What happened
On June 12, 2008, a Piper PA-34-200T, registration EC-IHS, was conducting a multi-engine flight instruction mission departing from Valencia Airport. The crew, consisting of an instructor and two students, initiated the climb and subsequently retracted the landing gear. Following retraction, the crew noticed that the landing gear in-transit warning light remained illuminated.
Upon attempting to extend the gear, the crew observed that while the main landing gear legs locked into position, the nose gear failed to provide a down-and-locked indication. Despite performing the emergency gear extension procedure, the nose gear remained partially retracted. Although the crew could visually see from the cockpit that the gear legs were extended, limited visibility through the inspection mirror prevented them from confirming they were fully locked. The crew requested permission from the tower to perform a low pass for visual confirmation. After the tower confirmed the gear was down, the pilot prepared for an emergency landing. To mitigate the risk of a nose-over, the crew moved the passengers to the rear seats to shift the center of gravity. The aircraft touched down on the main gear and maintained a nose-high attitude until the loss of airspeed caused the nose to strike the runway, resulting in the aircraft sliding approximately 20 meters. All 3 occupants were uninjured.
The investigation
The investigation focused on the nose gear assembly and the hydraulic retraction system. Physical examination of the nose gear strut revealed damage consistent with a collapse. Investigators inspected the tiller track, the steering arm assembly, and the attachment points to the bulkhead. The inspection revealed that the tiller track was deformed at both the upper and lower sections of its travel. Furthermore, the investigation found that the lower support of the steering arm assembly had broken away from the bulkhead at the weld seam. The mounting bolt hole was found to be ovalized, with a diameter approximately 1.5 times larger than the bolt itself, and the bolt threads showed signs of being crushed due to excessive play within the assembly.
Findings
- The nose gear retracted during the climb because it failed to complete its full extension stroke, preventing the overcenter lock from engaging.
- The primary cause was the failure of the steering arm assembly's lower support, which left the assembly attached to the bulkhead only by the upper support.
- The failure originated from a progressive breakage of the lower support, driven by the ovalization of the mounting bolt hole.
- This ovalization increased the tolerance between the bolt and the assembly, likely caused by improper torque applied to the bolt and nut connecting the steering arm assembly to the bulkhead.