Primary finding
Probable cause
The pilot's failure to use carburetor heat, which resulted in a loss of engine power. Factors included the ambient carburetor icing conditions and the lack of suitable terrain for the forced landing.
Investigator assessment
Analysis narrative
The pilot landed the single-engine helicopter in a muddy field after experiencing a loss of engine power while climbing through 200 feet. The pilot reported hearing and feeling a bang, then a jolt to the left, followed by a loss of engine power. The pilot landed the helicopter in a field with furrows, which forced the tail up resulting in a tail strike. After the accident, the pilot reported to the operator that he may have experienced carburetor icing. An overhaul of the engine did not reveal any anomalies that would have prevented the engine's operation. According to the FAA's Carburetor Icing Probability Chart with the reported temperature and dew point, the conditions existed for "Serious Icing at Cruise Power."
Source record
Factual narrative
On March 7, 2000, at 1020 Pacific standard time a Bell 47G-4A single-engine helicopter, N1354X, was substantially damaged during a forced landing following a loss of engine power after takeoff from a field near Wasco, California. The commercial pilot, who was the sole occupant, was not injured. The aircraft was registered to and operated by Inland Crop Dusters, Inc., of Bakersfield, California, as an agricultural application flight under 14 CFR Part 137. The flight had originated from a service truck shortly before the accident. Visual meteorological conditions prevailed at the time of the accident and a flight plan was not filed. According to a written statement provided by the pilot, he departed for a spray run after filling the hopper. When the helicopter reached 200 feet, the pilot "heard and felt a bang, then a jolt (to the left)," then the engine lost power. The pilot stated that he landed "softly straight ahead in a muddy field." He added that "the furrows in the field forced the nose down and the tail section up upon touchdown, causing a tail strike." The pilot told the operator that he may have experienced carburetor icing. The engine was overhauled after the accident, and no anomalies were noted during the overhaul that would have prevented its operation. At 0956, the weather observation facility at the Meadow Field Airport, Bakersfield, (located 25 miles southeast of the accident site), reported the wind from 130 degrees at 5 knots; 10 statute miles visibility; clear skies; temperature 52 degrees Fahrenheit; dew point 43 degrees Fahrenheit; and an altimeter setting of 30.01 inches of mercury. According to the Federal Aviation Administration's Carburetor Icing Probability Chart, dated June 1982, with a temperature and dew point of 52 and 43 degrees, respectively, the conditions existed for "Serious Icing at Cruise Power."