During an attempt to set a low-level speed record, the F-4 phantom experienced a PIO followed by a subsequent breakup of the aircraft as structural loads were increased beyond design limits. This accident occurred on May 18 1961. At 200ft altitude and Mach 1.1 the aircraft reached -4 and +14 Gs after only 3 oscillations. The PIO tendencies were pronounced if the stick forces were not completely trimmed out. The pilot had previously use the procedure of holding 20lb of push forces during low-altitude high-speed runs to create a nose-up safety margin if he relaxed pressure on the controls due to distraction.
- RTO-TR-029