V-22 Osprey program officials are investigating what caused an access door on the right-hand nacelle of the first newly configured Osprey to break off, damaging a vertical stabilizer in flight and prompting a precautionary landing in Arkansas on Aug. 17.
The latches that were supposed to keep the right-hand door attached to a panel on the nacelle are a focal point in the investigation, Inside the Navy has learned. The incident delayed by three days the arrival of the aircraft at Patuxent River, MD.
The access doors -- each of the two nacelles has one -- are new features meant to give V-22 maintenance personnel access to the aircraft's inner workings. Osprey No. 34, the first "Block A" aircraft, carries these and other changes designed to improve safety, maintainability and reliability. Each access door is 9 inches by 14 inches, program officials said.
Investigators are reviewing the design of, and the installation of, the door's latches. At press time (Aug. 22), Cmdr. Mark Whittle, the program's class desk officer, told Inside the Navy the latches "likely" caused the problem, but added the probe is continuing.
Prior to the incident, the latches were not flight tested as thoroughly as the door or the panel that holds the door, according to documents obtained by ITN. Unlike the rest of the door-and-panel design, the latches were not tested on Osprey No. 8, the only V-22 equipped to test for vibrations throughout the aircraft. If the program redesigns the latches, the new design would likely be tested on Osprey No. 8, Whittle told ITN.
On Aug. 16, a broken latch on the left-hand side led to the replacement of a door, but the right-hand door was checked and appeared normal, according to the documents.
The V-22 program is engaged in a flight test program aimed at addressing all concerns that were raised following two fatal Osprey crashes in 2000.
The aircraft involved in last week's incident -- Osprey No. 34 -- took off from Amarillo, TX, on the morning of Aug. 17 to join the Navy's test fleet in Maryland. But later that morning, the pilots noted increased vibrations during flight at approximately 9,000-feet altitude, which prompted them to land the aircraft at Ft. Smith, AR, according to an incident summary compiled by Bell Helicopter Textron, which makes the Osprey with Boeing. During a walk-around inspection, the crew noted damage to the right vertical stabilizer leading edge, which was hit by the detached door.
None of the people aboard that flight were endangered, said the Navy's V-22 program manager, Air Force Col. Craig Olson, in an interview with ITN.
"Absolutely not -- and I think that is borne out by how they handled it, how they were able to recover it and the damage that we noticed afterwards," he said. The pilots took the appropriate action by landing as soon as conditions permitted, he said, which is different from having to land as soon as possible.
Similarly, Philip Coyle, the Pentagon's former director of operational testing and evaluation, noted that damage to a vertical stabilizer would not cause a V-22 to lose control. But Coyle noted the incident might have been more serious if a rotor, rather than a stabilizer, had been hit.
Olson said the program is still investigating what led the door to come loose and no cause has yet been pinpointed. But he said investigators are looking at the panels, the latches and the interactions between the latches and the door.
Prior to the Sept. 17 trip, Osprey No. 34 had flown 20 hours, during which time the Block A latch configuration was tested, said Olson. But the latches were not tested on Osprey No. 8.
"It is the only one in the fleet that is fully instrumented to detect every vibration, every movement, all over the airplane," Olson said of Osprey No. 8.
Bell's incident summary, which was not intended for public release, notes this access door-and-panel design had been flight tested on Osprey No. 8 for "load transmission into structure," but that test "did not include the actual Block A latches."
Olson said it was according to the plan developed by the government and the contractors that the latches had not been tested on Osprey No. 8. Looking back, he said he wished the latches had been tested on that aircraft.
"Absolutely, in a perfect world, I would love to have everything fully analyzed before you go to the next step," said Olson. "But sometimes timing and budget doesn't allow you to exhaustively complete every step of design to simulation to flight, early."
Last week, V-22 engineers created a temporary fix that enabled the aircraft to complete its flight to Naval Air System Command in Maryland on Aug. 20. They did this by replacing -- on each nacelle -- the panel that holds the door. In place of these panels were installed older versions, each with no door at all. Engineers also patched the damaged stabilizer.
The program has a goal of having Osprey No. 34 ready for flight testing within two to three weeks, Olson said. But before Osprey No. 34 flies again, the program plans to finish its "root cause investigation" and develop and install a more permanent fix that allows that particular aircraft to retain the panels equipped with the access doors, he said. Also, Osprey No. 34 will receive routine modifications that all other V-22s in the test fleet have received, he added.
Olson downplayed the Aug. 17 incident, noting the Osprey is still an engineering and manufacturing development program that is not ready to be fielded because it is not fully mature.
"Since we're not done with tests and since you do it incrementally, to have this happen at this stage is not a bad thing," he said. "If I had delivered the airplane to the fleet and then it happened, that would be a bad thing. But even then, we're not going to deliver something that will never have an incident of any kind on it. I mean, of course not. You have to drive these things down to the absolute minimum and not have safety of flight at issue."
Olson noted the design changes associated with the Block A aircraft still need to undergo further testing. "And it's got very little time on it and that's why the airplane is here at Patuxent River, to do some developmental testing on this Block A configuration before we ever give it to the fleet," Olson said. -- Christopher J. Castelli