NTSB Identification: NYC97LA058
14 CFR Part 91: General Aviation
Accident occurred Wednesday, March 05, 1997 in WASHINGTON, PA
Probable Cause Approval Date: 04/10/1998
Aircraft: Aerospatiale AS-355F, registration: N101UC
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.

A mechanic changed one of the helicopter's lateral cyclic servos. The helicopter was test flown by the pilot with the mechanic onboard. After a successful test flight, the mechanic exited the helicopter and the pilot was to reposition the helicopter to the hospital helipad. When the pilot raised the collective, the helicopter lifted about 2 to 4 feet above the ground, and then began to roll left. The pilot attempted to correct for the left roll; however, the helicopter did not respond and the main rotor blades struck the ground. Examination of the helicopter revealed control continuity, and that the hydraulic servos were installed correctly. No preimpact failure of the airframe was observed. Examination of the servos revealed that two of the units tested to manufacturer's parameters. The master servo unit failed the bench test, had the appearance that it had been worked on, and did not meet manufacturer's specifications. The helicopter manufacturer stated that this would not induce a 'hard over.'

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The malfunction of a cyclic servo which resulted in a cyclic hard over at a hover.

Full narrative available

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