THRUST REVERSER
SYSTEM
GENERAL
The thrust reverser system is installed as stan-
dard equipment on the Learjet 45. The thrust
reversers are electrically controlled and hy-
draulically actuated target type thrust reversers
(Figure 7-24) which operate independently of
each other. When the thrust reverser doors are
deployed, engine exhaust is deflected in a for-
ward direction.
Major system components consist of upper
and lower clam shell shaped doors, located on
the nacelle afterbody of each engine. The re-
verser doors are equipped with hydraulic ac-
tuators and associated linkages that position
the doors upon command to either stow or de-
ploy positions.
Mechanical latches hold the reverser doors in
the stowed position until released by unlatch
actuators.
Thrust reverser operation is controlled through
the thrust reverser levers, piggy-back mounted
to the thrust levers. Indications of thrust re-
verser operation (normal and abnormal) are
presented in the engine field on the EICAS and
through CAS messages. There is no dedicated
control or indicator panel for the thrust re-
versers.
When the thrust reversers are deployed and the
levers are pulled to the full aft position, the
DEECs will limit engine rpm (N1) to a sched-
ule based upon the airplane’s airspeed (Figure
7-29).
Hydraulic pressure is provided from the main
hydraulic system for operation of the thrust re-
verser unlatch actuators and the primary ac-
tuators. Auxiliary hydraulic system pressure
is not provided to the thrust reversers and the
thrust reversers do not have a backup accu-
mulator dedicated to thrust reverser operation.
An automatic emergency stow system, which
includes an automatic throttle-retard feature,
is incorporated to provide protection against
inadvertent deployment.
Safety pins and flags are provided for secur-
ing the reverser doors in either the stowed or
deployed position for ground servicing or
safety.
COMPONENTS
Electronic Control Unit (ECU)
An ECU for each thrust reverser is located in
the tailcone of the airplane. The ECUs inte-
grate all deploy and normal stow, auto-stow,
and annunciation functions of the thrust re-
verser system through logic circuits. Each of
the logic circuits is initiated with a combina-
tion of switches and relays. These logic cir-
cuits are all powered through separate circuit
breakers.
DEPLOY circuit breakers provide DC power
to the deploy circuits in each ECU. A STOW
circuit breaker on each side provides power for
the normal stow and auto-stow function, and
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
7-33
FOR TRAINING PURPOSES ONLY
FlightSafety
international
Figure 7-24. Thrust Reverser (Dee Howard
TR 5045)
