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Aviation Accident

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NTSB Identification: CEN15LA042
14 CFR Part 91: General Aviation
Accident occurred Saturday, November 08, 2014 in Angleton, TX
Probable Cause Approval Date: 06/09/2015
Aircraft: MOSIER ROBERT S MOSQUITO XET, registration: N922RM
Injuries: 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot reported that he noticed the helicopter abruptly shudder during the crosswind turn. The pilot lowered the collective control, entered an autorotation, and turned back toward the airport. As he approached the runway area, the helicopter skids passed over a row of trees by about 5 or 10 ft. Immediately after the skids cleared the trees, the pilot began a cyclic flare, which resulted in the tail rotor striking a tree and a subsequent loss of directional control.
Examination of the helicopter revealed that the belt for the secondary drive reduction unit was loose, which allowed the belt to jump the drive cogs on the pulley. The belt was loose due to excessive wear of the pulley, which resulted in an abrupt in-flight shudder. The helicopter operating manual preflight inspection includes a check for proper belt tension. 


The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
  • The pilot’s failure to maintain adequate clearance from trees during a precautionary landing. Contributing to the accident was the pilot’s inadequate preflight inspection during which he failed to detect a loose drive belt, which resulted in an in-flight shudder.