WPR18FA131

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.

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.

The 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. During the 11 years preceding his last FAA medical examination, the pilot had reported hypertension, glucose intolerance, a knee replacement, and in 2009, back surgery for nerve compression that did not completely relieve the nerve issue. He was left with permanent left ankle weakness (a foot drop) which required use of a brace, after which he was certified with a special issuance FAA medical certificate. In 2012, he received a Statement of Demonstrated Ability (SODA), after successfully completing a medical flight test in a Cessna 172. In 2013, he underwent a repeat procedure to decompress the spinal nerves. His pain improved but his foot drop remained. He continued flying with special issuance medical certificates until 2016, when the FAA decided that a special issuance certificate was no longer necessary. At the time of the pilot's most recent medical exam, he reported using a combination of lisinopril and hydrochlorothiazide to control his blood pressure. These medications are not considered impairing, and he was issued an FAA second-class medical certificate limited by a requirement he have available glasses for near vision. According to the autopsy performed by the Washoe County Regional Medical Examiner's Office, Reno, Nevada, the cause of death was positional/traumatic asphyxia. Moderate coronary artery disease was identified on autopsy with up to 50% stenoses of the mid left anterior descending coronary artery, proximal circumflex coronary artery, and mid right coronary artery identified; however, the remainder of the cardiac exam was unremarkable. Toxicology testing performed by the FAA's Forensic Sciences Laboratory identified hydrocodone and two of its active metabolites (hydromorphone and dihydrocodeine) in urine, as well as tramadol and its metabolite O-desmethyltramadol. However, testing for hydrocodone in the pilot's peripheral blood was inconclusive and neither of its metabolites were identified in blood. Similarly, tramadol and its metabolite were not identified in blood. Hydrocodone is an opioid pain medication available as a Schedule II controlled substance. Tramadol is an opioid pain medication available as a Schedule IV controlled substance. Both are considered impairing and carry warnings about operating machinery. The 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 h