A failed pilot bearing caused an MQ-1 Predator unmanned aerial vehicle to crash in the U.S. Central Command area of responsibility March 30, according to an Air Force report released Aug. 4.

The Predator, assigned to the 57th Wing at Nellis Air Force Base, Nev., was performing an intelligence, surveillance and reconnaissance mission when the propeller lost forward thrust and caused the aircraft to crash.

The aircraft was severely damaged on impact. Because of the remote location of the crash, key components were removed and the remainder of the aircraft was destroyed. The loss is valued at about $4.4 million. There was no other damage to government or private property.

The pilot bearing, located within the propeller shaft, provides radial support for the push-pull shaft and allows the propeller shaft to spin freely around a fixed quill shaft. The investigation determined long and progressive failure of the pilot bearing caused the adapter, which holds the quill shaft in place, to sheer. Once the adapter sheered, the quill shaft then unscrewed itself from the variable pitch propeller servo and drove the propellers to an extreme reverse pitch, causing the aircraft to endure severe drag and a high rate of descent.

FMI: www.af.mil