STILLWATER, OK, USA
N444D
Beech BE35
During the initial climb, while passing through 1,600 feet agl, and shortly after the pilot adjusted the engine power for cruise climb, the airplane's engine lost power. The pilot adjusted the throttle, mixture, and propeller controls, switched the fuel selector from the left fuel tank to the right fuel tank, and manually pumped the fuel boost pump. Engine power was not restored. During the ensuing forced landing, the airplane impacted hilly terrain. A test flow of the pressure carburetor revealed that it would not flow within its specified limits. Disassembly of the pressure carburetor revealed that a few of the diaphragms were dry rotted, hardened, and fuel was found in the air section of the discharge diaphragm. The manufacture dates stamped on the fuel and air diaphragms of the regulator section of the carburetor were October 1958 and November 1953 respectively. It could not be determined when the carburetor had last been overhauled.
On November 28, 1999, at 0908 central standard time, a Beech BE35 airplane, N444D, was substantially damaged when it impacted terrain during a forced landing following a loss of power near Stillwater, Oklahoma. The airplane was owned and operated by the pilot. The private pilot sustained serious injuries, and his passenger sustained minor injuries. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The flight originated from the Stillwater Municipal Airport at 0900, and was destined for Blackwell, Oklahoma. The pilot, who had recently purchased the airplane, stated that when the airplane was delivered, several days prior to the accident, the delivery pilot reported that the engine experienced a 200 RPM power loss in flight, which could not be corrected. Two days prior to the accident flight, the pilot topped off the fuel tanks and performed a 20-minute run-up with the left fuel tank selected, and "everything checked normally." On the day of the accident, the pilot visually verified the fuel quantity in both fuel tanks and found that the fuel tanks were "virtually full." The pilot then flew the airplane from the Ponca City Municipal Airport, Ponca City, Oklahoma, to the Stillwater Municipal Airport and experienced no problems with the airplane and engine. The pilot stated that the flight to Stillwater took less than an hour. The pilot picked up his passenger, conducted an engine run-up and noted no anomalies. The airplane departed to the north from runway 35, and the pilot retracted the landing gear and adjusted power for cruise climb. According to the pilot, the engine lost power shortly after the power change, at 1,600 feet agl. He stated that it was "like the throttle had been shut." The pilot stated that he adjusted the throttle, propeller, and mixture controls with no change in engine power. He turned the airplane back toward the airport and established the airplane in a glide. The pilot added that he hand pumped the fuel boost pump, switched the fuel selector from the left fuel tank to the right fuel tank, and again pumped the fuel boost pump with still no change in engine power. During the ensuing forced landing, the airplane impacted hilly terrain in an unobstructed pasture. According to the FAA inspector, who visited the accident site, the airplane came to rest in an open field approximately 35 yards south of the initial ground scar. The FAA inspector stated that one propeller blade was undamaged and the other was bent aft 90 degrees. The right wing, empennage, and cabin area sustained structural damage. The right fuel tank was found empty, and the left fuel tank was found 3/4 full of fuel. The fuel selector was found positioned on the right fuel tank, and the fuel quantity indicator selector was positioned to indicate the quantity in the left tank. On December 13, 1999, the NTSB investigator-in-charge (IIC) examined the engine and airplane fuel system with the assistance of representatives from the engine and aircraft manufacturer. No anomalies with the aircraft's fuel system were noted, except that the fuel selector's fuel screen was found installed backward. The people who recovered the airplane reported finding no fuel in the right fuel tank and 10 gallons of aviation gasoline in the left fuel tank. The 17-gallon right fuel bladder was examined and no leaks or punctures were noted. The engine's crankshaft was rotated manually and crankshaft continuity, rocker arm movement, and cylinder thumb compression were confirmed. The magnetos were rotated using a hand-held drill and sparks were noted in all of the distributor cap towers. The carburetor was removed from the engine and was examined on January 12, 2000, by the NTSB IIC and representatives from the engine and aircraft manufacturer. The Bendix PS5C pressure carburetor (part number 380208-6, serial number 724094) was placed on a flow bench. The carburetor was unable to maintain test pressure throughout the entire flow test. The carburetor ran rich at the low test settings (equating to low power settings) and ran lean at the high test settings (equating to high power settings). At no time during the flow test was the carburetor within flow limits. The carburetor was disassembled and examined. Diaphragms in the idle section and regulator section of the carburetor were found dry rotted and hardened. Fuel was found on the air-side of the discharge diaphragm. The manufacture dates found on the regulator's fuel diaphragm and the air diaphragm were October 1958 and November 1953 respectively. The other diaphragms did not have a manufacture date present. According to the aircraft's maintenance records, the engine was overhauled on August 20, 1996, at an engine total time of 2,748.8 hours. The airplane and engine underwent their most recent and only inspection since the engine overhaul on November 24, 1998. At that time, the right fuel cell was removed and replaced. It could not be determined when the carburetor had last been overhauled. The airplane had been flown 22.57 hours since the engine overhaul and 11.07 hours since the last inspection.
The total loss of engine power due to the dry-rotted diaphragms in the pressure carburetor. A factor was the hilly terrain encountered during the forced landing.
Source: NTSB Aviation Accident Database
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