Piper PA 32-260 N3457W accident near Mukilteo, Washington

Probable cause

The improper maintenance of the carburetor, which resulted in a stuck float and a partial loss of engine power during takeoff.

NTSB analysis

The private pilot reported that, during the initial climb shortly after takeoff, the airplane lost partial engine power. He tried a series of troubleshooting steps, but with limited time available, he then performed a forced landing onto a street just beyond the runway. The airplane impacted power transmission cables and traffic lights during the descent, rupturing both wingtip fuel tanks and spraying ignited fuel onto cars at the intersection below. The airplane sustained substantial damage when it collided with the ground and came to rest on the street.

The airplane had been fueled almost to capacity just before takeoff and postaccident examination did not reveal any anomalies with the airframe or engine that would have precluded normal operation. Examination of the carburetor revealed multiple maintenance-related discrepancies, all of which could have resulted in a loss of engine power. One of the discrepancies was related to the float, which appeared to have been touching the wall of the carburetor bowl. A witness reported visible exhaust emissions coming from the engine during flight, and the spark plugs were coated in black soot. Both observations were indicative of an excessively rich fuel-to-air mixture, consistent with a stuck carburetor float. As such, the loss of engine power was likely the result of a stuck carburetor float.

Based on atmospheric conditions, carburetor icing could not be ruled out; however, the airplane began the takeoff ground roll almost immediately after the pilot performed the engine runup, which included the application of carburetor heat, and it is unlikely that the loss of engine power was the result of carburetor icing.

The pilot accepted an intersection takeoff due to a passenger jet performing taxi tests at the approach end of the runway. Had he chosen to use the full runway length, he likely would have had enough runway available to safely land the airplane following the loss of power.

Text from the NTSB. Open the NTSB docket for WPR17LA096 for the full record.