History of Flight
The pilot, engaged in a private VFR flight from Rand Aerodrome (FAGM) to Lanseria Aerodrome (FALA), retracted the undercarriage after takeoff. The right main gear failed to retract. The pilot recycled the undercarriage using the normal system and extended it again with both normal and emergency systems, but the right main gear indication light showed that the gear had not locked down properly. The pilot advised the FAGM air traffic controller of the problem and decided to continue to FALA for a landing with the right main gear in an unsafe condition. Upon landing on Runway 06L, the right main gear collapsed, and the aircraft veered off the runway onto the grass.
Injuries and Damage
No injuries occurred to the pilot or the three passengers. The aircraft sustained minor damage, limited to the bottom skin of the right wing and the main gear.
Aircraft and Personnel Information
The aircraft was a Piper PA-34 (registration ZS-MNJ). The pilot, aged 55, held a valid Private Pilot licence with a type rating and a night rating. Total flying experience was 256.8 hours, with 130.4 hours on type. The aircraft had a total airframe time of 4118.4 hours at the time of the incident. The last maintenance inspection was performed at 4096.1 hours on 31 April 2006.
Meteorological Information
At the time of the incident, wind was from 360° at 8 knots, visibility clear, temperature 20°C. The flight was conducted by day.
Wreckage and Impact Information
After the gear collapse, the aircraft came to rest on the grass to the left side of Runway 06L at Lanseria Aerodrome (coordinates S 25°56.451 E 027°55.416). The aircraft remained intact.
Findings
On-site investigation and examination of the aircraft on jacks revealed that the Link Assembly – main gear downlock (P/N 39472-03) of the right main gear had become inoperative. The link assembly bearing (P/N 452793) and two tapered bushings (truss assembly P/N 39487-02) were worn beyond safe limits. This wear allowed the link assembly installation of the right main gear assembly (P/N 39484-09) to move over the bolt (P/N 402978). The maintenance requirement for these parts was "on condition," relying on visual inspection, but the extent of the wear was not noticed during the last inspection. The investigation noted that pilots are expected to check undercarriage linkages during preflight inspection.
Probable Cause
The right-hand side main gear of the aircraft collapsed.
Contributory Factor
The Link Assembly – main gear downlock failed due to the link assembly bearing being worn to limits.