Accident Details
On April 7, 2013, at approximately 1540 eastern daylight time, a Piper PA-28-181, registration N3060B, operated by Piedmont Flight Training, was substantially damaged when the right main landing gear collapsed during rollout on runway 22 at Smith Reynolds Airport (INT), Winston Salem, North Carolina. The private pilot and flight instructor on board reported no injuries. The instructional flight was conducted under 14 Code of Federal Regulations Part 91 in visual meteorological conditions. No flight plan was filed for the flight, which had departed Asheville Regional Airport (AVL) around 1430.
The private pilot stated that after an uneventful cross-country flight, the landing touchdown was normal. However, during the rollout, the right main landing gear collapsed, and the airplane came to rest on the runway.
Damage and Examination
According to the operator, the accident landing left approximately 850 feet of skid marks from the right main landing gear tire, with no corresponding marks from the left main gear. An additional 435 feet of scrape marks continued beyond the skid marks, consistent with the gear collapse.
A Federal Aviation Administration (FAA) inspector examined the airplane and found substantial damage to the right wing. The right main landing gear trunnion was sent to the NTSB Materials Laboratory for further analysis. Metallurgical examination revealed extensive wear, fretting, hole elongation, and disturbed metal around the holes of the trunnion's lower flange. The wear was more pronounced at the two outboard holes. Two bolt heads recovered from the lower flange exhibited white paint, matching their preimpact location. The fracture surfaces of both bolt heads showed fatigue. The combination of bolt fatigue, excessive wear, and damage at the lower flange bolt holes was consistent with bolt looseness and wear over an extended period.
NTSB records indicated no similar events involving this type of failure in the past 10 years.
Maintenance History
A representative from the airplane manufacturer noted that similar wear patterns had been observed in aircraft used for student pilot training, often resulting from an unreported hard landing. The damage could propagate over time, making it difficult to determine when the initiating event occurred. The representative stated that mechanics typically check the bolts during annual and 100-hour inspections for condition and security, verifying proper thread count and cotter pin placement.
The airplane's maintenance manual for 100-hour inspections includes the task: "Inspect gear struts and mounting bolts for condition and security." The most recent annual inspection was completed on January 11, 2013, at 6,762 total flight hours. The airplane accumulated an additional 51 hours between that inspection and the accident. The operator did not employ in-house mechanics but contracted them as needed. The two mechanics who performed the annual inspection reported that they visually inspected the bolts and attempted to check retention and security with tools, but noted that the nuts were located in an area difficult to access.
Weather
At 1554, the recorded wind at INT was from 200 degrees at 10 knots, gusting to 17 knots, with variations between 150 and 230 degrees.