Question

One of the explanations for the accident with TWA 800 (exploded in midair after takeoff from JFK airport in New York) was as follows: wire cuts in the vicinity of the central fuel tank caused arcing to occur which ignited the fuel vapor present in the fuel tank. What safety assessment process deals with this kind of failures? Explain your answer.

Answer 1

An inerting system decreases the probability of combustion of flammable materials stored in a confined space, especially a fuel tank, by maintaining a chemically non-reactive or inert gas, such as nitrogen, in such a space. Inerted fuel tanks may be used on land, or aboard ships or aircraft.

Three elements are required to initiate and sustain combustion: an ignition source (heat), fuel and oxygen. Combustion may be prevented by reducing any one of these three elements. If the presence of an ignition source can not be prevented within a fuel tank, then the tank may be made non-ignitable by:

1) reducing the oxygen concentration of the ullage,the space above a liquid fuel,to below that capable of combustion (the combustion threshold).

2) reducing the fuel concentration of the ullage to below the lower explosive limit, the minimum concentration capable combustion.

3) increasing the fuel concentration to above the upper explosive limit, the maximum concentration capable of combustion.