Strange phenomena

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Tracker
Posts: 1
Joined: 08 Feb 2014, 21:49

Strange phenomena

Post by Tracker »

Good evening,

It is expertise that I hope to find here about two phenomena that I cannot explain up till now.

First the faint fifth contrail in two pictures.
It is either the APU, which should not be used at altitude, a cabin pressure outflow valve which is unlikely, too much cabin pressure loss..., or possible toilet waste vapour in stead of 'blue ice'.

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Secondly an observation in may 2009, by my daughter in Itegem, village center, looking East.

The snake like contrail is a mystery to me.
It is narrow, single engine jet?
Itegem, indicated by the red arrow, is a few miles West of Bruno VOR, see the included radio nav chart.
Foto 3 is a colour enhanced picture.
Foto 5 shows a contrail hit by a jetstream, feathery result.

All I can think of is a corkscrewing overly active jet-bojo, heading for Kleine Brogel...

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Wondering...

Tracker.

Flanker2
Posts: 1741
Joined: 05 Dec 2012, 23:15

Re: Strange phenomena

Post by Flanker2 »

First the faint fifth contrail in two pictures.
It is either the APU, which should not be used at altitude, a cabin pressure outflow valve which is unlikely, too much cabin pressure loss..., or possible toilet waste vapour in stead of 'blue ice'.
I suspect the RAM air outlet from the packs.
I don't know the exact configuration of the AC packs on the Jumbo, but as in most AC packs, ram air cools down and moisture is extracted from the bleed air, and jettisoned through a RAM outlet. The hot and moist air condensates in the cold ambient air.
Grey water can't be jettisoned in sufficient quantity to cause such a visible effect and such a leak from the toilet valves would have been too visible to miss during the turn-around.

It can also be the APU, sometimes an aircraft is dispatched with APU on and it's maintained in-flight.


The snake pattern is the effect of different wind speeds al altitude. It's a single contrail but it could be either a single engine jet or a small twin. A small twin's contrails tend to merge.

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