Air India Ahmedabad crash: Veteran NTSB investigator on what the video footage reveals, focus of the probe

Few people in the world know what to look for in the chaotic seconds after a plane lifts off and something goes terribly wrong. Greg Feith (67) is among them. A former senior air safety investigator with the US National Transportation Safety Board (NTSB), Feith has spent decades examining complex air crashes — including those that, like the Air India Express tragedy near Ahmedabad on Thursday, unfolded in the brief but critical moments after takeoff.

From the fiery plunge of ValuJet Flight 592 into the Florida Everglades in 1996, which killed all 110 people on board, to the mysterious crash of SilkAir Flight 185 over Sumatra in 1997 that claimed 104 lives, and the midair fire that brought down Swissair Flight 111 near Halifax in 1998, he has investigated some of the most devastating air accidents.

From your expert perspective, what is your initial impression of the air crash given that it occurred shortly after takeoff and below 1,000 feet?

One of the first questions, when looking at the video, is whether the airplane was properly configured for takeoff. During takeoff —when the aircraft is heavy, low, and slow—it needs extra lift, which is achieved by deploying the trailing-edge flaps (flaps are adjustable, hinge-like surfaces on the trailing edge of the wing that can be lowered to change wing shape in order to increase wing area and curvature, allowing the aircraft to operate efficiently at lower speeds during takeoff and landing). If the correct flap setting wasn’t used, the wings may not have produced enough lift to support the aircraft’s weight at low speed. This can lead to what we call getting on the “backside of the power curve” (an aviation expression for when an aircraft is flying so slowly that more power is required to maintain altitude than to maintain speed). So even with fully functioning engines, the aircraft can “mush” or settle into the ground if the wings aren’t properly shaped to generate sufficient lift. The thing that’s curious about the video is that the flaps appear to be up or at a minimal setting that wouldn’t be typical of a normal takeoff.