Richard E. Lyon

Molecular design of semi-inorganic rubbers has yielded flexible polysilphenylene-siloxane and polyphosphazene elastomers having the fire resistance of rigid, high-temperature engineering plastics (e.g., polyaramids, polyetherketones, and polyarylsulfones) based on the results of microscale combustibility data. In flaming combustion, a commercially viable polyphosphazene exhibited a 75% reduction in heat release rate compared to the polyurethane rubber currently used in fire-blocked foam aircraft seat cushions. A comparable reduction in heat release rate is obtained at lower cost by adding expandable graphite flakes to the polyurethane formulation. The graphite flakes exfoliate during heating to produce a 2000% volumetric expansion of the burned rubber which shields and insulates the underlying material from the heat source and lowers the heat release rate significantly. Future work will explore the use of relatively low-cost expandable graphite technology in semi-inorganic rubber to obtain a fireproof (zero heat release rate) seat cushion foam.

William M. Cavage and Ole Kils

Tests were performed in a 0.24 scale model of a Boeing 747SP center wing tank to validate the existing assumptions for inerting complex geometric spaces, which were developed from previous experiments, and to facilitate design of an efficient, cost-effective inerting gas deposit system for full-scale, ground-based inerting testing. The model was equipped with a variable nitrogen-enriched air distribution system, thermocouples, and oxygen analyzers that were monitored and recorded continuously by a data acquisition system during each test. The model was inerted in different configurations with different flow rates and bay distributions. The collected data was nondimensionalized in terms flow rate and tank size to allow for comparisons between tests.

Experiments in the tank verified that the volumetric tank exchange established from research with a simple box-style tank can be achieved in a more complex compartmentalized tank. It also indicated that the same volumetric tank exchange could be obtained with less gas distribution (less complex distribution system) and that modification of the venting configuration to eliminate cross-venting would improve the efficiency of the inerting process. Tests showed that the most efficient method of inerting the tank was to deposit all the nitrogen-enriched air in a single location, allowing for a lightweight, easily installed deposit system for an operational aircraft. Data from full-scale testing compared well with scale tank data illustrating that low cost, small-scale test articles can be an effective tool for developing inert gas distribution systems.

Richard E. Lyon and Richard Walters

A method for measuring the heat release rate of milligram-sized samples is described in this report. Pyrolysis-combustion flow calorimetry (PCFC) separately reproduces the solid-state and gas phase processes of flaming combustion in a nonflaming test by rapid controlled pyrolysis of the sample in an inert gas stream followed by high-temperature oxidation (combustion) of the pyrolyzate in excess oxygen. The rate at which the sample releases its heat of combustion is calculated from the oxygen consumption history. The heat of combustion is obtained from the time integral of the heat release rate.

Report of the Task Group on Halon Options International Aircraft Systems Fire Protection Work Group, R.E. Tapscott, L.C. Speitel, eds.

This report contains a summary of available fire suppression agents and their properties. The applicability of various technologies for each major onboard aircraft application is assessed. Classes of agents, with presently available agents listed, are recommended for use in the development of test protocols. The test protocol developed for a class of agents can be used, with minor modifications, to test all agents belonging to that class.

John W. Reinhardt

This report documents the full-scale evaluation tests of a water mist system, with and without nitrogen that would be available from an onboard inert gas generation system (OBIGGS) against a series of standardized aircraft cargo fires. These evaluation tests followed the testing protocols specified in the Minimum Performance Standard for Aircraft Cargo Compartment Gaseous Fire Suppression Systems modified with a draft new protocol for an exploding aerosol can fire scenario that would be applicable to nongaseous systems. The developmental work was performed in conjunction with the International Aircraft Systems Fire Protection Working Group. The results showed that a hybrid water mist and nitrogen system met the minimum performance standard, with lower cargo compartment temperatures than either plain water mist or halon, and with less weight of water consumed than halon.