Method and a device for issuing terrain avoidance warnings for a rotary wing aircraft

• US 9,199,744 B2
• Filed: 07/09/2014
• Issued: 12/01/2015
• Est. Priority Date: 07/10/2013
• Status: Active Grant

• Current Assignee: Airbus Helicopters
• Original Assignee: Airbus Helicopters
• Inventors: Petillon, Jean-Paul
• Primary Examiner(s): Trammell, James
• Assistant Examiner(s): Stroud, James E
• Application Number:
  US14/326,717
• Publication Number:
  US 20150266591A1
• Time in Patent Office: 510 Days
• US Class Current: 1/1
• CPC Class Codes: B64C 27/56 characterised by the control initiating means, e.g. manually actuated
• CPC Class Codes: B64C 27/57 automatic or condition responsive, e.g. responsive to rotor speed, torque or thrust
• CPC Class Codes: B64D 45/04 Landing aids; Safety measures to prevent collision with earth's surface
• CPC Class Codes: G08G 5/0086 for monitoring terrain radar or analogous systems specially adapted for terrain avoidance G01S13/935
• CPC Class Codes: G08G 5/045 Navigation or guidance aids, e.g. determination of anti-collision manoeuvers radar or analogous systems specially adapted for anti-collision between aircraft G01S13/933

Abstract

A method and a device (50) for issuing a terrain avoidance warning for a rotary wing aircraft (100) during which at least one bundle (N1, N2) of possible avoidance trajectories for said aircraft (100) is prepared in order to avoid a collision between said aircraft (100) and the relief (70) being overflown. A warning is then triggered as soon as said relief (70) being overflown is found to be at a distance from any one of said bundles (N1, N2) of possible avoidance trajectories that is less than a predetermined distance (Mv). Said avoidance trajectories are determined on the basis of a predetermined avoidance maneuver and on the basis of states of said aircraft (100), said predetermined avoidance maneuver being performed at a predetermined maximum power of said aircraft (100).

Claims

1. A method of issuing a terrain avoidance warning by a rotary wing aircraft, the method comprising the following steps performed repetitively:

preparing at least one bundle of possible avoidance trajectories for the aircraft in order to avoid said aircraft colliding with relief being overflown by said aircraft or with an obstacle if any; and

triggering a warning if any one of said bundles of possible avoidance trajectories leads to a distance from said relief being overflown or from said obstacle if any that is less than a predetermined distance;

wherein said possible avoidance trajectories are determined by a computer on the basis of a predetermined avoidance maneuver and on the basis of current states of said aircraft, said avoidance maneuver comprising;

a deceleration stage of deceleration down to a predetermined forward speed Va_final, said deceleration stage being obtained by said aircraft taking up a predetermined nose-up attitude and being performed at a predetermined maximum power of said aircraft; and

a final stage of said aircraft climbing, during which the forward speed of said aircraft is kept equal to said predetermined forward speed Va_final and the power from the engines is kept equal to said predetermined maximum power wherein said aircraft has a maximum continuous power and said predetermined maximum power of said aircraft is said maximum continuous power, and wherein said avoidance maneuver includes an initial stage of restoring said aircraft to straight line flight, which stage is performed before said deceleration stage.

2. A method according to claim 1, wherein said deceleration stage is performed with a cyclic stick of said aircraft so that during said deceleration stage, a portion of the kinetic energy of said aircraft is transformed into potential energy of said aircraft enabling a vertical speed Vv of said aircraft to be increased until said predetermined forward speed Va_final is reached.

3. A method according to claim 2, wherein said avoidance maneuver is performed with a collective stick of said aircraft so as to adjust the power developed by said aircraft to a value equal to said predetermined maximum power of said aircraft.

4. A method according to claim 1, wherein said distance between each bundle of possible avoidance trajectories and said relief being overflown or indeed said obstacle if any that is compared with said predetermined distance is along a direction that is vertical only.

5. A method according to claim 1, wherein said possible avoidance trajectories of each bundle constitute an envelope of fan shape over a first distance d1 with a radius of curvature R_e given by the relationship:

6. A method according to claim 1, wherein, in order to determine each avoidance trajectory of said aircraft, future states of said aircraft are determined on the basis of states of said aircraft during at least five seconds preceding the current state of flight of said aircraft.

7. A method according to claim 1, wherein a vertical speed Vv of said aircraft is determined by a formula:

8. A method according to claim 1, wherein said predetermined nose-up attitude of said aircraft is constant.

9. A method according to claim 8, wherein said predetermined nose-up attitude of said aircraft is 15°

relative to a horizontal plane.

10. A method according to claim 1, wherein said predetermined forward speed Va_final corresponds to a forward speed Vy producing an optimum speed for climbing.

11. A method according to claim 1, wherein each bundle of said possible avoidance trajectories corresponds to a predetermined assumed reaction time of a pilot for performing each avoidance trajectory of said bundle.

12. A method according to claim 11, wherein a first warning is triggered when said bundle of avoidance trajectories leads to a distance less than said predetermined distance from said relief or said obstacle if any that corresponds to an assumed pilot reaction time equal to 20 s, in order to inform the pilot of a risk of said collision.

13. A method according to claim 11, wherein a second warning is triggered when said bundle of avoidance trajectories leads to a distance that is less than said predetermined distance from said relief or from said obstacle if any that corresponds to an assumed pilot reaction time equal to 5 seconds, in order to warn the pilot of an imminent risk of said collision.

14. A method according to claim 1, wherein said avoidance trajectory does not include a resource stage at constant load factor and constant speed.

15. A method according to claim 1, wherein said aircraft has an autopilot and said avoidance trajectory is followed by said autopilot as soon as a warning is triggered.

16. A device for issuing a terrain warning and for installing on board an aircraft, said device comprising:

at least one computer suitable for performing a trajectory prediction algorithm;

at least a first database of the relief of flying zones of said aircraft connected to said computer; and

at least one warning means connected to said computer,

wherein said device is suitable for performing the method according to claim 1.

17. A rotary wing aircraft comprising:

at least a main rotor having a plurality of blades;

a cyclic stick controlling a cyclic pitch of said blades of said main rotor;

a collective stick controlling a collective pitch of said blades of said main rotor; and

a plurality of sensors providing information about atmospheric parameters concerning operation of said aircraft and about states of said aircraft;

wherein said aircraft includes a device according to claim 16.