Amateur-built ROTORWAY EXEC 162F N8707E accident near Smoketown, Pennsylvania

Probable cause

A loss of control during a post-maintenance test flight due to improper tracking of the helicopter’s main rotor blades by the pilot/aircraft builder.

NTSB analysis

According to the pilot/owner/builder of the experimental amateur-built helicopter, he had recently finished performing maintenance on the helicopter, which included tracking its rotor system. He then positioned the helicopter in front of his hangar and proceeded to perform an operational check, before attempting to hover the helicopter. Immediately upon entering the hover, the pilot felt a large amount of vibration in the cyclic control and the helicopter began moving to the left. The pilot pushed the cyclic control right in an effort to stop the left movement of the helicopter, but the control input was ineffective. The pilot then increased the helicopter's altitude to avoid a collision with nearby obstacles and attempted to maneuver to an open grass area. Realizing that the rotor rpm had decayed, he reduced the collective pitch and increased engine power. The helicopter then entered a settling-with-power flight condition and impacted a taxiway located between two hangars.

During a telephone interview conducted about 2 weeks after the accident, the pilot stated that the loss of control that precipitated the accident was most likely due to improper tracking of the helicopter's main rotor blades, related to the method of leveling the blades he had used during the helicopter's most recent maintenance.

A postaccident examination of the wreckage revealed that the cyclic control cross tube had separated from its attachment point at the left side of the fuselage, adjacent to a break in a repair weld of the fuselage's tubular frame. Detailed examination of the fracture surface revealed that while the weld was of a generally poor quality, the fracture exhibited features consistent with a failure in bending overload. Given the nature of the failure, it is most likely that the weld fractured during the impact sequence.

Text from the NTSB. Open the NTSB docket for ERA12LA373 for the full record.