Runway excursion Accident Beechcraft F33A N873BC,
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ASN Wikibase Occurrence # 278925
 
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Date:Saturday 20 July 2019
Time:16:20 LT
Type:Silhouette image of generic BE33 model; specific model in this crash may look slightly different    
Beechcraft F33A
Owner/operator:Private
Registration: N873BC
MSN: CE-1227
Year of manufacture:1988
Total airframe hrs:1634 hours
Engine model:Continental IO-520-BB37B
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: Substantial
Category:Accident
Location:Battleground, Washington -   United States of America
Phase: Landing
Nature:Private
Departure airport:Port Townsend, WA (0S9)
Destination airport:Battleground, WA (WA87)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot selected the most favorable runway and flew his approach to land at his home airport. The airplane touched down normally near the runway threshold at the pilot's normal landing speed. Based on landing distance calculations, he should have been able to stop the airplane before the end of the runway. However, it was not until the airplane was about midfield that the pilot realized the airplane was not decelerating. At this point, the pilot attempted to reduce power further by twisting the knob of the throttle control counterclockwise, but the engine power did not decrease. As the airplane rapidly approached the end of the runway, the pilot used the mixture control to shut down the engine, but the airplane overran the runway end and the left wing impacted a pole, which resulted in substantial damage.
Postaccident examination of the airplane revealed no anomalies with the engine and most of the engine controls except for the throttle control. During engine runs, the throttle knob push button became intermittently stuck in a depressed position. Normally, turning the throttle knob counterclockwise from this position would reduce power; however, during the postaccident engine runs, a corresponding minor increase in power was observed. Although disassembly of the throttle mechanism revealed a loose nut in the throttle control assembly, it likely did not contribute to the throttle failure, as the nut would not have affected the knob's use to make power adjustments. Further, the throttle control could still be manipulated by rotating the throttle knob during the postaccident engine run.
Based on the pilot's practices, it is likely that the pushbutton became partially depressed when the pilot reduced the engine power to descend while inbound to his home airport. When the pilot realized the airplane had not decelerated and attempted to make a minor power adjustment by rotating the throttle knob counterclockwise, the throttle control failed, and the pilot either experienced sustained or a subtle increase in engine power, which resulted in a runway overrun and impact with an obstacle. The reason for the failure of the throttle control assembly could not be determined based on available evidence.

Probable Cause: A failure of the throttle control assembly for reasons that could not be determined based on available evidence, which resulted in a runway overrun and impact with an obstacle.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: WPR19LA200
Status: Investigation completed
Duration: 2 years and 10 months
Download report: Final report

Sources:

NTSB WPR19LA200

Location

Revision history:

Date/timeContributorUpdates
05-Jun-2022 12:28 ASN Update Bot Added

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