Maximum takeoff weight determination of aircraft

Abstract

The aircraft has a first principle takeoff processor (PCE), a predictive flight envelope protection processor (PFEP), and a maximum takeoff weight processor. The PCE is programmed to predict a terrain clearance position and an energy state when the aircraft is terrain clearance on a runway. The PFEP is programmed to assess whether each of the plurality of potential trajectories conforms to or violates a predetermined flight envelope. The maximum weight processor is programmed to: indicate that the aircraft is capable of takeoff at an aircraft weight when any of the plurality of potential trajectories conforms to a predetermined flight envelope; iteratively reducing the input of aircraft weight to the PCE until the PCE indicates that any one of the plurality of potential trajectories conforms to a predetermined flight envelope; and the input indicating the reduced aircraft weight is the maximum allowable takeoff weight.

Description

[0001] This application is a divisional application of an application with an application date of September 23, 2022, an application number of 202211164912.3, and an invention name of “Determination of the Maximum Take-off Weight of an Aircraft”. Technical Field

[0002] The present disclosure generally relates to aircraft and aircraft systems that calculate maximum takeoff weights. More specifically, the present disclosure relates to modeling customized alternative departure procedures at various weights for single engine takeoffs and testing the customized alternative departure procedures for compliance with a flight envelope. Background Art

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Many airports have defined lateral and vertical departure paths, called Standard Instrument Departures (SIDs). Pilots must plan to execute SIDs even in the unlikely event of an engine failure after takeoff. However, the aircraft may not be able to meet the climb gradient required by the SID due to the reduced climb performance available in the event of an engine failure.

[0005] If the aircraft cannot meet the climb gradient required by the SID, the pilot has two options. The first option is to reduce the weight of the aircraft by reducing the number of passengers, eliminating cargo, or reducing the amount of fuel on board. In most cases, reducing the number of passengers or luggage is not an option. Reducing the amount of fuel on board may mean that the trip cannot be flown safely, or it may result in the need to perform one or more intermediate stops to refuel before the intended destination. Neither of these outcomes is desirable.

[0006] The second option is to execute an alternate departure procedure with a lower climb gradient. There are two main challenges with these alternate departure procedures, also known as Obstacle Departure Procedure (ODP) and Special Obstacle Departure Procedure (SODP). Challenge one is that ODP / SODP are created by 3rd party companies using different methods and processes, and they are usually not verified by any (simulated) testing or constrained by any maximum complexity limits (meaning that the crew needs to take multiple actions to stay on the desired flight path). The second challenge is that these procedures are not included in the onboard Flight Management System (FMS) database, so pilots must refer to paper or electronic versions during periods of very high workload to establish the correct flight path. Airline pilots may have practiced alternative departure procedures, but business aviation pilots may have never practiced ODP / SODP before. Summary of the invention

[0007] The embodiments described herein describe a system that allows the crew to know the maximum fuel they can have on board to leave an airport in the event of an engine failure, and the manner in which the crew can execute a single engine departure with the lowest possible workload so that they can complete the takeoff and departure safely.

[0008] In a first non-limiting embodiment, an aircraft has an aircraft weight and includes a first principle takeoff processor, a predicted flight envelope protection processor, and a maximum takeoff weight processor. The first principle takeoff processor is programmed and configured to: predict a liftoff position and an energy state of the aircraft when it lifts off on a runway based on the aircraft weight and environmental conditions. The predicted flight envelope protection processor is programmed and configured to: receive the energy state and the liftoff position from the first principle takeoff processor; generate a plurality of potential trajectories for the aircraft starting from the liftoff position based on the energy state; and evaluate whether each of the plurality of potential trajectories complies with or violates a predetermined flight envelope. The maximum takeoff weight processor is programmed and configured to: in response to the predicted flight envelope protection processor determining that any one of the plurality of potential trajectories complies with the predetermined flight envelope, indicate that the aircraft can take off at the aircraft weight; in response to the predicted flight envelope protection processor determining that all of the plurality of potential trajectories violate the predetermined flight envelope, iteratively reduce an input of the aircraft weight to the first principle takeoff processor, iteratively reduce until the predicted flight envelope protection processor indicates that any one of the plurality of potential trajectories complies with the predetermined flight envelope; and indicate that the iteratively reduced aircraft weight input is the maximum allowable takeoff weight.

[0009] In a second non-limiting embodiment, an aircraft takeoff weight protection system for an aircraft having an aircraft weight includes a first principle takeoff processor, a predicted flight envelope protection processor, and a maximum takeoff weight processor. The first principle takeoff processor is programmed and configured to: predict a liftoff position and an energy state of the aircraft when it lifts off on a runway based on the aircraft weight and environmental conditions. The predicted flight envelope protection processor is programmed and configured to: receive the energy state and the liftoff position from the first principle takeoff processor; generate a plurality of potential trajectories for the aircraft starting from the liftoff position based on the energy state; and evaluate whether each of the plurality of potential trajectories complies with or violates a predetermined flight envelope. The maximum takeoff weight processor is programmed and configured to: in response to the predicted flight envelope protection processor determining that any one of the multiple potential trajectories complies with the predetermined flight envelope, indicate that the aircraft is capable of takeoff at the aircraft weight; in response to the predicted flight envelope protection processor determining that all of the multiple potential trajectories violate the predetermined flight envelope, iteratively reduce the input of the aircraft weight to the first principles takeoff processor, iteratively reducing until the predicted flight envelope protection processor indicates that any one of the multiple potential trajectories complies with the predetermined flight envelope; and indicate that the iteratively reduced aircraft weight input is the maximum allowable takeoff weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations. The particular selection of drawings is not intended to limit the scope of the present disclosure.

[0011] Figure 1 is a side view of an aircraft with a maximum takeoff weight processor in a takeoff scenario according to some embodiments; and

[0012] Figure 2 is to illustrate according to some embodiments Figure 1 Flowchart of the method for reporting maximum takeoff weight to a pilot of an aircraft. DETAILED DESCRIPTION

[0013] In general, some embodiments described herein describe a system in which a processor interacts recursively, and a first principles takeoff engine or a performance calculation engine (PCE) provides a maximum dual-engine takeoff weight based on environmental conditions reported or forecasted at the departure airport. Environmental conditions may include temperature, wind, runway conditions, pressure altitude, and other conditions that affect takeoff performance. Given an aircraft of maximum takeoff weight, a predictive flight envelope protection processor may be executed to see if the aircraft can avoid all terrain and obstacles in the event of an engine failure given a set of input conditions representing a desired aircraft configuration (weight, CG). If not, the predictive flight envelope protection processor may be recursively executed to find a flight path requiring a minimum climb gradient, and then the solution is passed to the PCE to determine the maximum takeoff weight that will bring terrain and obstacle clearance in the event of an engine failure at a (regulatory) defined decision point during the takeoff roll. The PCE may then return the new input conditions to the predictive flight envelope protection processor system and rerun the calculation to verify or improve the overall solution. These operations can be run iteratively until the divergence / stability criteria are met and the results presented to the crew. These solutions can be determined for all available runways at the airport and all options presented to the crew.

[0014] refer to Figure 1 , an exemplary aircraft takeoff scenario 100 is shown in side view, according to some embodiments. Aircraft 110 has a control processor 112. Control processor 112 includes a first principles takeoff processor 114, a predicted flight envelope protection processor 116, and a maximum takeoff weight processor 118. Aircraft 110 is in a starting position for takeoff on runway 120. A first obstacle 122 is located after the end of runway 120. A second obstacle 124 is located after the end of runway 120 and is laterally offset from first obstacle 122, as shown by being behind obstacle 122.

[0015] During the mission planning portion of the flight until just before takeoff, the pilot will need to determine whether they can depart the airport given current or anticipated weather conditions, available runway based on wind or runway availability, and finally considering the mass of the aircraft. Depending on the mission duration, it is often critical that the aircraft maximize the amount of fuel carried while still accommodating the number of passengers and cargo.

[0016] The control processor 112 uses the reported or forecasted weather to allow the pilots to determine the maximum fuel they can have on board in order to leave the airport in the event of an engine failure prior to taxi / takeoff. In this case, it does not matter whether the airport has a published alternate departure procedure. For example, the control processor 112 can determine that the aircraft 110 will reach a V1 speed at decision point 130, will lift off at takeoff point 132, will be able to fly path 134, and will be clear of a first obstacle 136 based on a first input weight of the aircraft 110.

[0017] If the distance 136 is less than the safety factor distance for clearing the obstacle 122, the control processor 112 will repeatedly reduce the input weight and test the reduced input weight for compliance with the flight envelope using the first principles takeoff processor 114, the predicted flight envelope protection processor 116, and the maximum takeoff weight processor 118. For example, the control processor 112 may reduce the weight input to the first principles takeoff processor 114 to calculate a new decision point 140, a new departure point 142, a new path 144, and a new clearance 146 between the path 144 and the second obstacle 124. In the example provided, the clearance 146 complies with the flight envelope, and the reduced weight is indicated to the pilot as the maximum allowable takeoff weight.

[0018] The predictive processor 116 continuously evaluates multiple escape trajectories ahead of the aircraft. Broadly speaking, there are two types of predictive intervention. First, if the pilot exceeds the specified flight envelope limits, the predictive processor 116 will "nudge" them back to the normal flight envelope, thereby avoiding possible loss of control in flight. Second, if the pilot is flying towards terrain, the predictive processor 116 will intervene and safely maneuver the aircraft to avoid the terrain as the situation develops until only one possible escape trajectory remains. The predictive processor 116 system uses complex control laws, performance capability databases, and continuous calculation of paths / trajectories to avoid terrain as described above to achieve this. The predictive processor 116 system includes a high-fidelity 3-dimensional ground map database and an onboard navigation system to determine the vehicle position and attitude relative to the terrain. In some embodiments, the predictive processor 116 is a predictive flight envelope protection system described in U.S. Patent Application No. 16 / 552,629 filed on August 27, 2019, which is incorporated herein by reference.

[0019] The first principles takeoff processor 114 is a first principles calculation engine (PCE) for calculating aircraft field performance. The PCE uses first principles calculation methods to determine the required runway length (per FAA regulations) for a given set of environmental conditions, aircraft configuration, and aircraft mass. The PCE is primarily focused on reducing the complexity for the flight crew in performing these calculations while improving accuracy and reducing unnecessary conservatism. In the example provided, the first principles takeoff processor 114 is the system described in FAA Advisory Circular 25.1581-1 Change 1.

[0020] Reference now Figure 2 , and continue to refer to Figure 1 , a method 200 for alerting a crew member to a maximum allowable takeoff weight is shown in flowchart form. In the example provided, the tasks of the method 200 are performed by the control processor 112 of the aircraft 110.

[0021] Task 202 receives inputs. For example, a crew member may input weight, balance, flight plan, airport, and condition (e.g., dry, wet, contaminated) information into the control processor 112. The control processor 112 may receive inputs from a flight management system, including geographic location, flight plan (e.g., waypoints, altitude, required fuel), and maximum gross weight information. The control processor 112 may receive weather service inputs, such as wind, temperature, and pressure information. The control processor 112 may receive inputs from an airport database, such as available runways, runway dimensions, and the geographic location of the takeoff point for each runway.

[0022] Task 204 validates the PCE inputs. For example, the control processor 112 may validate the runway direction, wind direction and speed, environmental constraints, and elevation constraints for each runway. Task 206 determines whether the PCE constraints are satisfied.

[0023] When the PCE constraints are not satisfied, method 200 proceeds from task 206 to task 207. Task 207 indicates to the pilot that takeoff is not possible with the inputs provided.

[0024] When the PCE constraints are satisfied, the method 200 proceeds from task 206 to task 208. Task 208 calculates the PCE outputs. For example, the first principles takeoff processor 114 may calculate the required field length, distance to liftoff, speed at liftoff, and climb gradient at liftoff based on the input initial conditions of gross weight, runway dimensions, wind, temperature, pressure, and runway conditions. In some embodiments, the first principles takeoff processor 116 performs calculations based on engine loss at a decision point, thereby representing what would happen if the pilot could not stop within the remaining runway and operated with one engine out of service.

[0025] Task 210 evaluates compliance with the flight envelope during takeoff and climb. For example, the prediction processor 116 may use the takeoff point and energy state calculated by the first principle takeoff processor 116 as initial conditions for calculating the predicted recovery flight path. In the example provided, the prediction processor 116 uses the input of liftoff speed Vr, liftoff latitude and longitude, thrust tables, temperature, pressure, airport, elevation, weight and center of gravity information to calculate the predicted recovery flight path. The prediction processor 116 uses a high-fidelity terrain database, a thrust database, and environmental parameters to determine whether any potential path complies with the predefined flight envelope. For example, the prediction processor 116 may determine that a path over the second obstacle 124 requires a lower climb gradient and can comply with the flight envelope, even when a SID path over the first obstacle 122 with a higher required climb gradient violates the flight envelope.

[0026] As used herein, the term "complying with a predetermined flight envelope" means that the predicted recovery flight path will be a predetermined safe clearance distance from obstacles and terrain along the predicted recovery flight path. In some embodiments, the predetermined flight envelope includes operational limitations, such as maximum airspeed, maximum climb gradient, and other limitations that the aircraft should not exceed. In these embodiments with operational limitations, task 210 will determine that the corresponding predicted recovery flight path violates the predetermined flight envelope when the aircraft is predicted to exceed the operational limitations along the corresponding recovery flight path, regardless of terrain or obstacle clearance.

[0027] When task 212 determines that the input results in a flight envelope violation, method 200 proceeds from task 212 to task 214. Task 214 reduces the input weight input to the PCE and proceeds to task 215. Task 215 determines whether the input weight reduced by task 214 is permissible. For example, control processor 112 may determine whether the weight is less than or equal to the zero fuel weight plus a safety margin. When the weight is too low, method 200 proceeds to task 207. When the weight is permissible, method 200 returns to task 208.

[0028] When task 212 determines that the input indicates compliance with the flight envelope, method 200 proceeds from task 212 to task 216. Task 216 reports that the input weight (which may have been reduced in task 214) meets the maximum takeoff weight. For example, if method 200 has not performed task 214, control processor 112 may indicate that the initial input weight results in a safe takeoff in the event of an engine loss at the decision point. When control processor 112 performs task 214, the reduced weight may be reported to the pilot as the maximum takeoff weight. In some embodiments, control processor 112 calculates the amount of fuel that can be carried based on the reduced input weight.

[0029] Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that there are a large number of variations. It should also be understood that the exemplary embodiment or multiple exemplary embodiments are only examples and are not intended to limit the scope, applicability or configuration of the present invention in any way. On the contrary, the foregoing detailed description will provide a convenient roadmap for those skilled in the art to implement the exemplary embodiments as contemplated herein. It should be understood that various changes may be made to the functions and arrangements of the elements described in the exemplary embodiments without departing from the scope of the present invention as set forth in the appended claims.

Claims

1. An aircraft takeoff weight protection system, comprising: At least one processor configured to: Iteratively select input aircraft weights for the aircraft, and for each selected input aircraft weight: predicting a liftoff position on a designated runway and an energy state of the aircraft upon liftoff from the designated runway based at least in part on the selected input aircraft weight and environmental conditions; Based on the predicted energy state of the aircraft when it takes off from the designated runway, generating a plurality of potential trajectories for the aircraft starting from the liftoff position on the designated runway; evaluating each of the plurality of potential trajectories to determine whether any of the plurality of potential trajectories conforms to a predetermined flight envelope; as well as The input aircraft weight in which at least one of the plurality of potential trajectories is assessed to be consistent with the predetermined flight envelope is selected as the maximum allowable takeoff weight of the aircraft.

2. The aircraft takeoff weight protection system of claim 1 , wherein the at least one processor is further configured to predict the liftoff position on the designated runway and the energy state of the aircraft when it lifts off from the designated runway, further based on an engine loss at a decision point after which the aircraft may be unable to stop within the remaining runway length. 3 . The aircraft takeoff weight protection system of claim 2 , wherein the at least one processor is configured to generate the plurality of potential trajectories further based on operation of the aircraft in the event of a loss of the engine.

4. The aircraft takeoff weight protection system of claim 1 , wherein the at least one processor is configured to evaluate each of the plurality of potential trajectories to determine whether any of the plurality of potential trajectories complies with a predetermined flight envelope by determining whether any of the plurality of potential trajectories complies with a terrain clearance distance.

5. The aircraft takeoff weight protection system of claim 1 , wherein the at least one processor is configured to evaluate each of the plurality of potential trajectories to determine whether any of the plurality of potential trajectories complies with a predetermined flight envelope by determining whether any of the plurality of potential trajectories complies with an operating constraint.

6. The aircraft takeoff weight protection system of claim 1 , wherein the at least one processor is configured to iteratively select an input aircraft weight by using a maximum gross weight of the aircraft as an initial value for the selected input aircraft weight and reducing the selected input aircraft weight until at least one of the plurality of potential trajectories complies with the predetermined flight envelope. 7 . The aircraft takeoff weight protection system of claim 1 , wherein the at least one processor is further configured to alert a flight crew in response to the estimated weight of the aircraft being greater than the maximum allowable takeoff weight. 8 . The aircraft takeoff weight protection system of claim 1 , wherein the at least one processor is further configured to determine a maximum amount of fuel that can be carried on board the aircraft based on the maximum allowable takeoff weight.

9. The aircraft takeoff weight protection system of claim 1 , wherein the at least one processor is further configured to predict the liftoff position on the designated runway and the energy state of the aircraft when it lifts off from the designated runway further based on the weight balance of the aircraft and wind, temperature, and pressure received from a weather service.

10. The aircraft takeoff weight protection system according to claim 1, wherein the at least one processor is configured to predict the liftoff position on the designated runway and the energy state of the aircraft when taking off from the designated runway further based on the runway size received from an airport database and the starting point of takeoff on the designated runway.

11. An aircraft takeoff weight protection system, comprising: At least one processor configured to: Iteratively select input aircraft weights for the aircraft, and for each selected input aircraft weight: predicting a liftoff position on a designated runway and an energy state of the aircraft upon liftoff from the designated runway based at least in part on selected input aircraft weights and environmental conditions and an engine loss at a decision point after which the aircraft may not be able to stop within the remaining runway length, wherein the environmental conditions include wind, temperature, and pressure; generating a plurality of potential trajectories for the aircraft from the liftoff location on the designated runway based on the predicted energy state of the aircraft upon liftoff from the designated runway and further based on the operation of the aircraft in the event of a loss of the engine; evaluating each of the plurality of potential trajectories to determine whether any of the plurality of potential trajectories conforms to a predetermined flight envelope, the predetermined flight envelope including a terrain clearance distance and operating constraints; and The input aircraft weight in which at least one of the plurality of potential trajectories is assessed to be consistent with the predetermined flight envelope is selected as the maximum allowable takeoff weight of the aircraft.

12. An aircraft, comprising: At least one processor configured to: Iteratively select input aircraft weights for the aircraft, and for each selected input aircraft weight: predicting a liftoff position on a designated runway and an energy state of the aircraft upon liftoff from the designated runway based at least in part on the selected input aircraft weight and environmental conditions; Based on the predicted energy state of the aircraft when it takes off from the designated runway, generating a plurality of potential trajectories for the aircraft starting from the liftoff position on the designated runway; evaluating each of the plurality of potential trajectories to determine whether any of the plurality of potential trajectories conforms to a predetermined flight envelope; as well as The input aircraft weight in which at least one of the plurality of potential trajectories is assessed to be consistent with the predetermined flight envelope is selected as the maximum allowable takeoff weight of the aircraft.

13. The aircraft of claim 12, wherein the at least one processor is further configured to predict the liftoff position on the designated runway and the energy state of the aircraft upon liftoff from the designated runway further based on an engine loss at a decision point after which the aircraft may be unable to stop within the remaining runway length.

14. The aircraft of claim 13, wherein the at least one processor is configured to generate the plurality of potential trajectories further based on operation of the aircraft in the event of a loss of the engine.

15. The aircraft of claim 12, wherein the at least one processor is configured to evaluate each of the plurality of potential trajectories to determine whether any of the plurality of potential trajectories conforms to a predetermined flight envelope by determining whether any of the plurality of potential trajectories conforms to a terrain clearance distance.

16. The aircraft of claim 12, wherein the at least one processor is configured to evaluate each of the plurality of potential trajectories to determine whether any of the plurality of potential trajectories complies with a predetermined flight envelope by determining whether any of the plurality of potential trajectories complies with operating constraints.

17. The aircraft of claim 12, wherein the at least one processor is configured to iteratively select an input aircraft weight by using a maximum gross weight of the aircraft as an initial value for the selected input aircraft weight and reducing the selected input aircraft weight until at least one of the plurality of potential trajectories conforms to the predetermined flight envelope.

18. The aircraft of claim 12, wherein the at least one processor is further configured to alert a flight crew in response to the estimated weight of the aircraft being greater than the maximum allowable takeoff weight.

19. The aircraft of claim 12, wherein the at least one processor is further configured to determine a maximum amount of fuel that can be carried on board the aircraft based on the maximum allowable takeoff weight.

20. The aircraft of claim 12, wherein the at least one processor is configured to predict the liftoff position on the designated runway and the energy state of the aircraft when it lifts off from the designated runway further based on runway dimensions received from an airport database and a starting point for takeoff on the designated runway.

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