• Antiskid (25 model)
• Nose steering
• Stall warning test inhibit (Century III
wing)
• Takeoff trim light
SNs 24-210 through 24-357 and SNs
25-046 through 25-373
Left Switch
• Gear sequencing
• Thrust reverser
• Antiskid (25 model)
• Takeoff trim light
• Stall warning test inhibit (Century III
wing)
• Squat switch relay box to ground
Right Switch
• Gear sequencing
• Thrust reverser
• Antiskid (25 model)
• Stabilizer heat
• Stall warning test inhibit (Century III
wing)
• Squat switch relay box to ground
• Takeoff trim light
Individual Squat Switch Functions
Gear—Both squat switches must be in the air
position to allow gear retraction.
Stabilizer heat—Horizontal stabilizer heat is dis-
abled on ground.
Takeoff trim—Takeoff trim light is disabled
in flight.
Thrust reverser—Thrust reverser deployment in
flight is disabled.
Stall test inhibit—Stall warning testing flight on
aircraft with Century III wing disabled.
Antiskid—On model 25 aircraft, antiskid system
prevents brake application in flight.
Squat Switch Relay Box
Functions
• Nose steering
• Pressurization
• Windshield overheat lights
• Inlet heater light
• Hourmeter
Relay Panel Functions
Windshield overheat—Overheat light is con-
trolled by low-limit thermoswitch on ground.
Nosewheel steering—Nose steering is disabled
in flight.
Inlet heater light—Inlet heater light is disabled
in flight.
Cabin pressure—Cabin pressurization on ground
is prevented.
NOTE
If power is lost to panel or relays
do not find a ground, systems fail to
air mode.
OPERATION
Landing gear operation is controlled and
sequenced by microswitches wired in series. The
system incorporates two solenoid-operated
hydraulic control valves—one for operation of the
main gear doors and one for gear operation. Both
main gear doors must be fully open before gear
can be extended or retracted.
The gear door control valve is energized to the
door-open position when the landing gear
selector switch is placed in either the GEAR UP
14-6
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international