Hughes 369D N131AL accident near Meeker, Colorado

Probable cause

Main rotor contact with the tail boom resulting in tail boom separation.

NTSB analysis

While conducting deer capture operations,the crew felt a shudder or jolt through the helicopter and collective. The first jolt was immediately followed by a bang, at which time the helicopter started to rotate to the right. The helicopter pitched nose down with forward movement as it rotated to the right, impacting the ground. The pilot estimated that he was 40 feet above the trees and that the airspeed was between 25 and 30 knots when the shudder or jolt occurred. The empennage was located 70 feet to the east of where the helicopter came to rest. Examination of the helicopter, engine, and related systems revealed no mechanical anomalies. Metallurgical examination revealed features consistent with overstress separations on all fractures in the tail boom and the driveshaft. The damage and mode of separation of the empennage was consistent with an impact from a main rotor blade. The manufacturer noted that main rotor contact with the fuselage is only possible with a low rotor rpm state or with flight outside of the approved operational envelope. However, the pilot indicated that there were no bells, horns, or warnings prior to the bang and that he did not receive a low rotor warning or a chip light; the investigation was unable to conclude that low rotor rpm or flight outside of the approved operational envelope led to the separation of the tail boom.

Text from the NTSB. Open the NTSB docket for CEN11GA218 for the full record.