Arctic Aircraft Corp. S-1B2 accident near Big Lake, Alaska, April 23, 2004
On April 23, 2004, a Arctic Aircraft Corp. S-1B2, registered N55AD, was substantially damaged in an accident near Big Lake, Alaska. It was an instructional flight under general aviation rules (Part 91). 1 person was seriously injured and 1 person had minor injuries. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made September 29, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 23, 2004
- Place
- Big Lake, Alaska · map
- Type
- Accident
- Injuries
- 1 person was seriously injured and 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Arctic Aircraft Corp. S-1B2
- Registration
- N55AD · registry record · serial 1006
- Damage
- Substantial damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
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 NTSB's narratives can run to many pages; this is the opening. Read the full report at the NTSB.
Other NTSB records under N55AD the same tail number, which may have belonged to a different aircraft at the time
About this page
Everything above comes from the NTSB's public accident database and is rewritten in plain English only where the NTSB used codes; the probable cause and narrative are the NTSB's own words. This site never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number ANC04LA045.