Fatal F-15 crash caused by violent spin, Air Force says

Pilot error coupled with "aircraft anomalies" sent an F-15D Eagle into a violent spin during air combat training, causing the July 30 jet crash on Nellis Air Force Range, the leader of an Air Force investigation team said Monday.

Lt. Col. Thomas Bouley, the pilot, died in the crash of the two-seat fighter jet.

An unidentified British Royal Air Force flight lieutenant in the back seat survived by ejecting about 740 feet above ground. He suffered minor scrapes and bruises and has since returned to duty.

"He's a lucky man," said Brig. Gen. Robert Otto, president of the accident investigation board, during a telephone call with reporters from Beale Air Force Base, Calif.

"The seat worked absolutely as advertised, and he's in that gray area where he wouldn't survive that ejection every time," Otto said during the conference call coordinated by Air Combat Command in Langley, Va.

In the rapid descent, Bouley's seat didn't release until the out-of-control plane was 586 feet above ground, beyond the specifications for survival.

Bouley, who was commander of the 65th Aggressor Squadron at Nellis, exceeded the F-15D's limitations for less than a half second as the aircraft descended in a pre-planned, routine maneuver from 31,000 feet above sea level to 3,000 feet above ground level.

Otto said Bouley of North Las Vegas had performed that maneuver "hundreds of times. He did not mis-execute this maneuver. It was this yaw-roll phenomenon that created this spark" of uncontrolled flight that resulted in the jet spinning about 20 times in a span of less than 90 seconds, causing Bouley to become disoriented and misjudge how close the plane was above ground.

"I concluded he looked inside the cockpit to reset some switches for a short period of time and had an illusion he was in a spin in the opposite direction," Otto said.

The aggressor squadron's role in the Red Flag air combat exercises is to act as enemy aircraft. At the time of the mishap, Bouley's jet, valued at $38 million, was 40 miles from the nearest adversary.

Investigators found "clear and convincing evidence this mishap was caused by a sudden departure from controlled flight during a routine maneuver when the mishap pilot momentarily exceeded the allowable angle of attack," the board's 32-page executive summary concluded.

Other factors "substantially contributed to the mishap," the summary said. Those were an external wing fuel imbalance of roughly 750 pounds; a left yaw-roll phenomenon, or aerodynamic anomaly, related to a pair of external wing fuel tanks; and an imperfection in the nose cone that contains a radar device to help correct uncontrolled flight.

After dozens of simulations of the mishap, Otto said the board determined that a "boot," or thin protective cover over the nose cone radar, might have been torn or blistered, causing the control system to function improperly.

The protective covers had been used to prevent scratches and dents on the nose cone but, in retrospect, the boots themselves can cause problems, Otto said.

As a result, the boots are being removed when scheduled maintenance is performed. "The Air Force believes we'll do better without them," Otto said.

The board also recommended enhanced inspections of the nose cone to avoid potential malfunctions caused by defects.

Bouley was a command pilot with more than 4,200 total flying hours, including 265 combat hours in the F-15C and Tornado F-3 during operations Northern Watch, Southern Watch and Iraqi Freedom.

From October 2006 until he took command of the 65th Aggressor Squadron in February this year, he was the deputy commander of the Red Flag training squadron.

"He was a highly motivated, capable and highly respected pilot," Otto said.

Contact reporter Keith Rogers at krogers@reviewjournal.com or 702-383-0308.