Adityanand Girdhari

There is a need to effectively develop and test an advanced fire detection system for aircraft cargo compartments that significantly reduces false alarms and improves alarm time response. Title 14 Code of Federal Regulations Part 25.858 requires that aircraft detection systems alarm within 1 minute of the start of a fire. Gas concentrations, temperature fluctuations, and particulate levels are three main parameters representative of a complete fire signature. Current aircraft detection systems depend solely on one parameter, particulate levels, for the detection of this wide fire signature. Improved fire detection capabilities can be achieved by combining multiple fire signatures or parameters in specific algorithms.

An advanced fire detection system combining an ionization smoke detector, thermocouple, smokemeter, and a carbon monoxide (CO)/carbon dioxide (CO2) gas probe was installed in a Boeing 707 forward cargo compartment. A broad spectrum of fire and nuisance sources were tested to produce a matrix of extreme detector levels from all four sensors. This matrix provided alarm threshold criteria that aided in the development of a multisensor algorithm based on fire signatures such as CO and CO2 gas concentrations, temperature, ionization chamber voltage, and percent light transmission per foot. Multiple algorithms were created to determine the most effective multisensor algorithm that responded the fastest to fires while providing nuisance immunity. A spatial distribution analysis was conducted by using a Computational Fluid Dynamic (CFD) model to specify the physical range of the multisensor detector subjected to the optimized algorithm.

A multisensor algorithm combining CO2 gas concentrations, percent light transmission per foot, and ionization chamber voltage parameters produced a 100% success rate for detection of fires within 1 minute while providing nuisance immunity to those signatures tested. Comparison of computational and experimental alarm time, smokemeter, and ionization chamber results demonstrated the effectiveness of the CFD and provided strong evidence that the CFD can be used as a virtual detector to simulate fires with an average alarm time uncertainty of 2.57 seconds. Spatial distribution analysis from the CFD determined the physical range of the single multisensor detector to be at least 910 cubic feet, the volume of the Boeing 707 forward cargo compartment.

John W. Reinhardt

A comprehensive fire test program was conducted on aircraft ducting materials in an effort to continue mitigating the threat of in-flight fires. Previous work at the Federal Aviation Administration (FAA) William J. Hughes Technical Center has indicated that the current FAA vertical Bunsen burner test requirement could not adequately discriminate between materials that performed poorly and materials that performed well under realistic fire scenarios. From this effort, an alternative radiant heat panel test method was developed. It was demonstrated that this method was effective in evaluating the in-flight fire resistance qualities of aircraft ducting.

William M. Cavage

TKS anti-icing fluid is being used in a variety of platforms to provided anti-/deicing capability for smaller commercial aircraft. The flammable liquid is comprised of 85 percent ethylene glycol, 10 percent water, and 5 percent isopropyl alcohol, and questions about its potential hazards have been raised. These hazards include, but are not limited to, the heating of small puddles of fluid that were either spilled or leaked, dripping of the fluid on hot surfaces, and the contact of the fluid mist with ignition sources. Simple tests were performed to allow for a more basic characterization of the TKS anti-icing fluid flammability. These tests were (1) an ASTM D 56-87 flash point test, (2) a hot-pan flammability test, (3) a hot-surface ignition test, and (4) a spray flammability test.

As expected, TKS anti-icing fluid is flammable under the correct conditions. The flash point was found to be approximately 150°F, but the fluid appears to have a very low energy release when reacting. The fluid will burn if heated in a pan to approximately 250°F and subjected to an ignition source, but burns relatively cool. When dripped onto a hot surface, the fluid does not react but will probably display relatively violent characteristics if heated in a confined space above 750°F (approximate autoignition temperature). The fluid will burn in a mist at ambient temperature and pressure when exposed to a flame, but will not sustain a reaction when the flaming ignition source is removed. Only sporadic ignitions (no fireball) confined to small areas were observed when the mist was ignited with a spark.

Richard E. Lyon

Strategies for developing fireproof aircraft cabin materials are reviewed in light of environmental legislation that restricts the use of halogens in plastics. The important physical and chemical processes of flaming combustion in terms of their effect on the heat release rate of a burning material are flame inhibition, fuel replacement, heat resistance, and intumescence. These fire resistance mechanisms, acting simultaneously or synergistically, are particularly effective at reducing heat release rate of a new generation of transparent plastics suitable for aircraft cabin interiors.

Stanislav I. Stoliarov and Richard N. Walters

The amount of heat that is required to gasify unit mass of material is one of the key properties that define its ignition resistance and fire response. Knowledge of this property is necessary to assess a material’s fire hazard in a particular fire scenario. Nevertheless, even for the most common polymers, the values of this property are not well established. Here, a methodology is presented for determining the heat of gasification using differential scanning calorimetry and applied to a set of ten common plastics and engineering polymers.