American Airlines flight 587, which crashed while departing JFK on November 12 killing all on board, was likely brought down by wake turbulence. A JAL 747 cleared for takeoff about two minutes and 20 seconds before the American Airlines flight actually took off one minute and 45 seconds ahead of AA587, with the prescribed 4 NM separation. AA587 turned left inside the 747's departure path so that the two flew closer and closer together -- as close as 90 seconds apart. Upon crossing the 747 wake, AA587 received two jolts, followed by structural failure starting with departure of the vertical stabilizer. The passage of a heavy through the air results in a pair of horizontal, contra-rotating tornadoes, a roil of atmosphere too severe for safe passage by any craft. Because pilots of light craft tend to stay away from airspace occupied by heavies, during ordinary operations the possibility of wake turbulence may seem quite remote. But when that Galaxy flies past a few thousand feet AGL, you know it's shoving a helluva lot of air about. If you're aloft in a light machine, you expect a bit of buffeting, just like the canoeist feeling the wake of a passing riverboat. Unlike the canoeist, the aviator cannot see the approaching wake, and the chief hazard is being taken by surprise. Wake turbulence is not always invisible. Have a look at the smoke in the pictures below.
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