Accident Air Tractor AT-802A Fire Boss N397AS,
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ASN Wikibase Occurrence # 214431
 
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Date:Tuesday 14 August 2018
Time:15:00 LT
Type:Silhouette image of generic AT8T model; specific model in this crash may look slightly different    
Air Tractor AT-802A Fire Boss
Owner/operator:Air Spray USA, Inc.
Registration: N397AS
MSN: 802A-0563
Year of manufacture:2014
Total airframe hrs:559 hours
Engine model:PW Canada PT6A-67F
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Stevens County north of Northport, WA -   United States of America
Phase: Landing
Nature:Fire fighting
Departure airport:Deer Park Airport, WA (KDEW)
Destination airport:Northport, WA
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The accident airplane was one of three public aircraft that were supporting firefighting operations. The three airplanes had made four successful water drops and had just scooped water from a river to make a fifth drop. The airplanes were in a climb en route to the drop location when the pilot of the accident airplane heard a 'loud bang' followed by a total loss of engine power. The pilot made a forced landing to treetops in a heavily forested area.
During the on-site examination, a coat of oil was observed on the cowling and one of the wings. Damage was also observed to the engine. The engine examination revealed that a second-stage power turbine blade exhibited fatigue signatures, and molten debris was identified throughout the engine. The debris was subsequently identified as environmental particles, but the source of the debris was not determined from the available evidence for this investigation. The loss of engine power was likely due to the accumulation of foreign melted environmental debris on the engine's hot section components, which resulted in the first- and second-stage power turbine blades fracturing from tensile overload.

Probable Cause: A total loss of engine power during a climb due to an accumulation of molten environmental particles, the source of which could not be determined based on the available evidence, which resulted in a forced landing.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: WPR18LA222
Status: Investigation completed
Duration: 4 years 1 month
Download report: Final report

Sources:

NTSB WPR18LA222
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=397AS

Location

Revision history:

Date/timeContributorUpdates
15-Aug-2018 01:31 Geno Added
15-Aug-2018 03:31 Geno Updated [Narrative]
15-Aug-2018 03:36 Geno Updated [Source, Narrative]
16-Aug-2018 04:32 Geno Updated [Aircraft type, Registration, Cn, Operator, Phase, Source, Damage, Narrative]
26-Sep-2022 19:21 ASN Update Bot Updated [Time, Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Damage, Narrative, Category, Accident report]
26-Sep-2022 19:22 harro Updated [Operator, Nature, Source, Narrative]

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