Ercoupe 415 C N2788H accident near Cookson, Oklahoma

Probable cause

The pilot’s failure to properly secure the primer, which resulted in the loss of engine power during takeoff.

NTSB analysis

The pilot-rated passenger reported that he and the pilot aborted the first takeoff attempt due to a loss of engine power. They taxied the airplane back to the departure end of the runway and applied full and partial power several times but were unable to duplicate the engine problem, so the pilot chose to take off again. Shortly after the airplane became airborne, the engine lost power, and the pilot subsequently landed the airplane in wooded terrain.

A postaccident examination of the airplane and engine revealed that the fuel tanks were breached during impact; however, some fuel was found in the header tank and gascolator. The carburetor inlet fitting had broken off at impact, and the carburetor bowl was empty. The mixture arm was separated from the carburetor and not safety-wired in the full-rich position. The Nos. 1 and 3 plugs were found blackened. The engine was manually rotated via the propeller, and valve train continuity was established. The primer was found unlocked and partially pulled out. An unsecured primer can cause the engine to run richer than normal, which could result in a rough-running engine, loss of power, and blackened spark plugs.

Text from the NTSB. Open the NTSB docket for CEN14LA199 for the full record.