Cessna U206 accident near Near Iliamna, Alaska, July 25, 1983
On July 25, 1983 at about 5:30 am local time, a Cessna U206, registered N4661Z, was substantially damaged in an accident near Near Iliamna, Alaska. It was a flight of an unrecorded kind under charter and air-taxi rules (Part 135). No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The NTSB has not yet published a probable cause for this accident. Investigations usually take one to two years; this page updates when the final report is released.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 25, 1983 · about 5:30 am local time
- Place
- Near Iliamna, Alaska · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna U206 · all U206s on the register
- Registration
- N4661Z · registry record · serial U20605998
- Damage
- Substantial damage
- Flight
- Flight of an unrecorded kind · charter and air-taxi rules (Part 135)
The NTSB's narrative final · quoted from the NTSB record
THE ENG LOST POWER JUST AFTER A WATER TAKEOFF. THE ACFT LANDED STRAIGHT AHEAD IN MUSKEG & TUNDRA COLLAPSING THE FLOATS. ENG TEARDOWN REVEALED A METALLIC 'NUGGET' IN THE LEFT INTAKE MANIFOLD BETWEEN THE #4 & #6 PORTS. NUMEROUS MARKS WERE FOUND ON THE INSIDE OF BOTH INTAKE MANIFOLDS. THERE WAS MINOR DENTING, SCRATCHING & PEENING ON THE INTERIOR OF THE 90 DEG ELBOWS FROM BOTH ENDS OF THE CROSSOVER TUBE, INTAKE VALVE PORTS, SEATS & VALVE FACES OF CYLS 4,5 & 6. THE NUGGET WAS COMPOSED OF THE SAME MATERIAL AS THE AIRBOX ASS'Y, CESSNA P/N 1250705, WHICH CONTAINED TWO HOLES APRX 2-1/2 SQUARE INCHES EACH IN THE AIRBOX WALL. THE HOLES WERE CAUSED BY FATIGUE CRACKS. THE SOURCE OF LOADING CAUSING THE FATIGUE CRACKPROPAGATION WAS DUE TO MEMBRANE &/OR BENDING LOADS IN THE AIRBOX WALL CAUSED BY OUT-OF-PLANE DEFORMATION. THESE DEFORMATION WERE MOST LIKELY CAUSED BY EXCITING A NATURAL MODE OF VIBRATION IN THE WALL. THREE DUCT FAILURES WERE REPORTED TO THE FAA IN 1983, TWO OF WHICH WERE IN C-210 ACFT.
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: single-engine land; single-engine sea; instrument: airplane
- Flight time: 5,809 hours in all; 1,869 in this make and model; 233 in the last 90 days; 5,714 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 325 hours
- Last inspection: 100-hour inspection, July 13, 1983; 31 hours since
- Maximum gross weight: 3,600 lb
- Seats: 6
- Landing gear: fixed
- Engine: Continental IO-520-F (piston); 0 hours total
The flight
- Destination: Lake Clark AK
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 080° at 20 knots, gusting 25
- Visibility: 5 statute miles
- Sky: overcast at 1,500 ft; not recorded at 1,500 ft
- Temperature: 55°F (13°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 2 |
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.
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.