Accident Overview
On April 2, 2016, at approximately 1707 central daylight time, a privately owned Cessna 175B, registration N8115T, sustained substantial damage during a forced landing to a field near Hurley, Mississippi. The commercial pilot, who was the sole occupant, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under 14 CFR Part 91.
Flight Details
The flight originated about seven minutes earlier from Mobile Regional Airport (MOB) in Mobile, Alabama, and was destined for Slidell Airport (ASD) in Slidell, Louisiana. The pilot noted no discrepancies during the preflight inspection or engine run-up before this first flight after an annual inspection completed the previous day.
Loss of Engine Power
After takeoff, while in contact with air traffic control, the pilot climbed to between 1,200 and 1,500 feet mean sea level. After leveling off, he slowly leaned the fuel-air mixture. Upon moving the mixture control about a quarter to half an inch, the engine rpm abruptly decreased from 2,900 to 1,200. The pilot promptly pushed the mixture control full in, but engine power did not return. Twice he advanced the throttle fully forward, resulting in brief power increases before the engine returned to idle. When the descent reached below 1,000 feet, he informed the controller and received radar vectors to a nearby private airport.
Forced Landing
With insufficient altitude to glide to the airport and inadequate power for sustained flight, the pilot maneuvered for a forced landing to a field. During the landing roll, the nose landing gear contacted the upslope portion of a ditch, causing the nose gear to separate. The airplane slid about 100 feet and came to rest upright in a nose-low, tail-high attitude. The pilot exited, provided his mechanic the location coordinates, and rescue services were dispatched. He was taken to a nearby hospital, where he and the mechanic discussed possible causes. The mechanic advised that during an engine run, the engine had lost power quickly during manipulation of the mixture control.
Post-Accident Examination
Examination by a Federal Aviation Administration inspector revealed that the cockpit mixture control was in the full-rich position but was at the idle cut-off position at the carburetor. Pulling the mixture control did not cause complete movement of the mixture lever at the carburetor; pushing it in resulted in only half the lever's travel. A plastic sheath covered the mixture control cable between the carburetor lever and a baffle aft of the engine, secured by a clamp near the carburetor lever. Subsequent examination of the recovered airplane showed the cable and sheath were loose within the clamp, with no rubber grommets present. Moving the cockpit mixture lever from full lean to full rich resulted in only a fraction of an inch of movement at the carburetor lever, and cable flexing was observed.
Engine runs were conducted: with fuel from the wings plumbed to the left wing root and the mixture control at full rich, the engine started but lost power when leaned and did not recover when pushed to full rich. In a second test, the sheath and cable were placed in the clamp and tightened; when leaned, the sheath came out of the clamp, and the engine lost power again. In a final test, the carburetor mixture lever was fixed in the full-rich position; the engine started uneventfully and operated to 1,800 rpm with normal magneto drop, but higher rpm was avoided for safety. No engine anomalies were noted.
A review of the Illustrated Parts Catalog found no listing for plastic sheathing on the mixture control cable.
Maintenance Background
The 100-hour inspection checklist used by the mechanic specified inspection of engine controls and linkage for security, proper rigging, and binding. The mechanic indicated that during his inspection, the mixture control moved through full travel but not as far as he was accustomed. He also stated that he ran the engine twice during post-maintenance checks and was able to lean and secure the engine using the mixture control without issues.