Unfallbericht:The West Coast Air Twin Otter floatplane departed Vancouver-Coal Harbour around 15:10 for a scheduled 35-minute flight to Victoria Harbour. Soon after takeoff, at a height of 50-100 feet, the no. 2 engine failed. The aircraft struck the water about 25 seconds later in a nose-down, right wing-low attitude. The right-hand float and wing both detached from the fuselage at impact. The occupants managed to clamber onto the aircraft's pontoon and wing. Rescue boats, including a SeaBus passenger ferry, responded quickly to evacuate the passengers and crew from the plane.
|Datum:||01 NOV 2000|
|Zeit:||ca 15:10 PST|
|Flugzeugtyp:||de Havilland Canada DHC-6 Twin Otter 100|
|Fluggesellschaft:||West Coast Air|
|Baujahr:|| 1967-11-27 (32 years 12 months)|
|Triebwerk:|| 2 Pratt & Whitney Canada PT6A-20|
|Besatzung:||Todesopfer: 0 / Insassen: 2|
|Fluggäste:||Todesopfer: 0 / Insassen: 15|
|Gesamt:||Todesopfer: 0 / Insassen: 17 |
|Konsequenzen:|| Written off (damaged beyond repair)|
|Unfallort:||Vancouver-Coal Harbour, BC (Kanada)
|Flugphase:|| Anfangssteigflug (ICL)|
|Betriebsart:||Inländischer planmäßiger Passagierflug|
|Flug von:||Vancouver-Coal Harbour SPB, BC (CXH), Kanada|
|Flug nach:||Victoria Harbour, BC, Kanada|
FINDINGS AS TO CAUSES AND CONTRIBUTING FACTORS:
1. A planetary gear disintegrated in the propeller reduction gearbox of the No 2 engine and caused the engine drive shaft to disconnect from the propeller, resulting in a loss of propulsion from this engine.
2. The planetary gear oil strainer screen wires fractured by fatigue as a consequence of the installation at the last overhaul. This created an unsafe condition and it is most probable that the release of wire fragments and debris from this strainer screen subsequently initiated or contributed to distress of the planetary gear bearing sleeve and resulted in the disintegration of the planetary gear.
3. Although airspeed was above Vmc at the time of the power loss, the aircraft became progressively uncontrollable due to power on the remaining engine not being reduced to relieve the asymmetric thrust condition until impact was imminent.
Official accident investigation report
Since this accident, the operator has revised its pilot emergency training syllabus. The revised syllabus, approved by Transport Canada, places increased emphasis on aircraft handling and emergency procedures in response to loss of power at low altitude and low airspeed. The operator's revision goes beyond the minimum standards required by Transport Canada.
The operator has also revised its maintenance inspection program. The weekly airframe and engine inspection (A&E) now incorporates an electrical continuity test of the engine oil chip detector on the propeller reduction gearbox casing.
Pratt & Whitney Canada has confirmed that the Overhaul Manual applicable to the P&WC PT6-20 series engine RGB was revised in 1998 to clarify the installation procedure of the planetary gear oil strainer screens.