What happened
On May 26, 2009, a Cessna 180K, registration D-EGSW, was performing a local parachute transport flight at Portimão Aerodrome (LPPM) under visual flight rules. During the takeoff roll on runway 11, the aircraft had traveled approximately 110 meters when the left main landing gear leg suddenly separated from the airframe.
The pilot attempted to correct a sudden leftward swerve by applying rightward rudder, but the loss of the gear caused the aircraft to rotate 180 degrees on the runway. The aircraft continued to move along the runway until it came to a stop, having sustained damage to the propeller blades, the left wing tip, and the left main landing gear leg.
There were five occupants on board, including the pilot and four passengers; no injuries were reported.
The investigation
Investigators examined the landing gear assembly and discovered that the retaining nut for the left main landing gear attaching bolt was missing, having fallen onto the asphalt. The bolt itself was found to be bent and exhibited damaged threads.
A comparison between the installed hardware and the manufacturer's illustrated parts catalogue revealed significant discrepancies. The Cessna catalogue specifies an AN7-20A bolt and an AN365-720C self-locking steel nut for this component. However, the installed bolt featured a hole, which the original part does not have, and the installed nut was a non-self-locking variety with a distinct light golden color.
Findings
- The left main landing gear leg separated because the attaching bolt failed to perform its intended function.
- The installed bolt and nut did not match the original specifications required by the manufacturer.
- The bending of the bolt indicates that it was subjected to a lateral load.
- This lateral load may have been caused by a previous hard landing involving sideways movement, or it may have been introduced during normal operations due to the incorrect installation of the landing gear hardware.