Overview

The U.S. Federal Aviation Administration (FAA), along with other regulatory agencies throughout the world, requires that cargo compartments on passenger carrying aircraft be equipped with fire detection and suppression systems. Current regulations state that the detection systems alarm within one minute of the start of a fire. Flight tests are required to demonstrate compliance with these regulations. Due to the high costs of flight tests, extensive ground tests are typically conducted to ensure that the detection system will meet requirements during the flight tests.

In addition to costly test requirements, detection systems are prone to alarm from nuisance sources, such as dust and humidity and are inaccessible by crew members for inspection during flight. The false alarm ratio for cargo compartment detection systems is estimated to be on the order of 100:1, resulting in numerous unscheduled landings which are costly and potentially unsafe.

A physics-based Computational Fluid Dynamics (CFD) tool, which couples the heat, mass and momentum transfer phenomena in cargo compartment fires, has been developed to help address both of these issues. The simulation tool is expected to decrease the time and cost of the certification process by reducing the total number of both in-flight and ground experiments. The tool provides information on smoke transport in cargo compartments with varying fire and sensor locations, compartment geometry, ventilation, loading, compartment temperature, and compartment pressure; therefore, optimum sensor systems can be developed, thus reducing the number of false alarms. The fire source term is specified in the model based on Federal Aviation Administration measurements of the heat release rate, mass loss rate, and species generation rates of the newly-developed standardized fire source. The computational model and the standardized fire source are two aspects of an overall project to standardize the requirements for cargo compartment fire detection systems and to provide guidelines for more efficient certification of systems that are less susceptible to false alarms.

The smoke transport model has the potential to enhance the certification process by determining worst case locations for fires, optimum placement of fire detector sensors within the cargo compartment, and sensor alarm levels needed to achieve detection within the required certification time. The model was verified and validated using full-scale FAA experimental data. It is fast running and user-friendly to allow a large number of simulations to be run by individuals who are not CFD experts.

The code was developed by Sandia National Laboratories for the Federal Aviation Administration with funding from NASA Glen Research Center.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration. Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.

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