FTW03LA134

The pilot and his passenger/observer were assisting local authorities during a search mission involving a boating incident on the lake. The pilot flew the helicopter 20-30 feet over the water on a north-south pass parallel to the shoreline. Based on the observers sighting in the water, the pilot turned the helicopter to the left (made a 180 degree turn), flew over the lake, and then inbound near the shoreline. While hovering out of ground effect on a west southwest direction, the helicopter encountered a loss of tail rotor effectiveness and entered a spin to the right, which the pilot was unable to arrest. The helicopter impacted the water, and came to rest on its left side. The weather observation facility reported the wind from 130 degrees at 9 knots. The main rotor system hub assembly and components and the tail rotor driveshaft exhibited damage consistent with sudden stoppage associated with fuselage/water/ground. Metallurgical examination revealed that the main rotor driveshaft and, the tail rotor driveshaft fractured in torsional overload. Examination of the helicopter did not reveal any discrepancies or anomalies that would have prevented operation of the helicopter prior to the impact.

On April 19, 2003, approximately 1130 central daylight time, a Hughes 369HS helicopter, N16Q, was substantially damaged while maneuvering near the shoreline of Lake Conroe near Conroe, Texas. The helicopter was owned and operated by SKJ, Inc., of Montgomery, Texas, under 14 Code of Federal Regulations Part 91. The commercial pilot, who occupied the left front seat, and his passenger/observer, who occupied the right front seat, were not injured. Visual meteorological conditions prevailed for the local aerial observation flight, and a flight plan was not filed. The flight originated from the operators private helipad near Lake Conroe, approximately 1100.

On the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) the pilot reported that he and the observer were assisting local authorities during a search mission involving a boating incident on the lake. The pilot flew the helicopter 20-30 feet over the water on a north-south pass parallel to the shoreline. Based on the observers sighting in the water, the pilot turned the helicopter to the left (made a 180-degree turn), flew over the lake, and then inbound near the shoreline. After flying about 100 yards, the helicopter experienced a loss of tail rotor effectiveness and entered a spin to the right, impacted the water, and came to rest on its left side in approximately 2 or 3 feet of water.

A review of the available pilot records and the FAA records revealed the commercial pilot held airplane singe-engine land, multiengine land, and rotorcraft-helicopter ratings. He was issued a second class medical certificate on March 20, 2003, without limitations. On the Pilot/Operator Aircraft Accident report (NTSB Form 6120.1/2) the pilot reported a total of 2,235.8 hours (321.2 hours rotorcraft of which 194.4 hours was in N16Q).

At 1053, the local weather observation facility at Conroe reported the wind from 130 degrees at 9 knots, visibility 10 statue miles, scattered clouds at 2,600 feet, temperature 23 degrees Celsius, dew point 19 degrees Celsius, and altimeter setting of 29.88 inches of Mercury.

A review of available maintenance records indicated the airframe had accumulated 8,320.0 hours as of March 16, 2003. The last annual inspection was performed on December 6, 2002, at an accumulated time of 8,235.5 hours. During the annual inspection the following tail rotor service was performed: tail rotor gearbox attaching bolts, feather bearings, and conical bearings were replaced. The tail rotor hub and blade assembly were re-centered and tail rotor re-balanced. The last tail rotor balance check was performed on March 16, 2003, and the tail rotor balance was within limits and no adjustments were made to the system. In July 2001, the tail rotor transmission (gearbox) part number 369A5400-701, serial number A-824, was removed for chips "making metal", repaired, tested, and reinstalled at 7,160.2 hours.

The helicopter was recovered from the lake by Shoreline Services, Willis, Texas. The helicopter was examined by the manufacturer’s representative, under the supervision of the FAA inspector. According to the manufacturer's representative, the main rotor system hub assembly and components exhibited visible damage "consistent with sudden stoppage and high blade flapping angles associated with main rotor blade contact with fuselage/water/ground." Continuity was confirmed for the main transmission, and from the main transmission to the tail rotor output pinion and tail rotor driveshaft. The main rotor driveshaft would not turn, and the splined end of the main rotor driveshaft was fractured consistent with overload. According to the manufacturer's representative, the "tail rotor driveshaft was fractured and exhibited wind up associated with sudden stoppage. The driveshaft exhibited twisting in the shaft approximately 8 inches aft of the forward Bendix coupling." The main rotor driveshaft, the twisted portion of the tail rotor driveshaft, and the tail rotor transmission were retained for further examination.

On June 3, 2003, under the supervision of the FAA, the main rotor driveshaft (part number 369A5500-901, serial number 0123), the tail rotor driveshaft (part number 369A5518-601, serial number 8005), and the tail rotor transmission (part number 369A5400-701, serial number A824, were examined at The Boeing Company, Mesa, Arizona. According to the manufacturer's representative, the investigation "has not identified any fault or malfunction of any helicopter system that could be considered causal to the accident." Further, the main rotor driveshaft and the tail rotor driveshaft, "fractured in torsional overload."

The NTSB metallurgist, who reviewed the Boeing Company metallurgist report, concurs that the "report adequately describes the overstress fractures to the main driveshaft, the tail rotor driveshaft, and the forward Bendix coupling as well as the lack of damage to the tail rotor gearbox components. None of the damage to the components was causal to the accident."