ERA25LA028

About 15 minutes into the flight, while flying at 2,500 ft mean sea level (msl), the airplane encountered environmental conditions that were favorable for the formation of serious carburetor ice at cruise engine power settings. The flight continued and the pilot noted that the engine’s output dropped from about 2,300 rpm to about 1,500 rpm. He applied carburetor heat and left it applied, cycled the fuel shutoff valve, pumped the throttle, and checked the ignition switch, but those efforts did not restore power. After descending to 2,000 ft msl, he turned to return to the departure airport but performed a forced landing in a field after recognizing the flight was unable to reach the departure airport. The nose landing gear collapsed during the landing roll after encountering a furrow, resulting in substantial damage to the engine mount and right wing. Postaccident examination of the engine and its systems revealed no evidence of preimpact failure or malfunction. A High Resolution Rapid Refresh (HRRR) model sounding created for the approximate time and location where the pilot reported the airplane began descending consistent with the reported loss of engine power revealed that the temperature and dew point were 34.5° F and 33.8° F, respectively. The values were close to 100% relative humidity. Thus, it is likely that during cruise flight carburetor ice formed and subsequently resulted in the reported loss of engine power. The pilot’s delayed application of carburetor heat during the cruise portion of the flight while operating in environmental conditions favorable for serious carburetor ice at cruise power allowed for the formation of carburetor ice.

On October 26, 2024, about 1004 eastern daylight time, a Cessna 150H, N22197, was substantially damaged when it was involved in an accident near St. Agatha, Maine. The private pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that there were no discrepancies noted during the preflight inspection or engine run-up before departure. The flight departed with full fuel tanks and climbed to a cruising altitude of 2,500 ft msl while proceeding towards the destination. After passing Sinclair, Maine, or about 15 miles from the departure airport near Stockholm, Maine, while flying at 2,500 ft msl and at 2,300 rpm and 95 mph, the engine’s output dropped from about 2,300 rpm to about 1,500 rpm. The pilot applied carburetor heat and left it applied, checked the fuel shutoff valve by cycling it on and off, tried pumping the throttle, and moved the ignition switch to the left and right positions, but those actions did not restore power. While flying at 2,000 ft msl and 80 mph, he turned back toward the departure airport but when the airplane was over Sinclair, he knew he would be unable to reach the airport. He spotted a tilled field for a forced landing, then entered downwind, base, and final approach, maintaining 60 to 65 mph on final. During the landing roll the right wing contacted the ground and the nose landing gear collapsed after contacting a furrow. Postaccident examination of the airplane revealed substantial damage to the engine mount and to the right wing near the wingtip and wing root. Examination of the engine and its systems following recovery revealed no evidence of preimpact failure or malfunction. The carburetor heat control and valve were noted to work properly. A High Resolution Rapid Refresh (HRRR) model sounding created for the approximate time and location where the pilot reported the airplane began descending consistent with the reported loss of engine power revealed that the temperature and dew point were 34.5° F and 33.8° F, respectively. Review of the icing probability chart contained within Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35 revealed that the atmospheric conditions at the time of the accident were "conducive to serious icing at cruise power." The values were close to 100% relative humidity. According to FAA Advisory Circular 20-113, "To prevent accident due to induction system icing, the pilot should regularly use [carburetor] heat under conditions known to be conducive to atmospheric icing and be alert at all times for indications of icing in the fuel system." The circular recommended that when operating in conditions where the relative humidity is greater than 50%, "…apply carburetor heat briefly immediately before takeoff, particularly with float type carburetors, to remove any ice which may have been accumulated during taxi and runup." It also stated, "Remain alert for indications of inductionsystem icing during takeoff and climb-out, especially when the relative humidity is above 50 percent, or when visible moisture is present in the atmosphere."