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Old 20th Mar 2007, 15:15
  #5 (permalink)  
Plumb Bob
 
Join Date: Jan 2007
Location: Netherlands
Age: 74
Posts: 37
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Hi xfeed,

What you feel while being overtaken by a lorry really is its “bow wave”.
Finely streamlined airplanes generate only a small bow wave, which is not nearly as noticeable as their wake. The wake is a consequence of the wing sucking down (and pushing down) the air that it slices through.

The wake of a 757 indeed is quite (in)famous.
However, like I said in my previous post, that applies to the airplane shortly before a normal landing, in slow flight. Like a knife going through warm butter at an angle, curling it up. The wing really ‘plows’ through the air.

High-speed flight, on the other hand, is more like the knife going through the butter with the blade nearly parallel to the direction of movement. Not displacing much butter.

So: it may seem strange, but the strongest wake is generated by airplanes flying relatively slowly. The 757 into the Pentagon was going very fast. Airplanes are designed to be able to go fast without disturbing the air a lot. Therefore no wake-induced damage there.

IF lorries were normally driven on descending viaducts parallelling the final approach within feet of the wingtips of landing airliners, THEN such vehicles falling over would be an everyday occurrence, especially if the lorries could be driven at matching speeds.

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