What happened
On September 28, 2012, an Eurocopter AS-350 B3e helicopter, registration TG-FHD, was operating in the vicinity of La Aurora International Airport in Guatemala City. During the flight, the pilot transmitted a distress message to Air Traffic Control (ATC) stating that the aircraft had lost its tail rotor.
Shortly after the transmission, the aircraft impacted the ground in the Colonia El Maestro area, specifically at the intersection of 15 Avenida and 0 Calle, Zona 15. The impact occurred in a populated urban area, prompting ATC to issue an emergency alert to all aircraft in the vicinity to maintain clearance from the area due to the ongoing emergency.
The investigation
The investigation conducted by the DGAC/UIA focused on the structural integrity of the tail rotor assembly. Metallurgical examinations were performed on various components, including the blades and the laminated half-bearings.
Technical analysis of the rotor blades revealed significant damage. On the yellow blade, the skin on the lower face was completely disbanded, and the leading edge of the upper face also showed disbanding. X-ray inspections identified aluminum slices and elastomer debris from the laminated half-bearings within the yellow blade structure. Furthermore, micrographic examinations of the flexible beam showed a static translaminar failure, where fibers had completely separated from the resin.
Examination of the laminated half-bearings also revealed fatigue fractures in the elastomeric layers of both the red and yellow blades. Specifically, the red blade showed fatigue fractures in the third and fourth elastomeric layers on one-third of its surface.
Findings
- The primary cause of the accident was a structural failure of the tail rotor components.
- Fatigue fractures were present in the elastomeric layers of the laminated half-bearings on both the red and yellow blades.
- The flexible beam experienced a static translaminar failure, characterized by the separation of fibers from the resin.
- Debris from the failing half-bearings, including aluminum slices, migrated into the internal structure of the rotor blades, contributing to the disbanding of the blade skins.