Monday, January 19, 2015

Tail rotor separation blamed for Oshkosh crash

The NTSB has issued a probable cause for one of the accidents at this year's AirVenture at Oshkosh.

The more serious accident, the Breezy accident in which a passenger died, has yet to be settled.

But the NTSB has finished its investigation in the crash of a Mosquito.

Just after takeoff, the experimental, amateur-built helicopter started to rotate and then impacted the ground in a level attitude, which resulted in substantial damage to the helicopter. Examination revealed that one tail rotor blade had separated from the tail rotor and gearbox assembly and that the blade had separated cleanly from the assembly; neither the collar nor the pins used to secure the blade were located. The pilot reported that he had been testing this tail rotor design for 4 years. A tension/torsion strap and two steel pins were used to retain the blade. The strap was not completely restricted from movement, and, over time, movement and wear resulted in the failure of the retaining assembly. The tail rotor assembly was a unique design and was not used in any other application.

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