Cessna 310I N8170M accident near Salt Lake City, Utah

Probable cause

A loss of engine power for reasons that could not be determined based on the available information.

NTSB analysis

The pilot reported that, during engine start and run up, the left engine shut down twice when the throttle was reduced to idle, and during the engine run-up magneto checks, the engines ran rough with greater than normal losses in rpm. The pilot advanced the throttles and leaned the mixtures to both engines to “clear” what he thought was “carbon buildup on the sparkplugs” and the engines subsequently ran smoothly at idle. The pilot departed, and during the initial climb, noticed that the airplane did not accelerate as normal. The pilot reduced the angle of attack to aid in acceleration and noticed that both engines indicated fluctuations in power, fuel flow, and rpm. He confirmed that the propeller and throttle levers were full forward, and he placed the auxiliary fuel pump to “high.” The airplane continued to decelerate and began to yaw to the left. The pilot banked right and feathered the left propeller, but the airplane continued to descend, and the pilot reduced the mixture controls to idle-cutoff. The airplane impacted two power poles and the ground before skidding to a stop adjacent to a building. A postaccident fire ensued.

Examination of the engines revealed dark and sooty deposits on the sparkplug electrodes, consistent with a rich fuel/air mixture ratio. Additionally, the left engine tachometer generator cannon plug was separated and undamaged. It is possible that this plug disconnected during the takeoff and would have resulted in a tachometer indication of a loss of left engine power.

It is likely that the left engine fuel flow was not properly adjusted by maintenance personnel when the engine was installed earlier the month of the accident, which created an overly rich fuel-air mixture and resulted in the repeated loss of left engine power during ground operations; however, the reason for the loss of power during the takeoff and the airplane's inability to gain altitude/airspeed during the initial climb could not be determined based on the available information.

Text from the NTSB. Open the NTSB docket for WPR17LA187 for the full record.