Some Mechanical and Structural Aspects of the Smolensk Crash
By Dr. Gregory Szuladzinski, Ph.D., MSME
SCND2014GS

Appendix III. Fuel in Special Circumstances

The following applies to the behavior of aircraft fuel under accident conditions.

The liquid fuel can be ignited but only the vapors are really flammable.

A spark is needed to ignite, shock itself is not enough. Initially, degree of burning is fairly mild with a flame advancing at subsonic speeds (less than 340 m/s). It is called deflagration. Under favorable conditions, i.e. in sufficient concentration of vapor, the flame will accelerate, sometimes reaching very high speeds. It promotes detonation or the initiation of a blast. But in order for detonation to take place, one needs a complex set of conditions to fall into place.

Fuel explosions typically have a more even distribution of energy in the volume of the vessel than HE materials, resulting in splitting of the container into a few parts rather than shattering it into many debris.