an ANN circuit breaker, also one on each side,
provides power to the ECU circuits that relay
system status to the EICAS. The L/R RE-
VERSER DEPLOY, STOW, and ANN circuit
breakers are located in the engine group of cir-
cuit breakers on the left and right circuit
breaker panels respectively.
Actuators
Each engine is equipped with two primary
thrust reverser actuators, one on the inboard
side of the engine and one outboard (Figure 7-
25). These actuators position the doors to the
extend or stow position.
A hydraulic actuator is attached to each set of
latch hooks. Hydraulic pressure is routed to
these actuators to unlatch the hooks before
the doors can move to the deployed position.
A throttle retard actuator, located on the en-
gine, is attached to a lever arm which meets
with a lever arm on the FCU when the throt-
tle retard actuator is operated. Hydraulic pres-
sure to this actuator will cause the thrust lever
to be rapidly pulled back to the idle position
if not already there. This “throttle snatch”
will occur anytime stow (normal or auto) is
commanded by the ECU and the thrust lever
is not at the idle position.
Isolation Valve
Each thrust reverser system has an isolation
valve as a safety feature. It is a solenoid con-
trolled valve which isolates hydraulic system
pressure from the thrust reverser control valve
unless an armed condition exists. When the iso-
lation valve is opened, a pressure switch on the
outlet side of the valve provides a discrete
signal to indicate the thrust reverser is armed
(white “REV” annunciator on EICAS, as il-
lustrated in Figure 7-8). If the ENG FIRE
switch is depressed (firewall shutoff valve
CLOSED), the corresponding isolation valve
cannot be powered unless the corresponding
FWSOV circuit breaker is pulled out.
Control Valve
The control valve or hydraulic control unit
(HCU), located on the engine, is electrically
controlled through solenoids powered by the
ECU to route hydraulic pressure to the un-
latch actuators and to the deploy or stow side
of the primary actuators. Whenever the con-
trol valve is positioned to the stow position,
hydraulic pressure is also sent to the throttle
retard actuator (Figure 7-28).
Latches (Hooks)
Two pair of spring-loaded latches (one pair on
each side of each engine) secure the thrust re-
verser doors in the stowed position (Figures
7-25 and 7-26). Each hook engages a recep-
tacle on the forward corner of the doors. The
door receptacles have a lip on them that pre-
vent the hooks from releasing until the doors
are retracted a small amount. This is referred
to as “overstow.” For the normal deploy se-
quence an overstow is commanded first, then
the unlatch actuator causes the hooks to retract.
When the unlatch actuator moves, it trips an
associated unlatch switch that signals the ECU
to continue the deploy sequence (Figure 7-
26). When the hooks retract, they trip an un-
lock switch. These switch signals are used in
the normal deploy/stow sequence and are also
used to indicate an uncommanded unlock.
Indications
Thrust reverser status will be displayed as il-
lustrated in Figure 7-27. Both left and right
ECUs will send signals through the DAUs and
IC-600 symbol generators to the EICAS, re-
porting the status of that engine’s thrust re-
verser system. The appropriate color coded
thrust reverser annunciator is displayed above
the N1 digital display for each engine. A table
listing the annunciators and the color change
logic is included in Figure 7-27. Also shown
are CAS messages that will be presented with
certain thrust reverser malfunctions.
The CWP contains red L and R REV UNSAFE
annunciators which will illuminate in con-
junction with a red UNL or DEP annunciator
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
7-35
FOR TRAINING PURPOSES ONLY
FlightSafety
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