The electric clutch must be engaged to couple
the servo to the elevator linkage for elevator
positioning. The clutch engages when any one
of the following switches are positioned on:
• L STALL WARNING
• R STALL WARNING
• Autopilot ENGAGE
With all three of the above switches in the off
position, the electric clutch is disengaged, dis-
connecting the servo from the elevators.
By exerting sufficient force on the control column
to slip the mechanical clutch, the pilot can over-
ride any undesirable servo inputs to the elevators.
Autopilot operation is described in Chapter 16,
“Avionics.”
AILERONS
Aileron control is provided manually by dual-
control wheels and automatically by the autopi-
lot. Balance tabs are installed on both ailerons to
decrease the force required at the control wheel.
An aileron trim tab is installed on the left
aileron, and an aileron-rudder interconnect
assists turn coordination.
Figure 15-5 shows the aileron control system.
Roll Servo
(Autopilot Function Only)
The ailerons can also be positioned by the
autopilot roll servo. The roll servo is similar to
the pitch servo but does not incorporate an elec-
tric clutch. A mechanical slip clutch allows the
pilot to override undesired roll servo inputs
when the autopilot is engaged.
Balance Tab
The balance tab on each aileron (Figure 15-4)
provides aerodynamic assistance in moving
the aileron, thus reducing control wheel forces.
The tab is attached with one pushrod on model
23 airplanes and with dual pushrods on all
other airplanes.
Trim Tab
The aileron trim tab is attached to the inboard
trailing edge of the left aileron (Figure 15-4).
The tab is positioned by either control wheel
trim switch. Aileron trim tab position is indicat-
ed by a trim indicator on the pedestal.
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
15-6
FOR TRAINING PURPOSES ONLY
AILERON
WING
BALANCE
TAB
TRIM TAB
Figure 15-4. Aileron Tabs