Incident Overview
A pilot reported that during cruise flight at 500 feet above ground level, the engine oil temperature gauge indicated a reading just below the red line. Shortly thereafter, a popping noise was heard. The pilot initiated a power-on autorotation to perform a precautionary landing straight ahead toward an open area, with the intention of terminating at a hover.
Cockpit Indications
The engine out warning light did not illuminate, and the audio warning for engine failure did not activate. The remaining engine instruments appeared to be within normal parameters.
Landing Attempt
During the descent, the pilot began a deceleration at 50 to 60 feet altitude. At approximately 15 feet, collective pitch was applied while increasing power and leveling the helicopter. The selected landing area proved unsuitable, and the pilot observed a decrease in N2 (engine speed). Applying aft cyclic, the helicopter's ventral fin contacted the ground. The helicopter then rocked forward, causing the main rotor blades to strike the tailboom.
Post-Incident Examination
Inspection of the helicopter revealed a red shop rag caught in the oil cooler fan. A rigging check found no deficiencies. The engine was removed and tested in an engine test cell, where it started, ran at ground idle, and accelerated to takeoff power without issues.