Volcano, HI, USA
N4493M
McDonnell Douglas 369D
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 on June 13, 2003, and noted no discrepancies. This mechanic indicated that he normally did not perform engine maintenance for the company, but would routinely assist when requested for on the job training. He reported having replaced engine components on company aircraft. The mechanic could not recall what components had been overhauled recently, but remembered replacing a gearbox for loose studs about 4 to 6 weeks prior to the accident, and the starter generator had been replaced for overhaul purposes. The mechanic reported that while he was never provided with a training manual, he and other mechanics were not left alone while working on helicopter without first being trained for that particular job. He also reported that at all times the manufacturer's maintenance manuals were always available and used while working on the helicopters. He noted that the director of maintenance was responsible for updating the revisions to the manuals. WRECKAGE AND IMPACT INFORMATION The Safety Board IIC, and inspectors from the FAA Honolulu FSDO examined the wreckage at the accident scene on June 16, 2003. The accident site was located on the Pulama Pali at an active lava flow, approximately 2 miles north of the Chain of Craters road, and about 5 miles south of the Pu'u O'o Vents. The elevation at the accident site was 620 feet mean sea level (msl), with upsloping terrain; about 10 degrees. The primary wreckage was at 19 degrees 19.80 minutes north latitude and 155 degrees 04.97 minutes west longitude. The helicopter came to rest on a 270-degree magnetic heading, and a 320-degree magnetic bearing to ITO. The fuselage of the helicopter, the main wreckage, was in a small hole (made by the lava). The majority of the helicopter was in a 10-foot radius of the main wreckage. Portions of the landing gear skids and cross tubes were located northeast and upslope of the main wreckage, about 5 feet away. Pieces of Plexiglass windshield, and the passenger side door, were also found upslope of the main wreckage. There was no sign of smoke or fire residue on the Plexiglass windshield or passenger side door. The tail boom had separated into two pieces, and was laying 5 to 10 feet southeast of the main wreckage. One of the tail rotor blade tips was found downslope of the main wreckage about 50 yards. According to NPS personnel, one passenger was found outside of the helicopter, upslope, about 10 feet from the main wreckage. The pilot and the other two passengers were found within the main wreckage. MEDICAL AND PATHOLOGICAL INFORMATION The Hilo Medical Center Department of Pathology performed autopsies on the pilot and three passengers on June 17, 2003. The cause of death for all occupants was listed as thermal injuries that ranged from 90 to 100 percent of the body due to a helicopter accident. The pilot had a 17.1 percent carbon monoxide level, and the passengers' carbon monoxide levels ranged in levels from 0.5, 0.8, and 1.3 percent. The Bioaeronautical Sciences Research, Oklahoma City, Oklahoma, performed a toxicological analysis of the pilot from samples obtained during the autopsy. The results of the analysis of the specimens were positive for carbon monoxide, 15 percent detected in blood; positive for cyanide, 0.57 (ug/ml) detected in blood. The results for tested volatiles revealed no ethanol in the urine, and for tested drugs none were detected in the liver. TESTS AND RESEARCH Temporary Flight Restriction (TFR) NPS had established a TFR to fight a wildland fire in the park area. The TFR area was setup utilizing GPS coordinates that encompassed the Pu'u O'o vent to the shoreline. The GPS coordinates were as follows: Upper northwest corner ((3) Via): N19 degrees 23.000 minutes, W155 degrees 13.200 minutes Upper southeast corner ((2) Via): N19 degrees 23.000 minutes, W55 degrees 7.000 minutes Lower southeast corner ((1) Via): N19 degrees 18.890 minutes, W155 degrees 3.300 minutes Lower northwest corner: N19-degrees 16.360 minutes, W155 degrees 7.800 minutes NPS personnel plotted the coordinates of the accident site and noted that the site was located about 1/2-mile inside the TFR near the lower southeast corner border and the shoreline. He checked the National Fire website to view the TFR information and noted that it had been activated earlier in the week. He then received a phone call from an FAA supervisor at the Honolulu FSDO. He informed the FAA supervisor that the accident site was inside the TFR, and that there was no waiver for tour helicopter operations in the TFR near the lava flow. Follow-up Examination On June 16, 2003, Windward Aviation Helicopters, Maui, Hawaii, retrieved the helicopter from the lava field. The Safety Board IIC, FAA inspectors, and representatives from MDHI/Boeing Helicopters and Rolls-Royce Engines examined the wreckage at the Civil Air Patrol Hangar at ITO, on June 17 - 19, 2003. Approximately 20 percent of the airframe was recovered; the rest had been destroyed in the post-impact fire. The cockpit portion of the fuselage, forward of the firewall, sustained fire damage. Flight control continuity from the cockpit to the main rotor and tail rotor could not be established. The anti-torque pedal assembly separated at the attachment fitting, and one pedal had broken. The instrument panel had been destroyed. The visual inspection of the engine revealed no punctures in the case. The gearbox, the fuel control unit, and fuel pump remained connected and secured to the engine in their respective locations. The third and fourth stage compressor blades were visible with no damage observed to the compressor blades. The engine had sustained fire damage; however, it remained in place and attached to its mounts and the airframe. The lines aft of the firewall were intact and secure at their respective fittings. The lines forward of the firewall sustained fire damage. The fittings and portions of the hoses and lines were in place. The engine was removed from the airframe for further visual inspection. When the fuel lines were removed, no fuel was present in the lines. The fuel filter nozzle screen was removed, and was clean of debris and had not collapsed. The fuel filter was removed, and was clean of debris and absent of fuel. Drive train continuity to the main rotor head was established, and the static mast remained in place. The main rotor drive shaft had decoupled; however, the sun gear rotated freely. The overrunning clutch functioned properly. The main rotor hub was thermally damaged. The rotating and nonrotating swashplates were burned, and the upper and lower shoes had melted. The strap pack assembly was in place; however, the outside had been thermally distorted. Three of the five main rotor blades remained attached to the main rotor hub. Two blades were separated from the hub and were located in the immediate wreckage area. All of the main rotor blades showed minor leading edge damage. All five of the main rotor blades were delaminated at their respective trailing edges. The tail boom separated into two pieces. The pitch change housing was thermally destroyed. Both tail rotor blade tips separated from their respective blades about 11 inches from the tips. The lower portion of the vertical stabilizer had crushed inward. The engine was removed and shipped to Rolls-Royce Engine Services Oakland (RRESO), Oakland, California, for the teardown inspection. Engine Examination The party members reconvened at RRESO for the engine teardown inspection that was conducted on July 1 and 2, 2003. Also present was the FAA Aircraft Certification Office (ACO) inspector from Chicago, Illinois. RRESO personnel noted that the bolts for the fuel pump mounting pad were loose; no torque, and that the mounting pad itself had broken. The fracture face was granular and smooth with no shear lips and had broken at the base. RRESO personnel noted that the compressor case right side bolts had been installed backwards, and there was no damage to the compressor blades, the case or the cone. They also noted compressor blade marks, centrifugal rub, on the diffuser assembly inside the compressor housing, also referred to as "chatter marks." The Rolls-Royce (RR) representative indicated that the chatter marks were cons
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.
Source: NTSB Aviation Accident Database
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