Republic XF-84H Thunderscreech traveled faster than the speed of sound even at idle thrust, producing a continuous visible sonic boom that radiated laterally from the propellers for hundreds of yards. The shock wave was actually powerful enough to knock a man down; an unfortunate crew chief who was inside a nearby C-47 was severely incapacitated during a 30-minute ground run. Coupled with the already considerable noise from the subsonic aspect of the propeller and the T40's dual turbine sections, the aircraft was notorious for inducing severe nausea and headaches among ground crews. In one report, a Republic engineer suffered a seizure after close
Undercompressive shock wave Undercompressive shock wave An undercompressive shock wave is a shock wave that does not fulfill the Peter Lax conditions. Ordinary shock waves are stable, that is the speeds of characteristic behind the shock are greater than that of the shock itself, which is greater than the characteristics in front of the shock. The characteristic speed is the speed of small, travelling perturbations. These conditions are necessary for a shock wave to remain and not decay. If the peak of a wave moves faster than at its base, then the wave front becomes self-sharpening and eventually becomes a nearly discontinuous shock,