Tin67
Topic Author
Posts: 267
Joined: Mon May 10, 2004 3:49 am

Question About Overflying 747 Trails

Mon Nov 15, 2004 5:18 am

I was at this afternoon and took this shot of a 747 overflying. I was intrigued to the 5 trails.

Any idea what the centre trail from the fuselage is?

http://www.airliners.net/addphotos/big/ready/KA6S1754_LHR_AF_OVER.jpg



Regards
Martin

[Edited 2004-11-14 21:19:42]
 
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TupolevTu154
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RE: Question About Overflying 747 Trails

Mon Nov 15, 2004 5:22 am

I heard once that the aircraft occasionally dumps some water, there is a pic of a JAL 744 with a fifth trail, AH here it is!


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Photo © Bailey - AirTeamImages



Or it could be the APU?

Tom
 
Airplanepics
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RE: Question About Overflying 747 Trails

Mon Nov 15, 2004 5:24 am

Most probably the APU.


Simon
Simon - London-Aviation.com
 
Tin67
Topic Author
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RE: Question About Overflying 747 Trails

Mon Nov 15, 2004 5:29 am

I though the APU when I saw it, but it seems to be coming from under the fuselage rather that the APU exhaust.

I see the text on Bailey's photo posted above by Tom that suggests the sink drains from the toilets. Interesting.

Cheers
Martin
 
javibi
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RE: Question About Overflying 747 Trails

Mon Nov 15, 2004 5:56 am

As Bailey states, the fifth contrail is produced by water from the toilets and galleys sinks, which is thrown directly overboard via several drain masts.

The APU won't be running at cruise level, unless you have a serious problem.

Regards

j
 
Erwin972
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RE: Question About Overflying 747 Trails

Mon Nov 15, 2004 6:41 am


To add to that: the drains under the belly are also heated to prevent icing. APU isn't running at cruise.


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Photo © Erwin




Kind regards,
Erwin
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