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Old 6th Mar 2004, 08:52
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Metrosexual
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B747-100 Question

On the -100 series, behind the hump there is what can be described as a 'crickle'on the top of the fuselage.

Can anyone explain what this is and what it is for?
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Old 6th Mar 2004, 09:17
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slamer
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I may have the wrong "Crickle", but years ago I remember my ground Instructor saying their is/was provision for an Astro-dome (OK tracker!)
just aft of the Overhead escape hatch (Not kidding!), stick your head out (Not in flight) and have a look rearward, (Not 744/743) you may see the round panel that allow's for this installation.
about the size of a basketball hoop, maybe a bit bigger!

Last edited by slamer; 7th Mar 2004 at 08:59.
 
Old 6th Mar 2004, 16:44
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If it is a largish fairing right where the hump meets the fuse then it was an antenna ( possibly early attempt at SATCOM )
The round hole is a sextant mount ( hard to REALLY convince yourself that you no longer needed a NAV ) which later became the smoke evac device.
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Old 7th Mar 2004, 03:26
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Metrosexual
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In the photo on this shortcut, I am refering to the bulge/crinkle on the top of the fuselage above the letters d & a.

http://www.airliners.net/open.file/522612/L/
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Old 7th Mar 2004, 07:19
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The small dome was originally for an "astrotracker". When Boeing first offered the military the 747 one of the requirements was not INS but an astrotracker. It was a navigation device that locked onto the stars and provided heading, drift information to the navigator. I know they were in the B-52, SR-71 and some F-4s.

No doubt the airlines passed on that and went with INS instead.
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Old 7th Mar 2004, 16:13
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That's the one Jet-A
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Old 8th Mar 2004, 05:25
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Thanks guys - been wondering about that for YEARS!
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