# NTSB ANC94LA125: Cessna 170B, N4457B, Fort Yukon, AK, August 31, 1994

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: August 31, 1994, 12:10 local (20:10 UTC)
- Place: Fort Yukon, AK
- Coordinates: 68.090026, -145.59967 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=68.0900&lon=-145.5997&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report May 9, 1995
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 2557
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC94LA125
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/2557/pdf
- Page: https://openairdocs.org/ntsb/ANC94LA125

## Probable cause

THE FATIGUE FAILURE OF THE RIGHT MAIN LANDING GEAR SPRING.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Gear collapsed, landing - roll
  - landing gear,main gear spring - fatigue (cause)

## Analysis

THE PILOT LANDED ON THE AIRSTRIP AND DURING THE ROLL OUT THE RIGHT MAIN LANDING GEAR COLLAPSED.  EXAMINATION SHOWED A FATIGUED AREA NEAR THE CENTER OF ONE OF THE AXLE'S UPPER MOUNTING BOLT HOLES.  THE AIRPLANE HAS BEEN USED ON SKIS DURING THE WINTER MONTHS.  THIS FLIGHT WAS ASSOCIATED WITH A HUNT/GUIDE OPERATION.  NO PASSENGERS WERE ON BOARD.

## Factual narrative

On August 31, 1994, at 1210 Alaska daylight time, a wheel equipped Cessna 170B airplane, N4457B, registered to and operated by the Pilot, a registered hunting guide, experienced a collapsed main landing gear during landing on an airstrip on the Upper Coleen River, located 100 nautical miles west of Arctic Village, Alaska.  The business flight, operating under 14 CFR Part 91, departed a field site in connection with a guided hunting trip.  The destination was the accident site.  No flight plan was filed and visual meteorological conditions prevailed.  The pilot, the sole occupant, was not injured and the airplane was substantially damaged.

According to the pilot, the left main gear leg broke through the wheel axle upper mounting hole.  Although the airplane was on wheels at the time of the accident, the airplane has been used on skis extensively during the winter months.

Visual examination of the landing gear leg showed a small area of striations.  The striations point to a spot near the center of the upper axle mounting bolt, on the inside of the gear leg.

According to the pilot, the landing gear leg had more than 1500 hours of total time.

## Aircraft

- Registration: [N4457B](https://openairdocs.org/aircraft/N4457B), registered now, S/N 26801, built 1956 (OpenAirDocs)
- Reported make and model: CESSNA 170B
- Registry model: [Cessna 170B](https://openairdocs.org/model/cessna-170b) (registry code 2072306) (OpenAirDocs)
- Registry engine: [Lycoming 0-360-A1D](https://openairdocs.org/engine/lycoming-0-360-a1d) (registry code 41504, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 26801
- Airframe hours: 5881
- Engines: LYCOMING O-360-A1A 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Business, Part 91
- Registered owner: Jamieson, David Y.
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, December 21, 1993, 184 hours before
- Departed: FIELD SITE, AK
- Airport: Upper Coleen River

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 50; private; airplane ratings: single-engine land, single-engine sea; medical: class 3, valid medical--no waivers/lim.; seat: left; flight hours: 4,900 total, 3,000 in this make and model, 4,840 as pilot in command, 100 in the last 90 days, 60 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 30 statute miles
- Lowest ceiling: none
- Temperature: 55 °F
- Altimeter: 30.00 inHg

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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