737 MAX Flight Crew Operations Manual
Fire Protection -
System Description
8.20.8
MN-FLT-OH-201
FAULT/INOP Test Detection
The fault detection circuits for both the engines and the APU are tested by pushing
and holding the FAULT/INOP and OVHT/FIRE TEST switch in the
FAULT/INOP position.
The indications for the FAULT/INOP test are:
• both MASTER CAUTION lights illuminate
• the OVHT/DET system annunciator light illuminates
• the FAULT light illuminates
• the APU DET INOP light illuminates.
OVERHEAT/FIRE Test Detection
The overheat and fire detection loops on both engines, the APU, and the fire
detector in the wheel well are tested by pushing and holding the FAULT/INOP and
OVHT/FIRE TEST switch in the OVHT/FIRE position.
The indications for the OVHT/FIRE test are:
• the fire warning bell sounds
• both master FIRE WARN lights illuminate
• both MASTER CAUTION lights illuminate
• the OVHT/DET system annunciator light illuminates
• both engine fire switches illuminate
• both engine start levers illuminate
• the APU fire switch illuminates
• both ENG OVERHEAT lights illuminate
• the WHEEL WELL fire warning light illuminates if AC power is
available
• on the ground, the wheel well APU fire warning horn sounds and the
wheel well APU fire warning light flashes.
Extinguisher Test
When the EXT TEST switch is positioned to 1 or 2, the green EXT TEST lights
illuminate, verifying circuit continuity from the squib to the engine and APU fire
switch.
Cargo Fire System Tests
The cargo fire detection and suppression system can be tested by pushing and
holding the cargo fire TEST switch. This sends a test signal to the forward and aft
cargo fire detector loops and verifies continuity of the extinguisher bottle squib
circuits. All test indications clear when the TEST switch is released
March 1, 2021
