Introduction
On 20 November 2024, at 1323 Mountain Standard Time, a CV-22B Osprey (tail number 11-0060) assigned to the 27th Special Operations Wing at Cannon Air Force Base, New Mexico, experienced an incident while conducting takeoff and landing practice approaches at Wilderness Helicopter Landing Zone in Melrose Air Force Range. The mishap crew, consisting of an instructor pilot, a pilot, and two flight engineers, was performing day qualification and tactical events for the pilot's training.
Sequence of Events
After takeoff from Wilderness HLZ, the pilot executed a climbing right-hand turn to approximately 315 feet above ground level at 113 knots calibrated airspeed. The instructor pilot contacted range control to request a return to Cannon AFB. Immediately following that call, the aircraft experienced a series of cascading warnings, cautions, and advisories, culminating in a one-engine-inoperative condition and a left-hand proprotor gearbox (PRGB) failure. The crew evaluated the situation, the instructor pilot directed a landing, and the pilot conducted a safe emergency approach to landing.
Investigation Findings
The Accident Investigation Board (AIB) President determined by a preponderance of the evidence that the cause of the mishap was a catastrophic failure of the left-hand PRGB Lower Input Idler Helical Gear (part number 901-044-105-101, serial number VL00205587) due to a material inclusion in the gear's rim-to-web radius interface. After the material failure, an 8-tooth section of the gear punctured the PRGB case, creating a 12-inch by 6-inch hole, resulting in loss of oil and oil pressure. This caused a no-load condition on the left engine, leading to an overspeed condition. The full authority digital engine control commanded a shutdown of the left engine as designed. Engine power was automatically transferred from the right PRGB to the left PRGB for the left proprotor, providing enough lift for the crew to maintain controlled flight and execute an emergency landing.
Damage and Aftermath
The estimated cost of damage to the aircraft was $2,795,884. There was no damage to civilian property, no fatalities, and no injuries. The incident occurred approximately 1 nautical mile north of Melrose Air Force Range on rancher-leased New Mexico state land.