N29042Piper J3F-65 · 1940

On June 26, 2016, about 1950 central daylight time (CDT), a Piper J3F-65 airplane, N29042, experienced a partial loss of engine power on climb out from Comanche Airfield LLC Airport (CO38) in Strasburg, Colorado. The pilot conducted a forced landing into a wheat field where during the landing the airplane nosed over. The airline transport pilot, the sole occupant, suffered minor injuries. The airplane sustained substantial damage to left-wing strut and fuselage longerons. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan.

The pilot reported he departed from Front Range Airport (FTG), in Watkins, Colorado, about 1900 with full (11 gallons) gas. After takeoff from FTG, he departed the traffic area to the east. He lined up for runway 17 at CO38 and conducted a touch and go landing. During climb out, the pilot reported "the airplane made enough power to clear an interstate roadway and some powerlines, but never really seemed to perform." The pilot stated he advanced the throttle to full power; however, the airplane started to descend. He checked the mixture and magnetos but neither stopped the descent. The airplane "settled into a wheat field," nosed over and came to rest inverted.

The routine aviation weather report at FTG, taken at 1854, about the time of takeoff, recorded a temperature of 27ºC and a dewpoint temperature of 10ºC. Per the "Carburettor icing-probability chart" in an article on carburetor icing published by Flight Safety Australia, dated November-December 2004, revealed that the airplane was operating in an area favorable for the formation of serious icing at a descent power setting. Further, the article stated that if ice forms in the carburetor of a fixed-pitch propeller aircraft, the restriction to the induction airflow would reduce power and force a drop in rpm. According to the FAA Pilot's Handbook of Aeronautical Knowledge, under certain conditions, carburetor ice can build unnoticed until power is added.