In the years following World War II, aerodynamic research and development entered one of the steepest learning curves it would ever encounter. With the advent of jet-powered aircraft, speeds climbed up to and beyond the sound barrier, and along the way, numerous phenomena were discovered. One area that required extensive study was the transonic regime, and the unique Northrop X-4 Bantam was developed to study it in depth.
During transonic flight, an aircraft can be flying well below the speed of sound, but local airflow around various parts of the wing and airframe can accelerate beyond the sound barrier and create serious concerns. The first documented accident involving these effects occurred in 1941, when a test pilot named Ralph Virden was performing a dive test in a Lockheed P-38 Lightning. Upon reaching Mach 0.675, a shock wave caused the inboard wing sections to stall. Virden lost control and perished in the ensuing crash.
