Taxi brake inhibit system
A taxi brake inhibit system overcomes problems of discontinuities in pedal “feel” that can occur by use of a taxi brake inhibit system, by adding a new pedal “feel” logic in which twice the brake force is commanded for a given brake pedal application when taxi brake inhibit is active. The taxi brake inhibit system relies upon two different brake force vs. brake pedal application curves to compensate for the difference in deceleration that is achieved for a given brake pedal application depending upon whether the taxi brake inhibit is active or inactive. Such system effectively eliminates undesirable deceleration bumps, yaw effects and changes in pedal feel during braking. The taxi brake inhibit feature is also shut off to both fore-aft brake pairs if any non-normal taxi brake inhibit condition exists on either fore-aft brake pair.
1. A system for controlling a taxi brake inhibit mode of operation of an aircraft brake system, the aircraft brake system including at least one landing gear, each of said at least one landing gear including a forward pair of wheel brakes and an aft pair of wheel brakes, at least some of said wheel brakes being deactivated from braking notwithstanding a brake pedal command for a commanded braking force during said taxi brake inhibit mode, the system comprising:
at least one electronic brake actuation controller operatively connected to said at least one landing gear and configured to control the operation of said forward and aft pairs of wheel brakes of said at least one landing gear, said at least one electronic brake actuation controller being operative to generate a status message indicating non-normal operation of said at least one electronic brake actuation controller; and
a brake system control unit operative to receive a brake pedal command for a commanded braking force, said brake system control unit being connected to said at least one electronic brake actuation controller and operative to control said at least one electronic brake actuation controller to generate a braking force greater than the commanded braking force of the brake pedal command, said brake system control unit being connected to said at least one electronic brake actuation controller to receive said status message indicating non-normal operation of said at least one electronic brake actuation controller.
2. The system of claim 1 , wherein half of said wheel brakes are deactivated during said taxi brake inhibit mode, and said brake system control unit is operative to control said at least one electronic brake actuation controller to generate twice the commanded braking force of the brake pedal command during said taxi brake inhibit mode.
3. The system of claim 1 , wherein said brake system control unit is operative to shut off taxi brake inhibit mode to said forward and aft pairs of wheel brakes of said at least one landing gear responsive to said status message indicating non-normal operation of said at least one electronic brake actuation controller.
4. A method for controlling a taxi brake inhibit mode of operation of an aircraft brake system, the aircraft brake system including at least one landing gear, each of said at least one landing gear including a forward pair of wheel brakes and an aft pair of wheel brakes, at least some of said wheel brakes being deactivated from braking notwithstanding a brake pedal command for a commanded braking force during said taxi brake inhibit mode, the method comprising:
generating a brake pedal command for a commanded braking force for a forward pair of wheel brakes and an aft pair of wheel brakes of at least one landing gear; and
receiving said brake pedal command; and
generating a commanded braking force according to a first pedal command vs. brake force curve when the taxi brake inhibit mode is inactive, and controlling actuation of said forward pair of wheel brakes and said aft pair of wheel brakes to generate a commanded braking force greater than the brake pedal command during said taxi brake inhibit mode according to a second pedal command vs. brake force curve, and transitioning from the first pedal command vs. brake force curve to the second pedal command vs. brake force curve when the wheel brakes are not applied to compensate for at least some of said wheel brakes being deactivated during said taxi brake inhibit mode responsive to said brake pedal command.
5. The method of claim 4 , wherein said second pedal command vs. brake force curve applies twice the brake force for a given brake pedal application.
6. The method of claim 4 , wherein said step of controlling actuation of said forward pair of wheel brakes and said aft pair of wheel brakes comprises transitioning from the second pedal command vs. brake force curve to the first pedal command vs. brake force curve via a transfer function tuned to minimize a change in overall brake force while active brakes are reducing their brake force at the same time the inhibited brakes are applying.
7. The method of claim 4 , wherein said step of controlling actuation of said forward pair of wheel brakes and said aft pair of wheel brakes comprises transitioning from the second pedal command vs. brake force curve to the first pedal command vs. brake force curve via a time delay that approximates a delay with which the deactivated brakes reapply.
8. The method of claim 7 , wherein said delay is approximately 0.3 seconds.
9. The method of claim 4 , wherein half of said wheel brakes are deactivated during said taxi brake inhibit mode, and said step of controlling actuation of said forward pair of wheel brakes and said aft pair of wheel brakes comprises controlling actuation of said forward pair of wheel brakes and said aft pair of wheel brakes to generate twice the commanded braking force of the brake pedal command during said taxi brake inhibit mode.
10. A method for controlling a taxi brake inhibit mode of operation of an aircraft brake system, the aircraft brake system including at least one landing gear, each of said at least one landing gear including a forward pair of wheel brakes and an aft pair of wheel brakes, at least some of said wheel brakes being deactivated from braking notwithstanding a brake pedal command for a commanded braking force during said taxi brake inhibit mode, the method comprising:
generating a brake pedal command for a commanded braking force for a forward pair of wheel brakes and an aft pair of wheel brakes of at least one landing gear; and
receiving said brake pedal command; and
controlling actuation of said forward pair of wheel brakes and said aft pair of wheel brakes of said at least one landing gear to generate a braking force greater than the commanded braking force of the brake pedal command to compensate for at least some of said wheel brakes being deactivated during said taxi brake inhibit mode responsive to said brake pedal command;
generating a status message indicating non-normal operation of actuation of said forward pair of wheel brakes and said aft pair of wheel brakes of said at least one landing gear;
receiving said status message indicating non-normal operation; and
shutting off taxi brake inhibit mode to said forward and aft pairs of wheel brakes of said at least one landing gear responsive to said status message indicating non-normal operation.