On April 25, 2018, at 1714 central daylight time, a Cessna 152 airplane, N89904, was substantially damaged during a forced landing after departing from Cullman Regional Airport (CMD), Cullman, Alabama. The pilot sustained minor injuries. The airplane was registered to and operated by Guest Aviation LLC under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Day visual meteorological conditions prevailed for the flight, which departed about 1709 and was destined for Northeast Alabama Regional Airport (GAD), Gadsden, Alabama.

According to the pilot, he departed CMD and climbed to about 2,500 ft above ground level. As he pulled the mixture control toward a lean position for cruise flight, the engine lost power. He pushed the mixture control to a full rich position and attempted unsuccessfully to restart the engine.

The pilot stated that the propeller continued to rotate after the engine lost power. Without an easily accessible engine restart checklist to reference, he relied on memory during the engine restart attempt. The pilot stated he "went through the emergency check, which included the avionics, master switch, fuel selector valve, mixture, and the primer…. although the engine was attempting to restart, it never regained full power".

The pilot did not activate carburetor heat during the flight and thought the throttle lever probably remained at a cruise power setting after the engine lost power. After one restart attempt, he turned his attention to maintaining a proper glide speed and searched for a forced landing area. After identifying a suitable area, he executed a forced landing into a field, during which the airplane nosed over and damaged the right wing.

Examination of the airplane at the accident site revealed the carburetor heat control was in the off position. The engine was started and ran normally at various power settings. No anomalies were noted with the engine or fuel system.

The recorded temperature and dew point data from a nearby weather station were plotted on a carburetor icing chart. The charted data showed that the weather was conducive to moderate icing at cruise power and serious icing at descent power about the time of the engine power loss.

According to the Pilot's Handbook of Aeronautical Knowledge:

When conditions are conducive to carburetor icing during flight, periodic checks should be made to detect its presence. If detected, full carburetor heat should be applied immediately, and it should be left in the ON position until you are certain that all the ice has been removed. If ice is present, applying partial heat or leaving heat on for an insufficient time might aggravate the situation. In extreme cases of carburetor icing, even after the ice has been removed, full carburetor heat should be used to prevent further ice formation. A carburetor temperature gauge, if installed, is very useful in determining when to use carburetor heat.