What happened
On 31 May 2003, a PIPER PA-28R-200, registration ZS-MHB, was conducting a training flight departing from Port Alfred Aerodrome. The flight involved a pilot and an instructor traveling to the local general flying area. Shortly after departing Runway 25, the pilot observed that the nose gear-in-transit light remained illuminated following gear retraction.
In an attempt to rectify the issue, the crew turned downwind and selected the landing gear to the down position. However, while the main landing gear showed green indications, the nose gear-in-transit light stayed on. Despite following manual gear extension procedures, the nose gear failed to lock. After contacting maintenance personnel and attempting several recovery procedures without success, the pilot proceeded to land on Runway 10 with the nose gear in an unlocked state. Upon touchdown, the nose gear collapsed, causing the aircraft to come to a stop on the runway. There were 0 fatalities and 0 injuries, though the aircraft sustained damage to the engine cowling, nose-gear doors, and exhaust tail pipes.
The investigation
The investigation focused on the mechanical failure of the nose landing gear assembly. Investigators examined the components of the nose gear trunnion and the associated hardware to determine why the manual extension procedures failed to secure the gear in the down position.
Findings
- The primary cause of the incident was the failure of the bolt connecting the lower torque-link to the nose gear trunnnion.
- This bolt failure caused the hardware to protrude from its intended position, physically obstructing the full extension of the nose gear.
- The failure of the bolt was identified as fatigue occurring around the circumference of the bolt near the nut end, with the final fracture occurring in the center of the shaft.
- Severe corrosion on the bolt was identified as a significant contributing factor to the fatigue failure.