What happened
On May 10, 2012, a Christen Industries Inc. A-1 Husky, registration I-ESML, was conducting a recreational flight departing from and returning to Belluno airport. While flying under Visual Flight Rules (VFR) over an area used for model aircraft activities, the pilot noticed irregular engine performance, likely caused by carburetor icing.
In response to the engine issues, the pilot decided to perform a precautionary landing on a nearby temporary landing strip located on a slope at Col Fenilon-Monte Grappa. During the landing sequence, the left main gear encountered a depression in the terrain. This impact caused the landing gear strut to fail, resulting in the propeller striking the ground. While the aircraft sustained significant damage, there were no injuries to the two occupants on board.
The investigation
The ANSV examined the structural damage to the aircraft to determine the mechanics of the failure. Investigators focused on the left landing gear assembly, specifically the shock absorber component. The inspection revealed that the cable constituting the elastic spring of the left gear strut had snapped, with frayed strands and irregular breaks observed at the failure point. This indicated that the cable had been subjected to extreme overstress due to excessive stretching.
Findings
- The primary cause of the propeller strike was the failure of the left landing gear's elastic spring cable.
- The failure of this cable was triggered by the excessive displacement of the strut's rocker arm.
- This displacement occurred because the left wheel struck a depression in the ground at high speed.
- The use of an unsuitable landing area for the precautionary landing contributed to the aircraft encountering the uneven terrain.