Leerjet 35/36 Developed for Training Purposes 4L-7
February 1998
Thrust Reversers
Aeronca TFE731
With the NORM/EMER STOW switch in NORM, aircraft weight
on the wheels, and the throttle levers in IDLE, the thrust
reverser system arms and is ready for deployment.
Placing the reverse thrust levers in the idle position releases
interlocks; this allows the crew to lift the levers up and aft to
complete a circuit through the idle arming switches in the throt-
tle quadrant to the deploy side of the reverser control relay.
The control relay then routes DC power to the pneumatic latch
control, directional control, and air-on valves. The latch control
valve opens; bleed air pressure then actuates the pneumatic
latches to the open position. The UNLOCK lights illuminate.
Bleed air flows to the pneumatic actuator through the open
directional control valve. The pneumatic actuator operates and
drives the pinon gearboxes through a flexible drive shaft. The
pinon gearboxes then move the translating structure aft. The
reverser begins deploying. When the translating structure
reaches the full deployed position, sequence latches disen-
gage from the gear racks. The gear racks travel within the
beam assemblies and are driven 5.5 inches farther aft. The
gear racks actuate the blocker doors to the closed position
through yoke assemblies.
A nulling cable, attached to the outboard gearbox, mechani-
cally repositions the pneumatic actuator and shuts bleed air off
to the system. Once the thrust reversers are fully deployed, the
deploy limit switches actuate and complete an electrical circuit
to release the throttle release solenoid, extinguish the
UNLOCKED annunciator, and illuminate the DEPLOY annunci-
ator.
A pressure switch in the thrust reverser is actuated when
engine bleed air reaches 50 PSIAduring reverse thrust applica-
tion. The BLEED VALVE annunciators illuminate. The
DEPLOY and BLEED VALVE annunciators remain illuminated
until the thrust reversers are commanded to stow.
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