What happened
On August 15, 2002, at approximately 13:45 local time, a Pilatus PC-6 B2-H2, registration F-GLTP, was conducting a skydiving mission near Massa Cinquale, Italy. After successfully completing the final jump of the day, the pilot began a turning maneuver to depart from the group of parachutists descending below. During this maneuver, the aircraft's right wing separated from the fuselage. The aircraft entered a clockwise spiral and plummeted into the sea approximately 50 meters from the shoreline. The impact resulted in the death of the pilot. The right wing, having detached in flight, drifted and landed about one kilometer away from the main wreckage.
The investigation
The ANSV investigation focused on the structural integrity of the wing attachment points. Examination of the wreckage revealed that the right wing's sub-wing attachment was broken at the bearing housing. The investigation also identified three primary static fractures on the strut trunk, caused by overload during a flexural-torsional event.
Investigators examined the aircraft's maintenance history and found that the required 100-hour inspection, which was due in mid-June, had not been performed. Furthermore, the investigation looked into the specific installation configuration of the strut attachments. While the aircraft used a mix of different generation attachments that were technically permitted, the right side utilized an older, less resistant version that was more susceptible to misalignment and asymmetric loading.
Findings
- The primary cause of the accident was the structural failure of the right wing due to fatigue damage that developed undetected within the strut's sub-wing attachment.
- The failure to perform the scheduled 100-hour inspection prevented the detection of the fatigue cracks before they reached a critical size.
- The absence of proper surface treatments, specifically anodization and primer on the right sub-wing attachment, likely facilitated the initiation of local fatigue damage.
- The use of an older-generation attachment configuration on the right side, which lacked the improved alignment features of later versions, contributed to abnormal stress distribution.
- The nature of the aircraft's mission—skydiving—placed additional, frequent stresses on the right strut due to jumpers typically bracing themselves against that side of the aircraft during exits.