Cessna 170B accident near North Pole, Alaska, May 16, 2002
On May 16, 2002 at about 6:20 pm local time, a Cessna 170B, registered N4669C, was substantially damaged in an accident near North Pole, Alaska (Bradley Sky Ranch airport). It was a personal flight under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The separation of the right main landing gear from the airplane during landing. A factor associated with the accident is the unapproved hardware used to attach the main landing gear.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 16, 2002 · about 6:20 pm local time
- Place
- North Pole, Alaska · Bradley Sky Ranch · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 170B · all 170Bs on the register
- Registration
- N4669C · registry record · serial 25613
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The right main landing gear leg separated from the airplane while landing on a gravel airstrip, which resulted in substantial damage to the airframe. The main landing gear had recently been rebuilt, and this was the second landing since the work was completed. The gear leg had been secured to the airplane with an AN7-20A bolt and an MS21044C stainless steel nut. The bolt, which remained attached to the separated gear leg was bent and the threads were damaged. The MS21044C nut had fractured, and was found in the right main landing gear bulkhead assembly. Examination of the nut determined it fractured due to circumferential overstress tension. The airplane manufacturer's parts catalog specifies a AN365-720C steel nut to secure the main landing gear legs. The military standard, under which the original AN365 nut was manufactured, requires any substitute nut to be of like material, plating, and thread size, and specifically excludes the substitution of the MS21044C nut in lieu of the AN365-720C nut. The proper substitute for the AN365-720C is the MS21044N, which is an all steel nut. However, the rated tensile strength of the AN365, MS21044C and MS21044N series nuts are all 125 ksi. Examination of the bolt revealed sheared threads adjacent to the bolt grip, indicating that the nut was intact on the bolt when the bolt/nut combination was loaded to failure. The bending deformation of the bolt indicated a side load was present during the failure. This side load could have resulted from a hard landing with the airplane moving sideways or improper reinstallation of the landing gear may have allowed normal landings to introduce side loads.
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: private
- Ratings: single-engine land
- Flight time: 557 hours in all; 1 in the last 90 days; 1 in the last 30 days; 535 as pilot in command
- Last flight review: January 10, 2002
- Medical certificate: Class 3 (valid medical--w/ waivers/lim.)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 1,262 hours
- Last inspection: annual inspection, May 10, 2002; 1 hours since
- Maximum gross weight: 2,200 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming O-360-A1A (piston); 0 hours total
The flight
- Departed from: PAFA Fairbanks AK at 12:31 pm
- Destination: 95Z North Pole AK
- Flight plan: not recorded
- Runway 33, 4,093 ft by 80 ft
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 70°F (21°C), dew point 0°F (-18°C)
- Altimeter: 29.90 inHg
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 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 N4669C 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.