The Osprey aircraft crash that killed all eight service members on board last November off the coast of Japan was caused by a “catastrophic failure” of a rotor gearbox and the pilot’s decision to continue flying after several warnings to land, a Air Force Investigation released Thursday revealed.
The Nov. 29 crash near Yakushima involving an Osprey CV-22B — one of four fatal Osprey crashes in the past two years — led to months of grounding of the aircraft among the military and sparked a major investigation into the crash.
Questions remain about whether the aircraft, which takes off and lands like a helicopter but flies like an airplane, is safe and whether it should remain in the military.
“By conducting a thorough review and accident and safety investigations, we hope to provide answers to the families of the Airmen who lost their lives and prevent future occurrences and tragedies,” said former Air Force Special Operations Command chief Lt. Gen. Tony Bauernfeind, the officer who convened an Accident Investigation Board into the incident, said in a statement.
The investigation found that the accident was “caused by a catastrophic failure of the left rotor gearbox that created a rapidly cascading failure in the aircraft’s propulsion system,” causing the Osprey to flip violently and fall into the water.
Decision-making by the crew also played a role in the accident, as it was too “casual” during the military exercise, with the pilots “removing any consideration of a previous landing at a different diversion site.”
Even with the problems, officials in charge of the V-22 Ospreys knew that “total loss of aircraft and crew would be possible” if the gearbox components failed, lead investigator Lt. Gen. Michael Conley told media at Wednesday, as reported byThe Associated Press.
Conley also told the outlet that he believes the pilot’s instinct to finish the exercise led him not to land sooner.
Additionally, the V-22 Osprey office did not share safety data that could have educated crews about the severity of the risks of not landing, according to the investigation.
Specifically, much of the proprotor gearbox, known as the pinion, was to blame. The gearbox is the aircraft’s transmission and contains five pinion gears that rotate to send power from the engine to the Osprey’s masts and rotor blades. The Air Force doesn’t know why the part failed.
The Osprey was flying along the coast of Japan toward Okinawa when two vibrations occurred in the aircraft, one in the drive shaft connecting the aircraft’s two engines, followed by one in one of the pinion gears.
The vibrations are seen as signs of possible problems, but the pilot, Major Jeff Hoernemann, and his crew were unaware this was happening, as this data can only be downloaded and inspected at the end of the flight.
The Hoernemann received six warnings that chips – flakes of metal coming off the Osprey’s gear and a sign of stress – were happening, sending a warning to the pilot each time. Pilots are instructed to “land as soon as possible” after three such incidents, according to official guidance.
Investigators found that the decision not to land after each warning contributed to the accident.
When Hoernemann and his crew were unable to find any other problems, including overheating, he told his co-pilot to monitor the situation and opted to continue the exercise over water, according to the report, which obtained a voice data recorder from the day of the accident. .
The Osprey also has a chip detector that can burn small pieces of metal and prevent them from traveling in the oil and/or potentially tearing the transmission.
Until the final minutes of the flight, Hoernemann was focused on finishing the exercise and rejected his copilot’s suggestions to identify the nearest airfield to land.
After the sixth chip warning, with the indication that the Osprey was no longer capable of burning them, the aircraft should have landed “as quickly as possible”, but it appeared that the crew did not pay such urgent attention.
Conley told reporters that three minutes before the crash, the Osprey gave a final “chip detector failure” warning as the detector “had so many chips it couldn’t keep up.”
Hoernemann mistook the warning and previous ones as errors caused by a faulty chip detector and said he was not concerned.
Just before the crash, the Osprey was preparing to land and was just 800 meters from an airfield in Yakushima, but pulled out after Japanese traffic controllers told them to wait for local traffic to take off.
Hoernemann directed his co-pilot to “make one more big turn to the right and get in and prepare to land” as the pinion was breaking.
About six seconds after breaking apart, the Osprey’s gears and interconnected propulsion system suffered a serious failure and the aircraft crashed. There was nothing the crew could have done to save themselves or the aircraft, according to the investigation.
Several changes emerged after the accident, including new instructions for pilots to land as quickly as possible after the first chip burns and as quickly as possible after the second. The Osprey program, which resumed operations last month, is also creating a new system that would send vibration data to pilots in real time.
This story originally appeared on thehill.com read the full story
