Amateur-built CHALLENGER II N2480Y accident near Moultonborough, New Hampshire

Probable cause

A loss of engine power due to a loss of compression in one of the engine’s two cylinders.

NTSB analysis

The pilot reported that a few minutes after takeoff, during the initial climb, the airplane’s two-stroke engine began to slowly lose power. The pilot attempted to restart the engine but was unsuccessful. He elected to make a forced landing in small field, resulting in substantial damage to both of the airplane’s wing struts.

Postaccident examination of the engine revealed that one of the engine’s two cylinders had no compression. It is likely that this lack of compression resulted in the loss of engine power reported by the pilot during the accident flight. Additionally, during the examination, a zip tie was found secured around the fuel line that provided fuel for that cylinder in a way that reduced its interior diameter. It is possible that the reduced diameter of the fuel line could have resulted in less fuel reaching the cylinder during high power operation, and that it was operating in an excessively lean condition. Operation in this state could have damaged the cylinder and resulted in the lack of compression observed during the engine examination. It could not be determined when the zip-tie was installed on the fuel line, though entries in the airplane’s maintenance logs indicated that its last condition inspection was completed about three months before the accident.

Text from the NTSB. Open the NTSB docket for ERA23LA360 for the full record.