I wouldn't have thought that it would be vortices, Jim, not at cruise speeds;I
should have said that contrails always came from the engines.
The other sort of "trail" is merely condensation because of the reduced
pressure in vortices – traditionally from the wingtips at high angles of
attack, but increasingly from further inboard as wings and fuselages become
more aerodynamically efficient
Your photo shows 2 contrails, it's just that one is distorted, making it look
like a total of 3.
Chris
On 30 Dec 13, at 20:41, Jim Nichols <jhnichols@xxxxxxxxxxxxx> wrote:
> Things get complicated, Bill. Yes, contrails can be formed as a result
> of moisture content in the engine exhaust. But they can also be formed
> by the pressure and temperature gradients in tip vortices. This can be
> affected by the presence or absence of "winglets". And the tail
> surfaces can also shed vortices.
>
> I would not count trailing condensation lines and equate that to the
> number of engines. From the sun's reflection off the large nacelles, I
> would associate the shape with that of a large twin-jet.
--
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