The fuel vapor conditions that may exist in aircraft fuel tanks and their relative flammability characteristics are very complex. These complexities result from the infinite conditions that may be produced by aircraft motion, atmospheric changes, and the multicomponent nature of turbine fuels. The objective of this investigation, which was sponsored by the FAA, was to define the effects that these many variables might have on fuel tank flammability, especially when considering turbulent flight conditions. By means of instrumental techniques which were developed primarily for this study, the equilibrium flammability characteristics were then compared to those which were conducted under simulated aircraft dynamics. It was determined that spraying fuel droplets into the tank vapor space by vibration can cause marked changes to the normal equilibrium flammability characteristics of turbine fuels.