737 MAX Flight Crew Operations Manual
Engines, APU -
Engine System Description
7.20.12
MN-FLT-OH-201
Thrust Reverser
Each engine is equipped with a hydraulically operated thrust reverser, consisting
of left and right translating sleeves. Aft movement of the reverser sleeves causes
blocker doors to deflect fan discharge air forward, through fixed cascade vanes,
producing reverse thrust. The thrust reverser is for ground operations only and is
used after touchdown to slow the airplane, reducing stopping distance and brake
wear.
Hydraulic pressure for the operation of engine No. 1 and engine No. 2 thrust
reversers comes from hydraulic systems A and B, respectively. If hydraulic
system A and/or B fails, alternate operation for the affected thrust reverser is
available through the standby hydraulic system. When the standby system is used,
the affected thrust reverser deploys and retracts at a slower rate and some thrust
asymmetry can be anticipated.
The thrust reverser can be deployed when either radio altimeter senses less than
10 feet altitude combined with an air/ground safety sensor in the ground mode.
Movement of the reverse thrust levers is mechanically restricted until the forward
thrust levers are in the idle position.
When reverse thrust is selected, an electro–mechanical lock releases, the isolation
valve opens and the thrust reverser control valve moves to the deploy position,
allowing hydraulic pressure to unlock and deploy the reverser system. An
interlock mechanism restricts movement of the reverse thrust lever until the
reverser sleeves have approached the deployed position. When either reverser
sleeve moves from the stowed position, the amber REV indication, located on the
Engine Display, illuminates. As the thrust reverser reaches the deployed position,
the REV indication illuminates green and the reverse thrust lever can be raised to
detent No. 2. This position provides adequate reverse thrust for normal operations.
When necessary, the reverse thrust lever can be pulled beyond detent No. 2,
providing maximum reverse thrust.
Downward motion of the reverse thrust lever past detent No. 1 (reverse idle thrust)
initiates the command to stow the reverser. When the lever reaches the full down
position, the control valve moves to the stow position allowing hydraulic pressure
to stow and lock the reverser sleeves. After the thrust reverser is stowed, the
isolation valve closes and the electro–mechanical lock engages.
March 1, 2021
