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Tests were performed at the Federal Aviation Administration William J. Hughes Technical Center by the Fire Safety Team of the Airport and Aircraft Research and Development Group to determine if intermixing different manufacturer cells within an aircraft nickel-cadmium battery has an effect on battery performance and if any such effect results in a safety of flight issue.
A series of tests from RTCA/DO-293 were conducted on two batteries, one consisted of all original equipment manufacturer (OEM) cells, and one consisted of ten OEM and ten Part Manufacturer Approval (PMA) replacement cells. The tests included several rated capacity tests, a charge stability test, a duty performance test, and an induced destructive overcharge test. Throughout the tests, only slight differences between the OEM and intermixed batteries were observed. The PMA cells consistently charged at a higher voltage; however, none of the cells exceeded the maximum voltage of 1.7 V. During some tests, individual cells showed some differences in behavior and recorded battery temperatures. The most notable difference occurred during the induced destructive overcharge tests, in which a larger number of cells from the intermixed battery recorded increased voltage readings, indicating signs of thermal runaway. The results show no indication of any safety of flight issues arising from the intermixing of OEM and PMA battery cells within a nickel-cadmium aircraft battery.
Following the Boeing 747 freighter airplane accident on September 3, 2010, at Dubai International Airport in the United Arab Emirates, the Federal Aviation Administration, Transport Canada, and the United Kingdom Civil Aviation Authority initiated a study to assess the magnitude of the potential threat to freighter airplanes from onboard cargo fires. As part of this study, a risk model was developed to assess the likely number of U.S.-registered freighter fire accidents through the year 2020 and the average annual cost due to their occurrence. The study focused on the potential fire threat from the bulk shipment of lithium batteries (primary and secondary) because they were likely contributors to two of the freighter fire accidents that occurred on U.S.-registered airplanes. For this reason, the risk model considered the potential threat from lithium batteries separately from other cargo.
This report summarizes the risk model, explains the data and algorithms used, and explains how the model may be used. Subsequent phases of this study will address cost benefit ratios for various mitigation strategies.
Click here to download the model (MS Excel 2007 or later, 101 MB)
The Airport and Aircraft Safety Research and Development Group Fire Safety Team performed tests at the Federal Aviation Administration William J. Hughes Technical Center using the environmental chamber and the Air Induction Facility (wind tunnel) to examine the variation in flammability exposure of a fuel tank composed of a composite material skin and a traditional aluminum skin. Tests were also conducted to examine the impact of material topcoat color on fuel tank temperature and hydrocarbon concentrations.
The correlation between high total hydrocarbon concentration measurements and high ullage temperature increases in all tests provided further indication that ullage temperature changes were the driving force behind in-flight flammability for fuel tanks when heated from above. This is contrary to what had been found for a heated center wing fuel tank in which the average bulk fuel temperature is the main driver behind fuel tank flammability.
The tests showed that composite panels, regardless of topcoat color, have the potential to result in a significant increase in flammability exposure because they transmit radiant heat into the fuel tank much more readily than a traditional aluminum fuel tank. However, the results also showed that under the right conditions, either through additional heat input or a change in material topcoat color, an aluminum fuel tank could behave similar to a composite fuel tank.
This report summarizes the Federal Aviation Administration research effort to develop a laboratory-scale test method for evaluating the thermal decomposition products produced inside an intact transport category fuselage during exposure to a simulated external fuel fire. An oil-fired burner, configured in accordance with Title 14 Code of Federal Regulations Part 25.856(b) Appendix F Part VII, was used to simulate the fuel fire, and a 4- by 4- by 4-foot steel cube box was used to mount representative test samples. The cube box simulated an intact fuselage and served as an enclosure to collect emitted gases during fire exposure. Test samples representing a variety of fuselage constructions were evaluated, including a noncontemporary prototype structural composite material (without thermal acoustic insulation). A typical cross section consisted of a 40- by 40-inch aluminum panel representing the fuselage skin and the accompanying thermal acoustic insulation blanket behind the skin. Two thermal acoustic configurations were also tested. The first contained a heat-stabilized polyacrylonitrile fiber blanket. The second contained a ceramic paper barrier sandwiched under a fiberglass blanket. Each was encased by a thin metallized polyvinylfluoride moisture barrier. These burnthrough-resistant configurations were primarily run to provide a baseline for comparing the emitted gas concentrations with the prototype structural composite material.
A specialized Fourier Transform Infrared/total hydrocarbon gas analysis system was used to continually measure the products of combustion collected within the enclosure. Additional analyzers continuously measured the amount of carbon monoxide, carbon dioxide, and oxygen in the collected stream.
During the tests, it was determined that a prototype multi-ply structural composite material produced minimal quantities of toxic and flammable gases during a 5-minute fire exposure. Approximately 7 plies of the 16-ply carbon/epoxy structural composite material were delaminated by the fire exposure. By comparison, the aluminum skin/insulation configurations generated higher gas concentrations.
Subsequent full-scale tests were conducted using these material systems inside a Boeing 707 fuselage. These tests were run to determine realistic levels of combustion products that can be generated inside the fuselage during a fuel fire when using burnthrough-compliant materials identical to those previously tested in the laboratory-scale tests. The full-scale tests used a fire-hardened steel cylinder test section in which insulation materials could be installed and evaluated against a standard 8- by 10-foot fuel pan fire. A comparison of the laboratory- and full-scale gas analysis results was made to determine the scaling factor for gas concentrations. By determining the scaling factors, an appropriate gas concentration acceptance level could be established for the laboratory-scale apparatus. The goal was to use this laboratory-scale test and scaling factors to predict thermal decomposition product concentrations for burnthrough-resistant insulation. The predicted full-scale concentrations can be used to assess the survival and health hazards of various insulation systems exposed to external fuel fires.
This technical note is an overview of Federal Aviation Administration (FAA) fire safety research over the past 10 or more years, with a focus on in-flight fire safety. The technical note emphasizes research accomplishments that have been, or are being, implemented into commercial aviation, as well as other important fire safety research. The research was driven by fatal accidents and safety concerns associated with new technology, such as:
Federal Aviation Administration