What happened
On 4 September 2021, a Piper PA-28-161, registration G-BRBA, was conducting a training flight from Wycombe Air Park. During the approach to Runway 06L, the instructor selected two stages of flap and reduced speed to 75 kt. At this moment, the aircraft began to exhibit an unusual surging motion. The pilot initially suspected engine issues and attempted various corrective measures, such as checking the mixture and fuel tanks, but soon realized the engine was performing normally.
Upon touchdown, the right main landing gear failed. The aircraft's right wing dropped, causing it to turn 180 degrees and slide off the runway onto the grass. The aircraft sustained damage to the right landing gear leg, the right lower wing skin, and the right flap. There were no injuries to the pilot or the student passenger.
The investigation
Investigators examined the aircraft's landing gear and found that the lower section of the right landing gear oleo had separated from the upper cylinder. The wheel assembly remained connected only by the flexible brake hose and had become wedged against the right-wing flap.
Detailed metallurgical analysis of the torque link upper attachment lugs revealed that the failure was caused by fatigue cracking. Scanning electron microscopy showed that cracks had initiated at the lower end of the inner radius of both lugs, progressing to a depth of 2 mm before the remaining metal could no longer support the load, leading to final separation.
Records indicated that the required inspection per Service Bulletin 1131A had been performed during the aircraft's previous 100-hour inspection, 33 flight hours and 110 landings prior to the accident, with no cracks detected at that time.