Hidden fire in the aircraft cabin has been characterized as a hazardous phenomenon to in-flight safety and could lead to catastrophic disaster. Detecting hidden fire at the earliest stage is required and can be achieved only through an improved understanding of the transport of hot gases and smoke due to a possible hidden fire. This research uses the computation fluid dynamics tool to simulate the heat and mass transport in situations of hidden fire in the overhead area of the aircraft cabin. The modeled temperatures are compared with the full-scale test results, and reasonable agreements are observed. The simulation also presents comprehensive hot gas transport information. Further investigations are performed to examine the effect of ambient pressure and the fire source location. It is found that at cruise altitude with reduced ambient pressure, ceiling temperature increases as a result of increased flame height and decreased air entrainment. The ceiling temperature is sensitive to the fire source location. Hot gases tend to migrate to the highest ceiling location. Obstruction thicker than the ceiling jet boundary layer at the ceiling level can result in extra hot spots.

The Next Generation (NexGen) (sonic) burner is a new burner designed by the FAA William J. Hughes Technical Center for the required FAA fire certification tests on power plant components. The objective of this study is to understand the performance of this burner and provide the benchmark to adapt the burner settings for future FAA fire tests. Tests have been conducted to study the burner performance and its sensitivity to operating conditions and changes in configuration. Tests were conducted on the old burner configuration consisting of the stator and turbulator, and the updated configuration consisting of the flame retention head and the static plate. Burner calibration was found to be sensitive to changes in fuel flow rate, but not to air mass flow rate, though burnthrough results were sensitive to both parameters. Results were not affected by fuel and air temperatures as long as the air mass flow rate was held constant at the different air temperatures. Changes in burner inclination were observed to affect the burner performance. For the updated burner configuration, tests were conducted to study the effect of changes in the internal configuration. The NexGen burner performance was observed to be robust, and tolerances have been specified for some of the internal configuration components.

This report discusses ongoing developmental efforts related to the NexGen burner. It should be noted that the burner construction and settings discussed in this report are not representative of the most recent ones used on the NexGen burner. For detailed construction drawings and to view other documentation and presentations that discuss the most up-to-date burner configurations, please visit the FAA’s Fire Safety Branch’s website at www.fire.tc.faa.gov.

To improve the accuracy of aircraft fire detection, new smoke detectors have been produced to differentiate between what is a real fire and what is a false alarm. Nontoxic theatrical smoke machines are used to test these new false resistant smoke detectors in flight. This research is based on characterizing the smoke from the machines to understand what alerts different types of smoke detectors, and what would best be used for testing them.

Two smoke detectors were utilized in testing. One was a Whittaker Model 601 smoke detector which is an optical beam smoke detector; the second is a Kidde Aerospace & Defense Smoke Detector Type II which is a prototype of the new false alarm resistant detector. Two smoke machines were also used: one using fluid that is oil-based (the Concept Smoke Systems Aviator UL 440) and one using fluid that is water-based (the Rosco 1700). The particle size and percent obscuration of the smoke from these machines have been determined and used to understand the requirements of alarm for the detectors.

By using the Phase Doppler Particle Analyzer (PDPA) to measure the particle size of the smoke leaving each machine, it was found that the smoke from the Aviator UL had much smaller particles than that of the Rosco. Optical density meters were used to measure the percent obscuration per foot of the smoke entering the detectors. Along with the smaller particle sizes recorded, the Aviator UL also alarmed at a significantly lower percent obscuration per foot. It is hypothesized to be that because of this smaller particle size, the Aviator UL was able to alarm the “false alarm resistant” Kidde detector whereas the Rosco, with the larger particle sizes was unable to force the alarm into detection until the level of obscuration was significantly higher than the Aviator UL.