Reno, NV, USA
N352BT
AMERICAN AIR RACING LTD THUNDER MUSTANG
The airline transport pilot of the high-performance air racing airplane was taking part in an in-flight photography mission with two other airplanes. About 1 hour into the second flight of the day, the group was getting fatigued and decided to return to the departure airport. As the airplanes approached the airport, the accident pilot transmitted a "mayday" call and reported that he was going to land on the runway located directly ahead of his position. The airplane began to descend while performing an S-turn, and touched down beyond the midpoint of the 9,000-ft-long runway at a slightly higher speed than normal. A 4-knot tailwind prevailed on the landing runway about the time of the accident. A 1,200-ft-long series of propeller strikes on the runway were consistent with the pilot applying heavy braking after touchdown. The airplane veered right as it reached the end of the runway, entered a gravel area, nosed over, and came to rest inverted. Given the airplane's nominal landing distance in addition to the factors that increased that distance on the accident landing, namely, remaining runway at the time of the touchdown, the airplane's higher landing speed, and the tailwind, the pilot would have had very little margin for error before the airplane's landing distance required exceeded the available runway. The vertical stabilizer collapsed when the airplane nosed over, which resulted in the canopy structure contacting the ground and subsequently failing. As a result, the pilot's head was impinged at an angle against the ground, resulting in airway restriction. The pilot's extraction from the airplane by first responders took about 45 minutes, and during that time, the pilot died of asphyxiation. However, unless he had been repositioned and his breathing enabled almost immediately following the accident, survival would have been unlikely, and based on the airplane's weight and inverted position, an immediate rescue was not possible. It could not be determined if the canopy bow was designed to be structural in nature; additionally, visual inspection revealed defects that would have further weakened its supporting properties. Examination of the engine revealed that the coolant pump drive pulley had detached due to fatigue failure of its attachment cap screws. Separation of the pulley resulted in the detachment of the engine's two parallel serpentine drive belts, which drove multiple other engine accessories. This design allowed for a single point of failure, which resulted in a total loss of engine oil pressure, propeller governor control, and auxiliary electrical power. The belts also dislodged a coolant line, resulting in the loss of all engine coolant. With these failures, the engine would have been able to operate for a short duration before experiencing catastrophic failure, negating the pilots ability to perform a go-around, and evidence suggests that it continued to operate at a low power setting during the descent and the landing roll. Hardness testing of the pulley attachment screws revealed that they were of the proper tensile strength. Substantial fretting damage was present on the pulley contact faces and under the screw contact areas, and thread wear was present in the pulley attachment holes. Evidence of the use of thread locking material was observed; therefore, it is likely that the screws detached due to insufficient tightening at the time of installation. Although the thread locking material used was consistent with the engine manufacturer installation instructions, product literature from the manufacturer of the thread locking material indicated that another type was available that was specifically tailored for pulley applications. Whether the use of the alternate thread locking material would have affected the outcome could not be determined. The pilot performed all the maintenance work on the engine, which had been overhauled about 20 flight hours before the accident; however, he performed multiple significant maintenance events on the engine between the overhaul and the accident flight, so the precise timing of the pulley installation could not be determined. The 80-year-old pilot had extensive experience in air racing and the airplane type, and had successfully dealt with multiple loss of engine power events in the airport environment and accident airplane type. However, under the specific circumstances of this failure, the design of the propeller was such that, following the loss of governor control, the propeller would have moved to a blade pitch angle that would have resulted in less drag and a longer gliding profile than the pilot had likely experienced in previous events. No logbooks of his flight experience were recovered; however, evidence suggests that he had cut back on his flying activities during the recent period leading up to the accident. The pilot was likely fatigued from the two flights on the day of the accident and appeared to be experiencing a gradual degradation in his general health, which may have begun to affect his performance. Although there was evidence that the pilot had used two opioid pain medications at some time before the accident, active drugs and their metabolites were found only in urine. This indicates the active compounds were no longer present in his system and therefore would not have been causing any effects. Overall, there is no evidence the pilot was impaired by a specific medical condition or use of medications or other substances at the time of the accident; however, the subtle impairing effects of withdrawal from the opioid medications cannot be eliminated.
HISTORY OF FLIGHTOn May 1, 2018, at 1931 Pacific daylight time, an experimental, amateur-built American Air Racing (AAR) Thunder Mustang (Blue Thunder II), N352BT, sustained substantial damage during a forced landing at Reno/Stead Airport (RTS), Reno, Nevada. The airline transport pilot was fatally injured. The airplane was registered to TM-1 Ltd. and operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which departed about 1815. The airplane was taking part in an in-flight photography mission with another Thunder Mustang, with the photographs being taken from a Beechcraft Bonanza. This was the second photography flight the group had flown that day. The first flight began about 1500 and lasted about 1 hour. About 1 hour into the accident flight, which included multiple north-south passes north of the airport, the group agreed that they were beginning to get fatigued and decided to end the mission and return to RTS. When the airplanes were about 5 miles from the airport, the accident pilot transmitted a "mayday" radio call over the common traffic advisory frequency. The pilot of the other Thunder Mustang asked for a confirmation, and the accident pilot responded again with a mayday call, adding that he intended to land on runway 14. The other pilot watched as the airplane began to descend toward the airport. He saw it overshoot the extended runway 14 centerline, then begin a wide 180° left turn followed by a right turn to rejoin the centerline. By this time, the airplane was midfield and low over the runway, flying at what the second pilot judged to be a high speed. He could not tell if the airplane had touched down or was still floating over the runway in ground effect, and as it approached the end of the runway, it veered off the right side and nosed over. The airplane came to rest inverted in a gravel area about 20 ft right of the runway edge and 80 ft short of the runway's paved end. The runway surface exhibited a 1,200-ft-long series of intermittent black tire skid marks and intermittent propeller blade gouges leading from the runway centerline to the airplane. The final stage of the accident sequence was captured by a video camera mounted on the airport operations building at the southeast corner of the airport, about 1,500 ft southwest of the end of runway 14. The camera was facing northeast with a field of view that included the last 2,000 ft of runway 14. When the airplane came into view, it was traveling from left to right with the main landing gear on the runway surface. As it progressed, the tail began to rise and as the airplane passed to the right and out of the camera's view, it had transitioned to a 45° nose-down attitude. The main wreckage was located about 50 ft beyond the point where it exited the camera field of view. A runway construction crew, along with the other pilots from the photography mission, arrived at the accident site within about 3 minutes, followed a few minutes later by the local fire department. They observed that the vertical stabilizer had folded against the right horizontal stabilizer and that the canopy was shattered by ground impact. The flaps were found in the 43° (full down) position, and the landing gear was extended. The pilot remained in his seat restrained by his four-point harness. His helmet was impinged against the gravel surface, and his head was tilted forward so that his chin was in contact with his chest. The first pilot to arrive stated that he could initially hear the pilot mumbling, and he reached into the cockpit and asked the pilot if he could turn off any switches, but the pilot did not respond. He did not hear the pilot make any more sounds. A paramedic arrived at the accident site about 11 minutes after the accident, assessed the pilot's condition, and reported that although the pilot initially appeared to be conscious, he became unresponsive after about 2 minutes. The group attempted to lift the airplane up by the wing to relieve the pressure on the pilot, but it was too heavy. Multiple attempts to move and lift the airplane were unsuccessful. The pilot was extracted about 45 minutes after the accident, when the fire department used a combination of lifting devices and dug a hole in the gravel under the cockpit. PERSONNEL INFORMATIONThe 80-year-old pilot held an airline transport pilot certificate with a rating for airplane multiengine land, type ratings for the B-707, B-720, B-727, DC-9, and DC-10, and commercial privileges for airplane single-engine land. He held an airframe and powerplant certificate (A&P), with inspection authorization (IA). The pilot was the sole owner of AAR and employed a crew of three mechanics in part- and full-time capacities. The pilot performed most of the work on the accident airplane, including engine removal and installation. He oversaw and signed off on all work performed, because the other mechanics did not hold Federal Aviation Administration (FAA) mechanic ratings. AAR performed maintenance work for multiple types of aircraft but specialized in the Thunder Mustang due to the owner's experience with the type. The pilot had extensive flight experience in air racing and reported 30,000 total civilian hours of flight time as of his last FAA medical examination on July 7, 2017. No pilot logbooks were recovered. The pilot's most recent flight experience was determined from his application as a participant in the Reno National Championship Air Races Pylon Racing Seminar (PRS). The application was dated March 13, 2018, and at that time the pilot reported 326 total hours of flight experience in the accident airplane make and model, of which 287 was in the accident airplane. He reported 34 hours of flight experience in the previous 90 days. The pilot also owned and flew a Piper PA-34, and according to employees of AAR, these were the only two airplanes he flew. Maintenance logbooks for the PA-34 indicated that it had accumulated 5.4 hours of flight time in the previous 3 months; the accident airplane had accumulated 2.48 hours of flight time during that period. Employees of AAR along with the pilots involved in the photography mission all stated that the pilot seemed to be his usual self before the accident. Although he needed assistance getting into the airplane, this was not unusual. Employees and the pilot's son all noted what they considered to be normal, "age-related" degradation over the years they had known him, but no recent acceleration or issues of concern. They also stated that he tended to be strong-willed and would not likely disclose any medical concerns. The pilot lived alone; therefore, a meaningful 72-hour history of his activities leading up to the accident could not be determined. One of the pilots in the photographic mission stated that the accident pilot expressed irritation that the maximum speed of the Bonanza was too slow to allow for stable flight of the Thunder Mustang while photographing it. He also noted that the accident pilot did not appear to be flying with his usual level of precision on both flights, and was not in as close formation as he should have been. Additionally, 2 days before the accident, a friend of the pilot saw the pilot struggle with his balance after leaning over to look at something on the hangar floor. As he stood back up again, he fell back to the ground after trying to avoid the wing strut of an airplane. His friend described the pilot as dizzy and disoriented. He had slight trouble walking after the event, and was unable to lift his foot to get into his golf cart. The pilots son, who was also there, stated that the pilot sometimes experienced these issues if he stood for too long, but on that day, he appeared to be back to normal a short time later. AIRCRAFT INFORMATIONThe airplane was a kit-built, 3/4-scale replica of the P-51 Mustang, composed primarily of composite materials. The original manufacturer of the kit (Papa 51) formed in the early 1990's and went out of business around 1998-1999. The company assets were subsequently purchased by the Thunder Mustang Builders Group (TBG), and then by an individual in 2012. According to TBG, 37 kits were originally sold, and 15 airplanes were flying at the time of the accident. The accident pilot was a member of the TBG, and had become known as an expert in the type. The airplane was equipped with a liquid-cooled, fuel injected, 12-cylinder engine manufactured by Ryan Falconer Racing Engines. The engine was based on the Chevrolet "small block" automobile engine and was designed for use in high-performance, custom-built marine, automobile, and aviation applications. Most of the engine's accessories were mounted on the rear of the engine and included the fuel pump, coolant pump, propeller governor, auxiliary alternator, and both the scavenge and pressure oil pumps. The accessories were driven simultaneously by the engine crankshaft via a parallel pair of Kevlar serpentine belts. The coolant pump was an automotive centrifugal type, driven by the belts via a pulley attached to the pump drive flange. The primary alternator was also attached to the rear of the engine, but driven by its own dedicated belt. Engine ignition was controlled by independent dual electronic engine control units, both powered simultaneously from the main and auxiliary electrical systems. The propeller was a 101.5-inch diameter, three-blade, hydraulically (engine oil) operated constant-speed propeller, manufactured by Hartzell Propellers exclusively for installation on Thunder Mustang airplanes. According to Hartzell, the propeller incorporated design features for air racing. Specifically, it included a 60° mechanical high pitch stop, designed such that in the event of oil pressure loss or a propeller governor failure at high airspeed, the propeller would move to the 60° blade angle position (higher than normal operation) and prevent a catastrophic engine overspeed. It did not have full feather capabilities, so that the airplane had "limp home" capability at the 60° blade angle if the engine continued to run. In the event of a total power loss, the 60° blade angle would reduce windmill drag without completely feathering; this would also facilitate airstart attempts if the cause of power loss was corrected. With the throttle at idle while in flight, under normal operation the governor would drive the propeller down to the 22° blade angle position. The airplane was equipped with retractable main and tailwheel landing gear, operated through a system of electrical, mechanical, and hydraulic components. Hydraulic pressure was provided though a pump mounted to an accessory pad on the forward end of the engine. The flaps were electrically controlled, and the airplane was equipped with conventional disc brakes, operated on a separate and dedicated hydraulic system. The pilot owned two Falconer engines for the airplane, serial number 12022, which was the accident engine, and serial number 12023, which was the engine used in air races. An engine overhaul was completed on the accident engine on March 18, 2016, and it was installed on April 2, 2016. The overhaul facility specialized in manufacturing and rebuilding specialized racing engines, primarily for marine and automobile use. The owner of the overhaul facility stated that the engine came back to him a short time later after sustaining an overheating event. It was repaired and subsequently reinstalled on March 17, 2017. According to the maintenance logbooks, the last condition inspection on the engine was performed on March 14, 2018, at a time of 17.15 hours since major overhaul (2.48 flight hours before the accident). The owner of the overhaul facility stated that he was aware of the engine being removed two more times by the pilot since he performed the repair work, and that during one of those events, the pilot was trying to swap the cylinder heads with his other race engine; however, he was not able to do so as they had different clearances. The airplane's flight manual and training guide indicated that the landing distance varied based on numerous factors, the primary being pilot technique. It stated that if a three-point landing was performed, 2,000 ft of runway was adequate, and that a wheel landing required 3,500 ft. It further explained that dynamics including approach speed, density altitude, and obstacle clearance need to be factored for every landing. An entry in the airplane's logbook recorded during the phase 1 flight testing period indicated the VSo speed (the stall speed or the minimum steady flight speed in the landing configuration) was 82 knots. METEOROLOGICAL INFORMATIONAt 1935, the automated surface weather observation facility at RTS reported a direct tailwind for runway 14 at 4 knots. Visibility was 10 miles, temperature 4°C, dew point 1°C, and the altimeter setting was 29.91 inches of mercury. AIRPORT INFORMATIONThe airplane was a kit-built, 3/4-scale replica of the P-51 Mustang, composed primarily of composite materials. The original manufacturer of the kit (Papa 51) formed in the early 1990's and went out of business around 1998-1999. The company assets were subsequently purchased by the Thunder Mustang Builders Group (TBG), and then by an individual in 2012. According to TBG, 37 kits were originally sold, and 15 airplanes were flying at the time of the accident. The accident pilot was a member of the TBG, and had become known as an expert in the type. The airplane was equipped with a liquid-cooled, fuel injected, 12-cylinder engine manufactured by Ryan Falconer Racing Engines. The engine was based on the Chevrolet "small block" automobile engine and was designed for use in high-performance, custom-built marine, automobile, and aviation applications. Most of the engine's accessories were mounted on the rear of the engine and included the fuel pump, coolant pump, propeller governor, auxiliary alternator, and both the scavenge and pressure oil pumps. The accessories were driven simultaneously by the engine crankshaft via a parallel pair of Kevlar serpentine belts. The coolant pump was an automotive centrifugal type, driven by the belts via a pulley attached to the pump drive flange. The primary alternator was also attached to the rear of the engine, but driven by its own dedicated belt. Engine ignition was controlled by independent dual electronic engine control units, both powered simultaneously from the main and auxiliary electrical systems. The propeller was a 101.5-inch diameter, three-blade, hydraulically (engine oil) operated constant-speed propeller, manufactured by Hartzell Propellers exclusively for installation on Thunder Mustang airplanes. According to Hartzell, the propeller incorporated design features for air racing. Specifically, it included a 60° mechanical high pitch stop, designed such that in the event of oil pressure loss or a propeller governor failure at high airspeed, the propeller would move to the 60° blade angle position (higher than normal operation) and prevent a catastrophic engine overspeed. It did not have full feather capabilities, so that the airplane had "limp home" capability at the 60° blade angle if the engine continued to run. In the event of a total power loss, the 60° blade angle would reduce windmill drag without completely feathering; this would also facilitate airstart attempts if the cause of power loss was corrected. With the throttle at idle while in flight, under normal operation the governor would drive the propeller down to the 22° blade angle position. The airplane was equipped with retractable main and tailwheel landing gear, operated through a system of electrical, mechanical, and hydraulic components. Hydraulic pressure was provided though a pump mounted to an accessory pad on the forward end of the engine. The flaps were electrically controlled, and the airplane was equipped with conventional disc brakes, operated on a separate and dedicated hydraulic system. The pilot owned two Falconer engines for the airplane, serial number 12022, which was the accident engine, and serial number 12023, which was the engine used in air races. An engine overhaul was completed on the ac
The pilot's failure to properly secure the engine coolant pump pulley during recent maintenance, which resulted in a loss of the engine's lubrication, cooling, and propeller control systems, and a forced landing, during which the airplane nosed over. Contributing was the design of the accessory drive system, which allowed for multiple simultaneous failures of critical engine components. Contributing to the pilot's fatal injuries was the inadequate support provided by the airplane's canopy structure, which did not protect him during the relatively innocuous nose-over event.
Source: NTSB Aviation Accident Database
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