CEN21FA304

The total loss of engine power due to a fatigue failure of a crankshaft counterweight mounting lobe, which resulted in a counterweight separation and catastrophic secondary damage to the engine drivetrain. Contributing to the accident was the mislabeled warning light, the pilot’s erroneous belief that the airplane was safe to operate after the metal contamination was observed in the oil filtration system, and his failure to maintain best glide airspeed during the forced landing, which resulted in the airplane exceeding its critical angle-of-attack and an inadvertent aerodynamic stall at a low altitude.

The pilot was conducting a cross-country flight when the airplane had a total loss of engine power while it approached the intended destination airport. Based on witness accounts, the pilot was unable to glide the airplane to the intended destination airport and entered an inadvertent aerodynamic stall at a low altitude. One witness reported that the airplane’s wings rolled left-and-right 2 to 3 times before the airplane “stalled” with the left wing down. The airplane impacted the ground in a left-wing down roll attitude and was destroyed during a postimpact fire. Postaccident examination of the engine determined that the loss of engine power was due to a fatigue failure of a crankshaft counterweight mounting lobe, which resulted in the separation of a counterweight and catastrophic secondary damage to the engine drivetrain. A couple days before the accident, an aviation mechanic found metal contamination in the engine oil filtration system after an associated warning light illuminated during a post-maintenance engine run. The mechanic and pilot discussed the metal contamination and agreed to have it submitted to a laboratory for identification. The oil filtration system was equipped with a ball-and-spring “bypass” switch, which when wired to a cockpit warning light offered a visual indication of when the filtration system was bypassing engine oil instead of flowing through the filter screen. A separate magnetic chip detector was offered as an optional feature for the oil filtration system; however, postaccident examination of the oil filtration system confirmed that the optional chip detector was not installed. As such, the warning light installed in the instrument panel was mislabeled “chip detector” instead of a label that conveyed the oil filtration system was in a bypass condition. When the mechanic saw the warning light illuminated during his post-maintenance engine run, it was a visual indication that the engine had produced enough metal contamination to restrict oil flow in the filtration system, resulting in a bypass condition. The mechanic cleaned the filtration housing, filter screen, and bypass switch. He then added new oil to the engine and performed another engine run, during which the “chip light” did not illuminate. The mechanic told the pilot not to fly the airplane until the laboratory results were returned, but he did not ground the airplane to prevent additional flights. The pilot conducted three flights, totaling at least 1.8 hours, following the maintenance. As such, it is likely he erroneously believed the airplane was safe to fly if the “chip detector” warning light was not illuminated, when, in fact, the engine was not in an airworthy condition due to the progressive failure of the crankshaft counterweight mounting lobe that likely produced the metal contamination found during the last maintenance. A review of automatic dependent surveillance-broadcast track data revealed that the pilot did not maintain the airplane’s best glide airspeed during the final minutes of the flight. Based on the published glide performance, the airplane did not have sufficient altitude to reach the runway at any point during the approach. However, had the pilot maintained best glide airspeed the airplane would have retained a safe margin above the aerodynamic stall speed and, as such, might have resulted in a less severe off-field landing.

An autopsy of the pilot was completed by Southwestern Institute of Forensic Sciences at Dallas, Dallas, Texas. According to the autopsy report, the pilot died as result of thermal and blunt force injuries, and the manner of death was accident. FAA toxicology testing did not detect any carboxyhemoglobin, ethanol, glucose, or tested-for drugs. The German-built Focke-Wulf FWP-149D airplane was manufactured as a military trainer and was not type-certificated by the Federal Aviation Administration (FAA). The airplane operated in the United States between 1994 and 2001 with an FAA experimental exhibition airworthiness certificate before it was exported to Canada where the airplane was refurbished and operated in Canada between May 2001 and August 2019. On August 31, 2019, the airplane was flown into the United States with a Canadian registration number and experimental airworthiness certificate. On September 23, 2019, the FAA issued the current experimental exhibition airworthiness certificate with associated operating limitations, and the airplane was re-registered as N9145. At that time, the airframe total time (AFTT) and engine time since overhaul (TSOH) were 2,454.6 hours and 497.5 hours, respectively. The airplane continued to operate in the United States as an experimental exhibition airplane until the accident. Recent Maintenance According to maintenance documentation, the airplane’s last condition and 100-hour inspections were completed on September 8, 2020. At that time, the AFTT and engine TSOH were 2,512.8 hours and 557.7 hours, respectively. On October 24, 2020, the pilot annotated his flight logbook that the “chip light came on” during the flight. A review of available maintenance documentation did not reveal any associated maintenance at that time. On June 19, 2021, the pilot annotated his flight logbook that the chip light illuminated again and that there was an unspecified magneto issue. On June 21, 2021, the pilot relocated the airplane from his homebase airport (ILE) to Draughon-Miller Central Texas Regional Airport (TPL), Temple, Texas, where his aviation mechanic was based. According to a mechanic statement, maintenance invoices, and a logbook entry, the mechanic inspected the ignition system and determined the right magneto required repair. The right magneto was removed from the engine and repaired by an overhaul shop on June 29, 2021. Additional maintenance tasks at that time included changing the engine oil, repairing the oil filler neck, and installing new gaskets for the propeller governor and its adapter plate. On July 2, 2021, the mechanic installed the repaired right magneto and completed an engine run. The mechanic reported that during the engine run the amber-colored “chip detector” warning light illuminated in the airplane’s instrument panel. He shut down the engine, drained the engine oil into a clean bucket, and followed the wiring associated with the “chip detector” warning light to the engine oil filtration system housing. Disassembly of the oil filtration device revealed metal contamination inside the filter housing and on the filtration screen. The mechanic then showed the pilot the metal contamination and with the pilot present determined that the metal contamination did not stick to a magnet. The mechanic and pilot agreed that the metal contamination needed to be sent to a laboratory for additional analysis. The pilot told the mechanic that he still intended to fly the airplane back to ILE. The mechanic told the pilot that they needed to determine the source of the metal contamination before the pilot flew any trips in the airplane. The mechanic collected samples before he cleaned the filtration housing, filter screen, and bypass switch. He added new oil to the engine and performed another engine run, during which the “chip light” did not illuminate. According to last maintenance logbook entry, dated July 2, 2021, the AFTT and engine TSOH were 2,577.7 hours and 620.6 hours, respectively. Flight History Following Recent Maintenance On July 3, 2021, the pilot repositioned the airplane from TPL to ILE. The mechanic stated that the pilot completed an engine runup before the airplane departed. The mechanic stated that he believed the airplane was going to remain at ILE until the laboratory results were returned concerning the metal contamination found in the oil filter screen. According to the pilot’s flight logbook, on July 3, 2021, the flight from TPL to ILE was 0.2 hours in duration. According to ADS-B track data, on July 4, 2021, the pilot flew the airplane from ILE to New Braunfels National Airport (BAZ), New Braunfels, Texas. The airplane was airborne about 0.8 hours during the non-stop flight. After landing at BAZ, the airplane was featured in a static-display of aircraft in conjunction with the airport’s Forth-of-July airshow. The accident occurred during the pilot’s return flight to ILE after the airshow. The airplane was airborne about 0.8 hours during the accident flight. The airplane’s tachometer was destroyed during the postaccident fire and, as such, the airplane’s AFTT and engine TSOH at the time of the accident were calculated using the last maintenance logbook entry, the pilot’s online flight logbook, and ADS-B track data. Based on available information, the pilot operated the airplane at least 1.8 hours following the last maintenance that was completed on July 2, 2021, and at the time of the accident the AFTT and engine TSOH were 2,579.5 hours and 622.4 hours, respectively. Engine Oil Filtration System The airplane was equipped with an Aviation Development Corporation (ADC) oil filtration system, part number 600010-1. A review of product literature revealed that the oil filtration system was equipped with a ball-and-spring “bypass” switch, which when wired to a cockpit warning light offered a visual indication of when the filtration system was bypassing engine oil instead of flowing through the filter screen. A separate magnetic chip detector was offered as an optional feature for the oil filtration system; however, postaccident examination of the oil filtration system confirmed that the optional chip detector was not installed. Figure 5. Instrument panel warning light labeled “chip detector” (Provided by pilot’s family). The main wreckage was in a level grass field with several groupings of trees. The airplane’s initial impact point was a ground scar containing fragments of red navigation light lens material, consistent with the airplane in a left-wing-low attitude at impact. The wreckage debris path was oriented on a 319° true heading and measured about 135 ft long. The main wreckage consisted of the cabin and cockpit, right wing, aft fuselage, engine, and propeller, as shown in figure 6. The main cabin and cockpit were destroyed by impact forces and the postimpact fire. All structural components and flight control surfaces were located at the accident site. All observed structural damage to the airplane was consistent with ground impact. Flight control continuity could not be established due to extensive damage but all observed flight control separations were consistent with ground impact, fire-related damage, or cuts to facilitate recovery of the wreckage. Figure 6. Main wreckage at accident site. The engine could not be rotated through the reduction gearbox using the attached propeller. Disassembly of the engine revealed the Nos. 3 and 4 connecting rods separated from their respective crankshaft journals. The Nos. 3 and 4 connecting rod beams were bent, twisted, and deformed. There was significant damage to the internal cavities of the engine crankcase, particularly along the rotational plane of the Nos. 3 and 4 connecting rods and associated rotating crankshaft components, as shown in figures 7 and 8. Figure 7. Crankcase (left side). Figure 8. Crankshaft and crankca