In article ,
"Morgans" wrote:

"Frank Ch. Eigler" wrote

But imagine the mass of smoke agent that would have to be dispensed in
order for it to be visible 5-10 miles behind the jet. There would be
a terrific amount of dilution through the air, moving at that kind of
speed.

Not to disagree with the fact that putting smoke systems on heavies would be
a bad idea, but I do wonder about how much smoke would have to be used.

I remember a few years ago at OSH, there was an older jet trainer (don't
remember which type) that had smoke generators carefully place on the
wingtips. The trail was tight, and spun fiercely for a very long time. ( 2
or more minutes?) I was fascinated.

That's actually what keeps the plane in the air.

See http://www.av8n.com/how/htm/airfoils...ation-vortices

rg