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).
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 November 2, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 23, 2004 · cases in 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 complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Flight instructor
- Certificate: airline transport pilot, flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; single-engine sea; instructor: airplane multi-engine; instructor: airplane single-engine; instructor: instrument airplane; instrument: airplane
- Flight time: 6,933 hours in all; 1 in this make and model; 24 in the last 90 days; 9 in the last 30 days; 4,859 as pilot in command; 2,774 on instruments
- Last flight review: September 18, 2002
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: rear
- Injury: serious injuries
Dual student
- Medical certificate: None
- Seat: frt
- Injury: minor injuries
The aircraft
- Airframe total time: 753 hours
- Last inspection: annual inspection, May 19, 2003; 29 hours since
- Maximum gross weight: 1,650 lb
- Seats: 2
- Landing gear: fixed
- Engine: Lycoming O-320-A2B (piston); 0 hours total
The flight
- Departed from: PAUO Big Lake AK at 7:00 pm
- Flight plan: none
- A second pilot was aboard
Weather at the time
- Light: daylight
- Visibility: 30 statute miles
- Sky: broken clouds at 5,000 ft; scat at 3,000 ft
- Temperature: 46°F (8°C), dew point 27°F (-3°C)
- Altimeter: 29.46 inHg
- Observation at 6:51 pm from PAUO, 8 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Other NTSB records under N55AD the same tail number, which may have belonged to a different aircraft at the time
Connections how this case links to the rest of the register
- N55AD on the register today · the tail number may have moved to another aircraft since
- Engine: Lycoming O-320-A2B 179 aircraft carry this series today · as the NTSB recorded it
- Willow Airport · departed from
- Accidents and incidents in Alaska 5,932 since 1982 · 826 in the last ten years
- Alaska 9,146 aircraft registered
- Other NTSB records under N55AD 2 records · the number may have belonged to another aircraft at the time
The whole map of how records connect · these connections as data: /graph/accident/ANC04LA045.json.
The bigger picture in Aviation Analytics: accidents over time since 1982, by model, by phase of flight and conditions, by place and on the map.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text does not name anyone involved, its policy at this time. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.