Odd and unusual sight today??

[JEM60]

Lying on sun lounger near Bury St. Edmunds at 13.10 BST today. Contrail of large aircraft heading west to east. Nothing unusual about that, but because of scarcity of activity for a few days, I had my powerful binoculars with me.
Before looking through them, I realised that the 'con-trail' was far out on the wings, only a matter of a few feet [apparently] from the wing tips. Looking through the bins, it was a 757 or an A330,767. I could plainly see both engines, and there was NO contrail from the engines at all, only from far out beyond the engines near the wing tips. The aircraft was in my estimate [been watching and flying on and off for many years] at about 20.000, flying perfectly normally, and I was looking up at about 40 degrees, so little in the way of parallax, and, as I said, my bins are very powerful, 20 times Zoom. The only time I have seen this before was on a 747 jettisoning fuel after a tail strike, and it was flying in circles to dump. This aircraft was flying on a constant heading towards the continent.
Any suggestions as to what was going on, for it was definately NOT engine exhaust. Intrigued, John.

[Glamdring]

Wing tip vapour trails due to high realtive humidity?

[TEEEJ]

The Chemtrail believers catch such activity on video.

You can see the vapour trails streaming from the wing tips of the E-3 Sentry.

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TJ

[JEM60]

Many thanks, guys. Just surprised I hadn't ever noticed it before in straight and level flight [except from flaps in high humidity of course

[Homesick-Angel]

I really wish i could remember more about the aerodynamic forces going on with this particular phenomenon (im far too lazy to walk over and get the book this late at night), but Im fairly sure that with all the air moving around the wing it tries to find a way to escape(to the lowest pressure) and this is often found on the outer edge of the wing which has less pressure than the middle portion of the wing.When you see a plane with winglets it is generally a design to hold in that lost pressure and keep more energy going into the lifting force as opposed to being lost.it is this escaping air moving out and up that creates vortices, and in the right conditions these become visible...I think:confused:..

When i am less asleep, i will attempt to give you a more "by the book" answer so all the people who really know please dont flog me until then!:}

[JEM60]

HOMESICK ANGE
Many thanks for your lucid explanation. Like you, if I'd thought about it more, then I would have come to the same conclusion, but,as my old flying instructor would say, my mind was in neutral and my thumb was in my b... No need to research on my behalf, because I'm sure that your explanation is correct. Better to sit down with a large single malt like me. Cheers.:):):)