Tucson, AZ, USA
N2388Q
Beech 23
The engine lost power during the takeoff initial climb and the airplane was damaged during a forced landing. The run-up check was uneventful. When the airplane was about 400 feet above ground level turning the left crosswind leg of the airport traffic pattern, the engine lost power completely. The pilot made a forced landing between a taxiway and the perimeter fence on the airport. Post accident test-run of the engine revealed that the mixture control cable was fractured 0.35 inches from the set screw, which attaches it to the carburetor, and the carburetor mixture arm was free to move, uncommanded. This fracture was hidden by the outer sheath that covers the mixture control cable and movement of the cockpit mixture control did not produce corresponding movement of the carburetor mixture arm. With the fracture surfaces realigned, the wire appeared to have been bent nearly 90 degrees from its normally straight path. A scanning electron microscopy (SEM) of both fracture surfaces of the wire revealed the existence of a fatigue crack about 1/4 of the wire's cross-sectional area and perpendicular to the wire's surface. The origin of the fatigue crack was on the outside surface of the 90-degree bend in the wire, which suggests that the crack initiated and propagated during service while the main portion of the wire was under compression loads. The presence of the fatigue crack is indicative of an installation problem, such as overtorquing of the set screw. The fracture of this cable would not allow the pilot to properly set the mixture from the cockpit control to the carburetor.
On May 7, 2005, at 0901 mountain standard time, a Beech 23, N2388Q, lost engine power during takeoff and made a forced landing at the Tucson International Airport, Tucson, Arizona. The private pilot, also the registered owner of the airplane, was operating it under the provisions of 14 CFR Part 91. The pilot sustained minor injuries; the airplane was substantially damaged. Visual meteorological conditions prevailed and no flight plan had been filed. The local area, personal flight was originating at the time of the accident. According to the pilot, the run-up check was uneventful. He departed and when the airplane was about 400 feet above ground level turning the left crosswind leg of the airport traffic pattern, the engine lost power completely. He made a forced landing between a taxiway and the perimeter fence on the airport. The approximate length from the airplane's touchdown point to where the airplane came to rest was about 200 feet. During the forced landing, the left main and nose landing gears were sheared from the airplane and the left wing was pulled aft. The pilot had about 50 gallons of fuel onboard. A fuel sample was drained from the right fuel tank by the Tucson Airport Police. The color and smell of the fuel was consistent with 100 low lead and no water or other contaminants were evident in the sample. There was no obvious oil spill at the accident site. According to aircraft recovery personnel, the left fuel tank sump would not drain fuel. In order to drain the fuel from the wing, he bent the drain with pliers until the fuel flowed from it. Approximately 1/2-cup of water was drained from the tank. The fuel selector was positioned to the right tank. The engine was test-run in the presence of the Federal Aviation Administration accident coordinator. The engine was started successfully; however, when full engine power was applied, the engine lost power. Closer examination revealed that the cable seemed loose between the mixture cockpit control and the attach point at the carburetor. Further examination showed that the mixture control cable attach point to the carburetor was fractured. This fracture was not evident until the outer sheath was removed from the cable. With this fracture, the mixture arm was free to move into any position, uncommanded. No other operational anomalies were noted. The fractured cable absent of its outer sheath, was sent to the National Transportation Safety Board Materials Laboratory, Washington, D.C., for examination. The mixture control cable examination was completed on August 23. The control cable fractured approximately 0.35 inches from the set screw, which attaches it to the carburetor. With the fracture surfaces realigned, the wire appeared to have been bent nearly 90 degrees from its normally straight path. A scanning electron microscopy (SEM) of both surfaces revealed the existence of a fatigue crack about 1/4 of the wire's cross-sectional area and perpendicular to the wire's surface. The origin of the fatigue crack was on the outside surface of the 90-degree bend in the wire.
a loss of engine power due to the fatigue fracture and separation of the mixture control cable. The fatigue crack resulted from inadequate installation techniques by unknown maintenance personnel.
Source: NTSB Aviation Accident Database
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