About the Fire Safety Branch
The Fire Safety Branch conducts, manages and supports research programs to improve fire safety in commercial transport aircraft. The research is comprised of two separate but complimentary, programs: Fire and Cabin Safety and Fire Resistant Materials. Fire and Cabin Safety is a near term program that addresses specific aircraft applications and/or problems, whereas Fire Resistant Materials is a long range program to develop the enabling technology for ultra-fire resistant interior materials
In-Flight and Postcrash Fire Safety
Aircraft fire safety entails two distinct fire protection activities in-flight fire prevention and postcrash fire survivability. The goals of each activity are different because the fire threats and period of protection are dissimilar.
In commercial transport aircraft, the in-flight fire problem is a hidden fire that occurs in an inaccessible location (e.g., cargo compartment) or that is difficult to locate (e.g., lavatory area). The initial design goal is to minimize the likelihood of a fire at any location throughout the aircraft. However, if a fire should occur, the goal is to reliably detect the fire and to extinguish or suppress the fire until the aircraft can be safely landed. Although rare, the consequences of an uncontrollable in-flight fire are great, as attested by the Valujet accident (May 11, 1996, 110 fatalities).
Unlike in-flight fires, which originate from relatively small ignition sources and usually take some time to develop, postcrash fires are extremely severe from their onset. In most cases, the fire originates from the ignition of large quantities of spilled jet fuel. The main concern is the spread of the fire into the aircraft and the effect of burning interior materials on passenger evacuation and the creation of untenable conditions. The primary design goals to enhance postcrash fire survivability are twofold: (1) additional available time for passengers to escape and (2) increased passenger evacuation rate.
Fire and Cabin Safety Program
The following is a brief description of the projects being conducted or planned under the Fire and Cabin Safety Program:
Halon Replacement. Consists of the conduct of full-scale fire tests to evaluate new extinguishing agents for equivalent performance to halon and the development of means of FAA approval of those agents determined to be suitable replacements for halon. Industry participation and harmonization with foreign airworthiness authorities is provided by the International Halon Replacement Working Group, chaired and administered by the Fire Safety Section. The final product is a set of minimum performance standards for each of four aircraft applications: lavatories, cabin (hand-held) extinguishers, cargo compartments and engine nacelles.
Regulatory Support/Accident Investigation. Provides relatively short-term, quick reaction activities when required as follows: (1) develop new or improved material fire test and/or procedures through the International Aircraft Material Fire Test Working Group, (2) support aircraft fire accidents and incident investigations conducted by NTSB, and (3) conduct studies and tests to formulate agency responses to NTSB recommendations. In addition to the above, products/deliverables include an updated Aircraft Material Fire Test Handbook, training videos and workshops for certification personnel, documentation of fire tests and chemical analysis in support of accident investigation, and witness testimony or participation at NTSB hearings.
Fuselage Burnthrough Resistance. Consists of full-scale and small-scale fire tests, and benefit analysis of past accidents, related to the hardening of aircraft fuselages against penetration by a postcrash, external fuel fire. The primary emphasis is on improvements in thermal acoustical insulation batts, including fiberglass insulation and film bagging material. Another consideration with the film is resistant against ignition and flame spread when subjected to in-flight fire ignition sources.
Smoke/Fire Detectors. Addresses two problems with cargo compartment smoke detectors: (1) lack of standard means of testing detectors to demonstrate compliance with regulatory response requirements and (2) extraordinarily high false alarm rates. The final product of the first subtask is a revision to AC 25-9A, "Smoke detection, Penetration, and Evacuation Tests and Related Flight Manual Procedures". The second subtask will consist of studies and tests to develop false-alarm-free detection concepts, focusing on multiple sensors and computer-aided signal analysis.
Oxygen/Nitrogen Gas Separation Membrane Technology. The final product is a prototype selective absorption membrane system to provide both emergency oxygen to passengers and a prototype inerting capability for fuel tanks or cargo compartments. The approach consists of testing of state-of-the-art membrane systems to assess feasibility for use on aircraft, determining the nitrogen inerting requirements for fuel tank or cargo compartment protection, developing a prototype system for installation in an aircraft, measuring the output performance of the system during flight tests and developing performance requirements.
Cabin Water Spray. Consists of the development of design criteria for an on-board cabin water spray system. Previous full-scale fire tests have demonstrated that cabin water spray significantly reduces postcrash fire hazards, thereby improving passenger/crew survivability. Important design issues that need to be addressed include the following: a separate fire performance test for spray nozzles, nozzle spacing, water discharge rate and total quantity, zone size, method of activation, crashworthiness considerations, aircraft size effects (e.g., ceiling height), utilization of potable water and safeguards against inadvertent activation.
Large Transport Fire Safety. Involves the development of fire safety design guidelines for future double-decked transports, carrying 500-800 passengers, such as the Very Large Comersial Transport (VLCT). Fire safety concerns are related to the large number of passengers and natural tendency of a fire to spread to the upper deck.
Cabin Safety. Primarily consists of the integration of cabin safety research undertaken or supported by the regulatory authorities in the United States, Europe, Canada and Japan. Activities include the development of an accident/incident database and a library of research publications, and the development of an accessible computer model to assess the benefit of a proposed safety improvement.
Fire Test Facilities
The Fire Safety Section operates extensive fire test facilities, devoted to the improvement of fire safety in civil aircraft. Testing capabilities span the full range of accident and environmental conditions, which may impact safety during postcrash and in-flight fires. Additionally, the scale of testing or sample sizes, depending on the test objectives, can be varied from a realistic, full-scale 130 foot-long wide body fuselage to milligram samples of advanced polymers. The behavior of materials and the effectiveness of fire detection and suppression systems are analyzed based on computer-recorded measurements and video/motion picture/photographic test coverage. Measurement capabilities include temperature, heat flux, smoke density, weight loss, pressure, agent concentration, and various gas concentrations such as carbon dioxide, carbon monoxide, oxygen, hydrogen cyanide, and other important toxic/acid gases. The temporal and spatial distribution of measurements are routinely determined. The following is a brief summary of the aircraft fire test facilities:
Full-Scale Fire Test Facility. This is the largest U.S. Government operated facility of its kind. Contains 130-foot-long wide body and narrow body fuselages for realistic, full-scale postcrash and in-flight fire tests. Designed to withstand a 20-foot-square postcrash fuel fire. Indoor full-scale test capability provides required assured control of postcrash fuel fire conditions lacking when tests are conducted outdoors. Detailed PDF
Chemistry and Material Science Laboratory. In the C&MS Laboratory, research and development of new or more fire resistant materials is conducted using state-of-the-art laboratory equipment for thermal analysis, calorimetry, spectroscopy, rheology, surface chemistry, microscopy, and multiaxial mechanical testing. Moreover, capabilities exist for identifying and quantifying the concentration of various toxic/acid gases produced during full-scale fire tests. Detailed PDF
Material Fire Test Facility. This facility is dedicated
to small-scale fire testing of aircraft materials and contains
all of the fire test requirements for aircraft materials
prescribed in the Federal Aviation Regulations (FAR 25.853).
The facility also contains screening tests for aircraft wiring
arc propagation and smoke emission and ignitability of aircraft
blankets and thermal acoustical insulation. A new fire test
for fuselage burnthrough resistance is under development
and a cone calorimeteris is employed for testing of advanced
fire resistant materials.
Aircraft Components Fire Test Facility. This facility houses two test bays designed and used for aircraft components or intermediate-scale fire tests. Recent/on-going testing includes the development of new fire test standards for flight recorders; evaluation of the fire hazards of solid oxygen generators, including the effectiveness of cargo compartment halon systems; development of a suitable simulant for certification of cargo compartment halon systems; evaluation of in-flight fire flammability of thermal acoustical insulation; and examination of the hazards of exploding aerosol cans and the effectiveness of halon systems. Detailed PDF
Engine Nacelle Fire Simulator. A simulator which mimics the environment of a high-bypass ratio turbine engine is used to evaluate halon replacement extinguishment agents. The simulator is an 80-foot-long duct containing the air supply equipment, approach and exhaust ducts, and a test section. Additional components provide for the delivery of different aviation fluids at desired temperature and quantity, precisely metered discharge of extinguishing agent, and simulator control and data gathering functions. A high speed, multi-channel gas concentration recorder provides for measurement of concentration histories of various agents. Detailed PDF
Airflow Induction Test Facility. This facility creates environmental conditions germane to in-flight fire safety. A large induction subsonic wind tunnel contains two test sections: high speed (Mach Number of 0.9, 5 ½ feet diameter by 16 feet long) and low speed (150 mph, 9 feet diameter by 20 feet long). A small low speed wind tunnel has accurate airspeed and six component force balance testing capability. An environmental test chamber can be programmed to simulate an entire flight, with pressure attitudes ranging from sea level to 100,000 feet and temperatures varying from -100° F to 250° F. A pressure vessel, measuring 5 feet in diameter by 20 feet long, with a working pressure of 600 psi, is being employed to examine the hazards of fuel tank explosions and exploding aerosol cans. Detailed PDF