Airport Aircraft Hangars: NFPA 409 AFFF Deluge, Groups I–III and 60-Second Activation

In aircraft hangars we protect airframes carrying more than 300,000 L (79,000 gal) of jet fuel. Once a fuel spill ignites, the fire spreads within 60 seconds, and an aluminum fuselage can fail structurally in as little as 5 minutes. NFPA 409 classifies hangars by size as Group I (wide-body), Group II (narrow-body) and Group III (general aviation), and requires an AFFF or high-expansion foam system in each.

Hangar Classification

• Group I: Area over 2,800 m² (30,000 ft²); wide-body aircraft such as the B747 and A380
• Group II: 1,115–2,800 m² (12,000–30,000 ft²); narrow-body aircraft such as the A320 and B737
• Group III: Under 1,115 m² (12,000 ft²); business jets and general aviation
• Group IV: Membrane-covered hangar structures
• Group V: Special-purpose military hangars

Group I: AFFF Deluge System

• Overhead system: 6.5 L/min/m² (0.16 gpm/ft²)
• Low-level system: 10.2 L/min/m² (0.25 gpm/ft²) under the aircraft
• Duration: 10 min overhead + 10 min low-level
• 3% AFFF: The transition to fluorine-free (F3) foam is under way
• Activation: The entire system must operate within 60 seconds

High-Expansion Foam

• Expansion ratio: 500:1 to 1000:1 (NFPA 11 defines high expansion as roughly 200:1 to 1000:1)
• Fill rate: 1 m (3.3 ft) rise per minute
• Coverage: Fills the hangar to a depth of 2–3 m (6.6–9.8 ft)
• Foam generator: Blower type; the fan is driven by an electric motor or a water motor (NFPA 11 A.3.3.13.2)
• Advantage: Water savings and three-dimensional filling of the volume

Detection and Alarm

• Optical smoke detection: Beam type, 100 m (328 ft) range
• UV/IR flame detectors: 30 m (98 ft) coverage diameter
• Heat detectors: Rate-of-rise type
• Manual pull stations: Spaced at 30 m (98 ft)
• Voice alarm: For evacuation announcements

Turkish Hangar Examples

• Istanbul Airport maintenance base: 8 Group I hangars
• Sabiha Gökçen: Airline MRO facility
• Esenboğa: Military Group V hangar
• Kayseri: F-16 production line
• İzmir Çiğli: Turkish Air Force base

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