Aeronautics and astronautics – Aircraft control
Reexamination Certificate
1999-09-14
2001-06-05
Jordan, Charles T. (Department: 3644)
Aeronautics and astronautics
Aircraft control
Reexamination Certificate
active
06241183
ABSTRACT:
DESCRIPTION
1. Technical Domain
This invention relates to a control process for aircraft control surfaces to prevent lateral deviation of the trajectory on the ground.
2. State of Prior Art
Some actions, for example cross wind, engine failure, thrust reverser failure, etc., may cause lateral deviation of the trajectory of an aircraft on the ground.
Thus French patent No. 2 694 738 describes a control process for aircraft control surfaces to compensate for lateral deviation of the trajectory at low speed during a take-off phase.
However, this invention relates to a landing phase or an interrupted take-off phase.
When the aircraft is on the runway during a landing phase, one of the pilot's objectives is to stop the aircraft while keeping it on the runway. Considering the stability of the moving aircraft, the cross wind component is a disturbance that tends to move the aircraft away from the required trajectory. The pilot can control this trajectory by acting on:
aerodynamic forces;
and/or driving forces;
and/or ground reaction forces.
Aerodynamic Forces
The aircraft speed creates aerodynamic lift. Thus if the speed is not zero, only part of the weight of the aircraft is supported by the landing gear.
The aircraft drag creates a force that tends to slow the aircraft.
The purpose of ground spoilers is to significantly reduce the wing lift and to “push” the aircraft down onto the ground, which increases the braking efficiency. They also increase the drag coefficient Cx of the aircraft and participate in deceleration.
The cross wind generates a yaw torque proportional to the aerodynamic sideslip. This torque tends to move the aircraft away from the runway center line. “The aircraft wants to turn into the wind”. The aerodynamic sideslip increases as the aircraft decelerates. The cross wind also generates a lateral force.
The rudder generates a yaw torque that helps to resist the torque due to the cross wind. It also generates a lateral force.
The cross wind also generates a roll torque that causes an asymmetric distribution of the forces supported by the main sets of landing gear. The ailerons or roll surfaces (spoilers) and the rudder also generate a roll torque.
The main effect of the pitch control surfaces (elevators) is to modify the load supported by the nose landing gear.
A yaw movement also generates a yaw torque which resists the movement.
Driving Forces
The use of thrust reversers contributes to deceleration of the aircraft. They generate a torque which modifies the load supported by the nose landing gear. Furthermore, they increase the stability of the aircraft during motion and can reduce the efficiency of the ground spoilers.
Asymmetric use of the engine thrust (in direct or inverse jet) can generate a yaw torque.
Ground Reaction Forces
The main landing gear sets, the central landing gear and the nose landing gear support all or some of the weight of the aircraft.
The position of the landing gear naturally has a stabilizing effect on the trajectory, secondly running friction tends to slow the aircraft.
The aircraft deceleration may be increased by action on the brakes. The antiskid system ensures that maximum grip capacity on the ground is achieved by producing a tangential force directly proportional to the vertical load supported by each landing gear. The maximum braking force that can be applied through the tires increases as the vertical load supported by the landing gear increases.
If the vertical loads supported by the main left and right landing gear sets are unequal, symmetric action on the brakes will create a braking force, and also a yaw torque.
The authority of the nose landing gear varies as a function of the speed, and can generate a yaw torque (by action on the pedals or the tiller). This nose landing gear will be more efficient as the vertical load supported by it increases.
Thus, the lateral trajectory of an aircraft on the ground is now controlled by:
the rudder;
the nose landing gear;
differential braking;
more rarely, asymmetric thrust.
The purpose of the invention is a process for using the ailerons and spoilers to control this lateral trajectory.
DESCRIPTION OF THE INVENTION
This invention relates to a process for controlling the control surfaces of an aircraft to resist lateral deviation of the trajectory on the ground when landing or during an interrupted take-off, in which the rudder is turned to resist this deviation, and all spoilers are extended to increase the pressure of the aircraft on the ground, characterized in that the spoilers are extended asymmetrically, by retracting at least one of the spoilers on the wing opposite the side towards which the rudder is turned.
In one embodiment of the invention, these spoilers are retracted following an order from the rudder pedal. Advantageously, these spoilers are retracted when the rudder pedal is turned by more than 20°.
These spoilers may advantageously be retracted progressively; for example, none of these spoilers will be retracted if the rudder pedal is turned by less than 20°, and all these spoilers will be retracted if the rudder pedal is turned by more than 28°.
The action of the rudder pedal on the spoilers may be a function of the aircraft speed. Thus, the pedals will have no effect on the spoilers if the aircraft speed exceeds 110 knots; the pedals may have an effect on the spoilers at a speed of less than 100 knots, and the spoilers are retracted progressively between these two speeds.
REFERENCES:
patent: 4143839 (1979-03-01), Antonov et al.
patent: 4744532 (1988-05-01), Ziegler et al.
patent: 5127608 (1992-07-01), Farineau et al.
patent: 5375793 (1994-12-01), Rivron et al.
patent: 2694738 (1994-02-01), None
Patent Abstracts of Japan vol. 016, No. 270 (M-1266), 17 Juin 1992 & JP 04 066394 A, (Mitsubishi Heavy Ind Ltd), 2 mars 1992.
Aerospatiale Societe Nationale Industriele
Burns Doane , Swecker, Mathis LLP
Jordan Charles T.
Palo Francis T.
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