NTSB Identification: SEA01LA168.
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Accident occurred Wednesday, September 05, 2001 in Carbonado, WA
Probable Cause Approval Date: 06/18/2002
Aircraft: Cessna 172RG, registration: N44EF
Injuries: 2 Minor.
NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot and passenger departed on a fire patrol flight in the Cessna 172RG. The pilot demonstrated basic flight techniques to the passenger and the aircraft proceeded into mountainous terrain. While flying southeast up a canyon the aircraft's engine performance began deteriorating. The pilot reported that about 10-15 seconds transpired between the time he initially noted the decrease in performance, to when the engine began to "cough," and that the aircraft was approximately 1,000 feet above the ground and 200 feet horizontally from the rising terrain. The aircraft impacted trees and terrain along the canyon's axis about 2,500 feet above sea level. Although the average gradient from the crash site along the aircraft's direction of flight was more than +11 degrees over the 12,000 foot distance beyond the site, the aircraft had sufficient lateral distance to execute a 180 degree turn under normal power. The pilot reported that he did not have time to exercise the carburetor heat when he began to troubleshoot. He also reported that he had not encountered carburetor icing previously. An examination of the aircraft at the accident site revealed the carburetor heat control in the "OFF" position. Moderate carburetor icing conditions existed based on temperature/dew point extrapolation from a nearby weather reporting source, and the pilot reported a ragged overcast with bases at 4,000-5,000 feet and rain showers along the route of flight. A post crash test run of the aircraft's engine was successful, however, the left magneto was found to be inoperative. It could not be determined whether the magneto became inoperative during the flight or as a consequence of the impact.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot-in-command's failure to utilize carburetor heat resulting in a loss of power and consequent descent into trees and terrain. Contributing factors were carburetor icing conditions and mountainous/hilly terrain. Full narrative available
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