Concorde Trim Control
Electric trim is provided for both manual and autopilot control. The system trims stick and, hence, elevon position to ensure that long-term forces are not held on the stick.
On Concorde, which has no trimming tail-plane, elevon-to-trim is ultimately removed by means of the fuel-transfer facility, thus minimising drag throughout the flight envelope.
The electric trim system also reduces the transients which occur when the autopilot is disengaged and has a failsafe auto-changeover facility
On each of the three axes (Roll, Pitch and Yaw), there is a mechanical trim control which can cancel out the loads provided by the artificial feel system by displacing the neutral position of the flight controls.
The pitch axis alone is controlled electrically (electric trim) enabling it to take the place of the mechanical trim and also carrying into effect the following functions:
Auto trim (in the Auto Pilot mode)
The trim control wheel is mounted on the centre console in the flight compartment, between the Captain and First Officer.
The number of turns of the control wheel is limited by a system of dog washers which engage one on the other for each turn of the wheel, the last washer forming the stop.
A graduated drum moves past a fixed index and indicates the elevon deflection value corresponding to a new neutral point of the artificial feel.
The control wheel transmission system is composed of universal joints, pinions, angle gearbox and chains.
The housing is articulated on the chassis of the artificial feel system and is equipped with a worm screw driven by the transmission system.
One end of the input lever has a toothed sector meshing with the worm screw. The other end has pivot points for attaching the roll mechanical control rods.
The housing is in the form of crank the two arms of which are linked to the artificial feel, (spring rod and jacks).
Rotating the trim control wheel causes the worm screw to rotate and give relative movement to the unit with respect to the input lever. The trim control offers two possibilities:
The displacement of the roll control neutral point and the cancellation of the reaction of the artificial feel system,
Elevon deflection in roll mode, this method of operation is used only in extreme emergences. The inertia and friction of the roll control being inferior to the artificial feel threshold, the trim operation alone causes displacement of the controls without causing an artificial feel reaction.