N8115TCessna 175B

On April 2, 2016, about 1707 central daylight time, a privately owned and operated Cessna 175B, N8115T, was substantially damaged during a forced landing to a field near Hurley, Mississippi. The commercial pilot, the sole occupant was not injured. Visual meteorological conditions prevailed at the time and no flight plan was filed for the personal flight that was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The flight originated about 7 minutes earlier from Mobile Regional Airport (MOB), Mobile, Alabama, and was destined for Slidell Airport (ASD), Slidell, Louisiana.The pilot noted no discrepancies during his preflight inspection or engine-run up in advance of the first flight after completion of an annual inspection that was completed the day before. After takeoff, while in contact with air traffic control, the pilot climbed to between 1,200 and 1,500 feet mean sea level (msl) and after levelling off, he slowly leaned the fuel to air ratio. After moving the mixture control about 1/4 to 1/2 inch, the engine rpm "abruptly" decreased from 2,900 to 1,200. He promptly pushed the mixture control full-in, but that action did not restore engine power. He twice advanced the throttle fully forward, and the engine power briefly increased, before again falling back to idle. When the flight descended below 1,000 feet msl, he informed the controller of the situation and was provided with radar vectors to a nearby private airport.

With insufficient altitude available to glide to the airport and inadequate power to sustain flight, he maneuvered the airplane for a forced landing to a field. During the landing roll the nose landing contacted the upslope portion of a ditch, causing the nose landing gear to separate from the airplane. The airplane then slid about 100 feet, and came to rest upright in a nose-low/tail-high attitude. The pilot then exited the airplane, provided his mechanic the location coordinates, and rescue services were dispatched. The pilot was taken to a nearby hospital and while there, he and the mechanic who performed the last inspection discussed the possible causes of the loss of engine power. During that conversation, the pilot reported being advised by the mechanic that during an engine run, the engine had lost power quickly during manipulation of the mixture control. The pilot did not question the mechanic on that detail at that time.

Examination of the airplane by a Federal Aviation Administration inspector revealed the mixture control in the cockpit was in the full rich position but was idle cut-off position at the carburetor. The mixture control was pulled out but this action did not cause complete movement of the mixture control lever at the carburetor. The mixture control in the cockpit was pushed in, and the mixture lever at the carburetor only travelled half the distance of full travel. Further examination of the mixture control cable revealed a plastic sheath covered the cable between the mixture control lever at the carburetor and a baffle located aft of the engine. The sheath covered the cable in an area that was secured by a clamp attached near the mixture control lever at the carburetor.

Following recovery of the airplane, further examination of the mixture control cable revealed it and the plastic sheath covering it were loose within a clamp near the carburetor, and no rubber grommets within the clamp were noted. The mixture lever in the cockpit was moved from full lean to full rich, but the mixture control lever at the carburetor only moved a fraction of an inch and flexing of the mixture control cable was noted. In advance of an engine run, fuel that was drained from the wings was plumbed directly to the fuel line at the left wing root and the mixture control in the cockpit was place in the full rich position. The engine was started and the mixture control in the cockpit was moved toward the lean position, but the engine began to lose power. The mixture control in the cockpit was pushed to full rich but the engine lost power. In advance of a second test run, the plastic sheath and mixture control cable were placed inside the clamp near the carburetor, and the clamp was tightened. The mixture control in the cockpit was placed in the full rich position, and the engine was started. The mixture control in the cockpit was leaned and the sheath came out of the clamp and the engine again lost power. In advance of the final test run, the mixture lever at the carburetor was fixed in the full-rich position. The engine started uneventfully and was operated to 1,800 rpm where normal rpm drop during magneto checks were noted. Engine operation at a higher rpm was not performed due to safety concerns. No anomalies were noted with the engine during the engine run with the mixture control fixed in the full-rich position.

A review of the Illustrated Parts Catalog revealed no listing for plastic sheathing to cover the mixture control cable.

The 100-hour inspection checklist utilized by the mechanic specified an inspection of the engine controls and linkage for security, proper rigging, and binding. The mechanic indicated that during his inspection of the mixture control he noted it moved full travel but did not move as far as he was accustomed. He also indicated that he twice ran the engine during post maintenance checks and was able to lean and secure the engine using the mixture control with no issues.