نظام إخماد الحرائق (Fire Suppression System)

What Is a Fire Suppression System?

An aircraft fire suppression system is an integrated set of detection, warning, and extinguishing equipment designed to identify and combat fires in the engine nacelles, auxiliary power unit (APU), cargo holds, wheel bays, and lavatories of a commercial aircraft. Fire is one of the most catastrophic threats in aviation; many of the industry's most significant historical accidents have involved uncontrolled inflight fires. Modern airworthiness standards (FAA 14 CFR Part 25 / EASA CS-25) require aircraft to be equipped with fire detection systems capable of alerting the crew to a fire within 5 seconds and suppression systems capable of controlling or extinguishing the fire within a defined time limit.

How It Works

Engine fire detection uses continuous loop sensors — pneumatic or resistance-based cables routed around the engine nacelle that trigger a cockpit warning at a defined temperature threshold. On warning, the crew execute the engine fire drill: closing the fuel shutoff valve, discharging one of two halon or HFO (hydrofluoroolefin) extinguisher bottles into the nacelle via a "squib" (explosive-activated valve). If fire persists after 30 seconds, the second bottle is fired. Cargo hold suppression uses metered discharge of halon-1301 (or replacement agents) via ceiling nozzles; concentration is sufficient to suppress a Class A fire for the duration of the flight plus a defined containment period. APU fire protection is similar to engine fire protection, with automated suppression on APU shutdown command.

Types and Standards

• Engine fire suppression: Dual-shot halon or HFO bottles per engine, pilot-activated from cockpit fire handle.
• Cargo hold suppression (Class C holds): Regulated discharge rate over a sustained period; lavatory waste bin units auto-discharge on smoke detection.
• Portable extinguishers: Halon 1211 or CO₂ units at crew stations throughout the cabin for contained fires.
• Lithium battery fire: An emerging challenge — halon suppresses surface combustion but does not quench thermal runaway. Water-based procedures are now recommended by some authorities for large lithium battery events in the cargo hold.

Interesting Facts

• Halon 1301 is highly effective as a fire suppressant but is an ozone-depleting substance; the aviation industry has secured a "critical use" exemption from the Montreal Protocol while alternatives are validated, as no replacement has yet matched its performance-to-weight ratio in engine applications.
• The in-flight fire that destroyed Swissair Flight 111 in 1998 (229 fatalities) originated behind the cockpit in insulation blankets ignited by in-flight entertainment wiring; the accident drove a wholesale redesign of flammability standards for cabin materials.
• UPS Airlines Flight 6 (2010) demonstrated the extreme danger of large lithium battery shipments; an uncontrolled cargo fire generated toxic fumes that incapacitated both crew members over Saudi Arabia.
• The lavatory smoke detector and automatic waste bin extinguisher system is specifically mandated following a 1983 Air Canada DC-9 cabin fire that killed 23 passengers after an in-flight lavatory fire was not detected promptly.