Haskell, OK, USA
N535CT
FLIGHT DESIGN GMBH CTSW
The sport pilot completed a preflight inspection of the airplane and noted that it had about 28 gallons of automotive fuel; he conducted a cross-country flight with no anomalies noted. After starting the engine before takeoff for the return flight, the pilot noticed that the engine gauges were normal but that the charging system had an inadequate output, so he shut down the engine. After consulting a mechanic, he restarted the engine and noted normal engine and charging indications. During the takeoff climb, about 500 to 600 ft above ground level, the engine starting "sputtering" and continued to run but the airplane did not maintain altitude. The choke was off, and the pilot applied various throttle settings to no avail. The pilot performed a forced landing to a field, and the airplane came to rest inverted. Postaccident examination of the airplane's fuel system was satisfactory and did not reveal any contamination. Further, examination of the engine revealed that the engine's left and right carburetor float bowls contained clean fuel. During a test run of the engine, the engine was started and run at idle before running up to power. The postaccident engine examination and test run did not reveal any evidence of preimpact malfunctions or failures that would have precluded normal operation. Weather conditions at the time of the accident were conducive to the accumulation of serious carburetor icing at glide power settings; however, the airplane was fueled with automotive fuel, which may have a different carburetor icing range than that depicted in Federal Aviation Administration guidance for aviation fuel. Additionally, the airplane was at takeoff power and not glide/idle power when the power loss occurred. Thus, it is not likely that the formation of serious carburetor icing occurred. A reason for the loss of engine power could not be determined.
On June 6, 2015, about 1258 central daylight time, a Flight Design CTSW, light-sport airplane, N535CT, performed a forced landing shortly after departing the Haskell Airport (2K9), Haskell, Oklahoma. The pilot and a passenger received minor injuries, and the airplane was substantially damaged during the off-airport landing. The airplane was registered to KT Aviation LLC, of Wagoner, Oklahoma, and was operated by a private individual as a 14 Code of Federal Regulations Part 91 personal flight. Day visual meteorological conditions prevailed and a flight plan had not been filed. The flight originated from 2K9 and was destined for Hefner-Easley Airport (H68), Wagoner, Oklahoma, at the time of the accident. The pilot reported that they had flown from H68 to 2K9 earlier in the day. Prior to departing H68, he did a normal preflight inspection, with no discrepancies noted and about 28 gallons of automotive fuel. After starting engine at 2K9, the pilot noticed the engine gauges were normal, but the charging system had an inadequate output, so he shut down the engine. After consulting a mechanic, he restarted the engine about 1245, with normal engine and charging indications. During the initial climb from 2K9 about 500 to 600 feet above ground level, the engine starting "sputtering". The engine continued to run but not enough to maintain altitude. The pilot selected a field for the forced landing; various throttle settings failed to restore engine power and the choke was off. The airplane touched down in a muddy field and came to rest inverted. An on-scene wreckage examination found substantial damage to the airplane's fuselage and damage to the airplane's landing gear. Fuel quality checks of the on-board fuel and the fuel facility were satisfactory. The wreckage was moved to a different location and a post-accident examination of the engine was conducted. Further examination revealed no water or debris were noted in the gascolator, the engine's left and right carburetor float bowls contained clean fuel, the sparkplugs appeared normal, and ignition spark was verified. A test run of the engine was conducted. The engine was started and run at idle before running up to power; no problems were noted during the engine examination or test run. The airplane's EFIS (Electronic Fight Information System) and EMS (Engine Monitoring System), were removed for extraction of volatile memory (NVM). The memory in the EFIS was corrupted and no useful information could be obtained. The EMS contained an eight-minute recording of engine parameters for the accident flight. A review of the EMS data revealed the engine acceleration to high power, followed by fluctuations and a reduction in the engine rpms. The NTSB's Vehicle Recorder Division's full factual report is located in the public docket for this case. The closest weather reporting station was located at the Okmulgee Regional Airport Okmulgee, Oklahoma, about 17 miles southwest from the accident site. At 1255, the station recorded wind from 150 degrees at 3 knots, visibility 10 miles, scattered clouds at 4,700 ft agl, temperature 88° F, dew point 70° F, and an altimeter setting of 30.00 inches of mercury. The carburetor icing probability chart included in Federal Aviation Administration Special Airworthiness Information Bulletin No. CE-09-35, Carburetor Icing Prevention, indicated that the airplane was operating in an area that was associated with a serious risk of carburetor ice formation at glide power settings.
The loss of engine power for reasons that could not be determined because a postaccident engine examination and test run did not reveal any evidence of preimpact malfunctions or failures that would have precluded normal operation.
Source: NTSB Aviation Accident Database
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