Fatigue fracture in wing lift strut assembly led to fatal 2019 in-flight breakup of a floatplane in Manitoba
Winnipeg, Manitoba, 6 January 2021 — In its investigation report (A19C0138) released today, the Transportation Safety Board of Canada (TSB) found that a fatigue fracture in the right-hand wing lift strut assembly led to the 2019 in-flight breakup of a floatplane near Little Grand Rapids, Manitoba.
On 26 October 2019, a float-equipped de Havilland DHC-3 Otter aircraft, operated by Blue Water Aviation, departed Bissett Water Aerodrome, Manitoba on a flight to Little Grand Rapids, Manitoba, with the pilot, two passengers and approximately 800 pounds of freight on board. While on approach to land on Family Lake, the aircraft’s right-hand wing separated from the fuselage. The aircraft then entered a nose-down attitude and struck the water surface. The pilot and the two passengers were fatally injured and the aircraft was destroyed by impact forces.
The investigation found that a fatigue fracture had developed in one of the two upper right-hand wing lift strut attachment fittings. This fatigue fracture eventually led to an overstress failure of the other fitting during the left turn prior to the final approach, followed by the separation of the right wing strut from the wing. It was determined that the detailed visual inspections prescribed by existing maintenance manuals, and required by an Airworthiness Directive, did not identify cracks that could form in the wing lift strut attachment fittings.
Following the occurrence, Viking Air Ltd. issued an Alert Service Bulletin calling for operators to perform more detailed testing on DHC-3 wing lift strut attachment fittings and lug plates. As well, the TSB issued an Aviation Safety Advisory letter, requesting that Transport Canada work with Viking Air Ltd. to amend maintenance manuals or issue a new Airworthiness Directive to include the inspection requirements outlined in the Viking Air Ltd. Alert Service Bulletin. Transport Canada subsequently issued an Airworthiness Directive requiring enhanced inspections of DHC-3 wing lift strut assemblies.
See the investigation page for more information.
The TSB is an independent agency that investigates air, marine, pipeline, and rail transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.
For more information:
Transportation Safety Board of Canada
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