Air Force releases results of aerospace accident investigation

by Air Force Global Strike Command Public Affairs

12/20/2013 - BARKSDALE AIR FORCE BASE, La. -- Air Force officials announced the results of a UH-1N helicopter accident investigation today.

The investigation into a Feb. 25, 2013 mishap near Minot Air Force Base, N.D., found clear evidence that the cause of the accident was due to a loss of tail rotor thrust following the failure of a driveshaft coupling. Lubricant starvation and contamination destroyed the gear teeth in the coupling, resulting in the loss of tail rotor thrust.

Approximately an hour into the flight, the crew from the 54th Helicopter Squadron heard a loud noise coming from the rear of the aircraft and felt an accompanying vibration. The pilot chose to make a precautionary landing in a snow-covered field.

During the approach to land, the helicopter lost tail rotor thrust about 100 feet above the ground. The pilot continued to autorotate - a procedure where the main rotor system turns by the action of air moving through the rotor rather than by engine power - to about 30 feet when he applied control inputs to level the aircraft and cushion the landing.

The helicopter's right rear skid impacted the ground first followed by the left skid. The aircraft continued to roll to the left until the main rotor blades struck the ground, coming to a rest on its left side.

The crew performed emergency shutdown procedures and exited the aircraft. Three crew members were injured as a result of the accident.

The mishap aircraft sustained major damage with a total loss valued at more than $2.3 million, but resulted in no civilian injuries or damage to civilian property.