Thomas L. Reynolds, Delbert B. Bailey, Daniel F. Lewinski, and Conrad M. Roseburg

The purpose of this technology assessment is to define a multiphase research study program investigating Onboard Inert Gas Generation Systems (OBIGGS) and Onboard Oxygen Generation Systems (OBOGS) that would identify current airplane systems design and certification requirements (Subtask 1); explore state-of-the-art technology (Subtask 2); develop systems specifications (Subtask 3); and develop an initial system design (Subtask 4). If feasible, consideration may be given to the development of a prototype laboratory test system that could potentially be used in commercial transport aircraft (Subtask 5). These systems should be capable of providing inert nitrogen gas for improved fire cargo compartment fire suppression and fuel tank inerting and emergency oxygen for crew and passenger use.

Michael Burns and William M. Cavage

This report documents a series of experiments designed to determine the quantity and purity of nitrogen-enriched air (NEA) required to inert a vented aircraft fuel tank. NEA, generated by a hollow fiber membrane gas separation system, was used to inert a laboratory fuel tank with a single vent on top designed to simulate a transport category airplane fuel tank. The tank ullage space could be heated as well as cooled and fuel could be heated in the bottom of the fuel tank to provide varying hydrocarbon concentrations within the ullage space.

Several inerting runs were performed with varying NEA gas purities and flow rates. The data was nondimensionalized in terms of NEA purity, volume flow rate, and fuel tank size to provide one universal inerting curve. Changing temperatures and hydrocarbon concentrations appear to have little effect on the amount and purity of NEA needed to inert the test specimen. A model of ullage washing developed by the Federal Aviation Administration Chief Scientific and Technical Advisor for fuel systems design, based on the volume exchange of gases of different concentrations, was compared with data obtained from the test article. Also, an exact solution based on uniform and instantaneous mixing was derived and compared with the test data. Both the model and exact solution showed good agreement in both trend and magnitude with the data obtained during the testing.

Michael L. Ramierz

This work has been conducted as part of the Federal Aviation Administration's (FAA) efforts to develop fire-resistant materials for commercial aircraft cabins. Polymers based on 2,2-bis-(4-hydroxyphenyl)-1,1-dichloroethylene (bisphenol C, BPC) have thermal and physical properties of bisphenol-A polymers but have an order of magnitude lower heat release in flaming combustion. This is due to a thermal degradation mechanism that yields only char and nor combustible gases in a fire. Two thermoplastics and one 'thermoset BPC-based polymer were studied to establish the decomposition mechanism of these materials. Thermal gravimetric analysis, differential scanning calorimetry, infrared spectroscopy, chromatography, and mass spectrometry were used separately and in combination to characterize the thermal degradation mechanism. Results showed that the major volatiles are hydrogen chloride (HCI) and the degradation products of the linking group. The rearrangement through stilbenes and acetylenes is responsible for the high char yield when burned.

John W. Reinhardt, David Blake, & Timothy Marker

This report documents the test results of the testing conducted during the development of a minimum performance standard for aircraft cargo compartment gaseous fire suppression systems. It also includes the final version of the standard. The development work was performed in conjunction with the International Halon Replacement Working Group.

Timothy Marker

A large number of small-, intermediate-, and full-scale flame propagation tests representative of an in-flight fire were conducted on various thermal acoustic insulation blanket materials. Results indicated that the current Federal Aviation Administration (FAA) vertical Bunsen burner test requirement could not adequately discriminate between poorly performing materials and materials that performed well under realistic fire scenarios. A radiant panel laboratory test was shown to be an effective method for evaluating the in-flight fire resistance qualities of thermal acoustic insulation.

In addition, a new laboratory test was developed for evaluating the postcrash fire burnthrough resistance of thermal acoustic insulation. The test method was based on full-scale tests in which a fuselage structure was subjected to jet fuel fires. Approximately 60 burnthrough tests were conducted on a variety of insulation materials. Insulation materials compliant with the new burnthrough test method will provide a minimum of 4 minutes of protection against a postcrash fuel fire.