S-4 COYOTE 1 N3156D accident near Chula Vista, California

Probable cause

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.

NTSB analysis

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.

Text from the NTSB. Open the NTSB docket for WPR22LA149 for the full record.