# NTSB ANC90LA019: Maule M-5, N6220M, Becky Lake, AK, December 10, 1989

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: December 10, 1989, 14:00 local (18:00 UTC)
- Place: Becky Lake, AK
- Coordinates: 64.4692, -148.570251 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=64.4692&lon=-148.5703&mi=10
- Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report September 30, 1991
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 5329
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC90LA019
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5329/pdf
- Page: https://openairdocs.org/ntsb/ANC90LA019

## Probable cause

FATIGUE FAILURE OF THE SKI ATTACH FITTING DUE TO BEING FABRICATED LOCALLY FROM THE WRONG STEEL WHICH RESULTED IN THE AIRPLANE NOSING OVER.

## Sequence of events

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

- Airframe/component/system failure/malfunction, takeoff - roll/run
  - landing gear,ski assembly - unapproved part (cause)
  - maintenance,major alteration - improper, other maintenance personnel (cause)
  - landing gear,ski assembly - fatigue (cause)
- Loss of control - on ground/water, takeoff - roll/run
- Nose over, takeoff - roll/run

## Analysis

SKI FORWARD ATTACHED FITTING (MAULE P/N 9027B) FOR LEFT SKI SAFETY & RIGGING CABLES FAILED IN FATIGUE. DURING SKI INSTALLATION IN 1985, ONE OF THE FITTINGS WAS MISSING & HAD TO BE FABRICATED LOCALLY. TESTS INDICATED FITTING MADE FROM WRONG STEEL.

## Aircraft

- Registration: [N6220M](https://openairdocs.org/deregistered/N6220M-2004-03-09), registration cancelled 2004-03-09, S/N 7195C, built 1978 (OpenAirDocs)
- Reported make and model: MAULE M-5
- Registry model: [Maule M-5-235C](https://openairdocs.org/model/maule-m-5-235c) (registry code 5460135) (OpenAirDocs)
- Registry engine: [Lycoming 0-540 series](https://openairdocs.org/engine/lycoming-0-540-series) (registry code 41532, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 7195C
- Airframe hours: 1150
- Engines: LYCOMING O-540-J1A5D 235 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: William F. Spear
- Registered owner: William F Spear
- Last inspection: Annual, May 27, 1989, 59 hours before
- Destination: ENN, NENANA, AK
- Airport: NONE

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 50; private; airplane ratings: single-engine sea, single-engine land; medical: class 3, valid medical--no waivers/lim.; seat: left; flight hours: 4,000 total, 3,000 in this make and model, 25 in the last 90 days, 10 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 0° at 3 knots
- Visibility: 5 statute miles
- Lowest ceiling: 2,000 ft overcast
- Temperature: 19 °F, dew point -0 °F

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19891210050389A](https://openairdocs.org/incident/19891210050389A), Dec 10, 1989: Maule M5235C, Becky Lake, AK, Substantial damage. Forward attach fitting for left ski rigging broke on frozen lake takeoff. Non standard fitting used fatigue failed.

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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