> our title:

USAF: Turbo Failure Caused Predator Crash

> original title:

MQ-1B Predator Accident Report Released

(Source: US Air Combat Command; issued Jan 08, 2015)

LANGLEY AFB, Va. --- Severe turbulence and a turbocharger failure led to the crash of an MQ-1B Predator high in the mountains north of Jalabad, Afghanistan, June 25, 2014, according to an Air Combat Command Abbreviated Accident Investigation Board report released today.

The aircraft and munitions aboard were destroyed on impact, with a loss valued at approximately $4.8 million. There were no injuries or damage to private property.

The aircraft was assigned to the 432nd Wing, Creech AFB, Nev., and its crew was assigned to the 27th Special Operations Wing based at Cannon AFB, N.M. When the accident occurred, the aircraft was conducting a combat support mission in support of Operation ENDURING FREEDOM.

The investigation board president found by a preponderance of evidence that the cause of the mishap was a turbocharger failure. The failure occurred as power was increased in an attempt to maintain its assigned mission altitude. After descending into mountainous terrain, the aircraft was unable to maintain a safe altitude due to downdrafts produced by severe turbulence.

Because the wreckage was unrecoverable, the investigation was unable to definitively pinpoint an exact cause for the failure. However, the manufacturer of the turbocharger stated the symptoms of this failure were similar to other failures caused by oil "coking" due to excessive crankcase pressure. Coking is the process by which oil breaks down at high temperatures, resulting in a solid residue which can prevent the turbocharger from spinning when power is increased. In this case, the resulting lower engine performance contributed to the inability of the aircraft to maintain a safe altitude.