What happened
On 6 May 2000, a Piper PA-34-200 T, registration EI-EIO, was conducting circuit training at a local military airfield when the starboard main landing gear began to collapse immediately after touchdown. The pilot applied full power and used left control input to level the aircraft, successfully lifting off. However, following the initial contact, the crew observed that the starboard green indicator light had extinguished and the red "gear unsafe" warning light had illuminated.
Despite attempts to recycle the undercarriage and utilize the emergency extension system, the gear remained in a partially retracted state. Ground personnel at the military airfield observed the starboard leg appearing only half-extended. After circling the airfield and attempting various procedures to secure the gear, the pilot decided to divert to Dublin Airport. An emergency was declared, and the crew performed a flapless approach with all electrical systems, fuel, and magnetos deactivated just prior to touchdown.
During the landing run on Runway 11, the reduction in lift on the starboard wing caused the compromised undercarriage to collapse outward. The aircraft slid toward the edge of the runway and came to a stop. The crew sustained no injuries and exited the aircraft via the right-hand door.
The investigation
The investigation focused on the structural integrity of the starboard undercarriage and the sequence of the gear failure. Investigators examined the damage to the starboard engine propeller, which showed forward-bent blade tips, indicating contact with the runway surface under power.
Physical examination of the landing gear revealed extensive damage to the starboard retraction mechanism. The upper and lower side brace links had fractured, and the hydraulic piston retraction fitting was bent and fractured. Laboratory analysis of the 12 mm bolt at the rod end showed a ductile overload fracture with no evidence of pre-existing fatigue or manufacturing defects. The investigation also considered the possibility that the gear was not properly locked prior to the initial touchdown, as the vertical impact forces would have been significantly magnified by the leverage of an unlocked, extended leg.
Findings
- The landing forces applied to the starboard undercarriage caused damage to the trunnion housing.
- Compressive forces acting on the locking mechanism resulted in the fracture of both the upper and lower drag brace links, causing the leg to partially retract into the wheel well.
- Before the final emergency landing, the gear leg moved into a vertical position, which then forced the gear to collapse toward the starboard wing tip upon touchdown.
- The damage to the starboard undercarriage was caused by the failure of the extension mechanism to properly lock before touchdown or its unlocking at the moment of impact.