Incident Details
During an aerial surveillance flight, the helicopter's engine chip light illuminated. The pilot decided to head toward a nearby heliport for a precautionary landing. To prepare for a possible engine failure on approach, the pilot established a steep fast approach. At approximately 100 feet above the ground and an airspeed of 65 knots, the pilot applied power and began to slow the helicopter. At that moment, the engine lost power, and the pilot entered an autorotation.
The helicopter landed hard, breaking both forward landing gear struts and spreading the rear struts. The main rotor blades impacted the tail boom, causing the tail boom to separate from the fuselage.
Examination Findings
Examination of the helicopter revealed heavy oil deposits on the inner surfaces of the engine compartment and on the exterior surfaces of the engine. The airframe engine oil reservoir contained no oil. The oil line leading from the engine gearbox to the oil pressure gauge was found cracked beneath the "B" nut securing it to the fitting on the engine gearbox. The N2 (power turbine) drive could not be rotated. Partial disassembly of the engine found damage to the number six, seven, and eight bearings, consistent with a lack of adequate lubrication.
Laboratory examination of the cracked oil line determined that fatigue cracking had propagated through an estimated 90 percent of the cross-sectional area of the tube. The cracking allowed lubricating oil to leak from the line, resulting in oil starvation to the bearings, which led to seizure of the power turbine.