Ray Cherry and Kevin Warren

The International Cabin Safety Research Technical Group’s Survivable Accidents Database was used to identify past worldwide transport aircraft accidents and extract detailed data for those accidents where explosion was an issue in the survivability of the occupants. Each of these accidents was analysed in depth to assess the number of lives and injuries that might be saved if the fuel tanks were protected with nitrogen inerting systems.

The objective of this analysis was to assess the potential benefits, in terms of reducing fatalities and injuries, resulting from three methods of aircraft fuel tank inerting. The methods analyzed were ground nitrogen inerting in centre fuel tank only, ground nitrogen inerting in all fuel tanks, and onboard nitrogen inerting in all fuel tanks.

Thirteen accidents to transport category aircraft were identified during the period from 1966 to 1995 that may have involved a fuel tank explosion. A mathematical technique was used to model each accident scenario and a Monte Carlo simulation was used to assess a high, median, and low value for the total achievable benefits.

J. G. Quintiere

Data were taken to show the flame spread characteristics of thin materials burning on an insulating substrate. Metalized polyethylene terephthalate (0.20 mm) and paper (0.17 mm) were burned on the surface of glass fiber insulation. Flame spread was measured in the upward or downward facing orientation for the material and in the directions of gravity assistance (up) or gravity opposition (down). Measurements were taken at various angles ranging from a vertical to a horizontal orientation.

A theoretical analysis was developed to predict the flame spread as a function of material properties, sample orientation, and flame spread direction. The one-dimensional theory was in reasonable agreement with paper data. Vertical upward spread was found to yield the highest velocity.

Ray Cherry and Kevin Warren

The objective of this analysis was to assess the potential benefits, in terms of reduction of fatalities and injuries, resulting from improvements in fuselage burnthrough resistance to ground pool fires. The process employed for assessing benefit is considered to give reasonably accurate and consistent results within the limitations imposed by the available data. The methodology gives a reasonable assessment of the tolerance on the predicted levels.

Fire hardening of fuselages will provide benefits in terms of enhanced occupant survival and may be found to be cost beneficial if low-cost solutions can be found. The maximum number of lives saved per year in worldwide transport aircraft accidents, over the period covered by the data, was assessed to be 12.5 for the aircraft in its actual configuration and 10.5 for the aircraft configured to later airworthiness requirements.

Steven M. Summer

This report discusses experiments performed within a simulated fuel tank approximately 1/20 the size of a typical B-747 center wing fuel tank (CWT). The vapors generated within the ullage of this tank were analyzed under different mass loadings in an effort to determine the effects of the mass loading and fuel distribution. It was determined from these tests that in order to have a substantial effect on the flammability of the vapor within the CWT, the mass loading would have to be somewhere between 0.08 and 0.15 kg/m3. A substantial effect was defined as a minimum 20% decrease in the maximum hydrocarbon count when compared to the average of all tests conducted with larger mass loadings. In addition, it was found that while the distribution of the fuel has no effect on the peak flammability (vapor composition) that is reached, it does have a significant effect on how long it takes to reach the final state. The less dispersed the liquid fuel is, the longer it will take the vapor to reach its maximum flammability point.

Douglas A. Ingerson

The primary fire suppressant used in commercial aircraft engine nacelles and auxiliary power units is Halon 1301. The period of fire suppression system development and its certification testing may be an arduous task requiring the discharge of substantial quantities of fire suppressant. Additionally, to demonstrate compliance with federal regulations, engine nacelle fire suppression systems are discharged in flight or at varying conditions simulating flight. These tests are recorded and evaluated with specialized gas analysis equipment. Currently, the certification process requires releasing Halon 1301 to accomplish such approvals.

Based on the Montreal Protocol and its amendments, the halon family of fire suppressants has been eliminated from production. This action is in response to the destructive capacity of halon with respect to the ozone layer within the atmosphere. This technical note describes a procedure for utilizing an ozone-friendly simulant during fire suppression system development and certification testing. It demonstrates a realistic potential to eliminate the release of Halon 1301 for purposes other than actual fire suppression. This step is perceived as an interim process to assist with the reduction of Halon 1301 release during the transition to chemicals which meet the intent of the Montreal Protocol.