NTSB Factual Report

On July 14, 2007, approximately 1430 central daylight time, a single-engine, turbine powered Aerospatiale SA-315 helicopter, N5770F, was substantially damaged during a forced landing following a loss of engine power while performing long-line external load operations near Stuart, Oklahoma. The commercial pilot, sole occupant of the helicopter, was not injured. The helicopter was owned and operated by Skydance Northwestern, Inc., of Minden, Nevada. Visual meteorological conditions prevailed, and a flight plan was not filed for the external load flight conducted under the provisions of 14 Code of Federal Regulations Part 133.

The pilot stated in the accident report (NTSB Form 6120.1), that while moving a heavy load on the external load, he noticed the fuel light "flickering." The helicopter returned to the base and reported the event. The pilot reported that a mechanic drained the fuel tank, purged the fuel lines, and replaced the engine fuel filter. The helicopter was then filled with "clean fuel" and test flown for approximately 30-minutes; with no problems noted. The pilot then resumed moving drills, and after moving 2 or 3 additional drills, and while repositioning to pick-up the next load, he felt "the engine surge slightly" so he elected to set the load back on the ground to scan the engine instruments. The engine instruments appeared normal and the pilot continue to move his load. The pilot added that when he applied engine power, the engine "cut back to ground idle" and the helicopter descended through the trees.

The Federal Aviation Administration inspector, who responded to the accident scene, reported the helicopter sustained structural damage during the forced landing. Fuel samples were taken by the operator and sent to a private lab for analysis.

The engine was removed from the airframe, and shipped to Heli-Support, Inc., in Fort Collins, Colorado, for further investigation. An initial engine examination was conducted on 29 August 2007, with representatives from the operator, engine manufacturer, and the NTSB present. The initial examination of the engine did not reveal any pre-impact anomalies. Additional fuel samples were taken and sent to a second lab.

The engine was then placed in a test cell for an engine run. Two engine starts were attempted; however, the engine failed to start. After the first attempt, the idling device strainer was found clogged and was replaced. The engine was disassembled after the second failed attempt and the examination revealed that the fuel tube was clogged, and fuel was not getting to the injection wheel in the engine.

Results of the fuel samples taken, failed to find containments in the fuel. A lab test of the substance that was found in the fuel tube, failed to identify the substance. A source for the contamination was not found.

At 1453, the automated weather observing system at MLC, located approximately 15 miles from the accident site, reported variable winds at 6 knots, 10 statute miles visibility, scattered clouds at 4,200 feet, temperature 86 degrees Fahrenheit, dew point 67 degrees Fahrenheit, and an altimeter setting of 29.94 inches of Mercury.

NTSB Probable Cause

The loss of engine power due to a clogged fuel tube. A contributing factor was the lack of suitable terrain for the forced landing.