ANC99LA042 · Cessna 180
Cessna 180 · Accident: gear collapsed during landing
From AK to Warren "Bud" Woods Palmer Municipal Airport (PAQ)
Event
- NTSB case
- ANC99LA042
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Cessna 180
- Aircraft type
- Cessna 180
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N420SB
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From AKTo Warren "Bud" Woods Palmer Municipal Airport (PAQ), Palmer, AK
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Landing · landing roll
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Gear collapsed
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Landing gear, main gear attachment › Collapsed
- Miscellaneous, bolt/nut/fastener/clamp/spring › Failure, total
- Other maintenance personnel › Maintenance, installation, improper
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB 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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC99LA042
- Event ID
- 20001205X00401
- Case number
- ANC99LA042
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 332f066ccea56a43feabba3ae308535b3108ad0bdc4779790e5a5537bdfcbc78; retrieved 2026-09-22T15:33:25.930Z.