Seward, AK, USA
N6194M
Maule M-5-235C
The private pilot, with two passengers, was flying one of two wheel-equipped airplanes en route to a remote beach site. The route of flight was over ocean waters, flanked by steep vertical cliffs to the waters edge. After passing over the last suitable landing site, an airport about 12 miles north, the accident pilot reported to the pilot of the second airplane that he had a severe engine oil leak, and was retuning to the airport. The pilot reported that once the oil stopped leaking, about 3 miles from the airport, the engine began to vibrate so violently that he thought the engine was going to be torn from its mounts, and he shut the engine off. He said he turned the airplane in an attempt to glide to the nearest beach, but he was unable to reach the beach, and was forced to ditch the airplane about 300 yards from shore. When the airplane's main landing gear wheels touched the water, it nosed over abruptly, and the cabin rapidly filled with water. The pilot said he struggled to free himself and the passengers from their seat belts, while upside-down, and submerged in cold ocean water. Once he was free, he swam to the rear of the airplane, kicked out one of the aft windows, swam to the surface, and summoned help. Rescue personnel discovered the two passengers still restrained within their seats. A postaccident examination of the engine revealed that a hex head plug at the front of the engine, in front of the propeller governor idler gear shaft, was missing, allowing engine oil under pressure to flow overboard. Additionally, the propeller governor idler gear shaft setscrew was loose, and the idler gear shaft was missing. There was no evidence that the hex head plug had been safety wired as required at the last engine overhaul, 299.6 service hours prior to the accident. According to the owner/pilot, he and a friend assembled the overhauled components of the accident engine in the pilot/owner's home-based shop. He said that that all work was accomplished in accordance with Textron Lycoming technical data. The pilot/owner did not possess an aviation mechanic's certificate. The pilot/owner reported that his friend, who owned and operated an aircraft maintenance facility, was supervising his work during the engine overhaul. A review of the engine logbooks revealed that the overhaul was certified by the pilot/owners friend, who also possessed inspector authority (IA).
HISTORY OF FLIGHT On August 15, 2004, about 1323 Alaska daylight time, a tundra tire-equipped Maule M-5-235C airplane, N6194M, sustained substantial damage during an emergency landing and ditching in the ocean waters of Resurrection Bay, about 1 mile southwest of Seward, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country personal flight under Title 14, CFR Part 91, when the accident occurred. Of the three people aboard, the private pilot sustained minor injuries, and the two passengers sustained fatal injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The accident airplane was one of two airplanes operating as a flight of two, en route to a remote beach site located about 24 miles southeast of Seward. Both of the airplanes departed from the Birchwood Airport, Chugiak, Alaska, about 1230. During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 24, the accident pilot reported that the flight from Birchwood to Seward was uneventful. He said that after passing over the town of Seward, both airplanes flew southbound over Resurrection Bay, en route to Johnstone Bay, their destination. He added that the shoreline along Resurrection Bay consists of rocky, vertical cliffs, and that roughly 12 miles south of the Seward airport, he noticed a heavy accumulation of bubbling black oil coming out of the engine oil dipstick access door, located just in front of the pilot's windscreen. He said that immediately after noticing the oil leak, he contacted the pilot in the second airplane and said, in part: "I've got an oil leak and I need to get back to Seward." He reported that the oil leak was so bad that he was unable to see out of the airplane's windscreen due to a heavy accumulation of engine oil, and that the pilot of the second airplane had to provide him with compass headings to Seward. The pilot said that while flying alongside the second airplane, his airplane continued to trail smoke and oil, but the smoke and oil stopped when the airplane was about 3 miles from the Seward Airport, and then the engine began to vibrate so violently that he was afraid that the engine was going to be torn from its mounts, and he shut the engine off. He said he turned the airplane to the right in an attempt to glide to the nearest beach, but he was unable to reach the beach, and when the airplane's main wheels touched the water, it nosed over abruptly, and the cabin rapidly filled with water. The pilot reported that he struggled to free himself and his passengers from the seat belts while upside-down and submerged in cold ocean water. Once he was free, he swam to the rear of the airplane, kicked out one of the aft windows, swam to the surface, and summoned help. About 1325, the Alaska State Trooper's dispatch center received several 911 telephone calls from witnesses who reported the accident. The accident site was located about 300 yards off shore of an area known as Fourth of July Creek. An off-duty Alaska State Trooper who was fishing from a boat close to the accident site was one of the first rescuers to arrive on scene. When the trooper arrived at the scene, he found the hypothermic, semiconscious pilot clinging to the partially submerged wreckage. Additional search and rescue personnel from the Alaska State Trooper's Tactical Dive Unit (TDU), U.S. Coast Guard, and Seward Fire Department, responded to the scene and discovered the two passengers inside, still restrained within their seats. On August 15, the NTSB IIC, and an airworthiness inspector from the Federal Aviation Administration Anchorage Flight Standards District Office, traveled to the accident site. After the airplane wreckage was recovered from the waters of Resurrection Bay, a postaccident wreckage examination of the airplane's Lycoming six cylinder O-540-J1A5D engine revealed that the three-quarter inch hex head plug at the front of the engine, which retains the propeller governor idler gear shaft, was not present. The three-quarter inch hex head plug is not visible when the propeller and starter ring gear is installed. The accident airplane's engine assembly was subsequently removed, and shipped to Anchorage, Alaska, for further examination. PERSONNEL INFORMATION The pilot held a private pilot certificate with airplane single-engine land and sea ratings. His most recent third-class medical certificate was issued on May 19, 2003, and contained the limitation that night flight operations were not permitted. According to the NTSB Pilot/Operator Aircraft Accident/Incident Report (NTSB Form 6120.1) submitted by the pilot, his total aeronautical experience consists of about 1,600 hours, of which 315 were accrued in the accident airplane make and model. In the preceding 90 and 30 days prior to the accident, the report lists a total of 70 and 25 hours, respectively. AIRCRAFT INFORMATION The airplane was equipped with a recording hour meter. According to the owner/pilot, the recording hour meter matched the airplane's total flight hours. At the accident scene, the hour meter was indicating 2,042.6. Examination of the airplane's maintenance records revealed that the last inspection (annual) was conducted August 11, 2003, 99.6 service hours prior to the accident. The airplane was equipped with a Lycoming, O-540-J1A5D engine. Examination of the airplane's engine records revealed that the engine had been overhauled on July 2, 2001, 299.6 hours prior to the accident. According to the owner/pilot, he and a friend assembled the overhauled components of the accident engine in the pilot/owner's home-based shop. He said that that all work was accomplished in accordance with Textron Lycoming technical data. He added that his friend owned and operated an aircraft maintenance facility located at the Birchwood Airport, the same airport where the accident airplane was based, and that all of his work was done while being supervised by his friend. At the time of the engine overhaul, the owner/pilot was working towards an aviation mechanic's certificate by attending a local aviation college. According to the engine records, the engine overhaul was certified by the pilot/owner's friend, a licensed airframe and power plant mechanic, who also possessed inspector authority (IA). METEOROLOGICAL INFORMATION The pilot reported that at the time of the accident, weather condition consisted of: Wind, light and variable; visibility, 50 miles; clouds and sky condition, clear; temperature, 75 degrees. COMMUNICATIONS During the emergency, the pilot transmitted a radio call for help to the pilot of the second airplane on the common traffic advisory frequency (CTAF) of 122.9 MHz. CTAF communications are not recorded in the Seward area. WRECKAGE AND IMPACT INFORMATION The airplane was ditched and partially sank, about 300 yards off shore. The wreckage was recovered prior to the arrival of the NTSB IIC, on the afternoon of August 15, 2004, by hoisting the airplane vertically out of the water by a cable attached to the propeller assembly. The wreckage was examined at a dry-dock facility, located adjacent to the accident site, on August 15 and 16. All of the airplane's major components were found at the main wreckage area. The left wing exhibited minor hydraulic crushing on the underside of the leading edge, about 12 inches outboard from the wing root. The underside of the wing had upward crushing. Both left wing lift struts were bent and broken. The right stabilizer also had minor wrinkling, and slight downward crushing of the upper surface. The left stabilizer displayed minor damage to the outboard end. The flight control surfaces remained connected to their respective attach points, and flight control system cable continuity was established throughout the airplane. The manual flaps were found fully extended. The engine crankshaft could not be rotated by the propeller. TESTS AND RESEARCH On August 23, 2004, an engine tear down and inspection was conducted under the direction of the NTSB IIC, at Alaskan Aircraft Engines, Inc., Anchorage, Alaska. Also present at the engine tear down and inspection was an airworthiness inspector from the Federal Aviation Administrations Anchorage Flight Standards District Office. A preliminary, external engine examination revealed a 1-inch hole in the crankcase, adjacent to the aft, left, number 6 cylinder, which exposed the underlying crankshaft and connecting rod assembly. According to a representative from Textron Lycoming, this type of catastrophic failure is consistent with oil starvation. Removal of the engine starter ring gear assembly revealed that the three-quarter inch hex head plug at the front of the engine, which retains the propeller governor idler gear shaft, was missing. The outer crankcase housing, adjacent to the hex head plug receptacle, had significant evidence of scoring and metal smearing that corresponded to starter ring gear rotation. A visual examination of the interior portion of the starter ring gear revealed witness marks and deep gouges that corresponded to the same location as the propeller governor idler gear shaft extending forward. The propeller governor idler gear shaft was also missing. According to a representative from Textron Lycoming, with the three-quarter inch hex head plug and the propeller governor idler gear shaft absent, engine oil under pressure would drive oil overboard through the unplugged hex head plug port. Neither the three-quarter-inch hex head plug, nor the propeller governor idler gear shaft, were recovered at the wreckage site. According to a representative from Alaskan Aircraft Engines, an FAA authorized engine overhaul facility, the three-quarter-inch hex head plug should be secured in place with safety wire after installation, to prevent a loss of torque on the plug, and subsequent loss of the plug. An inspection of an exemplary three-quarter-inch hex head plug revealed a safety wire hole drilled in the hexed portion of the plug. The plug is then secured to a safety wire tang, located below and slightly to the right of the hex head plug. There was no safety wire, or remnants of residual safety wire, noted on the accident engine during the inspection. An internal examination of the engine revealed heat and circumferential scoring to the crankshaft, connecting rods, and pistons. The oil pump and oil filter were contaminated with metal fragments. According to a representative from Alaskan Aircraft Engines, the metal fragments within the engine were consistent with oil starvation. When the engine crankcase halves were separated, the propeller governor idler gear and thrust washer were found lying in the lower portion of the forward oil gallery. When installed, the propeller governor idler gear shaft extends into the forward oil gallery, which houses the propeller governor idler gear and propeller governor drive shaft. The propeller governor idler gear shaft is held in place by a setscrew, accessible only when the engine case halves have been separated. At overhaul, installation procedures for the setscrew are provided in Textron Lycoming Service Instruction No. 1343A, dated February 4, 1991. After installation of the setscrew, using a small diameter center punch tool, the threads in the engine case that retain the setscrew are to be peened to prevent the setscrew from backing out. When installed, the pointed tip of the setscrew locks into a predrilled keyway located on the forward portion of the propeller idler shaft, which prevents the propeller idler shaft from moving or rotating. A copy of Textron Lycoming Service Instruction No. 1343A is included in the public docket for this accident. The setscrew was not disturbed during the engine tear down and inspection. At the completion of the engine tear down, the following engine components were sent to the National Transportation Safety Board's Materials Laboratory for examination and metallurgical investigation. Those items consisted of: A forward (sectioned) piece of the crankcase half that contained the setscrew, propeller governor idler gear, propeller governor drive shaft, and the thrust washer. Setscrew Examination A Senior Safety Board metallurgist reported that the setscrew was discovered loose within the crankcase half. He noted that the inner tip of the idler gear shaft setscrew was located about 0.01-inch back from the bore of the idler gear shaft hole within the idler gear shaft boss. Prior to removing the setscrew, a cotton swab was used to sample material in the area of the setscrew. According to the metallurgist, while taking the sample, he discovered that he was able to rotate the setscrew using just the tip of the cotton swab. After the setscrew was removed, a scanning electron microscopy (SEM) was used to examine the beveled setscrew tip end. The examination revealed a spiral pattern of deformation, and the tip set screw was fractured. He added that the lower edge of the setscrew hole had a deformation lip consistent with the rotation of the propeller idler shaft. The metallurgist reported that an examination of the hex end of the setscrew revealed a single area of flattened and deformed material, consistent with the peening process outlined in the Textron Lycoming Service Instruction No. 1343A. He added that the deformed material extended into the hex, but the material appears to have been moved back by the insertion of an allen wrench tool into the hex. He remarked that these signatures were consistent with removing or loosening of the set setscrew. Safety wire / Three-quarter inch hex head plug When assembled on the engine, the three-quarter inch hex head plug should be secured in place with safety wire that is threaded through a tang in the crankcase flange. A hole for safety wire was available, but no safety wire was present. Additionally, the owner/pilot reported that the entire crankcase was striped and repainted gray at the time of the overhaul. According to the Safety Board metallurgist who conducted the metallurgical investigation, a detailed inspection of the safety wire tang showed no evidence of paint disturbance or any other evidence of safety wire being applied at that location. For comparison, the section of the crankcase containing the safety wire tang was mounted in a vise and 0.032-inch-diameter safety wire was threaded through the safety wire hole. According to the Safety Board metallurgist, there was clear disturbance of the paint after threading the safety wire through the hole. A complete copy of the Safety Board's factual materials laboratory report is included in the public docket for this accident. WRECKAGE RELEASE The Safety Board released the wreckage, located at Seward, to the owner's representatives on August 16, 2004, but retained various engine components pending NTSB metallurgical investigation. The engine components were retained by the Safety Board for examination until their release on May 26, 2005.
The failure of an aviation mechanic/inspector to adequately inspect the pilot/owner's work during the engine overhaul, which resulted in a loss of engine oil and engine power during cruise flight, and a subsequent ditching. Factors associated with the accident were the inadequate installation of the idler gear shaft setscrew, and the lack of a safety wire on the three-quarter inch hex head (oil) plug in front of the idler gear shaft. Additional factors associated with the accident were the lack of suitable terrain for a forced landing, and ocean water.
Source: NTSB Aviation Accident Database
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