Cessna 172 N78192 accident near Manville, New Jersey

Probable cause

A total loss of engine power due to the ingestion of sealant material that had loosened inside the carburetor airbox.

NTSB analysis

The student pilot was approaching the airport to land at the conclusion of a solo cross-country flight. As he turned the airplane from the base to final approach leg of the traffic pattern, the engine started to run rough, and subsequently lost all power. He attempted to restart the engine, but was unsuccessful. He then performed a forced landing into 70-ft-tall treetops. The airplane came to rest in the treetops, resulting in substantial damage to both wings.

Examination of the engine revealed two pieces of debris inside the carburetor airbox downstream from the air filter element. The debris was consistent with epoxy/sealant used during repairs of the airbox. The airbox appeared to have been repaired and patched several times, and some of the sealant on the repairs appeared to be loose. When the debris was placed in the carburetor venturi for reference, it blocked about 50 to 75% of the opening. If the sealant debris came loose inside the airbox while the engine was running, it is likely that it would follow the air path into the carburetor venturi and block the air flow into the carburetor.

The weather conditions at the time of the accident were conducive to carburetor icing; however, the pilot reported applying the carburetor heat on the downwind traffic pattern leg and did not notice any anomalies with the engine at that time. Had significant ice built up in the carburetor during the descent, it is likely that the engine would run roughly soon after the application of the carburetor heat and continue to do so as the ice melted.

Text from the NTSB. Open the NTSB docket for ERA19LA280 for the full record.