System and method for automation of rotorcraft entry into autorotation and maintenance of stabilized autorotation
The system is configured for automation of rotorcraft entry into autorotation. The system can provide a means to assist the flight crew of a rotorcraft in maintaining rotor speed following loss of engine power. The system can automatically adjust control positions, actuator positions or both to prevent excessive loss of rotor speed upon initial loss of engine power before the flight crew is able to react. The system uses model matching to provide axis decoupling and yaw anticipation; it includes pitch control initially to assist in preventing rotor deceleration; and it makes use of collective, pitch, roll and yaw trim functions to provide tactile cueing to the pilot to assist when the pilot is in the loop. The system can reduce workload by assisting the crew with controlling rotor speed and forward speed during stabilized autorotation.
1. A method of automating an autorotation in an aircraft, the method comprising:
recognizing a failure of an engine;
analyzing a flight condition of the aircraft;
actuating a swashplate mechanism with a direct command from a flight control computer to an actuator coupled to the swashplate mechanism so as to change a pitch of a plurality of main rotor blades to a predetermined collective pitch value, the predetermined collective pitch value being chosen by the flight control computer referring to a look-up table containing desired collective pitch values for a variety of aircraft flight conditions; and
temporarily pausing the step of actuating the swashplate for a period of time after a pilot has made an overriding command.
2. The method according to claim 1 , further comprising:
confirming the failure of the engine.
3. The method according to claim 1 , further comprising:
confirming the failure of the engine by detecting a decrease in rotor speed of the plurality of main rotor blades.
4. The method according to claim 1 , further comprising:
calculating a desired rotor speed of the main rotor blades based in part upon the step of analyzing the flight condition of the aircraft.
5. The method according to claim 4 , wherein the step of actuating the swashplate mechanism includes changing the pitch of the plurality of main rotor blades to obtain the desired rotor speed.
6. The method according to claim 1 , further comprising:
commanding an actuation of a tail rotor actuator with the flight control computer in order to change a pitch of a plurality of tail rotor blades in order to correlate a change in a tail rotor thrust requirement because of a change in pitch of the plurality of main rotor blades.
7. The method according to claim 1 , further comprising:
actuating a collective stick with a trim actuator to cue a pilot when the flight control computer has commanded the change to the pitch of the plurality of main rotor blades.
8. The method according to claim 1 , wherein the step of actuating the swashplate mechanism with the command from a flight control computer to an actuator coupled to the swashplate mechanism so as to change the pitch of a plurality of main rotor blades includes collectively decreasing the pitch of the plurality of main rotor blades.
9. The method according to claim 1 , wherein the step of actuating the swashplate mechanism with the command from a flight control computer to an actuator coupled to the swashplate mechanism so as to change the pitch of a plurality of main rotor blades includes cyclically changing the pitch of the plurality of main rotor blades to increase an attitude of the aircraft so as to promote an airflow up through the plurality of main rotor blades.
10. The method according to claim 1 , further comprising:
actuating a swashplate mechanism with a flare command from the flight control computer to the actuator coupled to the swashplate mechanism so as to increase the pitch of the plurality of main rotor blades upon detection that the aircraft is at a predetermined distance from a ground surface.