Accident Description
On August 24, 2014, at about 0650 Pacific daylight time, a Robinson Helicopter Company R-44 II, registration N4246Z, was substantially damaged while conducting a practice emergency autorotation approximately 12 miles south of Pahrump, Nevada. The helicopter was operated by the pilot under 14 CFR Part 91. The commercial pilot sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local personal flight that departed North Las Vegas Airport (VGT) at about 0605.
The pilot reported a total loss of engine power at approximately 3,500 feet above ground level while reducing the throttle for a practice autorotation. The throttle was rolled back smoothly to achieve a small tachometer needle separation. After unsuccessful attempts to restart the engine, the pilot performed an autorotation emergency landing. During the landing, the helicopter slid forward about 20 feet, the skids dug into the dry lake bed, and the helicopter nosed over. The main rotor blades then struck the ground, and the helicopter rolled onto its right side.
Wreckage Examination
An FAA inspector observed substantial damage to the main rotor blades and tail boom. Fuel was leaking from both fuel tanks at the accident site. The pilot stated the fuel quantity was approximately 7/8 full before the event.
Subsequent examination by the National Transportation Safety Board investigator-in-charge and a Robinson Helicopter investigator revealed no evidence of internal damage to the fuel-injected engine or its accessories. The oil dipstick indicated a normal quantity. Continuity of all engine controls was verified. The lower spark plugs showed normal wear patterns when compared to the Champion Check-A-Plug comparison chart. Manual rotation of the crankshaft produced compression on all cylinders. It was determined that an engine run could be safely performed.
The engine was test-run using an external battery for electrical power and operated normally at various power settings. Switching the magnetos from left to right resulted in the expected RPM drop. Fuel from the helicopter was used to verify system continuity. The main fuel tank indicated about 3/8 full and the auxiliary tank about 1/4 full. No engine anomalies were observed during the run.
The main gearbox and drive system were examined and found free of anomalies. Flight control continuity was established for the cyclic and collective. Tail rotor continuity was confirmed in each direction from the separation point.
Additional Findings
A review of maintenance records showed the most recent annual inspection occurred on December 4, 2013, at an airframe and engine total time of 444.3 hours.
A Global Positioning System device recovered from the wreckage was sent to the NTSB Vehicle Recorder Division for analysis but contained no information relevant to the accident.