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Accident description
Last updated: 12 December 2017
Status:Final
Date:Wednesday 19 December 1984
Time:11:08
Type:Silhouette image of generic DH3T model; specific model in this crash may look slightly different
de Havilland Canada DHC-3T Cox Turbine Otter
Operator:Cox Aircraft Corp.
Registration: N4247A
C/n / msn: 421
First flight: 1964
Total airframe hrs:7445
Engines: 1 Pratt & Whitney Canada PT6A-135
Crew:Fatalities: 0 / Occupants: 1
Passengers:Fatalities: 0 / Occupants: 2
Total:Fatalities: 0 / Occupants: 3
Airplane damage: Substantial
Airplane fate: Written off (damaged beyond repair)
Location:West Seattle, WA (   United States of America)
Phase: En route (ENR)
Nature:Test
Departure airport:Seattle-Boeing Field International Airport, WA (BFI/KBFI), United States of America
Destination airport:Seattle-Boeing Field International Airport, WA (BFI/KBFI), United States of America
Narrative:
The re-engined turboprop Otter was performing a test flight maneuvers when problems with the modified fuel system occurred. Ice blocking a fuel vent line caused a partial collapse of the main (engine feed) fuel cell which produced an erroneous fuel quantity reading. In addition, the main tank overflow shutoff valve was leaking, so tank overflow occurred. The fuel overflow caution light illuminated and auxiliary tank fuel pump feed to main automatically shut down. Due to miscalibration, this system overrode pilot attempts to restart aux fuel pumps. The pilot remained in test area troubleshooting rather than an immediate return to base. He finally noted main tank gauge continued to read 'full.' En route to Boeing Field, fuel starvation occurred. He attempted a forced landing in a small athletic field in a residential area rather than ditch in Puget Sound. The aircraft touched down, then bounced across an adjacent street. The arresting action of telephone wires on the vertical fin brought the aircraft to rest in a residential backyard.

Probable Cause:

PROBABLE CAUSE:
fuel system,vent..blocked(total)
fluid,fuel..starvation
CONTRIBUTING FACTORS:
precautionary landing..delayed..pilot in command
terrain condition..none suitable
fuel supply..misjudged..pilot in command
fuel system,tank..distorted
engine instruments,fuel quantity gage..false indication
fuel system,fuel shutoff..leak

Classification:

Forced landing outside airport

Sources:
» NTSB


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