Cessna 180 accident near Iliamna, Alaska, April 4, 1999
On April 4, 1999 at about 10:30 pm local time, a Cessna 180, registered N420SB, was substantially damaged in an accident near Iliamna, Alaska. It was a personal flight under general aviation rules (Part 91). No one was hurt; 2 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The improper installation of the main landing gear attaching bolt by maintenance personnel, which resulted in total failure of the bolt and collapse of the landing gear.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 4, 1999 · about 10:30 pm local time
- Place
- Iliamna, Alaska · map
- Type
- Accident
- Injuries
- No one was hurt; 2 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 180 · all 180s on the register
- Registration
- N420SB · registry record · serial 18052313
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot was landing the wheel/ski equipped airplane on a frozen lake to wait for improving weather. During the landing roll, the pilot heard a 'whump' and the airplane settled onto the left wing. Inspection revealed the main landing gear attaching bolt had fractured in overload across a threaded area. The installed NAS-147R bolt was not the one specified for installation, and had a shorter smooth shank section (1.3 inches) than the specified AN bolt (1.43 inches). When an undamaged NAS-147R bolt is installed in the landing gear, a threaded area remains within the bolt hole. The bolt had been installed three weeks prior to the accident during the last annual inspection.
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
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; single-engine sea; instrument: airplane; rotorcraft: helicopter
- Flight time: 4,185 hours in all; 980 in this make and model; 18 in the last 90 days; 18 in the last 30 days; 4,177 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 3,990 hours
- Last inspection: annual inspection, March 5, 1999; 10 hours since
- Maximum gross weight: 2,800 lb
- Seats: 4
- Landing gear: fixed
- Engine: Continental O-470-R (piston); 0 hours total
The flight
- Departed from: AK at 5:00 pm
- Destination: PAQ Palmer AK
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 090° at 20 knots, gusting 30
- Visibility: 4 statute miles
- Sky: overcast at 1,000 ft; not recorded
- Temperature: 28°F (-2°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 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 N420SB the same tail number, which may have belonged to a different aircraft at the time
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 never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.