The decision to continue an unstable approach despite several indications of problems played a central role in the March 2016 accident involving a Mitsubishi MU-2B at Îles-de-la-Madeleine in Quebec, Canada's Transportation Safety Board (TSB) found. All seven occupants, including the two pilots, were killed.
According to the TSB, the problems started in cruise when the pilot modified his approach plan to begin the descent later, partially to save fuel. This led to higher-than-recommended approach speeds and altitudes for the published approach. Reported weather conditions at the airport included a broken cloud layer at 200 feet agl—lower than the published minimum descent altitude. The pilots never discussed this.
Soon after crossing a fix that called for a turn to intercept the runway centerline, the aircraft—flying 1,500 feet above the 3,000-foot recommended altitude and nearly 100 knots faster than the 140-knot approach speed—soon began "a meandering flight path," TSB wrote in its final report. "The pilot’s workload had increased significantly," and neither the approach nor before-landing checklists were done.
At about 1.5 nm from the airfield and flying at near stall speed to lose altitude, the pilot added full power. This led to an upset and rapid descent. "There was insufficient altitude to recover the aircraft," TSB wrote. The aircraft struck the ground 1.4 nm west of the airfield.
"At no time during the approach did the pilot discuss discontinuing the approach as an option available to reduce the workload," the TSB wrote. Its probe was aided by an onboard flight recorder, which was not required equipment.
Unstable approaches are one of three aviation-specific items on the TSB's Watchlist of key safety issues. Runway overruns and runway collision risks are the other two.