Boeing 747 fire detection and extinguishing

Fire protection on the 747 is divided into zones — each engine, the APU, the cargo holds and the toilets — each with its own detection and extinguishing hardware, all managed from a single fire-control module on the flight deck.

Key facts
Zones covered	All four engines, the APU, cargo holds, toilets
Extinguishing agent	Halon-type bottles discharged from the flight deck
Cargo compartments	Classed A/B/C; Class C holds must have detection plus automatic extinguishing
Fuel-tank safety	Fleet gained inerting after TWA Flight 800

The 747’s integrated fire-control installation covers its four engines, the APU and the main cargo compartment from one module. Cargo compartments are classed by accessibility: a Class C hold, which cannot be reached in flight, must have both fire detection and fully automatic extinguishing.

TWA Flight 800, a 747-100 destroyed in 1996 when fuel vapour in a nearly empty centre-wing tank ignited, transformed the industry’s approach. Subsequent 747s carry fuel-tank inerting hardware to keep oxygen out of tank ullage, and the 747-400’s master minimum equipment list includes a dedicated inert-gas-system page (ATA 47).

Sources

• Fire protection on Boeing 747 aircraft — US EPA (attachment)
• TWA Flight 800 overview — NTSB
• Cargo compartment fire protection — NIST
• Boeing 747-400 Master Minimum Equipment List — Transport Canada