What happened
On August 16, 2024, a Piper PA-28-181, registration SE-LKV, was preparing for a private flight from Varberg Airport to Anholt, Denmark. The pilot and one passenger had completed a pre-flight inspection that revealed no defects or deferred maintenance items.
During the takeoff roll on runway 30, the aircraft reached a speed of just over 50 knots when an unexpected noise and a sudden jolt occurred. The pilot immediately attempted to abort the takeoff. As the aircraft decelerated, the right wing dropped toward the ground, causing the aircraft to veer sharply to the right. The wing subsequently struck a runway edge marker, and the aircraft came to a halt off the runway, facing the opposite direction of the intended takeoff. There were no injuries to the occupants, though the aircraft sustained significant damage to the right wing, flap, aileron, and the right main landing gear.
The investigation
The Swedish Accident Investigation Authority (SHK) examined the wreckage and the aircraft's maintenance history. Investigators discovered that the lower portion of the right main landing gear had separated from the aircraft. A bolt used to secure the torque link to the lower part of the landing gear was found near the start of the runway.
Technical analysis of the recovered bolt (Piper part number 37881–003) revealed that it did not meet the manufacturer's specifications. Specifically, the part of the bolt intended to attach the torque link lacked a drilled hole for a cotter pin. This omission made it impossible to use a castle nut and cotter pin to create a secure, locked joint. While the aircraft had undergone a 100-hour inspection recently, the investigation noted that the location of the bolt joint is prone to dirt accumulation, which can obscure such defects during inspections.
Findings
- The primary cause of the accident was that the bolted joint for the torque link lacked a safe and adequate locking mechanism.
- The recovered bolt was non-compliant with Piper specifications because it lacked the required hole for a cotter pin.
- Because the joint was not properly secured, the nut likely vibrated loose during the takeoff roll, especially given the vibrations inherent in operating on a grass runway.
- The failure of the bolt allowed the lower part of the landing gear to detach as the gear fully extended during liftoff, leading to the loss of directional control.
Safety action
The SHK has issued recommendations to the Swedish Transport Agency to inform maintenance and airworthiness organizations about the necessity of ensuring torque link bolts on Piper PA-28 variants comply with manufacturer specifications. Additionally, inspectors are advised to pay particular attention to these specific bolted joints during airworthiness monitoring.