Back to home pageFire Protection

Home > Aircraft Systems > Fire Protection

Contents

Illustrated technical information covering Vol 2 Over 800 multi-choice systems questions Study notes and technical information Close up photos of internal and external components A compilation of links to major 737 news stories with a downloadable archive Illustrated history and description of all variants of 737 Detailed tech specs of every series of 737 Databases and reports of all the major 737 accidents & incidents General flightdeck views of each generation of 737's Description & news reports of Advanced Blended Winglets Press reports of orders and deliveries A collection of my favourite photographs that I have taken of or from the 737 Details about 737 production methods A compilation of links to other sites with useful 737 content Get the book of the website A quick concise overview of the pages on this site

spacer

Contents

See more details about the book

All of the information, photographs & schematics from this website and much more is now available in a 374 page printed book or in electronic format.

*** Updated 16 Sep 2016 ***

The 737 Tech Site on Facebook The 737 Tech Site on Twitter

Engines

Overheat / Fire Protection Panel  3-900 series

Overheat / Fire Protection Panel  -200C series. Notice fwd & aft cargo smoke detectors.

 

Engine & APU fire detection Battery bus

Engine, APU & Cargo fire extinguishing Hot battery bus.

There are two fire detection loops in each engine. Failure of both loops in one engine will illuminate the FAULT light. The individual loops can be checked by selecting A or B on the OVHT DET switches.

Fire switches will unlock in the following situations:

  1. Overheat detected
  2. Fire detected
  3. During an OVHT/FIRE test
  4. Pressing manual override buttons

Pulling a fire switch will do the following:

  1. Arm firing circuits
  2. Allow fire switch to be rotated for discharge
  3. Close engine fuel shut-off valve.
  4. Trip the associated GCR (i.e. switches off the generator)
  5. Close hydraulic supply to EDP & disarms its LP light (Not if APU)
  6. Close engine bleed air valve (If APU will also close air inlet door)
  7. Close thrust reverser isolation valve (Not if APU)

The engine fire bottles (NG)

 

Wheel-Well

There is a wheel-well fire detection system but although the engine fire bottles are located in the wheel-well, there is no extinguishing system for a wheel-well fire. (Suggest extend gear & land ASAP).

 

APU

The APU only has one bottle. This may be checked externally by looking for the two discharge discs (red for thermal overpressure & yellow for extinguisher discharge) and the pressure sight glass (where fitted) on the aft stbd fuselage.

 

 

 

Cargo Compartment (Optional)

Cargo Fire Panel

Cargo Fire Panel - Alternative version

The cargo holds have dual-loop smoke detectors powered by DC bus 1 & 2. There is only one cargo fire bottle, it is powered by the hot battery bus and can be discharged into either the fwd or aft hold. On later 737NG's the cargo fire smoke detector sends a signal to the cabin pressure control system. This triggers the cabin pressure to descend at 750 slfpm which helps prevent smoke penetration into the passenger cabin from the lower lobe. (This function is inhibited on the ground.)

Cargo Hold Smoke Detector

 

 

Lavatory Smoke Detection (Optional)

Some 737's have a warning light on the flight deck to warn of smoke in the lavatory. If the smoker is in the forward lav you can usually smell it on the flight deck within seconds without a warning light.

 

Passenger Compartment (Optional)

The cargo 737's had a pressurisation feature which allowed the crew to pressurise or unpressurise the passenger compartment for smoke clearance.

 

See also NG engineering notes by M Ferreira

Footer block

This site has had visitors to date.