"Michael Mcneil" wrote in message
news:9009dc8b5fe10d00759c8646af9396ec.45219@mygate .mailgate.org...
No, it's not about the mess a £4 like Spencer Hines is making on s.m.n.

Does anyone on here know the diameter of condensation trails of
aircraft?

How do they vary with size of plane, height, humidity and speed? If a
rough correspondence to the wing diameter could be given, that would be
enough for me to gauge it.


I am a retired airline pilot. I do have to say that I could never of course
see my own contrails. The nearest I got to seeing my own was as shadows on
the ground or on cloud below me. But I did plenty of contrails made by
other aircraft.



The trail is initially produced some distance (circa a few tens to a hundred
metres) behind the engines. It is the engines that provides the hygroscopic
nuclei on which the condensation can occur.



Then other factors come into play. All aircraft produces vortices from the
wing tips. These affect the contrail and result in the swirling pattern
that can often be seen when close. From the ground, this rotation is hard
to observe (try binoculars) so tends to show itself as a serrated pattern.



The next step depends on numerous factors. Often in very dry air, the trail
quickly dissipates - it appears as a very short trail, often looking like a
needle with an eye (the eye being the divided trail from the pair or the
four engines). But when conditions are just right, the injection of these
condensation nuclei can be the trigger for yet more condensation to occur
and the trail spreads laterally and becomes persistent. It can be many
times wider than the aircraft that initially produced it and can last for a
very long time.



We casually talk about condensation trails. In fact trails are made of ice
crystals. When flying at altitude, persistent trails acts like any other
cirrus being ice cloud and can cause sun dogs (parhelia). Sun dogs are seen
very frequently when flying.



Jack