SYSTEM OPERATION
General
The reverser levers control the deployment
and stow cycles through the ECUs (electronic
control unit) on each engine. The left and right
controls are totally independent; therefore,
for simplification, the following description
of the system operation will be for one engine,
although normally both thrust reversers are de-
ployed and stowed simultaneously and the se-
quence is identical.
Arming
When the thrust lever is at idle and both squat
switches indicate weight on wheels, the sys-
tem is automatically armed. At this point, the
isolation valve (one for each engine) is ener-
gized open by the ECU providing hydraulic
pressure to the control valve. When the iso-
lation valve opens, hydraulic pressure will
trip a pressure switch causing the white REV
annunciator to illuminate above the N1 indi-
cator. If pressure is detected at the output port
of the isolation valve and the airplane is air-
borne, or if the corresponding thrust lever is
above approximately 82% and the airplane is
on the ground, the color of the REV annunci-
ator will be amber (Figure 7-27).
Deploy
When the thrust reverser lever is raised to the
idle deploy position (hard stop provided by the
throttle balk solenoid), the ECU will command
the thrust reverser hydraulic control valve to
reposition. It will first send hydraulic pressure
to the stow side of the primary actuators (one
on each side of the engine) to cause what is re-
ferred to as an “overstow”. This is necessary be-
fore the door hooks can be released. After
overstow has occurred and the unlatch switches
indicate the latches have been released, the
ECU will command the control valve to the
deploy position and send a signal to the DEEC
to activate the reverse thrust limit schedule.
Signals from the unlock switches will cause the
amber UNL annunciator to display on the
EICAS until the doors are fully deployed. When
the doors are fully deployed, a deployed switch
(Figure 7-25) will cause the UNL annunciator
to extinguish and a green DEP annunciator to
illuminate. The thrust reverser doors should
fully deploy within 1 second.
Reverse Thrust
When the deployed signal is received by the
ECU, it energizes a throttle balk solenoid in
the throttle quadrant which allows the pilot to
pull the thrust reverser levers aft of the idle de-
ploy position. The throttle balk solenoids for
each engine are independent, and one can re-
lease without the other releasing. This allows
single engine reversing. If the pilot is apply-
ing too much aft pressure on the reverser levers
when the throttle balk solenoids are energized,
they may not release.
The amount of reverse thrust applied is de-
pendent on the amount of aft rotation of the
piggy-back reverser levers. The DEEC will
limit the maximum engine rpm at the full aft
position of the thrust reverse levers based upon
airplane airspeed (Figure 7-29). At touchdown
speeds of 110 to 130 KIAS, the DEEC will
limit N1 to approximately 82% of rated take-
off N1, and decreasing to approximately 65%
of rated takeoff N1 at 80 KIAS. If the reverser
levers are held in the full aft position as the air-
plane decelerates, the DEEC will decrease the
engine rpm to maintain the schedule down to
60% of rated takeoff N1 by 30 KIAS. However,
the
AFM
limits the use of maximum reverse
thrust to speeds of 40 KIAS and above. If op-
erating the engines in the MANual mode, or
when the DEEC’s are off, thrust reversers must
be limited to idle reverse.
At 40 KIAS, the reverser levers should be
smoothly moved forward toward the idle de-
ploy position. Use of maximum reverse power
below 40 KIAS could cause reingestion of ex-
haust gases or possible foreign object damage.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
7-37
FOR TRAINING PURPOSES ONLY
FlightSafety
international