Chula Vista, CA, USA
N3156D
DIETRICH RYAN S-4 COYOTE 1
The pilot of the accident airplane was attempting to depart after his airplane had recently been returned to service following a hard landing about 9 months before that had collapsed the right main landing gear and damaged the wing strut. During the takeoff attempt on the day of the accident, when the pilot started to rotate, the airplane immediately entered an uncommanded right roll. The pilot’s attempts to counteract the roll were unsuccessful and the airplane impacted the ground. Postaccident examination of the airplane revealed that the right wing’s aft lift strut was not bolted to the right wing attachment clevis. As the left wing was intact and continued to produce lift, the unsecured right wing would have reduced the lift force acting on the right wing and, therefore, inhibited the pilot’s ability to maintain level flight. This condition is what likely resulted in an uncommanded right roll and impact with the ground. The airplane had recently been repaired by the pilot (who was also the owner) with assistance from his mechanic. During the rebuild, the mechanic placed a bolt upside down and with a finger-tight nylon locknut in the right wing’s aft lift strut to secure it to the right wing attachment clevis while they transported the airplane to a new hangar. The pilot and the mechanic never removed the bolt and the strut was never properly secured to the wing as required by the build manual before the accident flight. Both the pilot and mechanic performed the rebuild together and were both aware of the temporary measure used to secure the right wing’s aft lift strut to the right wing. The mechanic should have correctly completed the installation before he returned the airplane to service and the accident pilot should have recognized the absence of the hardware before he departed on the accident flight. Further, the pilot also missed the absence of the improper installation, having incorrectly assumed that the mechanic had performed a preflight inspection for him while they developed a preflight checklist.
On April 8, 2022, about 1530 Pacific standard time, an experimental amateur-built Rans S4 Coyote 1, N3156D, was substantially damaged when it was involved in an accident near Chula Vista, California. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot, who was also the owner of the airplane, stated that the airplane suffered a hard landing about 9 months prior, which resulted in damage to the right wing, the wing strut, and right main landing gear. This was the pilot’s first flight in the accident airplane after it was repaired. According to the pilot, he completed a preflight inspection of the airplane with his mechanic and then started the airplane and taxied to runway 27. He aligned the airplane with the runway centerline and then gradually advanced the throttle for takeoff. When the airplane was about 300 ft into the takeoff roll he applied back pressure to the control stick and the airplane started to transition into a climb. However, the airplane immediately began a right roll when it was only a few feet above the ground. The pilot rapidly applied left control stick, but the airplane continued to roll to the right. He then pushed the control stick forward and applied left rudder to remain in ground effect and increase his airspeed, which slowed the right roll. The airplane was to the right of the right runway edge at an altitude of about 10 ft above ground level as it approached the departure end of the runway when the pilot decided he had insufficient control of the airplane to fly safely. At this point he reduced the engine power to idle and placed the airplane in a left crab, which allowed him to maintain a level attitude. As he pulled back on the flight stick to begin a landing flare, he felt the right wing drop again. The airplane touched down on the right main landing gear, which immediately collapsed, and the right wing impacted the ground. Inspection of the wreckage revealed that the right-wing’s aft strut was not bolted to its attachment clevis at the wing. Maintenance records indicated that the pilot performed the repair work on the airplane and signed it off on March 29, 2022, which involved replacing the right wing’s aft lift strut. According to the pilot’s mechanic, he assisted the pilot with the rebuild, and then completed an annual inspection at the end. After the inspection, the mechanic used a long 5/16” bolt with a finger-tight nylon locknut to secure the right wing’s lift strut to the right wing clevis while they moved the airplane to a new hangar. The pilot did not know what the mechanic used to pin the lift strut to the right wing but was aware of the temporary bolt. The airplane’s parts manual showed that the right wing’s aft lift strut is normally attached to the right wing clevis with one 5/16” bolt. The bolt is secured by a lockring. A logbook entry dated April 4, 2022, showed that the mechanic had performed an “annual condition inspection” and certified that “the aircraft, engine, and propeller have been inspected in accordance with the scope and detail of FAR Part 43 subpart D and found to be in condition for safe operation.” According to FAR Part 43 Appendix D (referenced as “subpart” in the logbook endorsement), “(f) Each person performing an annual or 100-hour inspection shall inspect (where applicable) all components of the wing and center section assembly for poor general condition, fabric or skin deterioration, distortion, evidence of failure, and insecurity of attachment.” Figure 1: Right wing aft strut and attachment clevis The pilot’s mechanic reported that, just before the accident flight, he and the pilot decided to create a written preflight checklist for the airplane, which did not have one at the time. The mechanic walked around the airplane dictating items to include in the inspection while the pilot recorded the inspection items. The pilot stated that he thought the mechanic was performing a preflight inspection as he walked around the airplane; however, the mechanic maintained that he was not performing an inspection at that time.
The pilot/owner and maintenance personnel’s improper installation of the right wing’s aft lift strut to the right wing, which resulted in a loss of lift during takeoff, an uncommanded right roll, and an impact with terrain.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
