# NTSB SEA85FA034: de Havilland DHC-3 Turbo, N4247A, West Seattle, WA, December 19, 1984

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: December 19, 1984, 11:08 local (19:08 UTC)
- Place: West Seattle, WA
- Coordinates: 47.569309, -122.399299 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=47.5693&lon=-122.3993&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious, 2 minor
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 40024
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA85FA034
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/40024/pdf
- Page: https://openairdocs.org/ntsb/SEA85FA034

## Analysis

ACFT WAS PERFORMING TEST FLT 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 ERROUNEOUS 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 PLT ATTEMPTS TO RESTART AUX FUEL PUMPS. PLT REMAINED IN TEST AREA TROUBLESHOOTING RATHER THAN IMMEDIATE RETURN TO BASE, FINALLY NOTED MAIN TANK GAGE CONTINUING TO READ 'FULL.' EN ROUTE TO BOEING FIELD, FUEL STARVATION OCCURRED. PLTOPTED TO ATTEMPT FORCED LNDG IN SMALL ATHLETIC FIELD IN RESIDENTIAL AREA RATHER THAN DITCH IN PUGET SOUND. THE ACFT TOUCHED DOWN IN INTENDED LNDG AREA, THEN BOUNCED ACROSS AN ADJACENT STREET. THE ARRESTING ACTION OF TELEPHONE WIRES ON THE VERTICAL FIN BROUGHT THE ACFT TO REST IN A RESIDENTIAL BACKYARD.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, maneuvering
  - fuel system,vent - blocked(total) (cause)
  - fuel system,tank - distorted (contributing factor)
  - engine instruments,fuel quantity gage - false indication (contributing factor)
  - fuel system,fuel shutoff - leak (contributing factor)
- Airframe/component/system failure/malfunction, maneuvering
  - fuel system,pump - switched off
  - remedial action - not possible
- Loss of engine power(total) - nonmechanical, cruise
  - precautionary landing - delayed, pilot in command (contributing factor)
  - fuel supply - misjudged, pilot in command (contributing factor)
  - fluid,fuel - starvation (cause)
- Forced landing, descent - emergency
- In flight collision with terrain/water, landing
  - terrain condition - none suitable (contributing factor)

## Aircraft

- Registration: [N4247A](https://openairdocs.org/deregistered/N4247A-2015-05-15), registration cancelled 2015-05-15, S/N 421, built 1964 (OpenAirDocs)
- Reported make and model: de Havilland DHC-3 TURBO (DHC-3 TURB)
- Registry model: [Dehavilland DHC-3](https://openairdocs.org/model/dehavilland-dhc-3) (registry code 2800202) (OpenAirDocs)
- Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs)
- Category: Airplane
- Serial number: 421
- Airframe hours: 7445
- Engines: P&W PT-6A-135 787 horsepower turbo prop
- Damage: Substantial damage
- Flight: Part 91
- Registered owner: Cox Aircraft Corporation
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: 100 hour, November 21, 1984, 11 hours before
- Departed: BFI, SEATTLE, WA
- Airport: Boeing Field

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 61; airline transport, flight instructor, commercial; airplane ratings: multi-engine sea, single-engine sea, multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 8,500 total, 15 in this make and model, 7,500 as pilot in command, 15 in the last 90 days, 15 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 30° at 3 knots
- Visibility: 60 statute miles
- Lowest ceiling: 10,000 ft broken
- Temperature: 25 °F, dew point 18 °F
- Altimeter: 30.00 inHg
- Observed at: BFI, 5 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19841219014769A](https://openairdocs.org/incident/19841219014769A), Dec 19, 1984: Dhav DHC3, West Seattle, WA, Substantial damage. Header tank bladder loose, jammed float to full position, shut off valve leaked. Collection tank out vent plugged.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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