Amateur-built COZY MARK IV N294MV accident near Tucson, Arizona

Probable cause

The total loss of engine power during an approach due to clogged fuel filters, which resulted from an epoxide sealant used in manufacture of the airplane deteriorating and clogging the fuel filter.

NTSB analysis

During a local flight, the pilot was maneuvering the amateur-built experimental airplane to final approach in the traffic pattern when the engine lost total power. The pilot noticed that the propeller was not windmilling and attempted to restart the engine but was unsuccessful. Subsequently, the airplane impacted trees about 1,000 ft short of the runway threshold and sustained substantial damage to both wings.

Postaccident examination of the engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. However, examination of the fuel system revealed a clogged fuel filter on the left fuel line and a partially clogged fuel filter on the right fuel line. The pilot stated that he had the left fuel tank selected at the time of the accident.

Laboratory spectrum analysis determined the material clogging the fuel filters was consistent with an epoxide used in resins and sealants. Although the spectrum of the clogging material did not match that of an uncured sample of the sealant used during manufacture of the airplane, this was likely due to the cured state of the clogging material. The epoxide likely deteriorated, with the fragments becoming loose and clogging the fuel filters.

Text from the NTSB. Open the NTSB docket for WPR22LA138 for the full record.