CEN19LA260

The pilot reported that, shortly after takeoff, he reduced engine power to about 1,800 rpm and continued along a valley in a shallow climb. As the airplane approached a ridge, he turned the airplane back toward the valley and felt a “subtle sluggishness” of the airplane during the turn. He applied carburetor heat; however, it did not appear to have an effect, and he turned the carburetor heat off after about 20 seconds. The pilot continued toward an area of rising terrain because the engine was running smoothly and, he believed, producing enough power to return to the departure airport. The airplane descended and impacted trees, resulting in substantial damage to the wings, empennage, and fuselage. The recorded temperature and dew point at the time of the accident were conducive to the accumulation of serious carburetor icing at a glide power setting. Based on the available information, it is likely that the airplane lost partial power due to the accumulation of carburetor ice, which resulted in a gradual descent and impact with terrain.

On August 7, 2019, about 1945 mountain daylight time, a Moth Aircraft Corp DH60GM airplane, N919DH, was substantially damaged when it was involved in an accident near Cortez, Colorado. The commercial pilot and passenger received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, shortly after takeoff, he reduced engine power to about 1,800 rpm and continued along a valley in a shallow climb. As the airplane approached a ridge, he turned the airplane back toward the valley and felt a “subtle sluggishness” of the airplane during the turn. He noted that the engine rpm was still about 1,800 rpm, and he applied carburetor heat. After about 20 seconds with the carburetor heat on, he noticed no perceptible change in the engine, so he turned off the carburetor heat to obtain maximum power. He stated that, even though the airspeed had decreased by about 10 mph and the engine did not seem to be producing full power, he did not believe the airplane was losing altitude; however, he stated that the airplane’s lack of a vertical speed indicator and sensitive altimeter made it difficult to ascertain a gradual loss of altitude, especially over uneven rising terrain. He continued toward an area of higher terrain, as the engine was running smoothly and he believed was producing enough power to return to the departure airport. The airplane subsequently impacted trees and terrain and the pilot and passenger egressed. The wings, fuselage, and empennage sustained substantial damage. At 1953, the weather reported at Cortez Municipal Airport (CEZ), Cortez, Colorado, about 16 miles west of the accident site, included a temperature of 80.6°F and a dew point 50°F. The calculated relative humidity at this temperature and dewpoint was 34.45 percent. Review of the icing probability chart contained within Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35 revealed the atmospheric conditions at the time of the accident were, "conducive to serious icing at glide power."