N4492Cessna A185F · 1976

On August 11, 2010, at 1150 mountain daylight time, a Cessna A185F, N4492, registered to and operated by the pilot, was substantially damaged when it ground looped on landing at Four Corners Regional Airport (FMN), Farmington, New Mexico. Visual meteorological conditions (VMC) prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The pilot, the sole occupant on board, was not injured. The cross-country flight originated at Stinson Municipal Airport (SSF), San Antonio, Texas, approximately 0802 central daylight time, and was en route to FMN.

According to the pilot, very little crosswind correction was required for landing on runway 25. After rolling a few hundred feet, the airplane "swerved very strongly to the right." Opposite brake and rudder had no effect and the airplane departed the runway and impacted terrain. The left landing gear collapsed and the left elevator sustained leading edge damage. Across its entire width, the outboard portion of the left wing was bent up at a 20 degrees angle from the middle of the left aileron.

FAA inspectors examined the airplane and found the through-bolt that attached the inboard end of the gear leg to the airframe hard-point had pre-existing damage. The airplane was recovered and transported to Beegles Aircraft Services in Greeley, Colorado. After examining the through-bolt, Beegles agreed with FAA's assessment, that there were threads from the failed nut that remained stuck in the threads of the bolt. They were of the opinion that the nut failed and stripped off the bolt, leaving the inboard end of the gear leg loose and free to move up and down. This allowed the gear leg to move forward and aft. The chaffing on the longeron, inboard of the gear leg attach point, was indicative that the bolt-nut combination had been loose for some time. The bolt was measured and they questioned whether it was an AN7-22A instead of the called for AN7-20A, which would make the bolt 1/4 (8/32) inch too long. If the nut ran to the end of the bolt's threads, it would not have put enough tension between the bolt head (top) and the attaching block (bottom). FAA was unable to determine whether the bolt was a stretched -20A or a -22A. Beegles Aircraft Services also saw indications of looseness on the right gear leg attach bolt after the leg was removed for transport.

Examination of the wheels, brakes, and brake pads revealed no anomalies. A review of the logbooks and work order for the last annual inspection did not indicate whether the left gear leg attaching bolt was checked for correct torque or length. The right side bolt and nut were replaced at that time.

The pilot said that at the time of the accident, ATIS (Automatic Terminal Information Service) was reporting the wind to be variable from 150 degrees at 3 knots.