On 7 April 2016, a GippsAero GA8-TC 320 Airvan (GA8) aircraft, registered P2-MFM, was being flown from Kiunga to Yehibi, Papua New Guinea. Shortly after touch-down and around 140m into the landing roll, the wheel and axle assembly from the left main landing gear leg separated from the aircraft. The pilot was able to bring the aircraft to a controlled stop.
Subsequent inspection of the right landing gear leg from P2-MFM found that it was cracked in the welded region of the axle assembly. Inspections of other aircraft in the operator's GA8 fleet, identified that numerous main landing gear legs were cracked in the same location.
The Civil Aviation Safety Authority (CASA) commenced an airworthiness investigation into the circumstances surrounding this issue. CASA requested technical assistance from the Australian Transport Safety Bureau (ATSB) to conduct a detailed metallurgical examination of the main landing gear axles from P2-MFM. To facilitate this assistance, the ATSB initiated an external investigation under the provisions of the Transport Safety Investigation Act 2003.
The ATSB has completed its examinations. Fatigue cracking and fracture was associated with marginal weld penetration between the landing gear parts and was influenced by the manufacturer's original welding processes. The manufacturer revised the assembly drawing in 2009, including enhancements to the welding procedure, such that the latest axle design is likely to have improved fatigue endurance. The ATSB was not aware of any instances of cracking of axles manufactured to the latest revision.
On 7 June 2016, the manufacturer released service bulletin SB-GA8-2016-169 (Issue 1) that recommended inspections of the axle area be conducted at service intervals not exceeding 110 hours.
A report detailing the ATSB's examination and findings was provided to CASA, the aircraft operator and the aircraft manufacturer, on 6 October 2016. Enquiries relating to the investigation should be directed to CASA on 131 757.
Source: GippsAero / modified by ATSB