Covington, GA, USA
N900AW
BEECH A36
After takeoff, during cruise flight, the engine sustained a short duration of oil pressure fluctuations followed by a period of stabilized engine oil pressure. It then sustained a complete loss of oil pressure with a subsequent catastrophic engine failure. The pilot flying transferred control to the more experienced pilot-rated passenger, who maneuvered the airplane for a forced landing to a road. While on final approach to the road, the airplane’s left wing struck a tree and then the airplane then struck two street signs during the landing roll. The airplane came to rest in a ditch with substantial damage to one elevator. Postaccident examination of the engine revealed internal catastrophic failure consistent with oil starvation. Data from an engine monitor showed that the oil pressure during the accident flight was in the normal range before suddenly decreasing to 0 psi. The data also showed that about 11 days and 6 engine operational hours before the accident flight, while taxiing for a flight following installation of an engine-driven standby alternator, the oil pressure dropped to about 9 psi, and then dropped to about 3 psi during the takeoff roll. Both values were below the minimum 10 psi specified in the airplane’s Pilot’s Operating Handbook and Federal Aviation Administration (FAA) Approved Airplane Flight Manual. The near-0 psi actual oil pressure was only detected by the pilots after becoming airborne during that post-maintenance flight, resulting in an immediate return and uneventful landing. After landing, oil was found on the bottom of the fuselage and a large pool of oil was found on the taxiway where they had performed the first engine run-up to test the recently installed standby alternator. The maintenance facility then examined the engine and found that the standby alternator had not been installed (torqued) properly, resulting in the oil leak. Just over 4 quarts of oil remained in the engine. The standby alternator was replaced and installed properly. Oil was added to the engine, and a new oil filter was installed for an intended flight to another maintenance facility for an annual inspection. No contaminant was noted in the oil filter element what was removed from the engine. Normal engine oil pressure was noted for the majority of the flight to the maintenance facility except for one period when it temporarily dropped below 30 psi. As part of the subsequent annual inspection, the oil was changed again, and light metal debris was noted in the oil filter element. A new oil filter was installed, engine oil was added, and the airplane was then flown uneventfully on a short repositioning flight after the annual inspection. Normal oil pressure was noted during the repositioning flight. In total, the airplane was operated for about 6 hours between the installation of the standby alternator and the accident flight. Based on the available information, it is unlikely that the lubrication distress damage to the engine was initiated during the accident flight. Rather, the previous prolonged engine operation at high rpm with near 0 psi actual oil pressure started internal damage to the connecting rod bearings that was undetected by two maintenance facilities. Had the two maintenance facilities required a disassembly inspection of the engine in accordance with guidance contained in the engine manufacturer’s Standard Practice Maintenance Manual, it is likely that the internal damage to the connecting rod bearings would have been detected and repaired before the engine ultimately failed catastrophically during the accident flight.
HISTORY OF FLIGHTOn December 8, 2022, about 1810 eastern standard time, a Beech A36, N900AW, was substantially damaged when it was involved in an accident near Covington, Georgia. The commercial pilot and pilot-rated passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. Before departure from Griffin-Spalding County Airport (6A2), Griffin, Georgia, en route to Dekalb-Peachtree Airport, Atlanta, Georgia, the pilot-rated passenger checked the engine oil quantity and determined it to be 10 quarts. After takeoff, the left-seat pilot levelled the airplane at 5,500 ft mean sea level. Both pilots then heard a loud bang from the engine and observed a shower of sparks from the cowling, and the engine lost power. The pilots engaged the Garmin Smart Glide mode of the autopilot, and as designed the autopilot pitched up to attain and maintain best glide airspeed; it then advised that no airports were within glide range. Control of the airplane was then transferred to the pilot-rated passenger, who disengaged the autopilot. He declared an emergency while looking for a suitable landing site. The pilot maneuvered for a forced landing on a section of the road that appeared to be straight. Soon after asking the left-seat pilot to lower the flaps, the airplane’s left wing impacted part of a tree that was growing over the roadway. The airplane then touched down on the road and impacted 2 street signs before coming to rest in a ditch on the right side of the road. Engine data associated with the accident flight revealed the oil pressure was normal until about 1801, when extensive fluctuations occurred over the next 5 minutes but with the oil pressure remaining about 40 psi. At 1806, the engine rpm dropped to about 1,000 rpm, with a corresponding decrease of oil pressure, and a corresponding drop in exhaust gas temperatures and cylinder head temperatures. Then the rpm and oil pressure stabilized with the oil pressure remaining about 40 psi until about 1808:24. About that time, the oil pressure and engine rpm began decreasing to 0 psi oil pressure and 0 engine rpm. AIRCRAFT INFORMATIONThe airplane was equipped with a Garmin GDU 460, a Garmin GDU 470, and a Garmin GTN 750. The panel-mounted GPS receivers were retained for read-out by the National Transportation Safety Board (NTSB) Vehicle Recorder Division. The airplane’s Pilot’s Operating Handbook and FAA Approved Airplane Flight Manual (POH/AFM) specified that the minimum oil pressure at idle was 10 psi. The engine manufacturer’s Installation and Operation Manual (IOM) specified that the normal oil pressure (30 to 60 psi) was required between oil temperature of 75°Fahrenheit (F) to 240°F, while the minimum oil pressure at idle (600 rpm) was specified to be 10 psi when the oil temperature was at or below 240° F. A warning in the IOM manual associated with low oil pressure specified that if it dropped below 30 psi, an engine failure was imminent and to follow the procedures in the POH/AFM. The warning also indicated that if the oil pressure dropped suddenly from a normal indication of between 30 and 60 psi, the pilot should monitor oil temperature closely and land as soon as possible. The engine manufacturer’s Standard Practice Maintenance Manual had a warning that stated the following: “Operation with insufficient oil pressure may result in a catastrophic engine failure. Engines operated with oil pressure below the specified limitation, must be disassembled, inspected, and repaired as necessary to ensure the engine was safe for operation.” The airplane’s engine maintenance records revealed that a new engine was installed on the airplane in 2017. However, it was disassembled in 2018 due to a propeller strike; after repair, it was reinstalled on the airplane. Between 2018 and November 27, 2022, normal maintenance occurred with no engine lubrication system issues reported. On November 27, 2022, after having avionics work performed, which included the installation of a standby alternator, two pilots (both of whom were on the accident flight), boarded the airplane at 6A2 with the intention of flying to Cedar Ridge Airport (GA62), Griffin, Georgia, where an annual inspection was to be performed. According to the NTSB Electronic Flight Information System Specialist’s Factual Report, at 1636:40, while on the ground stationary with the engine rpm about 2,000, the oil pressure began to decrease from about 50 psi. While stationary, the oil pressure dropped to 9 psi at 1638:43. About 1 minute later with the oil pressure at 6 psi, the airplane began to taxi towards the approach end of the runway. During the takeoff roll at 1643:15, the oil pressure was 3 psi while the oil temperature was in the normal range at 152° F. The airplane became airborne and one of the pilots reported the engine “waivered” with the oil pressure at 3 psi, the oil temperature at 181° F, and the engine rpm at 2,720. The pilot of another airplane at 6A2 radioed them and advised smoke was trailing the airplane. The flight returned to 6A2 and landed uneventfully, with the engine rpm reaching 0 at 1645:52. After landing, oil was found all over the bottom of the fuselage and in a very large pool on the taxiway where they had performed the first engine run-up to test the recently installed standby alternator. The maintenance facility that had installed the standby alternator examined the engine. A borescope inspection of the engine was performed and just over 4 quarts of oil remained in the engine. The remaining engine oil was drained, and the oil filter element was examined with no discrepancies reported. The examination revealed that the standby alternator had not been torqued properly, resulting in the subsequent oil leak. A replacement standby alternator was installed and properly torqued. There was no maintenance entry made in the engine logbook for the oil and oil filter change after the diminished oil pressure. One of the pilots of the November 27th flight communicated what had occurred concerning the low oil pressure with the facility that had improperly installed the standby alternator and with the facility that planned to perform the annual inspection. The airplane was subsequently flown on November 29th from 6A2 to Cedar Ridge Airport (GA62), Griffin, Georgia, for the annual inspection. A review of engine data associated with the flight revealed normal engine oil pressure for the majority of recorded data with the exception of one point when the oil pressure dropped below 30 psi. During the annual inspection, the engine oil was drained through a 1,000-ppm strainer. While the engine logbook entry for the annual inspection indicated that no contamination was found in the oil filter element, an invoice associated with the inspection indicated, “Removed and cut filter with light metal debris found.” A new oil filter was installed and 11 quarts of oil were added. Additionally, a borescope inspection of the engine was performed with no discrepancies reported. After the annual inspection was completed on December 7th, the airplane was flown from GA62 to 6A2. A review of engine data associated with the flight revealed normal engine oil pressure throughout the flight. Based on maintenance records and downloaded data associated with the repositioning flight the day before the accident, at the start of the accident flight, the engine had accrued about 6 hours since the flight on November 27, 2022, when it had been operated at near-zero oil pressure and high rpm. AIRPORT INFORMATIONThe airplane was equipped with a Garmin GDU 460, a Garmin GDU 470, and a Garmin GTN 750. The panel-mounted GPS receivers were retained for read-out by the National Transportation Safety Board (NTSB) Vehicle Recorder Division. The airplane’s Pilot’s Operating Handbook and FAA Approved Airplane Flight Manual (POH/AFM) specified that the minimum oil pressure at idle was 10 psi. The engine manufacturer’s Installation and Operation Manual (IOM) specified that the normal oil pressure (30 to 60 psi) was required between oil temperature of 75°Fahrenheit (F) to 240°F, while the minimum oil pressure at idle (600 rpm) was specified to be 10 psi when the oil temperature was at or below 240° F. A warning in the IOM manual associated with low oil pressure specified that if it dropped below 30 psi, an engine failure was imminent and to follow the procedures in the POH/AFM. The warning also indicated that if the oil pressure dropped suddenly from a normal indication of between 30 and 60 psi, the pilot should monitor oil temperature closely and land as soon as possible. The engine manufacturer’s Standard Practice Maintenance Manual had a warning that stated the following: “Operation with insufficient oil pressure may result in a catastrophic engine failure. Engines operated with oil pressure below the specified limitation, must be disassembled, inspected, and repaired as necessary to ensure the engine was safe for operation.” The airplane’s engine maintenance records revealed that a new engine was installed on the airplane in 2017. However, it was disassembled in 2018 due to a propeller strike; after repair, it was reinstalled on the airplane. Between 2018 and November 27, 2022, normal maintenance occurred with no engine lubrication system issues reported. On November 27, 2022, after having avionics work performed, which included the installation of a standby alternator, two pilots (both of whom were on the accident flight), boarded the airplane at 6A2 with the intention of flying to Cedar Ridge Airport (GA62), Griffin, Georgia, where an annual inspection was to be performed. According to the NTSB Electronic Flight Information System Specialist’s Factual Report, at 1636:40, while on the ground stationary with the engine rpm about 2,000, the oil pressure began to decrease from about 50 psi. While stationary, the oil pressure dropped to 9 psi at 1638:43. About 1 minute later with the oil pressure at 6 psi, the airplane began to taxi towards the approach end of the runway. During the takeoff roll at 1643:15, the oil pressure was 3 psi while the oil temperature was in the normal range at 152° F. The airplane became airborne and one of the pilots reported the engine “waivered” with the oil pressure at 3 psi, the oil temperature at 181° F, and the engine rpm at 2,720. The pilot of another airplane at 6A2 radioed them and advised smoke was trailing the airplane. The flight returned to 6A2 and landed uneventfully, with the engine rpm reaching 0 at 1645:52. After landing, oil was found all over the bottom of the fuselage and in a very large pool on the taxiway where they had performed the first engine run-up to test the recently installed standby alternator. The maintenance facility that had installed the standby alternator examined the engine. A borescope inspection of the engine was performed and just over 4 quarts of oil remained in the engine. The remaining engine oil was drained, and the oil filter element was examined with no discrepancies reported. The examination revealed that the standby alternator had not been torqued properly, resulting in the subsequent oil leak. A replacement standby alternator was installed and properly torqued. There was no maintenance entry made in the engine logbook for the oil and oil filter change after the diminished oil pressure. One of the pilots of the November 27th flight communicated what had occurred concerning the low oil pressure with the facility that had improperly installed the standby alternator and with the facility that planned to perform the annual inspection. The airplane was subsequently flown on November 29th from 6A2 to Cedar Ridge Airport (GA62), Griffin, Georgia, for the annual inspection. A review of engine data associated with the flight revealed normal engine oil pressure for the majority of recorded data with the exception of one point when the oil pressure dropped below 30 psi. During the annual inspection, the engine oil was drained through a 1,000-ppm strainer. While the engine logbook entry for the annual inspection indicated that no contamination was found in the oil filter element, an invoice associated with the inspection indicated, “Removed and cut filter with light metal debris found.” A new oil filter was installed and 11 quarts of oil were added. Additionally, a borescope inspection of the engine was performed with no discrepancies reported. After the annual inspection was completed on December 7th, the airplane was flown from GA62 to 6A2. A review of engine data associated with the flight revealed normal engine oil pressure throughout the flight. Based on maintenance records and downloaded data associated with the repositioning flight the day before the accident, at the start of the accident flight, the engine had accrued about 6 hours since the flight on November 27, 2022, when it had been operated at near-zero oil pressure and high rpm. WRECKAGE AND IMPACT INFORMATIONExamination of the airplane revealed the main spar of one elevator was damaged during the forced landing. An initial examination of the engine revealed a large diameter hole in the engine crankcase adjacent to the No. 4 cylinder. The hole was from the backbone (top) of the crankcase parting surfaces to near the No. 4 cylinder parting surface. Following removal of the engine it was shipped to the engine manufacturer’s facility for disassembly examination. Examination of the lubrication system revealed the oil pump drive and driven gears were not fractured but the oil pump housing exhibited scoring consistent with hard particle passage. Small specks of contaminant were noted on both oil pump gears and a significant quantity of non-ferrous material was noted on the oil pressure relief valve plunger and inside the oil pressure relief valve housing. There were no obstructions of the internal portion of the camshaft, which was a path for oil from the oil pump to the main bearings, or for the oil galleries in the crankshaft that fed oil to the connecting rod bearings. Ferrous and non-ferrous material were found in the oil sump. Disassembly inspection of the engine revealed no evidence of main bearing lubrication distress. Lubrication distress was noted to nearly all the connecting rod journals and connecting rod bearings, with extrusion of varying degrees noted to the Nos. 1, 2, 3, and 6 connecting rod bearings. The No. 4 cylinder connecting rod was fractured and its connecting rod cap was fractured into multiple pieces.
A total loss of engine power due to oil starvation as a result of engine operation with low oil pressure. Contributing to the accident was the failure of two separate maintenance facilities to comply with guidance from the engine manufacturer to disassemble and inspect the engine following prolonged operation with actual oil pressure values well below the lowest specified limit.
Source: NTSB Aviation Accident Database
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