Beech E 55 N711YK accident near Bakersfield, California

Probable cause

The pilot’s failure to select the proper fuel boost pump setting for the left auxiliary fuel pump, which allowed for an excessive fuel flow to the left engine, which resulted in a total loss of engine power and airplane control during an attempted go-around.

NTSB analysis

The commercial pilot reported that, following an uneventful flight to break in the recently installed rebuilt left engine, he entered the airport traffic pattern. As the airplane crossed over the runway threshold, he reduced power, and the airplane began to settle into ground effect. Subsequently, the pilot initiated a go-around. When he applied power, the right engine responded; however, the left engine did not respond, and the airplane immediately began rolling and yawing left. The pilot reduced power and applied control inputs, but the airplane continued to yaw left and then impacted terrain.

Photographs obtained from airport management showed that, immediately following the accident, the left auxiliary fuel pump switch was in the "low" position. Both engines were test run in an engine test cell, and they started and operated normally at various power settings. The left auxiliary fuel pump was operationally tested and compared to the limits noted on the manufacturer's data plate. During functional tests in the low-boost setting, the fuel flow rate was almost double the minimum specification for the low-boost setting and higher than the minimum high-boost fuel flow rate. Leaking fluid was observed around the outlet fitting, so the outlet fitting was removed; an O-ring was found damaged, which likely resulted in fuel leaking around the outlet fitting. The investigation could not determine how or when the O-ring was damaged. A new O-ring was installed, and functional tests were conducted again. In the low-boost setting, the fuel flow rate was again more than double the minimum specification for the low-boost setting and higher than the minimum high-boost fuel flow rate. During a review of airframe and engine maintenance records, no entries were found pertaining to the left auxiliary fuel pump.

The Pilot's Operating Handbook specified that, before takeoff or landing, the auxiliary fuel pumps should be off unless the ambient temperature is 90°F or above, in which case they should be set at "low." The ambient temperature at the time of the accident was 64°F. Therefore, it is likely that, during the attempted go-around, the left auxiliary fuel pump was positioned to "low" and that this, in combination with the excessive fuel flow rate while positioned to the low-boost setting, resulted in the loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR17LA059 for the full record.