Aircraft control method

Abstract

The present invention provides a method for determining a flight trajectory of a vertical take-off aircraft (10) having a vector propulsion device (30, 32). The method includes: receiving one or more aircraft flight constraints; inputting the aircraft flight constraints into a trajectory planning algorithm to determine a minimum energy aircraft transition trajectory; and outputting a control plan to fly the aircraft (10) to the flight trajectory.

Description

Technical Field

[0001] The present disclosure relates to a method of controlling an aircraft. Background Art

[0002] Short take-off and landing (STOL), short take-off and landing (STOVL), and vertical take-off and landing (VTOL) aircraft are used in places where take-off and landing distances are limited, such as ships at sea. Traditional VTOL aircraft include helicopters, tilt-rotor aircraft, and tilt-wing aircraft.

[0003] In a tilt-wing aircraft, propellers are mounted to wings that pivot so that the wing-mounted propellers provide lift or forward thrust depending on the position of the wing. Existing tilt-wing aircraft are known, such as the XC-142, Vertol VZ-2, Kaman K-16B, Hiller X-18, and Canadair CL-84.

[0004] Tilt-rotor aircraft are also known, such as the Bell / Boeing V-22. In a tilt-rotor aircraft, the wings remain level relative to the fuselage, while the engines and rotors tilt to transition between hovering and forward flight.

[0005] Other VTOL aircraft configurations are also known, such as vectored thrust aircraft, autogyroplanes, and helicopters, including compound helicopters. In many of these aircraft types, either separate propellers are provided for ascent and cruise flight, or the engines must be tilted relative to the wings or fuselage between ascent and cruise flight. Flight during this "transition" between hover / ascent flight and forward / cruise flight can be difficult to manage, even for skilled pilots. If VTOL aircraft become more common, it will be necessary to reduce the skill level required to fly these aircraft types. Furthermore, given the competing demands for efficient flight under various constraints, such as maintaining stability, altitude, etc., optimization of the flight profile can be difficult for human pilots or conventional autopilot systems. Therefore, it would be desirable to provide an automated system that automates at least part of the flight state during the transition between hover and cruise flight in a VTOL aircraft in order to provide efficient, safe flight. Summary of the Invention

[0006] According to a first aspect, a method for determining a flight trajectory of a vertical take-off vehicle having a vectored propulsion device is provided, the method comprising:

[0007] receiving one or more aircraft flight constraints;

[0008] Receive aircraft flight data;

[0009] inputting the vehicle flight constraints and the vehicle flight data into a trajectory planning algorithm to determine a minimum energy vehicle transition trajectory; and

[0010] Output a control plan to make the vehicle fly the flight trajectory.

[0011] Advantageously, a method is provided for automatically planning an aircraft flight trajectory during a transition phase that minimizes the total energy used during the transition. This ensures that the aircraft is operated as efficiently as possible within the aircraft flight constraints using the aircraft flight data.

[0012] The one or more aircraft flight constraints may include one or more of an aircraft flight corridor, an aircraft handling envelope, and a transition end plan.

[0013] The aircraft flight path may include maximum and / or minimum allowed altitudes for the transition trajectory and may include maximum / minimum aircraft bank angles.

[0014] The aircraft handling envelope may include one or more of acceleration limits, roll, pitch or yaw rate limits, speed limits, propeller power limits, propeller power ratio limits, aircraft orientation limits, wing angle of attack limits, and actuator velocity limits.

[0015] The transition end plan may include a maximum time and / or distance for completing the transition to forward flight.

[0016] The method may include inputting real-time aircraft flight data into the trajectory planning algorithm to provide an updated trajectory. The real-time aircraft flight data may include one or more of current or projected speed, altitude, actuator feedback, and weather data.

[0017] The trajectory planning algorithm may include an aircraft flight model that relates aircraft flight control inputs to corresponding calculated trajectories. The aircraft flight inputs may include one or more of propeller thrust, propeller angles, wing and tail pitch angles, and aircraft flight control surface angles.

[0018] The trajectory planning algorithm may include a cost function algorithm.

[0019] The cost function algorithm may include a plurality of calculated trajectories and a total energy consumed by one or more thrusters for each calculated trajectory. The method may include determining, using the cost function algorithm, the calculated trajectory having the minimum total thruster energy consumption.

[0020] The method may include inputting the calculated trajectory into an aircraft flight model to determine a control plan.

[0021] The method may include outputting the control plan to an autopilot system to control the aircraft to the control plan. Alternatively, the method may include outputting the control plan to a user interface to provide flight control input instructions to a pilot.

[0022] According to a second aspect, there is provided an aircraft flight control system configured to control an aircraft having a vectored propulsion device, the system comprising:

[0023] a trajectory controller configured to calculate a minimum energy aircraft transition trajectory based on aircraft flight constraints and aircraft flight data according to the method of the first aspect; and

[0024] An aircraft flight controller is configured to fly the aircraft to a trajectory calculated by the trajectory controller.

[0025] According to a third aspect, there is provided an aircraft comprising one or more vector thrusters and the flight control system of the second aspect.

[0026] The vectoring thruster may be configured to provide vectored thrust relative to one or more of an aircraft fuselage and an aircraft wing.

[0027] In a first embodiment, the aircraft comprises a tilt-wing aircraft including one or more propellers fixedly mounted to wings, wherein the wings are capable of pivoting relative to the aircraft fuselage. The tilt-wing aircraft may further include one or more cruise propellers fixedly mounted to the aircraft and configured to provide forward thrust.

[0028] In a second embodiment, the aircraft comprises a tilt-rotor aircraft including one or more propellers pivotably mounted to wings, wherein the wings are fixedly mounted relative to the aircraft fuselage. The tilt-rotor aircraft may further include one or more cruise propellers fixedly mounted to the aircraft and configured to provide forward thrust.

[0029] Another aspect includes a non-transitory medium comprising instructions for performing the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, which are schematic only and not drawn to scale, and in which:

[0031] Figure 1 is a schematic side view of a tilt-wing aircraft in a hover flight mode;

[0032] Figure 2 It is in horizontal flight mode Figure 1 A schematic side view of an aircraft;

[0033] Figure 3 is a schematic side view of a tilt-rotor aircraft in a hover flight mode;

[0034] Figure 4 It is in horizontal flight mode Figure 3 A schematic side view of an aircraft;

[0035] Figure 5 is shown to determine during the transition between the hover flight mode and the level flight mode Figure 1 and Figure 2 A flow chart of a method for aircraft control planning of an aircraft;

[0036] Figure 6 is a flow chart illustrating a method of controlling an aircraft;

[0037] Figure 7 is an exemplary aircraft trajectory; and

[0038] Figure 8 is a flow chart illustrating a method of determining an aircraft trajectory. DETAILED DESCRIPTION

[0039] refer to Figures 1 to 3 , an aircraft 10 is shown. It should be understood that these figures are illustrative only and are not drawn to scale. The aircraft includes a fuselage 12 supported by landing gear 14. The aircraft 10 also includes a pair of forward main wings 16 positioned so that the center of lift of the main wings 16 in flight is approximately adjacent to the center of gravity. The aircraft 10 also includes an empennage 22 (also referred to as a tail section) including a horizontal (relative to when the aircraft is in horizontal flight) tail surface 18 and a vertical (relative to when the aircraft is in horizontal flight) tail surface 34 extending from the end of each horizontal tail surface 18. The fuselage 12 includes a nose 20 defining the front end of the aircraft 10 and a tail 22 defining the rear end of the aircraft 10.

[0040] Each wing 16 is mounted with one or more propellers in the form of propellers 30. Similarly, one or more further propellers in the form of propellers 36 are mounted to the empennage 22.

[0041] As can be seen from the figure, aircraft 10 defines several directions. When aircraft 10 is in level flight or parked on the ground, a longitudinal direction A extends in a generally horizontal direction between nose 20 and tail 22. A lateral direction (not shown) extends in a generally horizontal direction between the tips of main wings 16 in a direction perpendicular to longitudinal axis A. A vertical direction C extends in a direction generally perpendicular to the ground when aircraft 10 is in level flight or parked on the ground.

[0042] Both the main wing 16 and the horizontal tail surface 18 are capable of being in a horizontal flight configuration (e.g. Figure 1 as shown) and vertical flight configuration (as Figure 4 In other words, the main propeller has a fixed angle relative to the main wing 16, wherein the main wing 16 is pivotable. In the horizontal flight configuration (as shown in FIG. Figure 2 ), the wing 16 and the horizontal tail surface 18 present respective leading edges 26, 28 that face in the forward longitudinal direction A. The main wing 16 and the horizontal tail surface 18 are configured to pivot about a lateral direction to transition to a hover flight configuration with the leading edges 26, 28 pointing upward in a vertical direction, as shown. Figure 1 shown.

[0043] During VTOL operations, the aircraft is typically launched on the ground with the wings 16 and tail 22 in a hovering configuration, such as Figure 2 As shown. Figure 1 Prior to the horizontal flight mode shown, the aircraft takes off in a vertical orientation (although there may also be some horizontal thrust component). During the transition period, as speed increases, the wings 16 and tail 22 slowly pivot from hover to a horizontal position. Similarly, for landing, the aircraft again transitions from the horizontal mode to the hover mode. The transition phase of takeoff can be defined as the period between when the aircraft's wheels leave the ground and when the aircraft has sufficient forward airspeed to maintain horizontal flight without a vertical thrust component from the propellers 30, 32. Similarly, the transition phase of landing can be defined as the period between when the aircraft's speed drops below a speed at which horizontal flight can be maintained and when the wheels contact the ground.

[0044] Figure 3 A second aircraft 110, similar to the first aircraft 10, is shown, with a main wing 116 and a tail wing 122. A main propeller 130 is mounted to the main wing 116, and a tail propeller 132 is mounted to the tail wing 122. Aircraft 110 differs from aircraft 10 in that aircraft 110 has fixed wings 116 that do not pivot between hover and cruise flight. Instead, as seen from Figure 3 Hover flight configuration and Figure 4 As can be seen from the cruise flight configuration in FIG, the main wing and tail rotors 130, 132 pivot relative to the rest of the aircraft between the hover configuration and the cruise configuration, while the tail 22 and main wing 16 remain horizontal. This configuration is known as a "tilt rotor" aircraft.

[0045] Figure 5An overview of the control scheme for controlling the aircraft 10 during a transition phase (either during takeoff or landing) is shown. Briefly, the system is configured to first calculate a minimum energy aircraft trajectory using a reference trajectory controller. The autopilot then converts this reference trajectory into control inputs to fly the aircraft 10. As the aircraft 10 flies along this trajectory, the trajectory is updated based on the actual trajectory flown to recalculate a new minimum aircraft trajectory.

[0046] Figure 6 The system architecture is described in more detail. The system comprises a reference trajectory controller 40. The reference trajectory controller determines an optimal vehicle trajectory during a transition phase (take-off or landing) that minimizes the total thruster energy used for the transition.

[0047] The aircraft trajectory controller 40 calculates the aircraft trajectory, such as Figure 7 A trajectory generally comprises the path of an aircraft through space in a vertical plane, and may also include a path in a horizontal plane.

[0048] Once the trajectory is calculated, the aircraft trajectory controller 40 outputs one or more aircraft dynamic commands, which are continuously updated as the aircraft progresses through the transition phase. Typically, the dynamic commands include at least an altitude command and a forward velocity command. Therefore, the trajectory controller converts the aircraft trajectory into a series of altitude and forward velocity commands, which are broken down into individual time steps. The dynamic commands may also include a series of yaw, roll, and pitch commands for each time step.

[0049] These dynamic commands are then input to a flight controller 42, which converts the dynamic commands into flight actuator demands. The flight controller includes an aircraft flight model that includes a model of how the aircraft will react to given flight actuator inputs, and also includes aircraft actuator constraints such as maximum and minimum flight actuator positions and authorities, as well as maximum propeller power settings and lift rates, and aircraft dynamic constraints such as flight surface angle of attack, acceleration, loads, and stability envelopes. The aircraft flight model typically also includes aircraft configuration variables such as aircraft weight, and atmospheric variables such as air temperature and pressure altitude. The flight controller determines how to most efficiently implement the dynamic commands within the aircraft actuators and dynamic constraints. Once the efficiency is calculated, the flight controller outputs one or more actuator demands such as main thruster 30 and tail thruster 32 demands, elevator, rudder, and aileron position demands, flap demands, and wing and tail tilt demands.

[0050] These demands are then converted into actuator position commands by the various actuator controllers 44, which use feedback loops to ensure that the actuators are in the commanded states at the correct times. For example, an engine controller (not shown) is provided that converts the required thrust demands into individual motor / engine control parameters to meet the thrust demand input from the flight controller 42.

[0051] Simultaneously, aircraft data sensors 46 continuously sense aircraft dynamic parameters during flight. These data sensors may include air data sensors (such as pitot tubes) that provide atmospheric data such as air speed, altitude, etc. Additional aircraft data sensors such as aircraft position sensors and attitude sensors (e.g., GPS controllers, gyro sensors, etc.) provide a complete picture of the aircraft's ground speed, altitude, position, etc. The data from these sensors is then fed back to the flight controller 42, which updates the flight control requirements to account for deviations from the dynamic commands input to the actuators.

[0052] The flight controller 42 , actuator controller 44 , and aircraft data sensors 46 are continuously updated until the trajectory input from the reference trajectory controller is complete and the transition period ends.

[0053] If the aircraft deviates significantly from the optimal trajectory determined by the reference trajectory controller, data from the aircraft data sensors 46 is provided to the reference trajectory controller, which calculates an updated optimal trajectory based on the data. This process is repeated as needed until the transition period is over, at which point control is handed back to a conventional autopilot or a human operator.

[0054] Figure 8 The process of calculating the reference trajectory by the reference trajectory controller 40 is shown in more detail.

[0055] The reference trajectory controller 40 aims to provide an aircraft trajectory that minimizes energy usage (ie, fuel burn for thrusters, electrical energy, etc.) within certain constraints during the transition period.

[0056] This trajectory can be represented mathematically in Cartesian coordinates in the vertical plane as a series of positions starting from a conceptual origin in the horizontal (x-axis) and vertical (z-axis):

[0057] x(k|k),x(k+1|k),…,x(k+N|k)

[0058] z(k|k),z(k+1|k),…,z(k+N|k)

[0059] where x(k+i|k) and z(k+i|k) represent the future demands for the vehicle's horizontal position x and vertical position z, respectively, at i samples before time k, each sample T seconds in the future. k+i|k represents the demand for the vehicle's position at time (k+i)Ts at real time kTs. In principle, at this stage, positions x and z can take any value at any given time k. N represents the total number of time steps, which will be related to the maximum transition time and the temporal resolution of the process.

[0060] When computing this trajectory, one will typically first define the boundaries of the problem space. For example, an air traffic constraint may define a "flight corridor" for an aircraft, i.e., a maximum and minimum altitude C within which the aircraft must fly for a given position on the ground. z and distance C x :

[0061] C x (k+i|k)≤x(k+i|k)≤C x (k+i|k)

[0062] C z (k+i|k)≤z(k+i|k)≤C z (k+i|k)

[0063] Within these constraints, the reference trajectory controller 40 attempts to provide a trajectory that minimizes the energy consumption of the propulsion system during the time frame of the transition period. In some cases, the above constraints may not exist, such as where the aircraft has sufficient performance so that these constraints do not affect the calculated flight trajectory, or where the aircraft is operating in uncontrolled airspace.

[0064] Figure 7 An exemplary trajectory is shown (shown as a solid line), where a flight path is defined by a maximum altitude line and a minimum altitude line (shown as a dashed line). As can be seen, a variety of potential flight trajectories may exist within the flight path.

[0065] Figure 8 The process of selecting a minimum-energy aircraft trajectory is shown in a simplified form. First, an aircraft flight model is generated. This model is a state model that represents the aircraft's response to inputs such as control inputs and power inputs over time. Constraints such as airspace and aircraft constraints, such as bounded airspace, maximum and minimum flight speeds, are entered into the model. Aircraft data such as takeoff weight can also be added. Finally, the initial seeding trajectory is entered into the aircraft model.

[0066] The flight model is then used to determine the propulsion variables required to enable the aircraft to follow a given trajectory, in order to calculate the energy cost of the flight trajectory. These propulsion variables serve as the subject of a cost function. The cost function explores the flight model's variables to find a set of variables that outputs a trajectory with the minimum energy associated with that trajectory. The details of this system are outlined below.

[0067] To determine the trajectory, an aircraft flight model is used. An aircraft flight model has the following general form:

[0068]

[0069] in is some future state, X is the current state, and δ is a control input. For example, the state X can be a position in a coordinate system (e.g., Cartesian coordinates x, y, z), a velocity v (which can be ground speed or airspeed, such as indicated airspeed), an attitude (expressed as an angle), and an angular velocity. The control inputs can include the thrust of the aircraft's main thrusters 30 and tail thrusters 32, thruster / wing pitch angles, and flight control surface angles.

[0070] To determine the future state from the current state and control inputs A transition function f(X,δ) in the form of an aircraft flight model is defined. The transition function includes one or more equations of motion that describe how the aircraft responds to control inputs that vary with time and outputs the corresponding future state vector Typical aircraft control models are well known to those skilled in the art and are described in detail, for example, in McRuer and Graham, Aircraft Dynamics and Automatic Control, and Stengel, Flight Dynamics. Other aircraft control models include dynamic inversion, as described, inter alia, in Ryan James Caverly et al., “Non-Linear Dynamic Inversion of a Flexible Aircraft,” published in IFAC-PapersOnLine, Vol. 49, No. 17, 2016, pp. 338-342.

[0071] For example, an aircraft model might take the following form:

[0072]

[0073] The goal of the transition controller is to calculate the nominal wing and tail thrust trajectories at the given airspeed (V), flight path angle (γ), and wing / tail tilt i wTo provide a feasible trajectory in order to transition to level flight within a certain finite range of time N. Therefore, the system selects the wing, tail thrust, speed V and flight path angle and wing angle as the manipulated variables:

[0074] V(k+i|k),γ(k+i|k),i w (k+i|k), T w (i+k|k), T t (i+k|k)

[0075] Additional constraints are imposed on the system. First, the time horizon N for completing the transition must be finite and non-zero, and a maximum time horizon N can be chosen.

[0076] Obviously, when we want to transition to horizontal flight, the wings and tail must tilt from vertical to horizontal within a finite timeframe, which can be explicitly expressed as:

[0077] i w (k+N|k)≤X degrees

[0078] When the VTOL configuration becomes an aircraft configured for forward flight (i.e. the transition period can be said to have ended), it is appropriate to choose X < 8 degrees. In addition, the speed at the end of the time range N must be above the stall speed of the wing angle, and therefore an additional constraint is defined:

[0079] V(k+N|k)≥V 失速 (X)

[0080] In this example, for simplicity, we assume that both the tail and the wings are tilted simultaneously, where i w Indicates wing tilt. Depending on the design, the tail can be offset from the wing by -5 to 5 degrees. In other cases, tail tilt can vary independently of wing tilt.

[0081] One of the important factors for an effective VTOL transition is to keep the effective angle of attack below the stall speed. Therefore, the transition controller generates a feasible trajectory that ensures this. The trajectory also ensures that the angle of attack α of the wing and tail is w , α t Always below a certain critical angle (usually about two degrees or more below the stall angle)

[0082] α w (k+N|k)≤α1

[0083] α t (k+N|k)≤α2

[0084] The angle of attack of the wing and tail is a function of speed, the corresponding wing and tail thrust (if the wing is blown by, for example, a propeller mounted forward of the wing's leading edge), the flight path angle, and the pitch angle. The total wing and tail thrust is:

[0085] T w (k+i|k)

[0086] T t (k+i|k)

[0087] The purpose of the control method of this embodiment is to minimize the total energy consumed by the propulsion system during the transition period. It will be understood that the energy used will be equal to the total power consumed (integrated) over time. The total power consumed during the transition period can be expressed as a function of the gas turbine and battery power,

[0088] P t (k+i|k)=P gt (k+i|k)+P bat (k+i|k)

[0089] and is related to thrust via some function

[0090] P t (k+i|k)=f(T w (k+i|k), T t (k+i|k))

[0091] For a given set of trajectory control system variables V(k+i|k),γ(k+i|k),i w (k+i|k), T_w(k+i|k), T_t(k+i|k), for a given history, the corresponding wing propeller 30 power P will be required w (k+i|k) and tail propeller 32 power P t (k+i|k) to satisfy these variables. For example, reducing the wing tilt angle i w will tend to increase the aircraft forward airspeed V over time, but for a given power P w , P t Reducing altitude, and therefore increasing thruster power, may be necessary to keep the aircraft within the flight path. Each of these will also affect the total time to complete the transition, and therefore the total energy expended.

[0092] Control system variables V(k+i|k), γ(k+i|k), i w(k+i|k), T_w(k+i|k), T_t(k+i|k) can be related via an aircraft model, which can be similar to the aircraft model used by flight controller 32. Thus, the correspondence between actual aircraft behavior and expected aircraft trajectory can be ensured.

[0093] Therefore, a range of control system variable combinations can be explored, and the corresponding wing propeller 30 thrust T for each time interval can be determined from the aircraft model. w (k+i|k) and tail propeller 32 thrust T t (k+i|k). This can be converted into the corresponding wing propeller power and tail propeller 32 power, and added together to obtain the total propulsion system power P at each time step t :

[0094] P t (k+i|k)=f(T w (k+i|k), T t (k+i|k))

[0095] The total propulsion power over the transition period can then be integrated to give the total energy consumed.

[0096] The control system variable space can be explored by expressing the energy consumed by a given trajectory during the transition period (where the energy is to be minimized in an optimization problem using, for example, a neural network or other suitable computerized optimization problem solver) to select the minimum energy trajectory. For example, a finite-horizon, discrete-time linear quadratic regulator algorithm is as follows:

[0097]

[0098] Where the aircraft is a hybrid aircraft (where power is drawn from one or more batteries), this may be subject to further constraints, such as battery energy constraints.

[0099] A set of nominal control system variables or reference trajectories can be “seeded” into the cost minimization function as a starting point to ensure fast convergence.

[0100] Therefore, the system determines a minimum energy trajectory for the transition period in a vector propulsion system and directs the aircraft toward that trajectory. The inventors have determined that vector propulsion aircraft are generally less efficient during hover / transition flight than during cruise flight because lift is generated at least in part by the propellers rather than by the wings, which generate lift more efficiently. Therefore, by controlling the aircraft to minimize energy used in transition, overall aircraft flight cycle energy usage is minimized.

[0101] It should be understood that the above control scheme can be equally applied to Figure 3 and Figure 4 The tilt-rotor aircraft 110 is a tilt-rotor aircraft. However, the wing tilt angle will be omitted from the calculation. It will also be understood that the control scheme can be applied to other aircraft configurations, such as aircraft with vectored thrust jet propulsion, compound helicopters with vectored thrust systems, and other aircraft types.

[0102] It should also be appreciated that alternative methods may be used to convert the reference flight trajectory into actuator commands.

[0103] Various examples have been described, each featuring various combinations of features. Those skilled in the art will understand that, unless clearly mutually exclusive, any feature may be used alone or in combination with any other feature, and that the present invention extends to and includes all combinations and subcombinations of one or more features described herein.

Claims

1. A method for determining a flight trajectory of a vertical take-off vehicle having a vector propulsion device, the method comprising: determining a flight trajectory for an aircraft, the flight trajectory comprising a coordinate system comprising a series of positions from a horizontal and vertical notional origin, Characterized in that the method comprises: receiving one or more aircraft flight constraints; inputting the vehicle flight constraints into a trajectory planning algorithm to determine a minimum energy vehicle transition trajectory, the planning algorithm comprising a cost function algorithm including a plurality of calculated trajectories and a total energy expended by one or more thrusters for each calculated trajectory; and outputting a control plan to enable the aircraft to fly to the flight trajectory; The trajectory planning algorithm includes an aircraft flight model that makes the current state (X) and the aircraft flight control input (δ) correlate with the future aircraft state. associated, the aircraft flight control inputs (δ) comprising propeller thrust, and the method comprising integrating the total propulsion power within the calculated trajectory to give the total energy expended to determine an energy cost corresponding to the calculated trajectory; and The aircraft is flown along the determined flight trajectory using data from the aircraft position sensor and attitude sensor via an aircraft trajectory controller and a flight controller, the aircraft trajectory controller being configured to output one or more dynamic commands, the one or more dynamic commands including at least an altitude command and a forward velocity command, and the aircraft controller being configured to convert the dynamic commands into flight actuator commands. 2 . The method of claim 1 , wherein the one or more aircraft flight constraints include one or more of an aircraft flight corridor, an aircraft handling envelope, and a transition end plan. 3 . The method of claim 2 , wherein the aircraft flight path includes a maximum and / or minimum allowed altitude for the transition trajectory and can include a maximum / minimum aircraft bank angle.

4. The method of claim 2, wherein the aircraft handling envelope includes one or more of an acceleration limit, a roll, pitch or yaw rate limit, a speed limit, a propeller power limit, a propeller power ratio limit, an aircraft orientation limit, a wing angle of attack limit, and an actuator velocity limit.

5. The method of claim 2, wherein the transition end plan includes a maximum time and / or distance for completing the transition to forward flight. 6 . The method of claim 1 , wherein the method includes inputting real-time aircraft flight data into the trajectory planning algorithm to provide an updated trajectory. 7 . The method of claim 6 , wherein the real-time aircraft flight data includes one or more of current or projected speed, altitude, actuator feedback, and weather data. 8 . The method of claim 1 , wherein the trajectory planning algorithm includes an aircraft flight model that relates aircraft flight control inputs to corresponding calculated trajectories.

9. The method of claim 8, wherein the aircraft flight inputs include one or more of propeller thrust, propeller angles, wing and tail pitch angles, and aircraft flight control surface angles.

10. The method of claim 1, wherein the method includes determining a calculated trajectory having a minimum total thruster energy consumption using the cost function algorithm.

11. The method of claim 1 , wherein the method includes inputting the calculated trajectory into the aircraft flight model to determine the control plan.

12. The method of claim 11, wherein the method includes outputting the control plan to an autopilot system to control the aircraft (10) to the control plan.

13. An aircraft flight control system configured to control an aircraft having a vectored propulsion device, the system comprising: a trajectory controller configured to calculate a minimum energy aircraft transition trajectory according to the method according to any one of claims 1 to 12 and aircraft flight constraints and aircraft flight data; and An aircraft flight controller is configured to fly the aircraft to the trajectory calculated by the trajectory controller.

14. An aircraft comprising a vector thruster and a flight control system according to claim 13.

15. The aircraft of claim 14, wherein the vector thruster is configured to provide vector thrust relative to one or more of an aircraft fuselage and an aircraft wing.

16. A non-transitory medium comprising instructions for executing the method of claim 1.

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