Posts: 132
Joined: Thu Mar 18, 2004 3:28 pm

More Wake Vortex Questions...

Fri Sep 10, 2004 3:38 pm

What would be the effect of flying thru a wake vortex from the side, instead of from behind the aircraft that created it? I know it depends on the angle, but I'm assuming the flight path being at 90 degrees with respect to the aircraft creating the wake vortex...
Also, for the vortex to be strong, it would have to have been created little before another aircraft crosses it, so is it feasible for an aircraft to actually cross such a vortex?
And yet more... I've seen airplanes flying very close to the plane I was on, in the opposite direction during cruise (probable 1000 Ft separation). I understand that wake vortex generation is higher at higher angles of attack and slower speeds, but during cruise, is it a cause of concern?

I'll appreciate any answers, and please correct me if I'm wrong in any of the above statements...

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RE: More Wake Vortex Questions...

Fri Sep 10, 2004 4:47 pm

It’s not really a problem in cruise. As you stated, the vortices are weaker and the speeds of the aircraft are also higher, meaning any vortice encountered will have less impact (less time to act and more kinetic energy in the affected aircraft).

The same goes for the crossing of a vortex at a right angle. You’ll be in the vortex for such an immensely short time that it won’t really have time to do you much harm at all... unless you are in a really slow, small and light aircraft in which case you’d get a pitch disturbance.

The vortices linger longer than you’d think so the distances don’t have to be all that small.

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RE: More Wake Vortex Questions...

Sat Sep 11, 2004 12:22 am

Let's assume a take-off speed for a heavy of 150-160 knots, and a typical 2 minute separation used for take-off behind a heavy. Let's say the average speed of the heavy over these two minutes after take-off is about 250 knots. This means it is travelling approximately 4 miles/minute. Thus, it seems reasonable that typical in-flight separation could result in a plane passing through a wake perpendicularly, or at some angle. That said, FredT's reply seems right on the money, probably not a problem.

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