An imperfection in the tip of an F-15D's nose ultimately brought the Eagle down, causing it to crash on Oct. 8 in a north England field, the Air Force announced this week.
The F-15, assigned to the 493rd Fighter Squadron, RAF Lakenheath, crashed during a training flight. The pilot was able to ejected and sustained minor injuries. The F-15 was destroyed at a loss of more than $44 million, and the Air Force paid a local farmer more than $600,000 to clean the wreckage.
The F-15 was part of a two-ship flight performing basic fighter maneuver training that afternoon in the East Anglia airspace north of the base. During the third and final exercise, the F-15 participated in a short-range defensive engagement at about 18,000 feet when the pilot performed . The pilot began with a slightly nose-low, 7g turn at full after burner before performing a maneuver called "vertical jinks" as a way to get away from a trailing jet.
The pilot lowered the throttle and performed two nose-low - maneuvers, dropping about 2,000 feet and changing direction abruptly. During this maneuver, the F-15 began to oscillate and entered into a flat spin. The pilot began to follow instructions on his heads-up display, but was unable to recover.
About two minutes after beginning the maneuver, the pilot radioed to his wingman "I'm out, man," and ejected. The F-15 crashed into a local field, and the pilot was recovered by a pararescue crew out of Lakenheath.
Air Force investigators were able to recover the front section of the Eagle's radome, which showed an imperfection on the tip, called the nose cap. There was a gap between the radome body and the cap, with about 3/16th of an inch of sealant extruding from the section creating "an uneven aerodynamic surface," an Air Force Accident Investigation Board report stated.
The F-15 System Program Office told investigators that an imperfection like this is consistent with wind tunnel tests that found it would cause a high enough yaw rate to create an aircraft spin.
The accident board concluded that the F-15 crash was caused by this imperfection, combined with the pilot's abrupt aft-stick pull that put it the aircraft into the spin.
