What happened
On 20 May 2010, a Piper PA-28-140, registration ZS-JTO, was performing a private flight under visual flight rules. The pilot had flown from Wonderboom Aerodrome to the general flying area and was returning for landing on Runway 29. During the landing roll, the aircraft experienced a significant loss of control. After touching down approximately 5 to 10 metres past the threshold, the aircraft continued down the runway for about 710 metres before veering left into a rough grass area. During the excursion, the nose wheel separated from the aircraft due to high impact forces. The aircraft sustained substantial damage, but the pilot escaped without injury.
The investigation
SACAA AIID investigators examined the aircraft's maintenance history and local meteorological conditions. The investigation revealed that the right-hand main landing gear oleo strut had a history of recurring defects, specifically involving leaking seals that were frequently replaced. Upon disassembly of the strut, investigators found that an O-ring or quad ring seal had been severely damaged, causing it to twist within its slot.
Furthermore, the investigation scrutinized the wind conditions at the time of the accident. While air traffic control had reported "light and variable" winds, an observation of the windsock by another pilot on the frequency indicated a much stronger wind of approximately 15 knots blowing in the opposite direction of the runway, suggesting a significant tailwind or wind shear component.
Findings
- The aircraft landed deep on the runway because the pilot was facing strong and unexpected tailwind conditions at the threshold.
- The high ground speed resulting from the tailwind rendered the brakes less effective.
- A recurring defect in the right-hand main landing gear oleo strut was identified, with evidence of a damaged seal.
- There was no documented evidence that the required 50-hour progressive inspections had been performed, which might have detected the seal issue earlier.
- The nose wheel failure was caused by the high impact forces encountered while traveling over uneven ground.