Introduction
On September 6, 2009, at approximately 1400 central daylight time, a Messerschmitt-Boelkow-Blohm BO-105S helicopter, registration N131EH, sustained substantial damage during a post-maintenance flight near Thibodaux, Louisiana. The helicopter was operated by ERA Helicopters LLC, of Lake Charles, Louisiana, under a company flight plan for a 14 Code of Federal Regulations Part 91 local flight. Visual meteorological conditions prevailed at the time.
Accident Sequence
The pilot, who was the sole occupant, reported that while the helicopter was in a 3-foot hover, it began an uncommanded roll to the right. The pilot applied full left cyclic input in an attempt to arrest the roll, but the roll continued. Shortly afterward, the right landing skid contacted the ground, followed by the main rotor blades. The helicopter came to rest in a right-side-low upright position. The pilot was able to exit the helicopter without assistance and sustained minor injuries.
Maintenance Findings
According to a Federal Aviation Administration (FAA) inspector who examined the accident site, the flight's purpose was to conduct an operational check of maintenance performed on the cyclic control system. Prior to the flight, a company mechanic had removed both the lower lateral and longitudinal cyclic control tubes to replace the rod ends. Although the lateral and longitudinal tubes share the same part number, they are adjusted to different lengths. The investigation revealed that the mechanic had inadvertently swapped the two control tubes during reassembly, resulting in an out-of-rig condition in the cyclic control system.
Hydraulic and System Examination
A bench check and teardown of the hydraulic control pack showed no anomalies. Continuity in the non-boosted cyclic control system was established, and no anomalies were noted. The cyclic system above the hydraulic pack was damaged during the accident but remained functional. Examinations of the swashplate system and main rotor system also revealed no anomalies.