What happened
On February 14, 2021, a Seamax M-2/2 amphibious ultralight aircraft, registration I-7608, crashed near Buccella, in the municipality of Vigevano, Italy. The aircraft had departed from the "Leonardo da Vinci" airpark for a local recreational flight carrying two people: the pilot and one passenger. Approximately four minutes after takeoff, the aircraft plummeted into a heavily wooded embankment. The impact destroyed the aircraft, and both occupants were found deceased.
The investigation
The ANSV investigation focused on the structural integrity of the aircraft's wing assembly. Investigators examined the wreckage and performed scanning electron microscopy on the components. The analysis centered on the right wing's attachment point, specifically the aluminum tubular structure of the wing rib where the lower end of the wing strut is secured. The investigation also reviewed the aircraft's maintenance history and the manufacturer's technical documentation.
Findings
Technical analysis revealed that the accident was caused by a structural failure resulting from the separation of the right wing. The investigation established that the aluminum tube within the wing rib, which serves as the attachment point for the lower wing strut, had suffered significant degradation.
Key contributing factors included:
- Extensive use of the aircraft in a marine environment, which led to severe corrosion of the aluminum tubing.
- The presence of through-thickness corrosion in the horizontal aluminum tube, which was difficult to detect via external visual inspection due to the fiberglass fairing covering the area.
- A maintenance program that was not sufficiently targeted to identify effective inspections of these specific critical structural components.
Safety action
The ANSV has issued safety recommendation ANSV-2/39-21/1/A/23 to the manufacturer, Seamax Aircraft Ltda. The recommendation urges the manufacturer to:
- Re-evaluate the structural design of the wing rib, specifically the use of mixed materials (aluminum tubing combined with fiberglass and carbon fiber) when exposed to saltwater environments.
- Alert owners of Seamax M-22 aircraft to perform extraordinary inspections of the wing structure integrity.
- Develop a more robust maintenance program capable of monitoring the condition of these critical components before structural integrity is compromised, potentially including scheduled replacements.