Flaw in Osprey Gears Was Known a Decade Prior to Deadly Japan Crash, Internal Report Shows

Internal safety documents obtained by Military.com show that warnings related to a mechanical issue that caused an Air Force Osprey to crash off the coast of Japan last year, killing eight airmen, had been identified as far back as 2013 but seemingly went unaddressed.

An investigation released earlier this month by the Air Force pointed to an issue in the controversial tilt-rotor aircraft's prop rotor gearbox as a cause of the Nov. 29 crash. Specifically, the service identified a single high-speed planetary pinion gear that had fractured.

But an internal Safety Investigation Board report -- which has not been made public -- showed that other gears in that gearbox similarly failed in 2013 and warnings related to that part failure were brought to the Pentagon a year later. Plus, serious manufacturing issues plagued the components for years.

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The Osprey, call sign Gundam 22, was on an Air Force Special Operations Command training mission off the coast of Yakushima Island, Japan. As the single gear began to shred, it sent debris throughout the gearbox, which in turn began to fail and caused the left proprotor to stop operating. The aircraft then fell out of the sky.

It was the deadliest CV-22B crash in the Air Force's history, claiming the lives of Maj. Jeffrey T. Hoernemann; Maj. Eric V. Spendlove; Maj. Luke A. Unrath; Capt. Terrell K. Brayman; Tech. Sgt. Zachary E. Lavoy; Staff Sgt. Jake M. Turnage; Senior Airman Brian K. Johnson; and Staff Sgt. Jake Galliher.

History of Gear Defects

Both the Air Force's public report, called an Accident Investigation Board, or AIB, and its internal Safety Investigation Board, or SIB, reports into the crash agree that Gundam 22 was brought down by the fracturing of a single gear -- a high-speed planetary pinion gear -- into five large pieces, which caused other failures in the proprotor gearbox.

The reports also go on to fault the Air Force Special Operations Command crew for not heeding the warning lights even though, according to members of the Osprey community, the warnings the crew received were considered common and the community often saw them as just part of the aircraft's operation.

However, the internal safety report found that the high-speed gear that failed on Gundam 22 because of a single crack was "similar to those seen on seven previous failures in low-speed planetary pinion gears." The two sets of gears sit next to each other in the gearbox and are made from the same alloy.

It notes that in all the other instances the Ospreys landed before the gear failed completely.

Later analysis showed that five of those prior failures, which go back to 2013, were caused by "non-metallic inclusions" -- a defect in the metal alloy from which the gears were made. Air Force investigators say that Gundam 22's gear also cracked "most likely due to non-metallic material inclusion."

Furthermore, the report found that, given the rate at which those inclusions were making it into the alloy used in the gears, a failure such as the one Gundam 22 experienced was bound to happen.

"The number of failures in low-speed planetary pinion gears will have a similar ratio to high-speed planetary pinion gears," the Air Force investigators wrote, before noting that, given "five such failures in low-speed planetary pinion gears ... one failure in the high-speed planetary pinion gear can be expected."

In 2014, the Joint Program Office, which oversees the Osprey program for the Pentagon, was sent a formal risk assessment titled "Gear Metal Raw Material Impurities" by Bell Textron and Boeing, the companies that build the Osprey. But, according to the Air Force internal investigation, the notice "did not adequately assess risk of high-speed gear failure."

Investigators also found that there was no testing of the high-speed gears done at the time, which meant there wasn't an "adequate understanding of the failure that occurred in this mishap."

When the Osprey program office -- part of Naval Air Systems Command, or NAVAIR -- received the notice in 2014, it did not fully process it to determine whether the risks it outlined would just be accepted by the military or somehow mitigated. It is not clear from the Air Force investigation why that did not occur.

Instead, the report found that "NAVAIR implemented contractual financial withholds in hope the contractor would correct deficiencies in the [alloy] processing that had resulted in previous gear failures."

That contractor -- Universal Stainless -- made the alloy that later failed in Gundam 22 and since 2014 has supplied "a significant proportion" of the alloy used in the Osprey gearboxes that are now under scrutiny.

Yet, since that Bell-Boeing risk assessment was issued in 2014, Air Force investigators found that "there have continued to be inclusion failures in [alloy], suggesting contractual financial withholds did not prompt corrective actions."

Military.com reached out to Bell Flight, the point of contact for questions regarding the V-22, for comment but did not receive a reply in time for publication.

Military.com also specifically asked the Joint Program Office whether NAVAIR still stands by its choice to use a financial approach as a way to handle substandard materials in V-22 component manufacturing or if Universal Stainless still makes parts for the aircraft.

The program office declined to comment.

J.J. Gertler, an aviation analyst and expert with the Teal Group, told Military.com in an interview that such an approach is "not unusual" but said ultimately the aircraft was approved to be received at the end of those negotiations.

"There are progress payments that go on during the course of a contract. It's not that they get all the money at the beginning or the end, and those progress payments are often withheld or modified until certain criteria are met, like you've got to hit this standard on that part or this amount of durability," Gertler said.

Ultimately, he said, somebody approved the aircraft to be received by the military.

Joint Program Office Role

Within the public report on the deadly crash in Japan was also a suggestion that the Joint Program Office had a role to play in the crash.

Air Force investigators found "that inadequate action at the program level and

inadequate coordination between the program office and the services prevented comprehensive

awareness" of the risks of the failures within the gearbox, and "substantially contributed to the mishap."

While the public report does not offer further detail about what actions the Osprey program office should have taken, the internal report shows that it was aware of at least five instances of gear failures on the low-speed side of the same gearbox that was at fault in the Gundam 22 crash.

Military.com reached out to the Osprey program office with nearly a dozen questions stemming from our review of the internal Air Force report, but officials declined to comment specifically on the safety investigation board findings.

An Air Force Safety Center spokesman declined to authenticate parts of the document, citing "the integrity of the information that may come from it." The documents obtained by Military.com are marked "Controlled Unclassified Information" -- a label used for nonsecret but internal information that the government wants to keep out of public view.

"Safety investigations are highly effective because of their inward-facing, limited-use analysis and follow-up action, a product of military safety privilege," Keith Wright, a spokesman for the Air Force Safety Center, told Military.com earlier this month. "The Accident Investigation Board is the official release mechanism for accident information."

The details about previous gear failures in the Osprey also cast doubt on the statements and assurances of top NAVAIR officials who claimed the issue that brought down Gundam 22 had not been encountered before or seemingly came out of left field.

Vice Adm. Carl Chebi, the head of NAVAIR, which oversees all V-22 operations across the military, said during a June 12 congressional hearing on Osprey safety "that data was presented to myself that indicated that the platform had experienced a catastrophic material failure that we have never seen before in the V-22 program."

NAVAIR and the V-22's Joint Program Office did not return a request for comment asking them to clarify Chebi's comments.

Past indications about possible safety issues with the gearbox were also not fully communicated to those flying and maintaining the aircraft.

Rebecca Heyse, a spokeswoman for the Air Force's Special Operations Command, told Military.com -- citing the public accident report findings -- that NAVAIR has done safety assessments on the gearbox and said those analyses found "failure to be remote or improbable, but also indicated that total loss of aircraft and crew were possible."

Heyse added that program-wide changes, such as advising less risky responses in certain situations, "were not always implemented, or were implemented in a manner that did not stress the severity of the risk." She noted that aircrew training on how to react to gearbox indications wasn't modified and that the findings "were not always communicated to the military services, limiting opportunities for service-specific changes."

Military.com reported earlier this month that AFSOC has now changed some of its protocol for aircrews in the wake of the crash.

Chebi has previously said that he doesn't expect the V-22 to be fully operational again until at least "mid-2025." But Lt. Gen. Michael Conley, the head of Air Force Special Operations Command, told reporters earlier this month he hopes to be supporting combatant commanders with the Air Force's Osprey by the end of the calendar year.

The revelations about the history of the gear problems come as family members from the Japan crash, as well as families of Marines who died in a 2022 V-22 Osprey training crash in California, are seeking legal representation.

Family members of the Marines filed a wrongful death lawsuit in May against Bell Textron and Boeing, which oversee the aircraft design, and Rolls-Royce, which manufactures the engines. It was not yet clear whether the families of the Japan crash victims are seeking a similar lawsuit.

Related: Pilots, Family Members Say Crew Is Being Unfairly Blamed for November's Deadly Air Force Osprey Crash