Accident Summary
On 15 June 2020 at 0827 Z (0927 L), an F-15C, tail number 86-0176, assigned to the 493rd Fighter Squadron at Royal Air Force Lakenheath, United Kingdom, crashed into the North Sea approximately 124 nautical miles northeast of the base. The aircraft was destroyed and the pilot, the sole occupant, was fatally injured. The mishap occurred during a local combat training sortie.
Sequence of Events
The mission was a local combat training flight. Weather in the training airspace included multiple cloud layers up to 25,000 feet, so the sortie was conducted using Instrument Meteorological Conditions (IMC) rules when IMC was encountered. During an air-to-air training engagement, the mishap pilot (MP) was flying east at 20,300 feet and was directed by his element lead to execute a hard right turn toward the west to look for an adversary aircraft (AA) at a lower altitude. The MP made a descending right turn, locked onto the AA with radar, and executed a simulated missile shot. After receiving a radio transmission indicating the shot was a miss, the MP continued maneuvering to re-engage the AA, which was then 5.5 nautical miles southwest of his position.
The MP entered a descending left turn through IMC, lowering the aircraft's pitch attitude to 42 degrees nose-low with varying left bank angles from 21 to 107 degrees. During the maneuver, the MP experienced 0.3 to 3.8 G-forces and accelerated to 579 knots true airspeed, reaching a maximum descent rate of 38,800 feet per minute. The MP descended below the briefed training floor of 4,000 feet. At approximately 1,000 feet, the MP maneuvered the aircraft to nearly wings-level and pulled 8.2 G-forces in an apparent attempt to recover, but the aircraft impacted the water at 10 degrees pitch low, 4 degrees left bank, and 566 knots true airspeed. The MP did not eject.
Weather and Environment
Forecast and observed weather indicated multiple cloud layers up to 25,000 feet with reduced visibility. The lack of a discernible horizon contributed to the pilot's spatial disorientation.
Medical and Human Factors
The mishap pilot was qualified and had no known health issues. Toxicology tests were performed as part of the investigation. Human factors identified included fixation on the intercept of the adversary aircraft, breakdown of visual scan in IMC, and spatial disorientation.
Probable Cause
The Accident Investigation Board found, by a preponderance of the evidence, that the cause of the mishap was the pilot’s fixation on his intercept of the adversary aircraft and failure to execute cockpit instrument visual scans when the pilot encountered IMC. Reduced visibility and lack of a discernible horizon resulted in spatial disorientation. The pilot's inability to accurately sense the pitch attitude of the aircraft due to spatial disorientation substantially contributed to the undesirably low pitch attitude, rapid descent, and the mishap.