What happened
On a night approach to Runway 16 at St. John's Airport, Newfoundland, under instrument meteorological conditions, an Inter-Canadien Fokker F2/8 Mk 1000C experienced a runway excursion. The aircraft, registration not provided, was performing a localizer approach to a runway featuring a displaced threshold and a wet surface. During the descent, the aircraft's autopilot disconnected, requiring the captain to hand-fly the approach. The aircraft crossed the threshold with a higher-than-intended profile and touched down approximately 1200 feet past the displaced threshold.
Upon touchdown, the crew attempted to use both normal and alternate braking systems, but the aircraft failed to decelerate effectively. As the aircraft continued down the runway, the heading began to oscillate. The aircraft eventually exited the runway end, 420 feet beyond the pavement. During the overrun, the nose gear collapsed after striking debris, causing the aircraft to skid on its nose. The incident resulted in 5 passengers and 2 crew members sustaining minor injuries.
The investigation
The TSB examined the aircraft's mechanical state, specifically focusing on the braking and lift dumping systems. Investigators found that the lift dumpers had been intentionally disabled in accordance with the minimum equipment list due to a previously reported malfunction. The investigation also reviewed the flight data recorder and radar to reconstruct the flight profile, noting a high descent rate and an approach profile that exceeded desired parameters.
Testing of the braking components revealed that while no single failure caused a total loss of braking, an anomalous voltage was being supplied to the right-hand inboard wheel antiskid control valve, which reduced braking effectiveness to that specific wheel by 30%. Additionally, investigators looked into the effectiveness of the evacuation and the communication between the cockpit and cabin crew.