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FIRE EXTINGUISHER DISCHARGE INDICATORS
Two disk-type indicators are flush-mounted in the fuselage under the
left engine pylon. If the contents of either or both containers have been
discharged into the engine nacelles, the yellow disk will be ruptured . If
the contents of either or both containers have been discharged overboard
as the result of an overheat condition causing excessive pressure
within the containers, the red disk will be ruptured. If both disks are intact,
the system has not been discharged. The indicators are readily
available for visual inspection .
2-14
PM-121
Change 3
Learjet 31A
Piloes Manual
24290
FIRE EXTINGUISHING SYSTEM
Figure 2-3
PM-121
2-15
Original
Pilot's Manual
Learjet 31A
THRUST REVERSERS (OPTIONAL)
Each engine may be equipped with an independent, electrically controlled,
hydraulically actuated, clamshell-type thrust reverser. The
thrust reverser system consists of an engine nacelle afterbody installation
on each engine, a control panel above the glareshield annunciator
panel, reverse thrust levers on the main thrust levers, associated hydraulic
plumbing, and associated electrical wiring . Each nacelle afterbody
installation consists of an upper and lower blocker door, a door
actuator, a door deployed switch, inboard and outboard latch mechanisms,
latch position switches, and a throttle retard mechanism. Hydraulic
power for thrust reverser operation is supplied by the aircraft
hydraulic system ; however, a precharged (900-1000 psi [6205-6895
kPa]) hydraulic accumulator and a check valve in the thrust reverser
system provide sufficient hydraulic pressure for one deploy and stow
cycle in the event the aircraft hydraulic system malfunctions.Aselector
valve for each thrust reverser is installed in the tailcone. The selector
valves control hydraulic flow to the associated system actuators in response
to electrical inputs from the associated thrust reverser lever and
position switches. Electrical power for thrust reverser control and indication
circuits is 28 VDC supplied through the 3-amp Land R TR PWR
and the 2-amp Land RTR CONT circuit breakers on the pilot's and copilot's
circuit breaker panels respectively.
In order to armthe thrust reversers, the aircraft squat switches must be
in the ground mode (aircraft weight on the main gear), the main thrust
levers must be in the IDLE position, andARMmust be selected on the
control panel. Once armed, the thrust reversers maybe deployed and
stowed by operating the reverse thrust levers . When the deploy cycle is
initiated, hydraulic pressure is applied to the stow side of the door actuators
which move the doors into an overstowed condition. Overstowing
the thrust reversers allows the latch actuators to release the
latches. After the latches release, hydraulic pressure is applied to the
deploy side of the door actuators which push the doors open. When
stow is selected, hydraulic pressure is applied to the stow side of the
door actuators and the doors move towards the overstow position. As
the doors reach overstow, the spring-loaded latches close. When the
latches close, the latch position switches signal the selector valve to release
the stow pressure on the door actuator. Exhaust gas pressure and
springs return the doors to the normal stowed position .
2-16
PM-121
Change 3
Learjet 31A
Pilot's Manual
Each thrust reverser system incorporates an automatic emergency stow
feature which will automatically stow the thrust reverser in the event
the associated doors become partially unlatched or deployed. When
deploy has not been selected and two latch position switches on the
same side (inboard or outboard) detect an unlatched condition, the
thrust reverser system will arm itself, retard engine thrust to idle, and
initiate thrust reverser stow. The associated ARM annunciator will illuminate
to indicate the system has self armed. The associated DEPLOY
annunciator will flash to indicate automatic emergency stow has been
activated. The affected engine's thrust lever will go to the IDLE position.
The hydraulic stow pressure will continue until at least one of the
two latches returns to the latched position or power is removed from
the reverser circuits.
An automatic throttle retard mechanism is installed on each thrust reverser
to ensure that thrust reverser stow and deploy does not occur
with an engine thrust setting above idle. The throttle retard mechanism
consists of an actuator, crank, and lever. Whenever hydraulic stow
pressure is applied to the thrust reverser actuators, the throttle retard
mechanism will position the engine fuel control input shaft to idle.
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