Systems 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 maintaining an autorotation in an aircraft, the method comprising:
measuring a rotor speed of a main rotor having a plurality of main rotor blades;
analyzing a flight condition of the aircraft and calculating a desired rotor speed of the main rotor based upon the flight condition of the aircraft;
calculating a desired pitch of the plurality of rotor blades that would achieve the desired rotor speed;
actuating a swashplate mechanism with a direct command from a flight control computer to an actuator associated with the swashplate mechanism so as to change a pitch of a plurality of main rotor blades in order to achieve the desired pitch of the plurality of rotor blades; and
actuating a trim actuator to cause a tactile cueing in a pilot control.
2. The method according to claim 1 , wherein:
the step of actuating a trim actuator occurs with a direct command from a flight control computer.
3. 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.
4. The method according to claim 1 , wherein the step of actuating the swashplate mechanism with the command from the flight control computer to the actuator associated with 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.
5. The method according to claim 1 , wherein the step of actuating the swashplate mechanism with the command from the flight control computer to the actuator associated with 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.
6. The method according to claim 1 , further comprising:
actuating the swashplate mechanism with a flare command from the flight control computer to the actuator associated with 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.
7. The method according to claim 1 , further comprising:
actuating the swashplate mechanism with a flare command from the flight control computer to the actuator associated with 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 altitude.
8. The method according to claim 1 , wherein the steps of actuating a swashplate mechanism and actuating a trim actuator occur simultaneously.
9. The method according to claim 1 , wherein the step of actuating a trim actuator occurs subsequent to the step of actuating a swashplate mechanism.
10. The method according to claim 1 , wherein the tactile cueing mimics the change in the pitch of the plurality of main rotor blades.
11. The method according to claim 1 , wherein the pilot control comprises at least one of the following: a collective stick and a pedal.