Method of automatically controlling a rotary wing aircraft having at least one propulsion propeller, an autopilot device, and an aircraft

Patent metadata

Field	Value
Publication number	US-10023306-B2
Application number	US-201213543957-A
Country	US
Kind code	B2
Filing date	Jul 9, 2012
Priority date	Jul 12, 2011
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

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*).

First claim

What is claimed is:

1. A method of automatically piloting a rotary wing aircraft having at least one propulsion propeller provided with a plurality of propulsion propeller blades configured to contribute to propulsion of the aircraft, a rotary wing independently operable from the propulsion propeller and having a main rotor provided with a plurality of main rotor blades, an adjustment mechanism having a servo-control arrangement configured to adjust pitch of the main rotor blades, a collective control system connected to the adjustment mechanism and configured to control a collective pitch of the main rotor blades via the adjustment mechanism, and a cyclic control system connected to the adjustment mechanism and configured to control a cyclic pitch of the main rotor blades via the adjustment mechanism, the method comprising:
operating by a pilot the propulsion propeller to adjust a longitudinal forward speed of the aircraft;
while the pilot is operating the propulsion propeller to adjust the longitudinal forward speed of the aircraft, automatically controlling, by a processor unit, (i) the collective control system to control the collective pitch of the main rotor blades so as to control a vertical air speed of the aircraft such that the main rotor blades have a collective pitch in which an aerodynamic angle of attack (α) of the aircraft is maintained equal to a reference angle of attack (α*) and automatically controlling, by the processor unit, (ii) the cyclic control system to control the cyclic pitch of the main rotor blades such that the main rotor blades have a cyclic pitch in which a longitudinal attitude (θ) of the aircraft is maintained at a reference longitudinal attitude (θ*);
operating by the pilot the cyclic control system to modify the cyclic pitch of the main rotor blades to adjust the longitudinal attitude (θ) of the aircraft;
while the pilot is operating the cyclic control system to adjust the longitudinal attitude (θ) of the aircraft, automatically controlling, by the processor unit, the collective control system to control the collective pitch of the main rotor blades to control the vertical air speed of the aircraft such that the main rotor blades have a collective pitch in which the aerodynamic angle of attack (α) of the aircraft is maintained equal to the reference angle of attack (α*) and servo-controlling automatically, by the processor unit, the reference longitudinal attitude (θ*) to a current value of the longitudinal attitude (θ) of the aircraft; and
wherein the longitudinal attitude (θ) of the aircraft is equal to the sum of the aerodynamic angle of attack (α) of the aircraft and an air-path slope of the aircraft, the air-path slope is dependent on the vertical air speed of the aircraft and a true air speed of the aircraft, and the true air speed of the aircraft is dependent on the longitudinal forward speed of the aircraft.

2. The method according to claim 1 , wherein the collective pitch of the main rotor blades is controlled automatically so as to control the vertical air speed of the aircraft in such a manner as to maintain the aerodynamic angle of attack (α) of the aircraft equal to the reference angle of attack (α*) by application of the following relationship:
α*=θ−arc sin(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. The method according to claim 1 , the method further comprising setting a value of the reference angle of attack (α*) to be equal to the current value of the aerodynamic angle of attack (α) of the aircraft at the moment that the longitudinal forward speed of the aircraft is adjusted by the pilot operating the propulsion propeller.

4. The method according to claim 1 , the method further comprising modifying a value of the reference angle of attack (α*) in flight.

5. The method according to claim 1 , wherein the reference angle of attack (α*) is bounded.

6. The method according to claim 1 , the method further comprising displaying a first symbol representing a reference air speed vector on an artificial horizon so that the pilot can visualize a reference air-path slope and consequently the reference angle of attack (α*).

7. The method according to claim 6 , the method further comprising displaying a second symbol representing a reference longitudinal attitude (θ*) on the artificial horizon.

8. The method according to claim 6 , the method further comprising displaying a third symbol representing a current air speed vector on the artificial horizon and displaying a fourth symbol representing a current ground speed vector on the artificial horizon.

9. The method according to claim 6 , wherein with at least one symbol being displayed on an artificial horizon to illustrate the reference angle of attack (α*), the color of the symbol is modified whenever automatic control of the collective pitch of the main rotor blades in order to maintain the reference angle of attack (α*) requires power greater than a threshold power, and the method further comprising modifying automatically the reference angle of attack (α*) in order to comply with the threshold power.

10. An autopilot device for automatically piloting a rotary wing aircraft having at least one propulsion propeller provided with a plurality of propulsion propeller blades configured to contribute to propulsion of the aircraft, a rotary wing independently operable from the propulsion propeller and having a main rotor with a plurality of main rotor blades, an adjustment mechanism having a servo-control arrangement configured to adjust pitch of the main rotor blades, a collective control system connected to the adjustment mechanism and configured to control a collective pitch of the main rotor blades via the adjustment mechanism, and a cyclic control system connected to the adjustment mechanism and configured to control a cyclic pitch of the main rotor blades via the adjustment mechanism, the device comprising:
a processor unit configured to automatically control the collective control system to control a collective pitch of the main rotor blades;
an automatic system configured to automatically control the cyclic control system to control a cyclic pitch of the main rotor blades;
wherein while a pilot is operating the propulsion propeller to adjust a longitudinal forward speed of the aircraft, the processor unit is configured to automatically control (i) the collective control system to control the collective pitch of the main rotor blades so as to control a vertical air speed of the aircraft such that the main rotor blades have a collective pitch in which an aerodynamic angle of attack (α) of the aircraft is maintained at a reference angle of attack (α*) and to automatically control (ii) the cyclic control system to control the cyclic pitch of the main rotor blades such that the main rotor blades have a cyclic pitch in which a longitudinal attitude (θ) of the aircraft is maintained at a reference longitudinal attitude (θ*);
wherein while the pilot is operating the cyclic control system to modify the cyclic pitch of the main rotor blades to adjust the longitudinal attitude (θ) of the aircraft, the processor unit is configured to automatically control the collective control system to control the collective pitch of the main rotor blades to control the vertical air speed of the aircraft such that the main rotor blades have a collective pitch in which the aerodynamic angle of attack (α) of the aircraft is maintained equal to the reference angle of attack (α*) and to servo-control automatically the reference longitudinal attitude (θ*) to a current value of th

Assignees

• Eglin Paul
• Airbus Helicopters

Inventors

• Eglin Paul

Classifications

• B64C27/22

  Compound rotorcraft, i.e. aircraft using in flight the features of both aeroplane and rotorcraft · CPC title

• G05D1/0858

  specially adapted for vertical take-off of aircraft · CPC title

• B64C27/57 Primary

  automatic or condition responsive, e.g. responsive to rotor speed, torque or thrust · CPC title

• B64D45/00

  Aircraft indicators or protectors not otherwise provided for · CPC title