The U.S. Air Force and Navy adhered to the operational pause called by NAVAIR after a precautionary landing in November caused by an engine failure.
Flight operations of the V-22 Osprey tiltrotor have been paused once again on Dec. 9, 2024, after a recent incident. In fact, the U.S. Air Force and Navy adhered to the operational pause called by Naval Air Systems Command (NAVAIR) on Dec. 6, after an Osprey performed a precautionary landing due to an engine failure.
NAVAIR recommended an operational pause “out of an abundance of caution” based on the initial investigation. “The safety of our V-22 aircrew is our top priority. We are committed to ensuring our Sailors, Airmen and Marines are able to successfully complete their missions and return home safely,” NAVAIR said.
The Associated Press, which first reported the news, said that this pause is indefinite as the services look at how the safety issue can be mitigated. It is unclear at this time if the Marines and Japan also adhered to the pause.
The incident
The incident which prompted the pause involves an Air Force Special Operations Command (AFSOC) CV-22 and happened at Cannon Air Force Base, New Mexico, on Nov. 20. According to the Associated Press, the incident presents similarities to the crash off the coast of Japan in November of last year, and the measures adopted after it allowed to save lives.
In fact, it is being reported that the CV-22’s received similar warnings in the cockpit shortly after takeoff and subsequently lost an engine. The crew was able to quickly perform a safe landing and put the tiltrotor on the ground.
The initial investigation found that metal parts broke and shown metal weaknesses similar to the one found in the Osprey crashed in Japan. The unspecified part that failed, however, is reported to be different than the Prop Rotor Gear Box.
Lt. Col. Becky Heyse, AFSOC spokeswoman, said in a statement that the command is “in close coordination with the V-22 Joint Program Office and aware of their operational pause recommendation. In concurrence with their recommendation, Lt. Gen Michael Conley, AFSOC commander, has directed a pause for all CV-22 flight training operations.”
“A pause in flight training operations allows time and space for us to understand what happened in the most recent event before we accept risk with unknown variables,” Heyse added.
HMX-1’s Osprey grounding
Few days after the incident at Cannon AFB, an Osprey of the Marine Corps HMX-1 being used to ferry White House staff and government officials from an event in New York was grounded due to a safety concern. The staff and officials were removed from the aircraft and transferred to a second Osprey to continue their trip accompanying President Joe Biden.
One witness reported seeing flames under the right engine, according to the Associated Press, shortly before staff were notified the Osprey would be grounded. A similar incident happened a year before, in November 2023, with the tiltrotor grounded after four loud “pops” were heard and smoke was seen.
The Associated Press also mentions that the incident happened on the same day lawmakers sent a letter to Defense Secretary Lloyd Austin asking him to re-ground the military’s entire fleet of V-22 Ospreys until solutions can be put in place to address safety and design issues. The letter said that “given the current concerns about the safety of the V-22, the aircraft should be grounded, and should not be deployed again until the platform’s significant deficiencies are fully addressed.”
Japan’s crash
Previous accidents involving the Osprey were attributed to a recurring “hard clutch engagement,” a result of a design flaw in the component. However, in the November 2023 crash, investigators pointed to the gearbox as the cause in their preliminary findings.
The tilt-rotor CV-22 has a prop-rotor gearbox in each engine nacelle which transmits power from the engine to the proprotor and reduces the speed of the shaft. The catastrophic failure was located in the Osprey’s left-hand PRGB, where a crack high-speed pinion gear caused it to fail, breaking apart and causing an onset of rapidly cascading malfunctions.
This resulting “instantaneous asymmetric lift condition” was unrecoverable by the mishap crew. The crew received three “PRGB CHIP BURN” alerts on the CDU screen, followed by a “L PRGB CHIPS” flash. This meant the chip detectors found pieces of metal that couldn’t be burnt off.
In October 2024, an independent investigation by Hunterbrook has narrowed down poor manufacturing processes and inadequate quality control as the causes of the catastrophic failure in the PRGB. These issues were traced back to Universal Stainless, the manufacturer of the alloy used in the gear that failed on the ill-fated Osprey.