What happened
On March 11, 2022, at approximately 17:30 local time, a Bell 412 helicopter was engaged in forest fire suppression operations in a rural area of Coelemu, Ñuble Region, Chile. While performing water loading from a local reservoir, the pilot experienced significant vertical vibrations within the aircraft. In response to these vibrations, the pilot executed a precautionary landing. The aircraft struck the ground with sufficient force to cause a hard landing, resulting in damage to the airframe, though the pilot escaped the cabin without any injuries.
The investigation
DGAC Chile investigators examined the aircraft and the landing site, a flat, grassy area belonging to a timber company. The investigation focused on identifying the source of the reported vertical vibrations and assessing the extent of the damage caused by the impact.
Physical inspections of the aircraft revealed significant structural damage. The nose section exhibited fractures and deformation, and the radar protection fairing was heavily fractured. The landing skids were deformed, with the cross tubes bent and the rear fittings fractured. Additionally, several windows, including the right windshield and lower side windows, were destroyed or cracked.
To investigate the vibrations, the aircraft was moved to a hangar where the main rotor, tail cone, and landing gear were disassembled. The investigation included a specialized analysis by the Bell Textron Inc. Engineering Laboratory. The laboratory performed static and dynamic testing on the Isolation Pylon Mounts and the Pylon Friction Dampers.
Findings
- The primary cause of the incident was a hard landing following the onset of vertical vibrations.
- Extensive damage was sustained to the fuselage, landing gear, and cockpit glazing due to the impact.
- Detailed inspections of the main rotor, tail rotor, and transmission components revealed no mechanical failures or structural defects prior to the impact.
- Laboratory testing of the Isolation Pylon Mounts and Pylon Friction Dampers confirmed that these components met all manufacturer specifications and were functioning correctly.
- The aircraft's maintenance records indicated that all required inspections and maintenance programs were up to date, and the aircraft was in a condition for service prior to the event.