What Happened
On 12 August 2023 at approximately 1440Z, a pilot conducting circuit-and-landing exercises on Runway 21 at Vereeniging Airfield (FAVV) in Gauteng province experienced a failure of the right main landing gear. During a wheeler landing, the pilot heard a noise from below the aircraft and noticed the right wing sinking. He performed a go-around and requested a visual inspection from the aircraft owner on the ground. After another soft landing resulted in the same wing sinking, the pilot executed another go-around and landed on the grass beside Runway 21 at about 50 mph. During the landing roll, the right-side landing gear collapsed, causing the aircraft to yaw 90° to the right. The tail lifted, and the left wing tip contacted the ground. The aircraft sustained substantial damage, including a bent propeller, dented spinner, bent engine mounts, dented cowlings, damaged boot cowl, dented firewall, dented exhaust, buckled lift struts, and dented left wing and wing tip. The pilot was not injured.
Aircraft Information
The aircraft was a Piper Aircraft Corporation PA-22-150 Tri-Pacer, registration ZU-AKE, serial number 22-6033. It was operated under Part 94 of the Civil Aviation Regulations. The pilot held an Airline Transport Pilot Licence and had 7,134 total flight hours, with 29.8 hours on type. The aircraft had accumulated 375.33 total airframe hours at the time of the accident.
Investigation Findings
Visual inspection of the right-side landing gear revealed that the Hydrasorb shock absorbers had failed on the bottom mounting boss. The boss exhibited a fatigue crack with extensive rust, pitting corrosion, and dirt, indicating the crack had existed for an extended period. Only a small portion of the original diameter of the boss remained intact. The failure of the mounting boss caused the right landing gear to disconnect from the suspension and collapse when weight was applied. The left-side main landing gear Hydrasorb unit was intact. The shock absorbers were installed in 2010 during a rebuild, and there were no records of inspections as per the owner's manual or manufacturer's specifications.
Probable Cause
The probable cause of the accident was that during a wheeler landing, the right-side mounting boss broke, leading to the failure of the right main landing gear as a result of an undetected fatigue crack on the Hydrasorb shock absorbers bottom mounting boss.