Accident Summary
A pilot reported that the left engine lost power, followed by the right engine. During the event, the pilot initiated a left turn to return to the airport but did not shut down the engines in accordance with emergency procedures. The aircraft yawed left and fell off on the left wing, as if it had stalled. The pilot regained partial control and aimed for a street. The aircraft struck the roof of a house while in a right bank, then cartwheeled across the street.
Findings
Examination of the left engine revealed severe detonation damage. The turbocharger wastegate door was missing its antivibration spring, and the pin connecting the door and actuator had failed. Evidence indicated that the pin had failed prior to the accident flight. Soot inside the left wastegate indicated that the door had been fully closed for some time. No evidence of failure or malfunction was found in the right engine. The right propeller showed damage indicative of rotation under power at the time of ground impact.
Probable Cause
The pilot in command's failure to follow emergency procedures and his failure to maintain airspeed following loss of power in one engine resulting in an inadvertent stall and the inflight loss of control with subsequent inflight collision with an object and the terrain during an uncontrolled descent.