On-Going Research

Wing Tank Flammability
Although the FAA has studied center-wing fuel tank flammability in detail, many assumptions relating the understanding of commercial transport wing tank flammability remain to be validated. Simple calculation models used by the FAA have also not been validated and could be modified given good comparison data. Tests are being performed at the William J. Hughes Technical Center by the Fire Safety Branch of the Aircraft Research and Development Division using the environmental chamber as well as the air induction facility (wind tunnel) to examine individual effects that contribute to commercial transport wing fuel tank flammability. This data will then be compared with previously acquired wing tank flammability measurements made during flight tests in an effort to gauge the fleet average flammability exposure time. The flight test data will also be compared to existing simple calculation models and additional calculation methods will be employed in an effort to see if calculations agree with existing flight test data.

Modeling of Ullage Flammability
An 18 cubic-foot aluminum fuel tank inside of an environmental chamber was used to simulate CWT in-flight conditions to validate calculations made by a multi-component fuel vaporization computer model. Fuel, surface, ullage, and ambient temperatures were measured, as well as ambient pressure and total hydrocarbon concentration with a flame ionization detector through a heated sample train. Temperatures, ambient pressure, and assumed fuel composition were used as inputs into the computer model, which then made calculations to determine the amount of fuel vapor present in the ullage over the course of the experiment, considering mass flux in and out of the tank as well as phase change in the tank. Calculated vapor composition was in good agreement with measured total hydrocarbon concentration. Future work will be done to simulate actual flight test scenarios in the laboratory as well as using recorded data from previous flight tests as model inputs to compare measured vapor concentration with recorded ullage hydrocarbon concentration. In addition, work is being performed to attempt to modify this model such that it will accurately predict flammability evolution in wing tanks throughout various flight conditions.