as input a desired vertical force and / or a desired longitudinal force and may output at least one of a pitch command (e.g., pitch angle) or a thrust vector demand. A thrust vector demand may include longitudinal thrust (e.g., mix of nacelle tilt and front propeller thrust) and vertical thrust (e.g., combined front and rear thrust). In some embodiments, Longitudinal Outer Loop Allocation 926 may determine output based on a determined flight mode. For example, in a hover flight mode, Longitudinal Outer Loop Allocation 926 may achieve a desired longitudinal force by lowering a pitch attitude and by using longitudinal thrust, and may achieve a desired vertical force with vertical thrust. In a forward-flight mode, Longitudinal Outer Loop Allocation 926 may achieve a desired longitudinal force with longitudinal thrust (e.g., front propeller thrust). In a cruise flight mode, Longitudinal Outer Loop Allocation 926 may achieve a desired vertical force by commanding pitch (e.g., raising pitch attitude) and demanding thrust (e.g., increasing longitudinal thrust).

[0140] Inner loop control laws 928 may be configured to determine moment commands based on at least one of a roll command, yaw command, or pitch command from Lateral / Directional Outer Loop Allocation 924 or Longitudinal Outer Loop Allocation 926. In some embodiments, Inner loop control laws 928 may be dependent on sensed Vehicle Dynamics (e.g., from Vehicle Sensing 931). For example, Inner loop control laws 928 may be configured to compensate for disturbances at the attitude and rate level in order to stabilize the aircraft. Additionally or alternatively, Inner loop control laws 928 may consider periods of natural modes (e.g., phugoid modes) that affect the pitch axis, and may control the aircraft appropriately to compensate for such natural modes of the vehicle. In some embodiments, inner loop control laws 928 may be dependent on vehicle inertia.Agent Ref: 16499-0038-00304

[0141] Inner loop control laws 928 may determine moment commands using one or more stored dynamics models that reflect the motion characteristics of the aircraft (e.g., the aerodynamic damping and / or inertia of the aircraft). In some embodiments, the Inner loop control laws 928 may use a dynamic model (e.g., a low order equivalent system model) to capture the motion characteristics of the aircraft and determine one or more moments that will cause the aircraft to achieve the commanded roll, yaw, and / or pitch. Some embodiments may include determining (e.g., by inner loop control laws 928 or other component) a moment command based on at least one received command (e.g., a roll command, yaw command, and / or pitch command) and a determined (e.g., measured) aircraft state. For example, a moment command may be determined using a difference in the commanded aircraft state and the measured aircraft state. By way of further example, a moment command may be determined using the difference between a commanded roll angle and a measured roll angle. As described below, Control Allocation 929 may control the aircraft (e.g., through flight elements) based on the determined moment command(s). For example, Control Allocation 929 may control (e.g., transmit one or more commands to) one or more electric propulsion system(s) of the aircraft, including tilt actuator(s), electric engine(s), and / or propeller(s). Control Allocation 929 may further control one or more control surface(s) of the aircraft, including flaperon(s), ruddervator(s), aileron(s), spoiler(s), rudder(s), and / or elevator(s).

[0142] While the embodiment shown in Fig. 9 includes both Inner Loop Control Laws 928 and Outer Loop Allocations 924 and 926, in some embodiments the flight control system may not include Outer Loop Allocations 924 and 926. Therefore, a pilot inceptor input may create roll, yaw, pitch, and / or thrust commands. For example, a right inceptor may control roll and pitch and a left inceptor and / or pedal(s) may control yaw and thrust.

[0143] Control Allocation 929 may accept as inputs one or more of force and moment commands, data received from the one or more aircraft sensors, envelope protection limits, scheduling parameter, and optimizer parameters. Control Allocation 929 may be configured to determine, based on the inputs, actuator commands by minimizing an objective function that includes one or more primary objectives, such as meeting (e.g., responding to, satisfying, addressing, providing output based upon) commanded aircraft forces and moments, and one or more secondary, which can include minimizing acoustic noise and / or optimizing battery pack usage.

[0144] In some embodiments, control allocation 929 may be configured to compute the limits of individual actuator commands based on the actuator states and envelope protection limits. Envelope protection limits may include one or more boundaries that the aircraft shouldAgent Ref: 16499-0038-00304 operate within to ensure safe and stable flight. In some embodiments, envelope protection limits may be defined by one or more of speed, altitude, angle of attack, or load factor. For example, envelope protection limits may include one or more bending moments and / or one or more load constraints. In some embodiments, control allocation 929 may use envelope protection limits to automatically adjust one or more control surfaces or control settings. Doing so may prevent the aircraft from undesirable scenarios such as stalling or structural strain or failure. In normal operation, the minimum command limit for a given actuator may include the maximum of: the minimum hardware based limit and the minimum flight envelope limit; and the maximum command limit for a given actuator may include the minimum of: the maximum hardware based limit and the maximum flight envelope limit. In the case of an actuator failure, the command limits for the failed actuator correspond to the failure mode.

[0145] Control allocation 929 sends commands to one or more flight elements to control the aircraft. The flight elements will move in accordance with the controlled command. Various sensing systems and associated sensors as part of Vehicle Sensing 931 may detect the movement of the flight elements and / or the dynamics of the aircraft and provide the information to Feedback 912, 916, 918, 922, Outer Loop allocation 924 and 926, Inner Loop Control laws 928, and Control Allocation 929 to be incorporated into flight control.

[0146] In some embodiments, FCS 401 of Fig. 4 may include Lateral / Directional Outer Loop Allocation 924, Longitudinal Outer Loop Allocation 926, Inner loop control laws 928, and / or Control Allocation 929. In some embodiments, Control Allocation 405 of Fig. 4 may include Lateral / Directional Outer Loop Allocation 924, Longitudinal Outer Loop Allocation 926, Inner loop control laws 928, and / or Control Allocation 929.

[0147] As described above, Vehicle Sensing 931 may include one or more sensors to detect vehicle dynamics. For example, Vehicle Sensing 931 may capture how the aircraft moves in response to pilot inputs, propulsion system outputs or ambient conditions. Additionally or alternatively, Vehicle Sensing 931 may detect an error in the aircraft’s response based on exogenous disturbances (e.g., gust causing speed disturbance). Further, Vehicle Sensing 931 may include one or more sensors to detect propeller speed, such as a magnetic sensor (e.g., Hall effect or inductive sensor) or an optical sensor (e.g., a tachometer) configured to detect the rotor speed of the aircraft engine (and thereby the speed of the propeller). Vehicle sensing 931 may include one or more sensors to detect a nacelle tilt angle (e.g., a propeller rotation axis angle between a lift configuration (e.g., Fig. 2) and forward thrust configuration (e.g., Fig. 1)). For example, one or more magnetic sensors (e.g., Hall effect or inductive sensor),Agent Ref: 16499-0038-00304 position displacement sensors, linear displacement sensors, and / or other sensor(s) associated with the tilt actuator may detect a tilt angle (e.g., relative to the aircraft and / or wing), which may be provided to system 900. Further, one or more pitot tubes, accelerometers, and / or gyroscopes may detect a pitch angle of the aircraft, which may be provided to system 900. In some embodiments, Vehicle Sensing 931 may combine tilt angle sensor measurements and aircraft pitch measurements to determine an overall nacelle tilt angle for the propellers. Vehicle sensing 931 may include one or more sensors configured to detect an engine torque and / or thrust, such as one or more current sensors or voltage sensors, strain gauges, load cells, and / or propeller vibration sensors (e.g., accelerometers).

[0148] Vehicle sensing 931 may include one or more sensors configured to detect vehicle dynamics, such as acceleration and / or pitch orientation sensors (e.g., accelerometer(s), 3-axis accelerometer(s), gyroscope(s), 3-axis gyroscope(s), and / or tilt-position sensors to determine angles of engines) and airspeed sensors (e.g., pitot tube sensors). Vehicle sensing 931 may further include one or more inertial measurement units (IMUs) to determine an aircraft state based on these measurements. An aircraft state may refer to forces experienced by, an orientation of, a position of (e.g., altitude), and / or movement of, the aircraft. For example, an aircraft state may include at least one of: a position of the aircraft (e.g., a yaw angle, roll angle, pitch angle, and / or any other orientation across one or two axes), velocity of the aircraft, angular rate of the aircraft (e.g., roll, pitch, and / or yaw rate), and / or an acceleration of the aircraft (e.g., longitudinal, lateral and / or vertical acceleration), or any physical characteristic of the aircraft or one of its components.

[0149] In some embodiments, Vehicle Sensing 931 may include an inertial navigation systems (INS) and / or an air data and / or an attitude heading reference systems (ADAHRS). The inertial navigation systems (INS) and / or an air data and attitude heading reference systems (ADAHRS) may include one or more inertial measurement units (IMUs) and corresponding sensors (e.g., accelerometers, gyroscopes, three-axis gyroscopes, and / or three- axis accelerometers). In some embodiments, the INS and / or ADAHRS may filter and / or otherwise process sensor measurements to determine an aircraft state (e.g., acceleration or angular rate). For example, in some embodiments, the INS and / or ADAHRS may determine angular rates based on gyroscope measurements and may determine acceleration based on measurements from an accelerometer.

[0150] The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the artAgent Ref: 16499-0038-00304 from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein.

[0151] In some embodiments, FCS 401 of Fig. 4 may receive data or information from Vehicle Dynamics Sensing 931. In some embodiments, Vehicle Sensing 407 of Fig. 4 may include Vehicle Dynamics Sensing 931.

[0152] The features and advantages of the disclosure are apparent from the detailed specification, and thus, it is intended that the appended claims cover all systems and methods falling within the true spirit and scope of the disclosure. As used herein, the indefinite articles “a” and “an” mean “one or more.” Similarly, the use of a plural term does not necessarily denote a plurality unless it is unambiguous in the given context. Words such as “and” and “or” mean “and / or” unless specifically directed otherwise. As used herein, unless specifically stated otherwise, being “based on” may include being dependent on, being interdependent with, being derived from, being associated with, being defined at least in part by, being influenced by, or being responsive to. As used herein, “related to” or “relating to” may include being inclusive of, being expressed by, being indicated by, or being based on. Further, since numerous modifications and variations will readily occur from studying the present disclosure, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.

[0153] Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the implementations disclosed herein. It is intended that the architectures and circuit arrangements shown in figures are only for illustrative purposes and are not intended to be limited to the specific arrangements and circuit arrangements as described and shown in the figures. It is also intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims. The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein. It is also intended that the sequence of steps shown in figures is only for illustrative purposes and is not intended to be limited to any particular sequence of steps. As such, those skilled in the art can appreciate that these steps can be performed in a different order while implementing the same method.

[0154] The embodiments may be further described using the following clauses:Agent Ref: 16499-0038-00304

[0155] Clause 1 : A computer-implemented method of controlling an aircraft, comprising: receiving a pilot input command; determining whether the pilot input command is commanding an ascent or descent of the aircraft; determining which one of a plurality of aircraft flight parameters to hold constant, the aircraft flight parameters comprising an altitude of the aircraft, a vertical speed of the aircraft, and a flight path angle of the aircraft, wherein determining which one of the plurality of aircraft flight parameters to hold constant is based on both a speed of the aircraft and the determination of whether the pilot input command is commanding an ascent or descent of the aircraft; and controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant.

[0156] Clause 2: The method of clause 1, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the speed of the aircraft is below a first speed threshold, determining to hold the altitude of the aircraft constant.

[0157] Clause 3: The method of any one of clauses 1-2, wherein the pilot input command is associated with one or more parameters including at least one of a commanded flight path angle (FPA) or a commanded rate of altitude change.

[0158] Clause 4: The method of any one of clauses 1-3, further comprising determining whether the one or more parameters associated with the pilot input command are within a threshold range.

[0159] Clause 5: The method of any one of clauses 1-4, wherein determining whether the one or more parameters of the pilot input command are within the threshold range comprises determining whether a commanded flight path angle (FPA) associated with the one or more parameters of the pilot input command is within the threshold range.

[0160] Clause 6: The method of any one of clauses 1-5, wherein determining whether the pilot input command is commanding an ascent or descent of the aircraft comprises determining whether the commanded flight path angle (FPA) of the received pilot input command is positive or negative.

[0161] Clause 7: The method of any one of clauses 1-6, further comprising using the commanded flight path angle (FPA) to determine which one of the plurality of aircraft flight parameters to hold constant.

[0162] Clause 8: The method of any one of clauses 1-7, wherein determining which one of the plurality of flight parameters to hold constant includes, when the commanded flight path angle (FPA) associated with the one or more parameters of the pilot input command is within the threshold range, determining to hold the altitude of the aircraft constant.Agent Ref: 16499-0038-00304

[0163] Clause 9: The method of any one of clauses 1-8, wherein determining whether the one or more parameters associated with the pilot input command are within the threshold range comprises determining whether a commanded rate of altitude change associated with the received pilot input command is within the threshold range.

[0164] Clause 10: The method of any one of clauses 1-9, wherein determining whether the pilot input command is commanding an ascent or descent of the aircraft comprises determining whether the commanded rate of altitude change associated with the one or more parameters of the pilot input command is positive or negative.

[0165] Clause 11 : The method of any one of clauses 1-10, further comprising using the commanded rate of altitude change to determine which one of the plurality of aircraft flight parameters to hold constant.

[0166] Clause 12: The method of any one of clauses 1-11, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the commanded rate of altitude change associated with the one or more parameters of the pilot input command is within the threshold range, determining to hold the altitude of the aircraft constant.

[0167] Clause 13: The method of any one of clauses 1-12, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the speed of the aircraft is above a second speed threshold and at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is greater than the threshold range, determining to hold a flight path angle of the aircraft constant.

[0168] Clause 14: The method of any one of clauses 1-13, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the speed of the aircraft is greater than or equal to a first speed threshold and less than or equal to a second speed threshold and at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is greater than the threshold range, determining to hold a vertical speed of the aircraft constant.

[0169] Clause 15: The method of any one of clauses 1-14, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the speed of the aircraft is greater than or equal to a first speed threshold and at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is less than the threshold range, determining to hold a flight path angle of the aircraft constant.

[0170] Clause 16: The method of any one of clauses 1-15, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameterAgent Ref: 16499-0038-00304 constant includes holding the altitude of the aircraft at a constant value, when the speed of the aircraft is below a first speed threshold.

[0171] Clause 17: The method of any one of clauses 1-16, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includes holding an altitude of the aircraft at a constant value, when at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is within the threshold range.

[0172] Clause 18: The method of any one of clauses 1-17, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includes holding a vertical speed of the aircraft at a constant value while allowing the flight path angle of the aircraft to vary, when the speed of the aircraft is greater than or equal to a first speed threshold and less than or equal to a second speed threshold, and wherein at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is greater than the threshold range.

[0173] Clause 19: The method of any one of clauses 1-18, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includes holding the flight path angle of the aircraft at a constant value while allowing a vertical speed of the aircraft to vary, when the speed of the aircraft is above a second speed threshold, and wherein at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is greater than the threshold range.

[0174] Clause 20: The method of any one of clauses 1-19, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includes holding a flight path angle of the aircraft at a constant value while allowing a vertical speed of the aircraft to vary, when the speed of the aircraft is above a first threshold, and wherein at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is less than the threshold range.

[0175] Clause 21 : The method of any one of clauses 1-20, wherein the pilot input command comprises an inceptor command.

[0176] Clause 22: The method of any one of clauses 1-21, wherein the pilot input command comprises a beep command.

[0177] Clause 23: The method of any one of clauses 1-22, further comprising displaying to a pilot of the aircraft an indication of the determined aircraft flight parameter held constant.

[0178] Clause 24: The method of any one of clauses 1-23, further comprising transmitting an alert indicating the determined aircraft flight parameter held constant.Agent Ref: 16499-0038-00304

[0179] Clause 25: The method of any one of clauses 1-24, the ascent or descent is determined based on the pilot input command and a sensed aircraft condition.

[0180] Clause 26: The method of any one of clauses 1-25, wherein the ascent or descent is determined by comparing a sensed aircraft condition to an aircraft condition threshold.

[0181] Clause 27: The method of any one of clauses 1-26, the determined flight parameter is held constant until another pilot input is received.

[0182] Clause 28: The method of any one of clauses 1-27, further comprising transmitting information about a vertical speed of the aircraft held constant, or a flight path angle held constant, and displaying the transmitted information at a user interface of the aircraft.

[0183] Clause 29: The method of any one of clauses 1-28, comprising transmitting information associated with the aircraft flight parameter held constant.

[0184] Clause 30: The method of any one of clauses 1-29, wherein the threshold range is an altitude hold threshold range.

[0185] Clause 31 : The method of any one of clauses 1-30, further comprising determining at least one of the plurality of aircraft flight parameters to hold constant.

[0186] Clause 32: The method of any one of clauses 1-31, wherein controlling the aircraft based on the pilot input command comprises holding at least one determined aircraft flight parameter constant.

[0187] Clause 33: The method of any one of clauses 1-32, further comprising determining at least one of the plurality of aircraft flight parameters to hold constant and controlling the aircraft based on the pilot input command while holding constant the determined at least one of the plurality of aircraft flight parameters.

[0188] Clause 34: The method of any one of clauses 1-33, further comprising determining at least two of the plurality of aircraft flight parameters to hold constant.

[0189] Clause 35: The method of any one of clauses 1-34, wherein controlling the aircraft based on the pilot input command comprises holding at least two determined aircraft flight parameters constant.

[0190] Clause 36: The method of any one of clauses 1-35, further comprising determining at least three of the plurality of aircraft flight parameters to hold constant.

[0191] Clause 37: The method of any one of clauses 1-36, wherein controlling the aircraft based on the pilot input command comprises holding at least three determined aircraft flight parameters constant.

[0192] Clause 38: A system for controlling an aircraft, comprising: a pilot input device; and at least one processor configured to carry out the method of any one of clauses 1-37.Agent Ref: 16499-0038-00304

[0193] Clause 39: A computer-readable medium containing instructions for performing operations for controlling an aircraft, the instructions when executed by one or more processors cause the one or more processors to carry out the method of any one of clauses 1-37.

[0194] Clause 40: A method of controlling ascent of an aircraft, comprising: obtaining a pilot input command; determining whether the pilot input command is commanding an ascent or descent of the aircraft; determining which one of a plurality of aircraft flight parameters to hold constant, the aircraft flight parameters comprising an altitude of the aircraft, a vertical speed of the aircraft, and a flight path angle of the aircraft, wherein the determination of which one of a plurality of aircraft flight parameters to hold constant is based on both an airspeed of the aircraft and the determination of whether the pilot input command is commanding an ascent or descent of the aircraft; and controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant.

[0195] Clause 41 : A method of controlling ascent of an aircraft, comprising: obtaining a pilot input; determining that the pilot input command is commanding an ascent of the aircraft; and controlling the aircraft based on the pilot input command, wherein controlling the aircraft comprises: at airspeeds below a predetermined threshold, holding a vertical speed of the aircraft at a constant value while allowing a flight path angle of the aircraft to vary, and at airspeeds above the predetermined threshold, holding the flight path angle at a constant value while allowing the vertical speed to vary.

[0196] Clause 42: A method of controlling an aircraft, comprising: obtaining a pilot input command; determining whether the pilot input command is commanding an ascent of the aircraft or descent of the aircraft; and controlling the aircraft based on the pilot input command, wherein controlling the aircraft comprises: at airspeeds below a first predetermined threshold, holding an altitude of the aircraft when a pilot releases a vertical speed command; at airspeeds above the first predetermined threshold when an ascent is commanded, holding a vertical speed of the aircraft at a constant value while allowing a flight path angle of the aircraft to vary; at airspeeds above a second predetermined threshold when an ascent is commanded, holding the flight path angle at a constant value while allowing the vertical speed to vary; and at airspeeds above the first predetermined threshold when a descent is commanded, holding the flight path angle at a constant value while allowing the vertical speed to vary.

Claims

Agent Ref: 16499-0038-00304CLAIMS1. A computer-implemented method of controlling an aircraft, comprising: receiving a pilot input command; determining whether the pilot input command is commanding an ascent or descent of the aircraft; determining which one of a plurality of aircraft flight parameters to hold constant, the aircraft flight parameters comprising an altitude of the aircraft, a vertical speed of the aircraft, and a flight path angle of the aircraft, wherein determining which one of the plurality of aircraft flight parameters to hold constant is based on both a speed of the aircraft and the determination of whether the pilot input command is commanding an ascent or descent of the aircraft; and controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant.

2. The method of claim 1, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the speed of the aircraft is below a first speed threshold, determining to hold the altitude of the aircraft constant.

3. The method of claim 1 or 2, wherein the pilot input command is associated with one or more parameters including at least one of a commanded flight path angle (FPA) or a commanded rate of altitude change.

4. The method of claim 3, further comprising determining whether the one or more parameters associated with the pilot input command are within a threshold range.

5. The method of claim 4, wherein determining whether the one or more parameters of the pilot input command are within the threshold range comprises determining whether a commanded flight path angle (FPA) associated with the one or more parameters of the pilot input command is within the threshold range.

6. The method of claim 5, wherein determining whether the pilot input command is commanding an ascent or descent of the aircraft comprises determining whether the commanded flight path angle (FPA) of the received pilot input command is positive or negative.Agent Ref: 16499-0038-003047. The method of claim 5 or 6, further comprising using the commanded flight path angle (FPA) to determine which one of the plurality of aircraft flight parameters to hold constant.

8. The method of any one of claims 5-7, wherein determining which one of the plurality of flight parameters to hold constant includes, when the commanded flight path angle (FPA) associated with the one or more parameters of the pilot input command is within the threshold range, determining to hold the altitude of the aircraft constant.

9. The method of any one of claims 4-8, wherein determining whether the one or more parameters associated with the pilot input command are within the threshold range comprises determining whether a commanded rate of altitude change associated with the received pilot input command is within the threshold range.

10. The method of claim 9, wherein determining whether the pilot input command is commanding an ascent or descent of the aircraft comprises determining whether the commanded rate of altitude change associated with the one or more parameters of the pilot input command is positive or negative.

11. The method of claim 9 or 10, further comprising using the commanded rate of altitude change to determine which one of the plurality of aircraft flight parameters to hold constant.

12. The method of any one of claims 9-11, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the commanded rate of altitude change associated with the one or more parameters of the pilot input command is within the threshold range, determining to hold the altitude of the aircraft constant.

13. The method of any one of claims 3-12, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the speed of the aircraft is above a second speed threshold and at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is greater than the threshold range, determining to hold a flight path angle of the aircraft constant.Agent Ref: 16499-0038-0030414. The method of any one of claims 3-13, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the speed of the aircraft is greater than or equal to a first speed threshold and less than or equal to a second speed threshold and at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is greater than the threshold range, determining to hold a vertical speed of the aircraft constant.

15. The method of any one of claims 3-14, wherein determining which one of the plurality of aircraft flight parameters to hold constant includes, when the speed of the aircraft is greater than or equal to a first speed threshold and at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is less than the threshold range, determining to hold a flight path angle of the aircraft constant.

16. The method of any preceding claim, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includes holding the altitude of the aircraft at a constant value, when the speed of the aircraft is below a first speed threshold.

17. The method of any one of claims 3-16, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includes holding an altitude of the aircraft at a constant value, when at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is within the threshold range.

18. The method of any one of claims 3-17, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includes holding a vertical speed of the aircraft at a constant value while allowing the flight path angle of the aircraft to vary, when the speed of the aircraft is greater than or equal to a first speed threshold and less than or equal to a second speed threshold, and wherein at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is greater than the threshold range.

19. The method of any one of claims 3-18, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includesAgent Ref: 16499-0038-00304 holding the flight path angle of the aircraft at a constant value while allowing a vertical speed of the aircraft to vary, when the speed of the aircraft is above a second speed threshold, and wherein at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is greater than the threshold range.

20. The method of any one of claims 3-19, wherein controlling the aircraft based on the pilot input command while holding the determined aircraft flight parameter constant includes holding a flight path angle of the aircraft at a constant value while allowing a vertical speed of the aircraft to vary, when the speed of the aircraft is above a first threshold, and wherein at least one of the commanded flight path angle (FPA) or the commanded rate of altitude change is less than the threshold range.

21. The method of any preceding claim, wherein the pilot input command comprises an inceptor command.

22. The method of any preceding claim, wherein the pilot input command comprises a beep command.

23. The method of any preceding claim, further comprising displaying to a pilot of the aircraft an indication of the determined aircraft flight parameter held constant.

24. The method of any preceding claim, further comprising transmitting an alert indicating the determined aircraft flight parameter held constant.

25. The method of any preceding claim, wherein the ascent or descent is determined based on the pilot input command and a sensed aircraft condition.

26. The method of any preceding claim, wherein the ascent or descent is determined by comparing a sensed aircraft condition to an aircraft condition threshold.

27. The method of any preceding claim, wherein the determined flight parameter is held constant until another pilot input is received.Agent Ref: 16499-0038-0030428. The method of any preceding claim, further comprising transmitting information about a vertical speed of the aircraft held constant, or a flight path angle held constant, and displaying the transmitted information at a user interface of the aircraft.

29. The method of any preceding claim, further comprising transmitting information associated with the aircraft flight parameter held constant.

30. The method of any one of claims 3-29, wherein the threshold range is an altitude hold threshold range.

31. A system for controlling an aircraft, comprising: a pilot input device; and at least one processor configured to carry out the method of any one of claims 1-30.

32. A computer-readable medium containing instructions for performing operations for controlling an aircraft, the instructions when executed by one or more processors cause the one or more processors to carry out the method of any one of claims 1-30.

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