DEN03LA153 · Sharp Corben Baby Ace D

The airplane was being ferried to its new owner. The pilot said he was cruising at 8,000 feet msl (1,000 feet agl), using a power setting of 2,400 rpm with the mixture leaned "for altitude." About 1 hour after takeoff, the engine began "sputtering and backfiring." Engine power dropped from 2,400 rpm to approximately 1,000 to 1,100 rpm. Unable to restore power, the pilot made a forced landing on rough, uneven terrain. During the landing roll, the airplane struck a hole and nosed over, coming to rest inverted. The accident site was at an elevation of 6,955 feet msl. The pilot told a sheriff's deputy that "it was either engine failure or [the] carburetor iced up." Temperature and dew point recorded at an automated weather observation station (AWOS) station, located 48 miles east of the accident site, were 4 degrees and 0 degrees C., respectively. According to the Carburetor Icing Probability Chart, the temperature and dew point correspond to "serious icing at cruise power." The computed relative humidity was 76 percent. The pilot said he had had "carburetor ice before and the onset was always a gradual onset of power loss requiring changes in the throttle setting until ice was recognized. This was NOT the case in this incident as the power loss was instant and no actions affected it after they were tried." According to FAA's Flight Training Handbook, the onset of ice may be subtle or sudden, particularly if ice forms on the carburetor jets, because it "tends to choke off the flow of air and reduce the power output, or even prevent the engine from operating." The engine was functionally tested to 2,100 rpm, and no discrepancies were noted. Additional power output was not possible due to the intake manifold being crushed during the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset