Prompt fire detection in cargo compartments on board transport aircraft is an important safety feature. Concern has been expressed for the activation time of contemporary detection technologies installed on aircraft. This project will deliver a continuation of research on the issues that have been identified relative to fire detection improvements in cargo compartments on aircraft, with a particular emphasis on freighters. Gas sensors and dual wavelength detectors were demonstrated in a previous phase to be responsive to fires in the previous experiment program. Detectors placed inside a Unit Loading Device (ULD) responded quickly to the array of fire sources. Thus, a further exploration of these observations is conducted including wireless technology along with an analysis of the effects of leakage rates on fire signatures inside ULDs. One primary goal is to assess the differences in fire detection time for detectors located within ULD versus those located on the ceiling of the cargo compartment for fires which originate in a ULD. The results indicated the detector location with the shortest activation time is inside of the ULD. Within the ULD, the wireless detector outperformed both air sampling detectors, however, the results could vary if threshold levels were more restrictive.
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 smoke density scales with volume, 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.
The FAA has published two previous versions of the Aircraft Materials Fire Test Handbook: DOT/FAA/CT-89/15 and DOT/FAA/AR-00/12. The main purpose of the Handbook is to describe various fire test methods for aircraft materials in a consistent and detailed format. The Handbook provides information to enable the user to assemble and properly use certain test methods. The FAA adopted policy that made the first two versions of the Handbook an acceptable method of compliance for certain requirements in 14 Code of Federal Regulations (CFR) Part 25. This third-generation Handbook supports an FAA effort to revise the flammability requirements for Transport Category Airplanes in 14 CFR Part 25.
This Handbook organizes the test methods according to the threat posed by the material and its function. It describes various types of flammability tests in a consistent and detailed manner, and provides information to help the user assemble, operate, and use the test methods. Appendices contain additional information to broaden the utility of the Handbook.