Amateur-built CHALLENGER II N269MM accident near Greeley, Colorado

Probable cause

The loss of engine power due to the engine seizure, which resulted from damage caused by the ingestion of carburetor ice into the engine intake ports.

NTSB analysis

The pilot reported that, after starting the engine, he taxied the experimental, amateur-built airplane to the runway at idle power. Shortly after takeoff, the engine lost total power, and the pilot subsequently performed a downwind, off-airport landing. During the landing roll, the airplane impacted terrain, which resulted in the collapse of the nose landing gear, a complete separation of the left main landing gear, and substantial damage to the lower fuselage. The airplane came to rest upright, and the two occupants exited the cockpit unassisted.

A postaccident examination revealed that the two-cylinder, two-stroke carbureted engine was seized and could not rotate because of a mechanical restriction. The piston rings were found damaged, and evidence of vertical scoring was found on the pistons and cylinder walls; the scoring appeared to have originated near the cylinder's intake port. The weather conditions at the time of the accident were conducive to the formation of serious icing at glide power. It is likely that the carburetor accumulated ice while the pilot taxied the airplane to the runway at idle power and that the engine ingested that ice sometime after takeoff, which resulted in mechanical damage to the engine and its subsequent loss of power. The airplane was not equipped with provisions for carburetor heat nor was it required to be.

Text from the NTSB. Open the NTSB docket for CEN13LA298 for the full record.