.
the EGT reaches 725°C
.
the engine fails to accelerate properly after N2 reaches 32%.
If a normal start occurs, the alert indication can be reset by pressing the fuel used reset switch on the EIS panel. The alert indication is automatically reset when zero fuel flow is sensed
Engine Ignition System
Each engine has two igniters. The ignition select switch selects either the left, right, or both igniters for both engines. The ignition select switch is bypassed when the engine start switch is in FLT.
IGN L, powered by the AC transfer bus, provides high energy ignition to the left igniter. IGN R, powered by the AC standby bus, provides high energy ignition to the right igniter.
Engines, APU -Engine System Description 737 Operations Manual
With the engine start switch in the GRD position, the selected igniter(s) are energized when the engine start lever is positioned to IDLE. The CONT position energizes the selected igniter(s) continuously. The FLT position energizes both igniters when the engine start lever is positioned to IDLE.
Copyright . The Boeing Company. See title page for details.
7.20.8 December 1, 2000
Engines, APU -Engine System Description 737 Operations Manual
Engine Start and Ignition System Schematic
FLT
CONDITION:
BLEED AIR N2 ROTATION BELOW STARTER CUTOUT SPEED.
ENGINE BEING STARTED
FUEL
On all 737-300s delivered after November, 1988, circuitry added to close engine bleed air valvewhen the engine start switch is placed to GRD.
Engines, APU -Engine System Description 737 Operations Manual
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 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, or when the air/ground safety sensor is 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 electromechanical lock releases (on some airplanes), 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 REVERSER UNLOCKED light on the center instrument panel illuminates. As the thrust reverser reaches the deployed position, 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 commands the reverser to stow. Once the thrust reverser is commanded to stow, 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.
The REVERSER light, located on the aft overhead panel, illuminates when the thrust reverser is commanded to stow and extinguishes 10 seconds later when the isolation valve closes. Any time the REVERSER light illuminates for more than approximately 12 seconds, a malfunction has occurred, and the MASTER CAUTION and ENG system annunciator lights illuminate.
Copyright . The Boeing Company. See title page for details.
7.20.10 June 6, 2003
Engines, APU -Engine System Description
737 Operations Manual
When the reverser sleeves are in the stowed position, an electromechanical lock (on some airplanes) and a hydraulically operated locking actuator inhibit motion to each reverser sleeve until reverser extension is selected. Additionally, an auto–restow circuit compares the actual reverser sleeve position and the commanded reverser position. In the event of incomplete stowage or uncommanded movement of the reverser sleeves toward the deployed position, the auto–restow circuit opens the isolation valve and commands the control valve to the stow position, directing hydraulic pressure to stow the reverser sleeves. Once the auto–restow circuit is activated, the isolation valve remains open and the control valve is held in the stowed position until the thrust reverser is commanded to deploy or until corrective maintenance action is taken.
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