The Scalability of Smoke Density and the Viability of New Detection Methods in Aircrafts
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Fire detection is a topic of interest in aircraft applications, specifically cargo compartments, given the unique operating environment and accessibility challenges in the event of a fire. The use of unit loading devices inside cargo compartments have also presented a delay in alarm challenge due to their enclosed nature. However, despite the importance of detection, there is yet to exist a standard testing and certification method for fire detection in cargo compartments. The current requirement for a cargo compartment detection system is that a fire has to be detected in 1 minute, and in that time be so small that the fire is not a significant hazard to the airplane. Nuisance alarms also plague the industry, with upwards of 90% of fire alarms being false warnings. These problems have been partially addressed through the analysis of smoke density and state of the art detection technology. Both flaming and smoldering fires were conducted using an array of materials such as heptane, polyurethane foam, shredded paper, wood chips, suitcase, baled cotton, and boiling water. The response of aspirating smoke detectors, dual wavelength technology, and gas detectors were analyzed. It was found that small scale tests replicate large scale behavior, leading to the suggestion that detection testing could happen outside of cargo compartments and results be appropriately scaled. The response of aspirating smoke detectors, dual wavelength technology, and gas detectors were all found to follow patterns similar to that of light obscuration measurements and were thus deemed viable options for use in cargo compartments. Carbon dioxide and the loss of oxygen were detected 100-600 seconds faster than visible smoke for smoldering polyurethane and smoldering cotton tests, suggesting an increase in gas concentration could be a precursor to visible smoke in certain situations. All new detection technologies were identified for their theoretical improvement in nuisance immunity. Gas detection was identified as the outstanding detection technology and recommended for use over photoelectric detection in cargo compartments.