Touchdown orientation control system for a rotary wing aircraft and method

1. A rotary wing aircraft control system comprising:

an airframe;

a main rotor assembly supported by the airframe;

a control system arranged in the airframe and operatively connected to the main rotor assembly, the control system including a flight control computer (FCC), at least one control inceptor device and a touchdown orientation control system, the touchdown orientation control system including a computer readable program code embodied therewith, the computer readable program code, when executed by the FCC, causes the FCC to:

sense, by a sensor operatively connected to a flight control computer (FCC), an altitude of the rotary wing aircraft relative to a landing surface;

determine, through the FCC, one of a landing state rearward velocity reference limit value and a landing state lateral velocity reference limit value associated with the altitude; and

selectively limit, by the FCC, an in-detent flight envelope of the rotary wing aircraft to the one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value.

2. The rotary wing aircraft according to claim 1 , wherein the one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value is reduced as the rotary wing aircraft approaches touchdown on the landing surface.

3. The rotary wing aircraft according to claim 1 , wherein determining, through the FCC, one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value includes determining at least one of an in-detent rearward velocity reference limit value and an in-detent lateral velocity reference limit value.

4. The rotary wing aircraft according to claim 1 , wherein determining, through the FCC, the one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value includes setting a zero velocity reference limit value for the one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value when the altitude is lower than about 30-feet (9.15 meters).

5. The rotary wing aircraft according to claim 1 , wherein the control incepter comprises a cyclic incepter.

6. The rotary wing aircraft according to claim 1 , wherein the airframe includes an extending tail supporting a tail rotor assembly.

7. The rotary wing aircraft according to claim 6 , wherein the main rotor assembly includes a rotor hub that rotates about a main rotor axis and the tail rotor assembly includes a plurality of tail rotor blades that rotate about a tail rotor axis that is substantially perpendicular to the main rotor axis.

8. The rotary wing aircraft according to claim 1 , wherein the landing state flight envelope of the rotary wing aircraft is further limited as the rotary wing aircraft approaches the landing surface.

9. A method of controlling touchdown orientation for a rotary wing aircraft comprising:

sensing, by a sensor operatively connected to a flight control computer (FCC), an altitude of the rotary wing aircraft relative to a landing surface;

determining, through the FCC, one of a landing state rearward velocity reference limit value and a landing state lateral velocity reference limit value associated with the altitude; and

limiting, by the FCC, a landing state flight envelope of the rotary wing aircraft to the one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value.

10. The method of claim 9 , wherein an landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value is reduced as the rotary wing aircraft approaches the landing surface.

11. The method of claim 9 , wherein determining, through the FCC, one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value includes determining each of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value.

12. The method of claim 9 , wherein determining, through the FCC, the one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value includes setting a zero velocity reference limit value for the one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value when the altitude is lower than about 30-feet (9.15 meters).

13. The method of claim 9 , further comprising: overriding the one of the landing state rearward velocity reference limit value and the landing state lateral velocity reference limit value by moving a control inceptor out of detent.

14. The method of claim 13 , wherein moving the control inceptor out of detent includes moving a cyclic incepter out of detent.

15. The method of claim 9 , limiting, by the FCC, the landing state flight envelope of the rotary wing aircraft includes activating a fly-by-wire system.