Accident Summary
A helicopter sustained substantial damage during a forced landing following an in-flight loss of engine power while operating under 14 CFR part 137. The pilot and passenger reported no injuries. The accident occurred during an observation maneuver at 75 feet above ground level (AGL) and airspeed below 20 mph.
Pilot Report
The pilot stated that the engine lost power while performing the observation, and he executed an autorotation landing into a neighboring soybean field. The aircraft had 20 gallons of fuel on board and no agricultural treatment products. The pilot noted damage to the aircraft but no injuries to occupants.
Conditions and Charts
After the accident, the engine was test run and operated normally. At the time of the accident (1915), the temperature was 29°C and the dew point was 23°C, yielding a calculated density altitude of 3,025 feet. When plotted on a carburetor icing chart, the temperature and dew point fell in the serious icing - descent power area. Additionally, the observation airspeed and altitude were plotted on a height/velocity chart, and their intersection fell in the avoid continuous operation area.
Regulatory References
The Bell 47G-2 flight manual stated: "PASSENGERS PROHIBITED DURING SPECIAL PURPOSE OPERATIONS. Persons other than minimum crew necessary for the purpose involved shall not be carried during special purpose operations in restricted category aircraft." FAA regulation § 91.313 states: "Restricted category civil aircraft: Operating limitations. ... (d) No person may be carried on a restricted category civil aircraft unless that person- (1) Is a flight crewmember; (2) Is a flight crewmember trainee; (3) Performs an essential function in connection with a special purpose operation for which the aircraft is certificated; or (4) Is necessary to accomplish the work activity directly associated with that special purpose."