What happened
A scheduled VFR flight departed Victoria Harbour at 17:18 local time, bound for the Vancouver Harbour water-aerodrome. The flight, operated by a commercial carrier, initially proceeded without incident, maintaining an altitude of 2,000 feet as it passed Active Pass to comply with Vancouver Control Zone procedures. As the aircraft transitioned out of the control zone, the crew began a gradual descent toward the destination.
Upon reaching the Third Beach reporting point, the pilot received landing clearance from the Harbour Tower. However, as the Twin Otter reached an altitude of approximately 175 feet above the water, witnesses reported hearing a loud noise originating from the aircraft. Following this sound, the aircraft C-FAIV experienced a sudden left yaw and roll, plunging into the harbour in a nose-down and left-wing-down attitude roughly 2,500 feet from the intended landing site. An Emergency Locator Transmitter signal was detected by air traffic control 54 seconds after the final radio transmission. The impact resulted in 11 fatalities (comprising both pilots and nine passengers) and 2 injuries. The aircraft was completely destroyed.
Findings
Investigations into the crash determined that the flight was proceeding normally until an unexpected noise preceded a total loss of control. At the moment of impact, the entire left flap system was found to be in the retracted position.
Technical analysis revealed that the inboard span-wise push-pull flap control rod suffered from severe stress corrosion, exhibiting at least three longitudinal cracks. This component eventually separated from its inboard fitting. The in-flight failure of the left-hand inboard flap control rod caused the immediate retraction of the left flap system, making the accident unavoidable for the crew. Additionally, it was noted that passengers had not received briefings regarding evacuation procedures.