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Unusual Con Trail

Old 18th Mar 2017, 00:24
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Unusual Con Trail

Just observed an unusual con trail which had regularly closely spaced mini cumulus like blobs developing below the main con trail stream.
Aircraft was likely a twin jet.
Am finding it hard to comprehend how the blobs could be triggered from steady state conditions at a rate of about 10 per second considering the aircraft's air speed. The only non steady state I can think of would be engines out of synch.
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Old 18th Mar 2017, 21:11
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Must have been the Aurora.
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Old 19th Mar 2017, 11:03
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Folks .. Milt is a VERY experienced pilot and TP. Ergo, his question should be taken a bit more seriously. I, for one, am interested in the answer ...
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Old 19th Mar 2017, 12:39
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Milt, pure speculation.
With the advent of modern aerodynamics and wing tip add-ons perhaps the effect is due to an unusual interaction between the wing and engine exhaust.
The effect would then depend on aircraft type / add-on.

I noticed another oddity recently with what appeared to be an A380. This type quickly forms two trails from the four engines, suggesting a wing effect. However, as a one off, two additional faint trails formed apparently below the two main trails, somewhat like an inverted rooster tail. From a distance the effect was similar to fighter aircraft tanking, but there was only one aircraft.

A consideration for both effects is a flight path at the boundary of sufficiently different air masses so that an aircraft wake could actually form cu cloud in your instance, or a stratus like trail in mine.

P.S. Yours?
https://www.google.co.uk/imgres?imgu...CwwLA..i&w=900

Mine were similar to this twin jet.
https://www.google.co.uk/imgres?imgu...AowCg..i&w=700

P.P.S also see https://cloudappreciationsociety.org/november-2016/

Note that all of the photos are associated with a cloud layer, may be relevant.

Last edited by safetypee; 19th Mar 2017 at 17:07. Reason: PPS
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Old 19th Mar 2017, 23:17
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TangoAlphad

Con trail was horizon to horizon with remarkable regularity.
Wish I had taken a photo.
Reminds me of the very rare sightings I have seen of the full circle of a rainbow.
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Old 19th Mar 2017, 23:28
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safetypee

Your first image clearly shows the unusual blobs I observed.
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Old 20th Mar 2017, 12:09
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Blobs mentioned here:

http://www.pprune.org/spectators-bal...don-today.html
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Old 20th Mar 2017, 21:51
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I've seen them before

More than once, in flight, but as to the cause, I cannot add further than some guesses: possible relative variations of humidity, temperature layers, direction of the aircraft, its resultant contrail in relation to dominant crosswind, or perhaps in an area of rather low winds, between changing vectors of wind direction.

Last edited by stator vane; 20th Mar 2017 at 21:51. Reason: addition
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Old 20th Mar 2017, 22:19
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Milt, still without explanation, I recall that there was extensive RAE research into wake turbulence which involved photos of contrails. I cannot locate any references; circa 1970s.
You might wish to contact Genghis who should have contacts in this area.

Alternatively, read up on chaos theory; interactions of vortex systems.
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