Bell 412 crash near Amadorio Reservoir, near Villajoyosa, Alicante, Valencian Community, Spain

The Bell 412 was on a training flight with an underslung firefighting bucket, practising a landing with simulated tail rotor lockup. In the final phase of the manoeuvre, with the bucket already on the ground and the helicopter very low, it began to vibrate intensely in the vertical axis. The crew raised the collective but the vibration did not change and the aircraft became uncontrollable, falling a few metres further on and striking the shore of the Amadorio reservoir where it forms a steep slope above the water. It then fell into the reservoir and sank to around six metres. The instructor and pilot both escaped unaided and swam ashore. The investigation attributed the accident to loss of control caused by structural failure of the main transmission support case attachments to the airframe, with a significant difference between the stiffness values of the mounts identified as a contributing factor, possibly producing asymmetry in the pylon's pitch and roll behaviour. Final report A-002/2022.