Thrush S2R N6216M accident near Hawkinsville, Georgia

Probable cause

A failure of the electric main fuel pump due to the carbon brushes having completely worn away.

NTSB analysis

The pilot reported that during the takeoff roll for the aerial application flight, the airplane used more runway than normal, and that after takeoff it “didn’t seem to produce power as usual.” He began a right turn and noticed “the power and airspeed [were] slowing.” He checked the gauges and noticed that that the fuel pressure was fluctuating, and then turned on the emergency fuel pump. He then jettisoned the chemical load, and the airplane continued to descend until it impacted trees.

A postaccident examination of the airplane found that the electric main fuel pump did not operate. Disassembly of the pump’s electric motor revealed that the carbon brushes had completely worn away, with no brush material remaining in either of the two brush holders. Examination of the engine revealed no anomalies that would have precluded normal operation.

Given that the pilot reported a longer than usual takeoff roll and a reduction in engine power throughout the flight, the pump may not have been operating properly or at all before takeoff. The reduction in power may have been due to the engine operating on only its internal fuel pump. The pilot did not report that the condition improved after he activated the emergency fuel pump. Whether or not the emergency pump had no effect or there was insufficient time to recover before the airplane struck trees could not be determined.

Text from the NTSB. Open the NTSB docket for ERA22LA239 for the full record.