What happened
On 8 June 2002, a CESSNA 402B, registered ZS-ALV, was conducting a private flight for the purpose of aircraft familiarization. The flight, involving the aircraft's new owner and an instructor, originated from Wonderboom aerodrome. The flight profile included maneuvers such as stalls and steep turns within the General Flying Training Area, utilizing various flap configurations and extended landing gear.
Following these maneuvers, the crew proceeded to Freeway aerodrome to perform two touch-and-go landings on Runway 20. After repositioning for Runway 02, the aircraft attempted a second touch-and-go landing with full flaps selected. Approximately 120 feet after touchdown, the right-hand main landing gear collapsed. This caused the aircraft to veer to the right, eventually coming to a stop adjacent to the runway. While the right-hand propeller and wingtip sustained damage, there were zero injuries to the two occupants.
The investigation
Investigators examined the mechanical state of the landing gear and the cockpit indications present during the approach. The pilot reported that all landing gear indicators showed the gear was down and locked, noting "three greens," and confirmed that the gear warning horn did not activate during the landing sequence.
Technical scrutiny included a metallurgical analysis of the failed landing gear components. This examination found no evidence of pre-existing defects, fatigue, or prior failures that could have contributed to the incident. The analysis concluded that the structural failures were the direct result of an overload condition during the landing roll.
Findings
- The primary cause of the collapse was that the side braces were not driven into the fully extended over-center position before landing.
- This failure was attributed to improper or poor rigging of the landing gear system.
- Due to the faulty rigging, the bellcrank for the right-hand gear failed to lock the side braces into the over-center position when the gear lever was moved to the down position.
- The structural failure of the components occurred only because of the mechanical overload experienced during the landing.