METHOD OF AUTOMATICALLY CONTROLLING A ROTARY WING AIRCRAFT HAVING AT LEAST ONE PROPULSION PROPELLER, AN AUTOPILOT DEVICE, AND AN AIRCRAFT

• US 20130175385A1
• Filed: 07/09/2012
• Published: 07/11/2013
• Est. Priority Date: 07/12/2011
• Status: Active Grant

• Current Assignee: Airbus Helicopters
• Original Assignee: Eurocopter
• Inventors: Eglin, Paul
• Granted Patent: US 10,023,306 B2
• Time in Patent Office: Days
• US Class Current: 244/17.13
• CPC Class Codes: B64C 27/22 Compound rotorcraft, i.e. aircraft using in flight the features of both aeroplane and rotorcraft
• CPC Class Codes: B64C 27/57 automatic or condition responsive, e.g. responsive to rotor speed, torque or thrust
• CPC Class Codes: B64D 45/00 Aircraft indicators or protectors not otherwise provided for camouflage F41H3/00
• CPC Class Codes: G05D 1/0858 specially adapted for vertical take-off of aircraft

Abstract

An autopilot device (10) and method for automatically piloting a rotary wing aircraft (1), having at least one propulsion propeller (2), said rotary wing comprising at least one rotor (3) with a plurality of blades (3′), said device comprising a processor unit (15) co-operating with at least one collective control system (7) for controlling the collective pitch of said blades (3′). The device includes engagement means (20) connected to the processor unit (15) for engaging an assisted mode of piloting for maintaining an angle of attack, said processor unit (15) automatically controlling the collective pitch of the blades (3′) when the assisted mode of piloting for maintaining an angle of attack is engaged by controlling said collective control system to maintain an aerodynamic angle of attack (α) of the aircraft at a reference angle of attack (α*).

Claims

1. A method of automatically piloting a rotary wing aircraft, said aircraft having at least one propulsion propeller, said rotary wing comprising at least one rotor provided with a plurality of blades, wherein during an assisted mode of piloting for maintaining an angle of attack, the aerodynamic angle of attack (α

) of the aircraft is maintained equal to a reference angle of attack (α

*) by automatically controlling the collective pitch of said blades.

2. A method according to claim 1, wherein the collective pitch of said blades is controlled automatically so as to control a vertical air speed of the aircraft in such a manner as to maintain the aerodynamic angle of attack of the aircraft equal to said reference angle of attack by application of the following relationship:

α

*=θ

−

arcsin(VZ/TAS)

where “

VZ”

represents the vertical air speed of the aircraft, “

TAS”

represents the true air speed of the aircraft, “

θ

”

represents a current longitudinal attitude, and “

α

*”

represents the reference angle of attack.

3. A method according to claim 1, wherein the reference angle of attack (α

*) is equal to the current aerodynamic angle of attack (α

) of the aircraft at the moment that the assisted mode of piloting for maintaining an angle of attack is engaged.

4. A method according to claim 1, wherein the value of the reference angle of attack (α

*) is modified in flight.

5. A method according to claim 1, wherein the longitudinal attitude (θ

) is automatically maintained equal to a reference longitudinal attitude (θ

*), the current longitudinal attitude being equal to said reference attitude (θ

*).

6. A method according to claim 5, wherein the reference attitude (θ

*) is servo-controlled automatically to the current value (θ

) of the longitudinal attitude when a pilot operates a longitudinal cyclic flight control for controlling the cyclic pitch of the blades of the rotary wing so as to modify the longitudinal attitude.

7. A method according to claim 5, wherein the reference longitudinal attitude is kept constant when a pilot operates a longitudinal cyclic flight control so as to modify the longitudinal attitude.

8. A method according to claim 1, wherein the reference angle of attack (α

*) is bounded.

9. A method according to claim 1, wherein a first symbol representing a reference air speed vector is displayed on an artificial horizon so that a pilot can visualize a reference air-path slope and consequently the reference angle of attack.

10. A method according to claim 9, wherein a second symbol representing a reference longitudinal attitude (θ

*) is displayed on said artificial horizon.

11. A method according to claim 9, wherein a third symbol representing a current air speed vector is displayed on said artificial horizon.

12. A method according to claim 9, wherein a fourth symbol representing a current ground speed vector is displayed on said artificial horizon.

13. A method according to claim 9, wherein with at least one symbol being displayed on an artificial horizon to illustrate the reference angle of attack, the color of said symbol is modified whenever automatic control of the collective pitch of said blades in order to maintain said reference angle of attack requires power greater than a threshold power, and the reference angle of attack (α

*) is modified automatically in order to comply with said threshold power.

14. An autopilot device for automatically piloting a rotary wing aircraft, said aircraft having at least one propulsion propeller, said rotary wing comprising at least one rotor with a plurality of blades, said device comprising a processor unit co-operating with at least one collective control system for controlling the collective pitch of said blades, wherein the device includes engagement means connected to the processor unit for engaging an assisted mode of piloting for maintaining an angle of attack, said processor unit automatically controlling the collective pitch of the blades when the assisted mode of piloting for maintaining an angle of attack is engaged by controlling said collective control system to maintain an aerodynamic angle of attack (α

) of the aircraft at a reference angle of attack (α

*).

15. A device according to claim 14, wherein the processor unit automatically controlling the collective pitch of said blades for controlling a vertical air speed of the aircraft in such a manner as to maintain the aerodynamic angle of attack of the aircraft equal to a reference angle of attack is in compliance with the following relationship:

α

*=θ

−

arcsin(VZ/TAS)

where “

VZ”

represents the vertical air speed of the aircraft, “

TAS”

represents a true air speed of the aircraft, “

θ

”

represents a current longitudinal attitude of the aircraft, and “

α

*”

represents the reference angle of attack, said device comprises a set of means connected to the processor unit in order to determine the vertical air speed of the aircraft, the true air speed of the aircraft, and the current longitudinal attitude.

16. A device according to claim 14, including adjustment means connected to the processor unit for adjusting the reference angle of attack.

17. A device according to claim 14, including an automatic system for maintaining a longitudinal attitude of the aircraft equal to a reference attitude, said automatic system co-operating with at least one longitudinal cyclic control system for controlling the cyclic pitch of the blades of the rotary wing.

18. A device according to claim 14, including a display connected to the processor unit to display at least one symbol illustrating the reference angle of attack.

19. A rotary wing aircraft including at least one propulsion propeller, wherein the aircraft includes an autopilot device according to claim 14.