An Army investigation into the helicopter crash that killed six U.S. military personnel in Italy in November concluded the crew lost control of the aircraft, but it’s not known exactly why, according to Army officials.

Evidence suggests either a foreign object jammed the controls, or a part in the flight controls failed, causing the UH-60 Black Hawk helicopter to crash with 11 servicemembers onboard, according to V Corps’ 15-6 investigation report, released Thursday. Pilot error and environmental factors were ruled out as causes for the crash.

No one will be disciplined in connection with the crash, officials said.

The helicopter went down in the Piave low-level training area north of Aviano Air Base on Nov. 8 while on a training flight.

The front portion of the aircraft was so badly damaged that investigators couldn’t draw any conclusions about whether material failures happened before or during impact. There was no flight-data recorder on board, officials said.

Investigators relied heavily on witness statements, video taken onboard by a passenger during the flight, laboratory analysis of parts and simulator analysis to draw their conclusions.

Officials say the Black Hawk made one circuit of the training area — a relatively small, narrow expanse — at low altitude before coming nearly to a stop at an altitude of 400 feet. While making a slow left turn, apparently to head back into the training area, the pilot experienced a “loss of yaw control” that sent the helicopter into a diving spin from which the crew could not recover.

Investigators focused on one part — one of 32 like it inside the crew cabin — which showed evidence of wear that likely happened before the crash. The part, known as a bell crank, was responsible for controlling so-called left-pedal turns.

Previous pilots had earlier complained about “popping” in this particular Black Hawk’s pedals, but mechanics believed they had fixed the problem during routine maintenance earlier in 2007.

Investigators and maintenance personnel tried to replicate the conditions that might have caused the part to wear, but were unable to do so, and no similar wear was noted on any other Black Hawk in Europe, according to officials.

The crew executed an emergency procedure for what they perceived sent them into the spin, officials said, drawing on information gathered from crash survivors. It was the correct emergency procedure for what they thought happened, according to the report.

The procedure failed to stop the spin, indicating that something else went wrong.

At the time, there was no emergency procedure in place for any of the three possible reasons for the loss of yaw control.

Three soldiers onboard were part of the crew. A fourth was new to the unit the helicopter was assigned to — Company G, 52nd Aviation Regiment, 1st Battalion, 214th Aviation Regiment.

The remaining seven passengers were all Air Force airmen along for a so-called incentive flight. One had done a favor for Company G, and brought along two co-workers. Another airman planned to re-enlist on the flight, and three airmen accompanied him.

Sign Up for Daily Headlines

Sign up to receive a daily email of today's top military news stories from Stars and Stripes and top news outlets from around the world.

Sign Up Now