ASN Wikibase Occurrence # 314437
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Date: | Saturday 3 December 2011 |
Time: | 08:30 LT |
Type: | Beechcraft 1900D |
Owner/operator: | Great Lakes Aviation Ltd |
Registration: | N247GL |
MSN: | UE-247 |
Total airframe hrs: | 31828 hours |
Engine model: | P&W PT6A SER |
Fatalities: | Fatalities: 0 / Occupants: |
Aircraft damage: | Minor |
Category: | Serious incident |
Location: | Denver International Airport, -
United States of America
|
Phase: | Standing |
Nature: | Unknown |
Departure airport: | Montrose Regional Airport, CO (MTJ/KMTJ) |
Destination airport: | Denver International Airport, CO (DEN/KDEN) |
Investigating agency: | NTSB |
Confidence Rating: | Accident investigation report completed and information captured |
Narrative:During a post flight inspection the pilot discovered a hydraulic leak on the nose landing gear that was emanating from a crack in the nose landing gear end cap. The end cap was examined and found to have failed in fatigue that initiated from multiple origins at an internal diameter. The fatigue had propagated significantly into the wall thickness of the end cap and through the thickness at one location. The striation count revealed that the fatigue crack had initiated and been growing in the end cap for at least 14,898 cycles. The end cap had been inspected using an ultrasonic method recommended by the manufacturer 485 cycles prior to the incident. The crack was present at the time of the inspection which indicated that the inspection method was ineffective in detecting the crack. The timing of the end cap inspection was in compliance with the manufacturer's recommendation. Examination of the microstructure of the material revealed that the longitudinal grain direction was oriented parallel to the shuttle valve bore in the end cap. Resistance to fatigue can be improved by aligning the principle tension stresses in the end cap with the longitudinal grain direction. It is probable that the manufacturer had determined that the grain direction was a contributing factor to fatigue failure in the end cap and revised the end cap drawing to require a grain direction along the longitudinal axis of the end cap in February 2010. No engineering data to support the drawing revision was made available.
Probable Cause: A failure of the nose landing gear end cap due to fatigue. Contributing to the failure were the ineffective inspection and the unknown effect of grain direction on fatigue life.
Accident investigation:
|
| |
Investigating agency: | NTSB |
Report number: | ENG12IA013 |
Status: | Investigation completed |
Duration: | 1 year and 8 months |
Download report: | Final report |
|
Sources:
NTSB ENG12IA013
Location
Revision history:
Date/time | Contributor | Updates |
02-Jun-2023 17:22 |
ASN Update Bot |
Added |
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