What happened
On November 19, 2005, a Piper PA-34-200, registration EC-IHS, was performing a flight instruction mission from Valencia Airport to Ibiza and back. The aircraft was operated by Airmed and carried an instructor and two students.
Upon returning to Valencia Airport, the crew performed a normal landing on runway 30. However, moments after the nose wheel made contact with the runway, the crew noticed the nose of the aircraft began to descend. The instructor immediately took control, pulling back on the control column to attempt to keep the nose elevated. As the aircraft decelerated, the elevator lost effectiveness, causing the nose to strike the runway. The impact caused both propellers to strike the pavement. The aircraft continued to slide on its forward fuselage before coming to a stop on the left side of the runway. All three occupants were uninjured and able to exit the aircraft on their own.
The investigation
Following the incident, investigators examined the aircraft's nose gear mechanism. While the gear appeared to function normally when the aircraft was jacked up, a detailed inspection revealed that the nose gear was not being held securely in the locked position. Specifically, the down lock link was failing to hold the spreader bar firmly.
Upon disassembly, investigators found that the screw connecting the down lock link to the retraction link was significantly bent. This deformation was attributed to bending stresses caused by improper tightening of the screw, which allowed for movement that the joint was not designed to withstand. Further inspection of the maintenance history showed that the nose gear components had been serviced during a 1,000-hour inspection in September 2005, following mandatory Airworthiness Directives, but the deformation likely occurred after that service.
Findings
- The nose gear retracted because the spreader bar was not properly secured by the down lock link.
- The failure of the down lock link was caused by a combination of incorrect length adjustment of the tensor and the deformation of the connecting screw.
- The deformation of the screw was likely caused by insufficient tightening, which introduced bending loads into a component designed primarily for shear loads.