What happened
On 10 September 2010, a Cessna 172RG, registration ZS-PMY, was conducting a private local flight departing from Cape Town International Aerodrome. After approximately one hour and forty-five minutes in the air, the pilot returned to the aerodrome for landing on runway 19.
During the landing sequence, the pilot confirmed the landing gear was down via the cockpit indicator lights. However, roughly 30 metres after the nose wheel made contact with the runway, the nose began to drop, causing the propeller to strike the runway surface multiple times. The pilot managed to apply back pressure to the control column, successfully raising the nose and stabilizing the aircraft for continued rolling.
As the aircraft turned right onto taxiway Charlie to vacate the runway, the nose landing gear suddenly collapsed. This second impact caused the propeller to strike the asphalt surface again. The aircraft came to a halt in a nose-down position. There were no injuries to the pilot or the two passengers, all of whom disembarked the aircraft unassisted.
The investigation
An investigation by the SACAA AIID examined the aircraft's mechanical state and maintenance history. The aircraft sustained substantial damage to the propeller and the nose gear doors.
Upon inspection of the aircraft on jacks, investigators found that while the landing gear could extend, the nose gear would not lock into the down position. Further technical examination revealed that one of the nose landing gear actuator down lock pins had failed due to fatigue. This failure prevented the locking mechanism from properly securing the gear in the down position.
Findings
- The primary cause of the nose gear collapse was the failure of a nose landing gear actuator down lock pin due to fatigue.
- A review of maintenance records showed that a Cessna Service Bulletin (SEB95-20), which specifically mandates inspections of these down lock pins to prevent such failures, had not been incorporated into the maintenance program for ZS-PMY.
- The pilot did not receive any 'gear unsafe' audio warnings during the initial landing or the subsequent collapse.