Cessna 172 N863AU accident near Opelika, Alabama

Probable cause

A partial loss of engine power due to a combination of fuel/oil contamination in the fuel injector assembly.

NTSB analysis

**This report was modified on April 29, 2025. Please see the public docket for this

investigation to view the original report.**

The pilot reported that, after starting the engine, it “sounded slightly rough” and then it ran smoothly “after a few seconds.” She continued with her engine run up and magneto check, neither of which indicated any anomalies. The pilot stated that, during the takeoff roll, the engine indications were “green,” but she was not sure of the static rpm achieved, and the airspeed was increasing “slightly slower than normal.” After reaching a rotation speed of 55 kts, the pilot rotated, but noticed during the initial climb that the engine was not producing full power, and the airspeed was low. She further characterized the engine performance as constant but sluggish. The pilot lowered the nose to prevent an aerodynamic stall and attempted a forced landing, during which the airplane impacted trees and came to rest inverted.

Postaccident examination of the airplane revealed substantial damage to both wings, the fuselage, and the engine mounts. The examination of the fuel injector assembly found a combination of fuel and oil had contaminated between the air diaphragm and the regulator cover. A service bulletin from the fuel injector manufacturer stated that with this type of contamination, an engine could exhibit “gradually deteriorating idle, difficulty starting and/or cold engine acceleration performance.” With the exception of magneto timing that was 3 degrees advance of the engine’s specification, no evidence of any preimpact mechanical malfunction or failure was observed with the engine or its subsystems. Based on the available information, it is likely that the contamination of the fuel injector assembly resulted in the lack of engine performance described by the pilot.

Text from the NTSB. Open the NTSB docket for ERA24LA152 for the full record.