LAX03FA200

a loss of engine power due to the fatigue fracture and separation of the compressor coupling adapter. The fatigue fracture was initiated by fretting on the pilot diameter due to both the inadequate design of the coupling and the coaxial misalignment of the spur adapter gear, compressor-coupling adapter, and compressor impeller during recent engine maintenance where the gearbox was removed and replaced. A factor in the accident was the unsuitable nature of the terrain to make an emergency landing.

The helicopter crashed onto a rugged hardened lava flow following a loss of engine power during cruise. The pilots of other helicopters heard the pilot make a mayday call with the clear "engine out" audio warning in the background. A post crash fire consumed the majority of the wreckage. An airframe examination revealed no evidence of a preimpact malfunction in what remained of the airframe. An engine inspection and a metallurgical examination revealed that the compressor-coupling adapter, a Parts Manufacturer Approval (PMA) part made by a company other than Rolls-Royce, had failed above the shear point due to fatigue cracking initiated by fretting on the pilot diameter, which had disconnected the compressor from the turbine section. The metallurgist noted that the damage was consistent with the rotation of the aft piece of the fractured compressor-coupling adapter within the stub shaft after it had separated. Fretting damage to the impeller corresponded to the fretting damage on the compressor-coupling adapter, and indicated relative movement between the parts. Rolls-Royce had records of 12 other compressor-coupling adapters that had fractured and failed, with all instances of the failure/fracture occurring in this specific new coupling design, which was significantly different than the previous design. The nature of the fretting and fractures indicated that the newly designed couplings have a small amount of longitudinal movement that is occurring between the outer diameter of the compressor-coupling adapter and the inner diameter of the impeller, which was not a factor in the previous design. If the spur adapter gear, compressor-coupling adapter, and compressor impeller (all coaxial spline joints) were in alignment, there would be no significant longitudinal movement of the pilot diameter. However, any axial misalignment of these components during engine buildup, for example, could induce a misalignment that would result in relative motion between the components with each engine rotation. The misalignment would also induce bending stresses into the compressor-coupling adapter in addition to torsion stresses that could result in fatigue. The combination of fretting damage and cyclic bending stresses are most likely the main factor in the failures of these couplings. One month prior to the accident, company maintenance personnel had changed out the engine gearbox due to finding a loose stud on the gearbox to turbine section mounting. Changing the gearbox would involve disturbing the coaxial spline joints between the spur adapter gear, compressor-coupling adapter, and compressor impeller.

HISTORY OF FLIGHT On June 15, 2003, at 0935 Hawaiian standard time, a McDonnell Douglas Helicopter, Inc., (MDHI) 369D, N4493M, impacted a lava field on the Pulama Pali in the Volcanoes National Park, Volcano, Hawaii. K & S Helicopters, d.b.a. Tropical Tour Helicopters, operated the helicopter under the provisions of 14 CFR Part 135. A post impact fire destroyed the helicopter. The commercial rotorcraft-helicopter certified pilot and three passengers were fatally injured. The local area flight to the volcanoes departed the Hilo International Airport (ITO), Hilo, Hawaii, at 0915. Day visual meteorological conditions prevailed, and a company visual flight rules (VFR) flight plan had been filed. The tour was scheduled as a 45-minute flight that would have entailed flying over the Pu'u O'o Vents, down towards the shoreline to see molten lava flowing into the ocean, and then back to ITO. For this tour, the helicopter was configured for the pilot side door to be removed, and with the passenger side door to remain in place. In an interview with the National Transportation Safety Board investigator-in-charge (IIC), the helicopter loader and manager for Tropical Tour Helicopters stated that on the morning of the accident he had conducted a visual inspection of the helicopter before the pilot arrived. Part of the inspection was to wash the belly of the helicopter off; the manager noted a normal condition with no stains or leaks. The pilot showed up at 0800, in good spirits. He saw the pilot conduct a preflight inspection of the helicopter before repositioning it to the ramp where the passengers were to be loaded. The manager reported that the women were loaded into the backseat first, and were assisted with their seatbelts and headsets. He then went to the front of the helicopter, opened up the pilot's side door, and handed him the flight manifest. The manager then loaded the male into the front seat of the helicopter and secured his seatbelt and the pilot assisted the passenger with the headset. The Tropical Tour Helicopters' manager stated that the flight departed at 0915. A company pilot departed at the same time as the accident pilot. She noted a scattered to broken cloud layer about 4,000 feet and light winds. Upon reaching Pahoa NDB (non-directional beacon), she turned toward the shoreline and noted that the accident pilot headed towards Pu'u O'o Vent. She recalled hearing occasional calls from the accident pilot reporting his location. As her tour continued, she turned uphill and heard a pilot flying for the Volcanoes National Park asking if anyone had heard a 'mayday' call, and that he thought he had heard a "500's audio warning in the background." She had not heard anything, and attempted to contact the accident pilot via radio. She received no reply. A pilot from Windward Aviation, and a crew of National Park Service (NPS) rangers, were searching for a lost hiker when they heard a mayday call over the common area traffic frequency. The pilot and flight crew stated that they heard the accident pilot call "Mayday, Mayday, Mayday," and could hear the "engine out" audio tone in the background. No further transmissions were made. At that point, the crew broke off the search for the hiker, and flew around the lava field until they found the accident site. The pilot and NPS rangers stated that the helicopter was fully engulfed in flames. The NPS rangers dropped 12 buckets of water on the accident site to put out the fire. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) airman records revealed the pilot held a commercial certificate with a rotorcraft-helicopter rating, issued on June 7, 1997. The pilot also held a mechanic certificate with a rating for airframe. The pilot held a second-class medical certificate that was issued on April 16, 2002, and had no limitations or waivers. At that time the pilot reported a total pilot time of 3,000 hours, with 150 hours in the past 6 months. The pilot's most recent Part 135 Airman Competency/Proficiency Check was successfully completed on May 30, 2003, and was administered by an FAA inspector from the Honolulu, Hawaii, Flight Standards District Office (FSDO). According to the operator's new hire information, the pilot completed his indoctrination training on May 30, 2003. His official hire date at the company was May 21, 2003. Prior to the pilot's Part 135 check ride, the director of operations (DO) for the company conducted the SFAR 71 flight check. The DO reported no problems with the flight check. At that time the pilot reported 3,300 hours of total flight time, with 2,800 hours in the accident make and model, 500 hours in the last 12 months, and 30 hours in the last 30 days. AIRCRAFT INFORMATION The helicopter was a McDonnell Douglas (Hughes) 369D, serial number 570137D. A review of the airplane's logbooks revealed a total airframe time of 7,859.3 hours. The last annual was completed on July 10, 2002; total time recorded at the last 300-hour inspection was 7,780.0 hours; and a total time recorded at the last 100-hour inspection was 7.856.5 hours. The helicopter was equipped with an Allison 250-C20B engine, serial number CAE 835428. A review of the maintenance records revealed that the compressor section was changed out on the following dates: December 20, 2000 (CAC80158); February 26, 2001 (CAC 33946); September 07, 2002 (CAC33946). At the time of installation in September 2002, the total time since new was reported as 2,343.7 hours at an airframe total time of 6,812.0 hours. The last logged entry in the rotorcraft log was at a total time of 7,850.8 hours. A Safety Board IIC estimated that the compressor section CAC33946 had at least 3,377.9 hours as of June 6, 2003. Fueling records from Air Service Hawaii - Hilo Station, Hilo, established that the helicopter had last fueled on June 14, 2003, with the addition of 42.2 gallons of Jet A fuel at 0930, and again at 1700, with the addition of 10.6 gallons. There was no fuel service provided to the accident helicopter on the morning of the accident. According to the weight and balance sheet, the flight would have departed with 219 pounds of fuel (50.8 percent). The Safety Board IIC reviewed the Daily Aircraft Flight Logs from May 1, 2004, to June 6, 2003. There were no unresolved maintenance discrepancies for the helicopter prior to departure on the accident flight. A 25-hour inspection was completed on June 3, 2003, at an aircraft total time of 7,836.1 hours, and 7,926.9 hours total engine time. During the 100-hour inspection conducted on May 13, 2003, at an aircraft total time of 7,781.3 hours, and engine total time of 7,870.6 hours, maintenance personnel noted in the DISCREPANCIES/MALFUNCTIONS section "loose stud on engine gearbox turbine attach." The CORRECTIVE ACTION was to remove the engine gearbox part number 6894171, serial number CAG 33861, time since new (TSN) 10,895.3 hours, time since overhaul (TSO) 5,791.2 hours. Gearbox serial number CAG 33731, TSN 7,902.1 hours, "TSO is TSN. Loaner ground run aircraft 30 minutes removed [and] cleaned chip plugs no chips." The operator reported that the Daily Aircraft Flight Logs were kept in the helicopter until the next inspection, or discrepancy was encountered. The logs from June 7 to the date of the accident were destroyed in the post-impact fire. A Safety Board investigator, along with FAA inspectors, interviewed a mechanic from K & S Helicopters. He reported that his job was to perform the 25- and 100-hour inspections every Tuesday, Thursday, and Saturday. He was also to work on any maintenance discrepancies reported by the pilots. The mechanic did not perform an aircraft inspection on Saturday June 14th or the day of the accident. He further indicated that on the 14th, the helicopter had been used for firefighting. The mechanic stated that he performed a 100-hour inspection