WPR10LA376

The pilot reported that, prior to initiating the takeoff roll, he did not lean the fuel mixture. The airplane initially accelerated slowly, which the pilot expected at the high density altitude airport. About 50 feet above the ground, the pilot observed the engine rpm decreased from 2,700 to 2,500 rpm; the airplane was also losing altitude. The pilot elected to reduce the power and land on the runway overrun area; during the landing, the airplane struck a rock with the left main landing gear, which resulted in substantial damage to the elevator. A postaccident examination revealed that the spark plugs were carbon fouled, indicating that the engine was operating too rich. During the first engine run-up, the engine ran rough. After the spark plugs were cleaned, the engine ran normally with no anomalies noted. The airplane’s takeoff checklist notes, MIXTURE -- LEAN for maximum power at airports above 3,000 feet in elevation. The elevation of the airport was 6,813 feet. The density altitude at the time of the accident was 8,895 feet.

On July 31, 2010, about 0910 mountain daylight time, a Cessna 177B airplane, N35296, sustained substantial damage following a partial loss of engine power during initial climb and subsequent forced landing at the Rawlins Municipal Airport (RWL), Rawlins, Wyoming. The certificated airline transport pilot and his sole passenger were not injured. Visual meteorological conditions prevailed for the planned cross-country flight, which was being operated in accordance with 14 Code of Federal Regulations Part 91, and a flight plan was not filed. The flight was originating at the time of the accident, with Scottsbluff, Nebraska the planned destination. In a statement submitted to the National Transportation Safety Board investigator-in-charge (IIC), the pilot reported that prior to his departure he noticed that a sign in the fixed based operator’s office indicated that runway 04 had an up hill gradient and that there was rising terrain at the end of the runway. The pilot stated that prior to taxiing for takeoff he noticed that the windsock pointed in a direction that favored runway 04. The pilot reported that at the end of runway 04 he performed his run up and preflight checks and that everything seemed to be normal; the pilot's statement also indicated that he failed to lean the fuel mixture prior to takeoff. The pilot further reported that he then taxied onto runway 04 and added full power for takeoff; a check of the engine revolutions per minute (RPM) and manifold pressure (Hg) indicated 2,700 RPM and 23 Hg respectively, with engine oil temperature and oil pressure readings both normal. The pilot revealed that the airplane accelerated slowly, which he said was to be expected at an altitude of 6,800 feel [mean sea level] (msl). The pilot stated that he rotated at normal speed and started to climb, and at about 50 feet above ground level, "...the aircraft vibration and sound changed." The pilot reported that he noticed that the RPM had dropped to 2,500 and that the airplane was losing altitude. The pilot further reported that at this point he “cut the power” and landed on the runway overrun. The pilot added that the airplane subsequently struck a rock with its left main [landing] gear before coming to a stop. The airplane sustained substantial damage to its elevator. At the request of the IIC, a certified Federal Aviation Administration (FAA) airframe and powerplant mechanic conducted a post accident examination of the airplane’s engine. The mechanic reported that a visual examination of the spark plugs revealed that cylinder #4 top and bottom spark plugs were carbon fouled out and that all of the engine’s spark plugs were observed to have carbon fouling. The mechanic further reported that all cylinders were borescoped with no anomalies noted. Additionally, the mechanic verified that both the intake and exhaust rocker arms were checked for movement, all of which checked normal. The mechanic stated that while rotating the engine’s crankshaft, spark wasverified at all ignition harness leads, the carburetor’s accelerator pump expelled fuel when actuated, and that the engine timing checked normal. The mechanic added that during the first run up of the engine it ran rough, but after the cylinder’s #4 spark plugs were cleaned, the engine ran normally at all power settings. In part, the mechanic concluded in his report that "...the engine ran too rich, [which] is why [the] engine would not operate properly..." At 0853, the weather reporting facility located at RWL reported wind variable at 3 knots, visibility 10 miles, temperature 21 degrees Celsius, dew point 10 degrees Celsius, and an altimeter setting of 30.21 inches of Mercury. The density altitude at the time of the accident was calculated to have been 8,895 feet. The Cessna 177B BEFORE TAKE-OFF checklist, item 6 states: Mixture – RICH (below 3000 ft.). Additionally, under the TAKE-OFF checklist, under MAXIMUM PERFORMANCE TAKE-OFF, item 5 states: Mixture -- LEAN for maximum power (above 3000 feet elevation). The airport elevation was 6,813 feet msl.