Pilot Exceeded Limitation Speed, Entered Spin

A combination of human factors and aircraft anomalies caused a spin during a July 30 crash of a two-seat F-15D Eagle during a Red Flag exercise at Nellis Air Force Base, NV according to an Air Combat Command accident investigation board report released this week.

The pilot in command, Lt. Col. Thomas Bouley, was killed in the accident. An observer pilot, a Royal Air Force flight lieutenant, sustained minor injuries and was treated and released.

According to the AIB report, the accident pilot momentarily exceeded a technical order maneuvering limitation that is in place when the F-15D has fuel in the external wing tanks. Additionally, spatial disorientation resulting from the aircraft spin hampered recovery and was also cited as a cause.

When the pilot momentarily exceeded limitations, the aircraft departed from controlled flight due to the "left yaw/roll phenomenon," an aerodynamic anomaly that affects some F-15D's with two external fuel tanks. The departure, when coupled with an external wing tank fuel imbalance, resulted in the F-15 going into a spin.

Through simulations, investigators concluded that once in this spin, recovery was delayed by a radome, or nose cone, imperfection. Although the nose cone was too damaged to analyze, simulations provided substantial evidence that a radome anomaly aggravated the aircraft's spin recovery.

The violent and prolonged spin left the pilot spatially disoriented, which hampered the dive recovery, necessitating ejection. The observer pilot, who was sitting in the F-15's backseat, was ejected first, and he survived the crash. The mishap pilot was ejected .4 seconds later and did not survive the crash.

The aircraft, valued at $38 million, was assigned to the 57th Wing at Nellis.

FMI: www.af.mil