NTSB Identification: ANC04LA045.
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Accident occurred Thursday, April 22, 2004 in Big Lake, AK
Probable Cause Approval Date: 01/24/2005
Aircraft: Arctic Aircraft Corp. S-1B2, registration: N55AD
Injuries: 1 Serious,1 Minor.

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 flight instructor was instructing the dual student in preparation for a private pilot certificate. It was their first flight together, and the instructor's first flight in the accident type airplane. The instructor initiated a simulated loss of engine power by reducing the engine power to 1,000 rpm, and the student made an approach to an abandoned airstrip. When the instructor told the student to recover and apply power, the engine would not respond. The instructor took control of the airplane, but collided with trees short of the airstrip. Postaccident inspection of the engine disclosed no obvious mechanical issues. The engine was placed on another airframe, and was readily started and operated through various power settings. At the time of the accident, visible moisture in the presence of cloud cover was present, and the temperature and dew point spread were conducive to the formation of carburetor ice. The instructor and the student disagree on what instructions were given by the instructor during the simulated emergency and subsequent loss of engine power. The instructor said he told the student what to do, including checking the carburetor heat. The student, the airplane owner, refuted that the instructor told him to activate the carburetor heat, and said that he did not activate the carburetor heat. The instructor wrote that he saw a knob pulled on the left side of the panel when he exited the airplane. Photographs taken shortly after the accident depict the carburetor heat control on the left side of the panel extended about 1/2 of its full travel. The photographs also revealed that the fuselage had been compressed several inches during the impact, and that the engine had been pushed in and down. The instructor said it was difficult for him to see the position of the carburetor heat control on the front panel from his rear-seat position.

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

The flight instructor's failure to insure that the carburetor heat was activated by the dual student following a simulated loss of engine power, which resulted in carburetor ice and the actual loss of engine power during a descent. A factor associated with the accident is carburetor icing weather conditions.

Full narrative available

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