WPR24FA182

The pilot’s improper installation of the control stick pushrod assemblies, which resulted in separation of the left pushrod and a total loss of roll control during flight. Contributing to the accident was the failure to detect the installation error during the airplane’s construction, inspection, and subsequent maintenance.

While returning to the airport from a routine pleasure flight, the pilot of the experimental light-sport airplane reported a total flight control failure while maneuvering to land. Data from the onboard electronic flight instrument system and witness statements indicated that after turning from the crosswind to the downwind leg, the airplane entered an uncontrolled descending left turn consistent with a spin or spiral, culminating in a collision with a warehouse roof about 0.75 mile from the runway threshold. Postaccident examination revealed that the left side (where the pilot was operating the airplane) control stick pushrod had become disconnected from the flaperon mixer bellcrank due to improper installation during construction. Both left and right pushrod rod-end eyebolt bearings had been installed in reverse orientation. The improper installation allowed the pushrod to gradually unscrew from its eyebolt, ultimately resulting in complete separation of the left pushrod. This condition rendered the primary roll control system on the pilot’s side ineffective. The aircraft was equipped with an autopilot system featuring a “Level” mode capable of providing roll control independent of the cockpit control sticks. Prompt activation of this feature—or use of the rudder to counteract the developing roll—would likely have allowed the pilot to retain some degree of control. Similarly, the pilot would have been able to fully control the airplane if he had reached to his right and used the other control stick. However, given the sudden onset and rapid progression of the event, it is unlikely the pilot had sufficient time or situational awareness to identify and employ these options before the airplane entered an unusual attitude and became uncontrollable. The pilot's autopsy identified heart disease, including severe coronary artery disease of a single coronary artery and mild thickening of the left cardiac ventricle. Although the pilot’s heart disease was associated with an increased risk of sudden impairment or incapacitation from a cardiac event, the circumstances of the accident were not consistent with a sudden medical event and it is unlikely that the pilot’s heart disease contributed to the accident. The improper assembly error was traced to the original construction of the airplane and was visible in build photographs taken in 2019. The oversight persisted through final inspection and three years of subsequent operation. The airplane kit manufacturer later issued a service bulletin addressing correct installation of the pushrods.

The pilot was issued his private pilot certificate in 2010. The last entry in his logbook was dated May 31, 2024, and at that time he had accrued about 270 hours of total flight time, of which 79.7 were in the accident airplane. The pilot completed a BasicMed education course on May 7, 2024, and reported completing a BasicMed Comprehensive Medical Examination Checklist on May 6, 2024. The pilot began construction of the airplane after purchasing the tail kit in 2011, and the airplane was issued a special airworthiness certificate in the experimental category on April 19, 2021, after inspection by an FAA Designated Airworthiness Representative (DAR-F). The King County Medical Examiner’s Office performed the pilot’s autopsy, with the cause of death reported as blunt force injuries. The left anterior descending coronary artery had up to 90% narrowing by plaque; other coronary arteries had scattered streaks of plaque but were not significantly narrowed. The left ventricle of the heart was described as mildly enlarged with mild concentric wall thickening. Visual examination of the heart was otherwise unremarkable. Microscopic findings included enlarged heart muscle cells. At the request of the Medical Examiner’s Office, postmortem peripheral blood was submitted for toxicological testing to the Washington State Patrol Seattle Toxicology Laboratory, which requested the specimen be tested by NMS Labs. According to the NMS Labs toxicology report, the specimen tested presumptively positive for caffeine. The FAA Forensic Sciences Laboratory also tested postmortem specimens from the pilot; no tested-for substances were detected. On June 6, 2024, at about 1200 Pacific daylight time, a Van’s Aircraft Inc. RV-12, N412JN, was substantially damaged when it was involved in an accident near Auburn, Washington. The pilot was fatally injured. The experimental light-sport airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The airplane departed from its base at Auburn Municipal Airport (S50), Auburn, Washington, for what family members of the pilot reported as a routine pleasure flight. The airplane was equipped with a Dynon Skyview Electronic Flight Instrument System (EFIS). Data extracted from the EFIS indicated that shortly after takeoff the airplane followed a southeast track, and after reaching the eastern foothills of Mt. Rainier, entered a 180° right turn and followed a reciprocal track back to Auburn. As the airplane approached the airport from the east, the pilot reported over the common traffic advisory frequency (CTAF) that he was just over midfield and intended to make a full-stop landing on runway 35. Correlation between recorded CTAF audio and EFIS data indicated that over the next 60 seconds, the airplane overflew the runway while descending from 1,500 to 1,250 ft mean sea level (the airport elevation was 63 ft). It then began a left turn, and as it rolled out onto the left downwind leg, the pilot transmitted, “Pan Pan RV412JN, I just had a control failure, I’m inbound for 35, without any controls.” Over the next 45 seconds, the airplane began a descending left turn that witnesses described as similar to a spin or spiral dive. A west-facing security camera, located on the exterior wall of a warehouse about 0.75 miles southwest of the runway 35 threshold, captured the final 3 seconds of flight. It showed the airplane come into view at the top of the frame while in a 45° descending left turn. The airplane’s roll rate rapidly increased, and the airplane struck the warehouse roof inverted in a 45° nose-down attitude. The airplane came to rest inside the reception area of the warehouse. The forward cabin was crushed through to the tailcone. The fuel tank was breached and leaking fuel; there was no evidence of pre- or post-impact fire. The complete right wing and the inboard section of the left wing remained attached to the fuselage by the main spar, and the outboard fragments of the left wing were located on the building’s roof. The tail section was largely intact. The outer surfaces of the airplane were not painted but instead had been covered with vinyl wrap. The wrap hindered a detailed review of pre-accident cracks, loose rivets, or corrosion to skin surfaces. The airplane’s roll control system consisted of full-length flaperons, connected to tandem control sticks through a series of pushrods, torque tubes, and a centrally mounted flaperon mixer bellcrank (figure 1). The control assemblies were mounted under the cabin floor and accessible through a series of inspection panels. Figure 1. Control stick assembly. Examination revealed that the left control stick pushrod (F-01264-1) was not connected to the inboard eyebolt bearing (CM-4MS) at the flaperon mixer bellcrank (figures 2 and 3). Figure 2. Standard flaperon bellcrank and control stick pushrods. Figure 3. Accident flaperon bellcrank and control stick pushrods. When compared with the airplane’s plans, the inboard eyebolts were installed reversed such that the eyebolt stud was connected to the pushrod, and its body to the mixing bellcrank, rather than the other way around (figures 4 and 5). In this configuration, the stud end of the eyebolt would be free to rotate within the threaded inboard section of the pushrod. If installed according to the plans, the body of the rod would have been inhibited from rotation by the stud (figure 4). The right control stick pushrod was also installed in the same way and, although it was still connected to the mixer bellcrank, its pushrod was starting to unwind from the stud, with almost two threads exposed (figure 5). The construction plans also called for a lock nut to be installed on the studded end of the eyebolt on each side; these nuts were not present (figure 4). Figure 4. Correctly installed CM-4MS bearing. Figure 5. Accident CM-4MS bearing, installed in reverse. Review of photographs taken during the airplane’s construction revealed that the build error was present during the advanced stages of construction in August 2019. The airplane’s last condition inspection was performed on April 14, 2024. The foot pedals remained attached to the forward fuselage and firewall, and the rudder cables were continuous from the rudder pedal arms to the rudder control surface horns. The autopilot was equipped with a “Level" button feature on the autopilot control panel. Pressing the button immediately commanded the autopilot to pitch the airplane to zero vertical speed and roll it to zero degrees of bank, whether the autopilot was already engaged or not. The autopilot roll servo was connected directly to the flaperon torque tube at the wing root, and its operation was not dependent on the integrity of the control stick. Impact damage prevented an accurate assessment of the autopilot operation; however, the Dynon data indicated it was not engaged at the time of the accident. The autopilot roll and pitch servos were examined at the facilities of Dynon Electronics following the accident. No anomalies were noted to either unit and both operated appropriately when tested. The airplane was equipped with a pilot-controlled electrical pitch trim actuator anti-servo tab assembly. It was found at its full forward travel limit, which corresponded to the anti-servo tab up (nose down) position. Examination and testing showed that the unit operated smoothly in both directions and shut off at its travel limits. Review of the Dynon EFIS data revealed that the airplane’s battery continued to supply electrical power to the main bus for about 2 hours after the accident. On June 24, 2024, Van’s Aircraft issued Service Bulletin 102, “Control Stick Pushrod Inspection.” This service bulletin called for the inspection of the F-1264 Control Stick Pushrod Assembly, with confirmation of the correct installation of rod-end assemblies.