ANC06LA038

The experimental category flight was being operated by the helicopter manufacturer under Title 14, CFR Part 91, when the accident occurred. The commercial certificated helicopter pilot was conducting a series of climbing and descending turns while a second helicopter, flying alongside, filmed the maneuvers. According to a safety representative for the helicopter manufacturer, all of the maneuvers were conducted within the normal limitations of the helicopter. The maneuvers were completed uneventfully, with no in-flight anomalies noted, and the helicopter returned to the manufacturer's base. While conducting a routine daily inspection of the helicopter in preparation for the next scheduled flight, maintenance technicians discovered damage to the main rotor hub's five pitch case assemblies, slightly aft of the upper damper cap. The damage was a result of the pitch cases striking the upper main rotor hub perimeter bolts. All five pitch cases were damaged beyond repairable limits, and were replaced. The safety representative for the helicopter manufacturer reported that the anticipated corrective action will be to increase the clearance between the pitch cases and the main rotor hub perimeter bolts by trimming additional material from the inboard and upper portion of the main rotor pitch case assemblies during the manufacturing process.

On March 22, 2006, about 1600 mountain standard time, an MD Helicopters MD 900 helicopter, N912LH, owned and operated by MD Helicopters, Inc., Mesa, Arizona, sustained substantial damage while maneuvering near Mesa. The commercial certificated pilot and one crewman were not injured. The experimental category flight was being operated as an air-to-air photographic flight under Title 14, CFR Part 91, when the accident occurred. Visual meteorological conditions prevailed at the time of the accident, and company flight following procedures were in effect. The local area flight originated at the Falcon Field Airport, Mesa, about 1530.

A postflight inspection of the helicopter disclosed damage to all five of the main rotor hub pitch cases.

During a telephone conversation with the National Transportation Safety Board investigator-in-charge on March 28, an aviation safety representative for MD Helicopters reported that the purpose of the flight was to photograph the accident helicopter during flight. During the flight, the pilot of the accident helicopter was required to maneuver the helicopter through a series climbing and descending turns while a second helicopter, flying alongside, filmed the maneuvers. The safety representative reported that all of the maneuvers were conducted within the normal limitations of the helicopter. All of the maneuvers were completed uneventfully, with no in-flight anomalies noted, and the helicopter returned to the MD Helicopters facility in Mesa.

According to the safety representative, on March 23, while conducting a routine daily inspection of the helicopter in preparation for flight, maintenance technicians discovered damage to the main rotor hub's five pitch case assemblies. He said that the damage to each main rotor hub pitch case was limited to the upper inboard lip, slightly aft of the upper damper cap. He described the impact damage as a result of the pitch cases striking the upper main rotor hub perimeter bolts. All five pitch cases were damaged beyond repairable limits, and were subsequently replaced.

In the NTSB Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1) submitted on behalf of MD Helicopters, the safety representative reported that following this event, the anticipated corrective action will be to increase the clearance between the pitch cases and the main rotor hub perimeter bolts by trimming additional material from the inboard and upper portion of the main rotor pitch case assemblies during the manufacturing process.