NTSB Identification: CEN09LA144
14 CFR Part 91: General Aviation
Accident occurred Thursday, January 29, 2009 in Anahuac, TX
Probable Cause Approval Date: 05/11/2010
Aircraft: COX WILLIAM M BEARHAWK, registration: N3WC
Injuries: 3 Fatal.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot and two passengers departed in a single-engine homebuilt airplane for a local sightseeing flight. Several witnesses reported that the airplane was "low" and "wiggling up-and-down or weaving side-to-side". They added that the engine sounded like it was "missing" or making "popping" noise before the airplane then disappeared behind a row of trees. The examination of the engine revealed that the carburetor's venturi throat and throttle plate were sooted and displayed signatures consistent with back-firing up through the induction system. The discharge nozzle was also sooted. Additionally, use of a carburetor icing chart showed the airplane was operating in the general area of "serious to moderate icing at cruise power or serious icing at descent power" at the time of the accident. A review of a video from a camcorder found in the wreckage revealed that the right seat passenger filmed part of the flight leading up to the mishap. A sound spectrum study of the tape revealed that the engine was operating at a constant 2283 rpm until the last 20 seconds of the recording. During the last section of recording the engine speed appeared to fluctuate between 2220 and 2500 rpm; however, it was not determined whether this fluctuation was actually the engine behavior or an induced effected caused by rapid movement of the camera during the recording. It was also noted that the video revealed what appeared to be a routine flight until the last moments of the tape, when the camcorder captured a quick change in the aircraft's bank, pitch (or both). The tape ended prior to the actual accident/impact sequence. Examination of the airframe and engine failed to identify any pre-impact malfunctions.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A loss of control in flight for undetermined reasons.

Full narrative available

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