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Hot-Surface Ignition and Fire-Suppression Tests in an Aircraft Engine Bay
 Hot-Surface ignition tests were conducted on full-scale aircraft (the F-18 and the AV-8B) and on simulated engine nacelles (F-16). For
the AV-8B, the conditions in an engine bay that promote the ignition of flammable fluids, and the suppression of subsequent fires, were investigated. Ignition by hot surfaces has been studied in the past
under laboratory conditions or in simulated aircraft engine bays. This test was conducted under full-scale and realistic engine-bay conditions
using an operable turbofan engine installed in an aircraft. The engine consisted of a forward zone (fan, compressor, and accessories) and an aft zone (combustor, turbine, and exhaust
plenum). In the aft zone, key metal surface temperatures exceeded the fluid Autoignition Temperature (AIT), and ignition was observed. In the forward zone, surface temperatures
exceeded the AIT but not the Hot-Surface Ignition Temperature (HSIT), and ignition was not observed. These ignition results, coupled with an examination of the heating conditions
of each zone, suggest that suitable temperature criteria for ignition are the AIT in the aft zone and the HSIT in the forward zone. Fires in the engine bay were repeatedly
extinguished by an automatic suppression system. When a manually actuated suppression system was used, with its inherent time delays, the fire was not extinguished.
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