Accident Details
On March 24, 2024, at 1330 eastern daylight time, a Cessna 172S, registration N863AU, was substantially damaged when it collided with trees and came to rest inverted during a forced landing near Opelika, Alabama. The private pilot sustained minor injuries. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
Pilot Report
The pilot completed a preflight inspection with no anomalies noted. During engine start, the engine sounded slightly rough but became smooth after a few seconds. The engine run-up revealed no unusual indications, and the magneto check was normal. During the takeoff roll, engine indications were within the green arc, but airspeed increased slightly slower than normal. The pilot noted that the engine did not appear to produce normal power, though she was uncertain of the exact static rpm achieved. At a rotation speed of 55 knots, the pilot initiated the climb. During the initial climb, airspeed remained between 60 and 65 knots, and engine rpm stayed at about 1,700 to 1,750 despite full throttle and mixture controls. The pilot lowered the nose and maneuvered toward a forced landing area. She reported that engine rpm did not increase then decrease during the flight and characterized the engine performance as constant but sluggish. The airplane subsequently impacted trees and came to rest inverted.
Postaccident Examination
Postaccident photographs showed substantial damage to both wings, the fuselage, and the engine mount. A postaccident examination of the engine found continuity of the crankshaft and valvetrain. Compression and suction were observed on all cylinders in the correct firing order when the crankshaft was rotated. Both magnetos were secure on their fittings, with timing measured at 28° before top dead center, whereas the engine data tag specified 25° before top dead center. The fuel injector assembly was removed and disassembled.
Fuel Injector Examination
Examination of the fuel injector revealed a combination of fuel and oil contamination between the air diaphragm (Avstar part number AV 2538295) and the regulator cover (part number AV 2577194). Service bulletin AFS-SB10 from the fuel injector manufacturer indicates that there have been occasional reports of engines exhibiting gradually deteriorating idle, difficulty starting, or cold engine acceleration performance, particularly when the servo is mounted in an updraft or nearly updraft configuration. The bulletin notes that close inspection may reveal green/blue oily contaminant in the servo bore, which can migrate into the air section of the regulator.