NTSB Factual Report

On July 28, 2006, about 0600 mountain standard time, a Robinson R44, N74780, collided with trees during an emergency landing near Flagstaff, Arizona. The pilot/operator was operating the helicopter under the provisions of 14 CFR Part 91. The private pilot sustained minor injuries; the helicopter sustained substantial damage. The cross-country personal flight departed Flagstaff Pulliam Airport, Flagstaff, Arizona, about 0555, with a planned destination of Phoenix Deer Valley Airport, Phoenix, Arizona. Instrument meteorological conditions prevailed, and no flight plan had been filed.

The pilot submitted a written report. He departed Flagstaff Pulliam Airport on the 185-degree radial of the Flagstaff very high frequency omni-directional radio range (VOR). About 9 nautical miles south of the airport, he encountered a lowering cloud layer, and could not maintain level flight. He decided to perform an autorotation into a clearing from about 100 feet above ground level. The helicopter touched down on its skids, but the landing area was slightly inclined. The tips of the rotor blades struck the ground and then hit a tree, causing the helicopter to roll over onto its right side.

The Flagstaff Pulliam Airport Automated Surface Observing System reported that the sky condition at 0556 was 800 feet overcast.

The airframe and engine had about 92 hours since new. The FAA, Robinson, and Textron Lycoming were parties to the investigation.

Investigators examined the wreckage at the Robinson factory under the supervision of the National Transportation Safety Board investigator-in-charge.

The engine remained attached to the airframe by the engine mount. The engine had sustained mechanical damage to the exhaust system, which had been displaced upward. Visual examination of the engine revealed no evidence of preimpact catastrophic mechanical malfunction or fire.

Investigators removed the bottom spark plugs. They rotated the crankshaft by hand utilizing a wrench at the cooling fan bolt. The crankshaft was free and easy to rotate in both directions. They obtained thumb compression in proper firing order on all six cylinders. They established mechanical continuity throughout the rotating/reciprocating group and accessory section. All spark plugs were clean with no mechanical deformation. The spark plug electrodes were gray, which corresponded to normal operation according to the Champion Aviation Check-A-Plug AV-27 Chart. The investigators reinstalled the spark plugs, and attached their respective leads.

Robinson personnel removed the engine from the airframe, and installed it onto a test cell dynamometer. A technician started the engine with the starter using standard procedures. The oil pressure indicated within the normal operating range at the test cell control panel oil pressure gauge. The engine driven fuel pump delivered a fuel pressure indication within the normal operating range. Once the engine was at operating temperature, the technician advance the throttle to about 1,600 rpm, at which time he checked the magnetos utilizing the test cell mounted ignition switch. Both magnetos operated within manufacturer's specifications. The magneto check produced a smooth 50 to 60 rpm drop at each detent. The engine ran smoothly during the operational check, and exhibited no anomalies, and no fuel or oil leaks. According to the Robinson Helicopter Company test cell operator, the subject engine reached all prescribed performance parameters. The test cell sheet has been attached for reference. He shut the engine down, which completed the test.

NTSB Probable Cause

the pilot's inadequate preflight planning decision to take off under a low ceiling into an area of mountainous terrain that resulted in an encounter with lowering clouds and forced the pilot to land in unfavorable terrain.