System and method for rotorcraft autorotation entry assist

1. A system, comprising:

one or more flight controls operational to control flight characteristics of a main rotor of a rotorcraft;

a main rotor revolutions per minute (RPM) sensor operable to determine a measured main rotor RPM at which the main rotor is turning; and

a monitoring system operable to:

detect an engine failure of an engine of the rotorcraft;

determine a main rotor RPM delta of the main rotor of the rotorcraft, wherein the main rotor RPM delta is a difference between the measured main rotor RPM and a target main rotor RPM;

determine a target flight control setting according to the main rotor RPM delta, wherein the target flight control setting is set to a first flight control setting value in response to the main rotor RPM delta being a first delta value, and wherein the target flight control setting is set to a second flight control setting value different from the first flight control setting value in response to the main rotor RPM delta being a second delta value different from the first delta value;

generate at least one rotor RPM related command according to the target flight control setting; and

perform an automated autorotation entry assist process by controlling the one or more flight controls according to the at least one rotor RPM related command.

2. The rotorcraft according to claim 1 , wherein the at least one rotor RPM related command comprises a first command to change a pitch attitude of the rotorcraft and a second command to change a collective blade pitch angle of main rotor blades of the main rotor.

3. The rotorcraft according to claim 1 , wherein the monitoring system is operable to perform the automated autorotation entry assist process in response to the measured main rotor RPM being below a main rotor RPM threshold.

4. The rotorcraft according to claim 1 , wherein the monitoring system is further operable to perform the automated autorotation entry assist process in response to a pilot being out of manual control of a pilot control of the rotorcraft.

5. The rotorcraft according to claim 1 , wherein the at least one rotor RPM related command comprises at least one of a first command to change a pitch attitude of the rotorcraft or a second command to change a collective blade pitch angle of main rotor blades of the main rotor; and

wherein the monitoring system being operable to determine the target flight control setting comprises the monitoring system being operable to determine the target flight control setting according to the main rotor RPM delta and a forward speed of the rotorcraft.

6. The rotorcraft according to claim 5 , wherein the first command comprises a command to pitch the front of the rotorcraft upwards.

7. The rotorcraft according to claim 1 , wherein the target flight control setting comprises at least a cyclic pitch setting for the main rotor, wherein the at least one rotor RPM related command comprises at least a first command to change a pitch attitude of the rotorcraft; and

wherein the monitoring system being operable to determine the target flight control setting comprises the monitoring system being operable to determine the target flight control setting according to the main rotor RPM delta and further according to a current main rotor blade pitch setting and a current forward speed of the rotorcraft.

8. The rotorcraft according to claim 1 , wherein the monitoring system is further operable to generate one or more forward speed related commands in response to a forward speed of the rotorcraft being above a target forward speed associated with a glide speed of the rotorcraft and according to at least a forward speed of the rotorcraft and the target forward speed; and

wherein the monitoring system being operable to perform the automated autorotation entry assist process by controlling the one or more flight controls comprises the monitoring system being operable to perform the automated autorotation entry assist process by controlling the one or more flight controls according to the one or more forward speed related commands and further according to the at least one rotor RPM related command.

9. A flight control computer, comprising:

a processor; and

a non-transitory computer-readable storage medium storing a program to be executed by the processor, the program including instructions for:

performing, in response to a failure of at least one engine of a rotorcraft:

determining a target main rotor revolutions per minute (RPM);

determining a main rotor RPM delta of a main rotor of the rotorcraft, wherein the main rotor RPM delta is a difference between a measured main rotor RPM and the target main rotor RPM;

determining a target flight control setting according to the main rotor RPM delta, wherein the target flight control setting is set to a first flight control setting value in response to the main rotor RPM delta being a first delta value, and wherein the target flight control setting is set to a second flight control setting value different from the first flight control setting value in response to the main rotor RPM delta being a second delta value different from the first delta value;

generating at least one rotor RPM related command according to the target flight control setting; and

sending the at least one rotor RPM related command to a device controlling a flight control.

10. The flight control computer according to claim 9 , wherein the at least one rotor RPM related command comprises a first command to change a pitch attitude of the rotorcraft and a second command to change a collective blade pitch angle of main rotor blades of the main rotor.

11. flight control computer according to claim 9 , wherein the target flight control setting comprises at least a cyclic pitch setting for the main rotor, wherein the at least one RPM related command comprises at least a first command to change a pitch attitude of the rotorcraft; and

wherein the instructions for determining the target flight control setting includes instructions for determining the target flight control setting according to the main rotor RPM delta and further according to a current main rotor blade pitch setting and a current forward speed of the rotorcraft.

12. The flight control computer according to claim 9 , wherein the at least one rotor RPM related command comprises at least one of a first command to change a pitch attitude of the rotorcraft or a second command to change a collective blade pitch angle of main rotor blades of the main rotor; and

wherein the instructions for determining the target flight control setting include instructions for determining the target flight control setting according to the main rotor RPM delta and a forward speed of the rotorcraft.

13. The flight control computer according to claim 9 , wherein the program further includes instructions for performing, in response to the failure of the at least one engine of the rotorcraft:

generating a forward speed related command in response to a forward speed of the rotorcraft being above a target forward speed associated with a glide speed of the rotorcraft and according to at least a forward speed of the rotorcraft and the target forward speed, wherein the forward speed related command comprises one or more commands to adjust a pitch attitude of the rotorcraft; and

controlling the flight characteristic of the main rotor by controlling the flight control of the rotorcraft connected to the main rotor according to the forward speed related command.

14. A method, comprising:

performing, in response to a failure of at least one engine of a rotorcraft, an autorotation process, comprising:

determining a target main rotor revolutions per minute (RPM);

determining a main rotor RPM delta of a main rotor of the rotorcraft, wherein the main rotor RPM delta is a difference between a measured main rotor RPM and the target main rotor RPM;

determining a target flight control setting according to the main rotor RPM delta, wherein the target flight control setting is set to a first flight control setting value in response to the main rotor RPM delta being a first delta value, and wherein the target flight control setting is set to a second flight control setting value different from the first flight control setting value in response to the main rotor RPM delta being a second delta value different from the first delta value;

generating at least one rotor RPM related command according to the target flight control setting; and

controlling one or more flight controls of the rotorcraft according to the at least one rotor RPM related command.

15. The method according to claim 14 , wherein the performing the autorotation process comprises performing, in response to the failure of the at least one engine of the rotorcraft, further in response to a measured main rotor RPM of the main rotor being below a main rotor RPM threshold, and further in response to a pilot being out of manual control of a pilot control of the rotorcraft.

16. The method according to claim 14 , wherein the at least one rotor RPM related command comprises a first command to change a pitch attitude of the rotorcraft and a second command to change a collective blade pitch angle of main rotor blades of the main rotor.

17. The method according to claim 14 , wherein the at least one rotor RPM related command comprises at least one of a first command to change a pitch attitude of the rotorcraft or a second command to change a collective blade pitch angle of main rotor blades of the main rotor; and

wherein the determining the target flight control setting comprises determining the target flight control setting according to the main rotor RPM delta and a forward speed of the rotorcraft.

18. The method according to claim 17 , wherein the first command comprises a command to pitch the front of the rotorcraft upwards.

19. The method according to claim 14 , wherein the target flight control setting comprises at least a cyclic pitch setting for the main rotor, wherein the at least one rotor RPM related command comprises at least a first command to change a pitch attitude of the rotorcraft; and

wherein the determining the target flight control setting comprises determining the target flight control setting according to the main rotor RPM delta and further according to a current main rotor blade pitch setting and a current forward speed of the rotorcraft.

20. The method according to claim 14 , further comprising generating one or more forward speed related commands in response to a forward speed of the rotorcraft being above a target forward speed associated with a glide speed of the rotorcraft and according to at least a forward speed of the rotorcraft and the target forward speed; and

wherein the controlling the one or more flight controls according to the at least one rotor RPM related command comprises controlling the one or more flight controls according to the at least one rotor RPM related command and further according to the one or more forward speed related commands.