What happened
On September 24, 2015, a Bell 407 helicopter, registration TG-PDF, was conducting a flight in the municipality of San Cristóbal Acasaguastlán, El Progreso, Guatemala. During the flight, the engine experienced a significant loss of power. The pilot identified a suitable landing area on a rocky, unpaved surface near a highway leading toward the northeast of the country. The pilot executed an emergency landing on the terrain. While the fuselage remained largely intact, the landing gear sustained damage to the cross tubes due to the impact during the power loss event. The pilot and passengers were able to egress the aircraft on their own and sustained no injuries.
The investigation
The DGAC/UIA investigation examined the aircraft's maintenance history, engine components, and the impact site. Investigators reviewed maintenance logs, which indicated the aircraft had been maintained according to manufacturer recommendations. The investigation focused on the engine's internal components following the discovery of metal particles in the magnetic chip detectors, the oil filter, and the accessory gearbox. An engine teardown performed by a facility in Canada revealed that a lubrication duct, specifically the "Piccolo Tube," was likely obstructed. This obstruction prevented adequate lubrication to the No. 2 bearing in the N1 section of the engine.
Findings
- The engine suffered an internal failure of the No. 2 bearing.
- Lack of lubrication to the No. 2 bearing caused progressive wear and high temperatures, leading to a fracture of the bearing's internal race.
- This failure caused misalignment between the compressor's front turbine and the impeller section, resulting in the imminent loss of engine power.
- Meteorological conditions at the time of the accident were optimal for VFR flight.
- The aircraft was airworthy and maintained in accordance with all applicable regulations at the time of departure.
- The fuel in the storage cells was uncontaminated and of the correct grade.