Overview
The function of the aileron trim is to decrease the aerodynamic load on the pilot's/copilot's control wheel during flight.
The flight crew set the necessary lateral trim of the aircraft with a switch on each of the two control wheels. An electrical signal from the switch operates a trim actuator. The trim actuator moves a trim tab in the left aileron control surface. There is also a balance tab at the outboard trailing edge of each aileron. The function of these balance tabs is to move in the opposite direction as the ailerons. This will help the pilot to adjust against the aerodynamic force on the ailerons.
Pitch/Roll Trim Switch
The location of the two trim switches is on the outboard handles of the pilot's and the copilot's control wheels. The pitch trim and arm functions are controlled by the same switch. Each trim switch contains a split-pole, four-throw toggle button (two directions for roll trim and two directions for pitch trim). A pushbutton in the center of the switch is pushed to arm the trim control.
Aileron Trim Actuator
The rotary trim actuator is installed in the leading edge of the left aileron. The body of the actuator is attached to the aileron structure and the output shaft connects to the trim tab through bell cranks and push rods.
Aileron Trim Tab
The aileron trim tab on the inboard, trailing edge of the left aileron can move 20 degrees away from its neutral position in each direction. Mechanical stops are installed in the trim actuator to limit the movement of the tab.
02/02/16
System Operation
Aileron trim control is given to the pilot in command through a trim tab on the left aileron. The pilot or copilot operates a trim switch on the applicable control wheel. An electro-mechanical actuator in the left aileron moves the trim tab.
Two rotary variable differential transducers (RVDTs) internal to the aileron trim actuator provide the surface indications. The RVDTs signals are processed by the data control units (DCUs) and transmitted to the EICAS primary page which shows the amount of trim set by the pilot. The aileron trim indication is in the upper, center area of the display and it has the legend AIL. There are two arcs with a line pointer between them. The legends LWD or RWD are shown when the aileron trim is set to a left wing down or a right wing down position.
The CONFIG AILERON TRIM warning message will show when the aircraft is on the ground for 30 seconds and the aileron trim is not correctly configured for take-off.
The EICAS message that follows is related to the aileron trim system:
| EICAS MESSAGE(S) | LEVEL (COLOR) |
|---|---|
| CONFIG AILERON TRIM | WARNING (red) |
