Rudder Trim - BOMBARDIER LEARJET 40 Pilot's Manual

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Pilot's Manual

RUDDER TRIM

The rudder trim system provides manual rudder trim tab control. The

manual trim control system enables the pilot and copilot to eliminate

out-of trim forces which may be present in the rudder control circuit.

This enables the airplane to be flown without either pilot having to

apply a constant force to the rudder pedals.

Rudder trim changes are effected through an electronically driven rota-

ry actuator mounted in the rudder and connected to the rudder trim tab

with dual pushrods. The actuator is controlled manually by a double-

pole, double-throw, center-off, momentary-action, rotary switch locat-

ed on the trim switch panel (Figure 5-4) in the center pedestal. This

switch is constructed in two sections with poles that are not mechani-

cally linked. One pole of the switch is used to provide control of the

rudder trim ARM circuit and is referred to as the ARM switch. The oth-

er pole of this switch is used to provide either nose left or nose right

trim commands and is called the rudder trim switch. These poles are in-

dependent of each other except of the fact that they are both rotated by

the same shaft. The failure of one pole will not affect the other. Since one

pole provides ARM control and the other provides the trim command

inputs, the failure of one pole will not result in a trim runaway. Setting

and holding the switch to the NOSE LEFT or NOSE RIGHT position en-

ergizes the trim tab actuator, resulting in the rudder rotating either

clockwise or counterclockwise. A trim tab position sensor is attached to

the rotary actuator shaft and provides input via the #2 data acquisition

unit for display of rudder trim position on the cockpit engine indicating

and crew alerting system.

Electrical power for rudder trim is provided from the R ESS BUS and

protected by TRIM-RUD 5-amp circuit breaker located on the copilot's

circuit breaker panel (FLIGHT group). Rudder trim can be stopped by

depressing and holding either control wheel master switch.

5-22

PM-132A

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