MV-22 Redux

On Friday, InsideDefense.com reported on the results of an investigation into the causes of a crash of an MV-22 Osprey tiltrotor aircraft in Morocco this past April:

A fatal MV-22 Osprey crash in Morocco this past spring was due largely to pilots' mistakes, but wind was also a key factor, according to a Marine Corps investigation report, which recommends no disciplinary action against the pilots and concludes the aircraft's flight manual had inadequate guidance for the circumstances involved.

On April 11, the pilots "made a decision to turn and take off with a tail wind so that they wouldn't endanger any of the folks that were in the rest of the landing zone," Lt. Gen. Robert Schmidle, the Marine Corps' top aviation official, told reporters today. With the wind at his tail, the pilot began to rotate the nacelles forward from helicopter mode to airplane mode, which moved the Osprey's center of gravity forward.

"So what happens now is that the aircraft turns; the nacelles roll forward; it begins to pitch forward; the wind catches the tail here, exacerbates the motion and pitches the nose down," Schmidle said. "While all that is happening, the control stick doesn't have enough movement at this point to move . . . the horizontal stabilizer on that tail up enough to get the nose positioned to come up. So what happens then is the aircraft now is committed, and it flies into the ground." Two Marines in the rear of the aircraft were killed. The pilot and copilot were seriously injured.

A significant factor in the crash was the pilots' failure to follow the flight manual's procedures for hovering in helicopter-mode and conducting low-speed flight, the report states, citing the 180-degree hover turn that placed the aircraft directly into a tail wind. The failure to correct for a nose-down attitude during the hover-turn made the situation more severe, the report states. Investigators also found the aircraft's nacelles were moved too far forward.

"The mishap aircraft co-pilot failed to adjust stick control margin during the pedal turn, preventing him from having enough aft cyclic stick control margin to overcome the effects of a nose-down attitude and transitioning to aircraft mode with a significant tail wind," the investigating officer wrote. The commanding general of the 2nd Marine Air Wing later recommended revising that wording to say the co-pilot "failed to adjust nacelles aft during the pedal turn."

We originally only had a 27-page version of the redacted report, but have since obtained a much more detailed analysis -- more than 400 pages -- that includes many enclosures.

Click here to view the more-detailed, 20-megabyte report.