Everything was normal as the Lockheed L-1011 Tristar slid down final at Dallas Fort Worth airport. But in aviation things can change quickly, and for Delta 191, they did … and catastrophically. The aircraft hit the ground one mile short of the runway striking a car and two water tanks as it disintegrated, killing 138 people including the crew and five cabin attendants.
The captain was a meticulous pilot with a history of making good weather decisions. The first officer had been assessed as “above average”. It is still bewildering today why they elected to fly through a thunderstorm.
Delta 191 was hit by a savage microburst that it didn’t have the power to out-climb, slamming the Tristar into the ground like it was a balsa wood toy.
If wind shear can do that to a professional crew in a heavy jet, what can it do to a PPL in a Cessna or an RPC in an LSA? And it doesn’t have to be a microburst; wind shear manifests itself in many forms, each one a challenge that can ruin the day for an unprepared pilot.
The good news is that wind shear is often predictable, detectable and avoidable, providing you’re not unprepared.
Shear dynamics
Wind shear has a nebulous definition. Technically, it’s a change in wind speed or direction. But aviators know that’s situation normal on most flights, so when does a change become a shear?
“In the Bureau of Meteorology, we most often use 15 knots.
