Accident Cessna 180J Skywagon 6 N420SB,
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ASN Wikibase Occurrence # 202105
 
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Date:Sunday 4 April 1999
Time:14:30 LT
Type:Silhouette image of generic C180 model; specific model in this crash may look slightly different    
Cessna 180J Skywagon 6
Owner/operator:Bobby Graham
Registration: N420SB
MSN: 18052313
Total airframe hrs:3990 hours
Engine model:Continental O-470-R
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: Substantial
Category:Accident
Location:Iliamna, AK -   United States of America
Phase: Landing
Nature:Private
Departure airport:, AK
Destination airport:Palmer, AK (PAQ)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
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.

Probable Cause: 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.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: ANC99LA042
Status: Investigation completed
Duration: 1 year and 2 months
Download report: Final report

Sources:

NTSB ANC99LA042

History of this aircraft

Other occurrences involving this aircraft
7 September 1985 N420SB Private 0 Egegik, AK sub
1 October 1988 N420SB Graham, Bobby 0 Wasilla, AK sub
11 November 1988 N420SB Private 0 Meshik Lake, AK sub
12 June 1991 N420SB Bobby Graham 0 Pilot Point, AK sub

Location

Revision history:

Date/timeContributorUpdates
26-Nov-2017 12:37 ASN Update Bot Added
08-Apr-2024 07:42 ASN Update Bot Updated [Time, Operator, Other fatalities, Departure airport, Source, Narrative, Category, Accident report]

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