What happened
On 6 January 2019, a Cirrus SR22T, registration ZS-ARI, was performing circuit exercises at Lanseria International Aerodrome (FALA) for the purpose of a private pilot license renewal. After successfully completing the first circuit, the aircraft approached Runway 07 for its second landing. During the landing roll, the nose landing gear suddenly collapsed. This caused the propeller to strike the runway surface, and the aircraft skidded approximately 30 metres before coming to a halt. The pilot and passenger were uninjured and were able to exit the aircraft without assistance. The incident resulted in damage to the engine cowling, the propeller, and the nose gear.
The investigation
SACAA AIID investigators examined the wreckage and maintenance records of the aircraft. The investigation focused on the structural integrity of the nose landing gear (NLG) strut assembly. Records indicated that the aircraft had undergone a mandatory periodic inspection and compliance with Service Bulletin SB2X-32-22R2 only 13.5 hours prior to the incident. Investigators also reviewed international precedents, noting similar nose gear failures investigated by the NTSB in the United States and Japan, which involved similar failure modes in the strut tube near the gusset tube welds.
Findings
- The primary cause of the collapse was a fractured strut tube located near the forward edge of the gusset tube attachment welds.
- It is probable that the fracture was caused by an undetected fatigue crack.
- While the aircraft had recently complied with relevant service bulletins, there was a possibility that the inspection was not correctly performed.
- Previous manufacturer interventions, including increased strut thickness and more frequent inspections, were found to be insufficient in preventing such failures.
Safety action
- A recommendation was made for the manufacturer to revise Service Bulletin SB2X-32-22R2 to include a requirement for non-destructive testing (NDT) of the nose landing gear strut tube to identify cracks.
- It was suggested that the Director of Civil Aviation consider issuing an Airworthiness Directive (AD) for all Cirrus SR22T aircraft to undergo NDT inspections during their next 100-hour inspection intervals.