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White dashed line

Old 1st Jan 2017, 16:41
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White dashed line

On the map screen of a Boeing (at least the 757), there is a white dashed runway centerline going through the Departure and Destination airport respectively. This line is, according to Mr. Boeing, 14.2 NM long (to either side).

Why an odd number like 14.2 NM?
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Old 16th Oct 2018, 12:42
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I think its something to do with glideslope. Been looking for the answers everywhere but no luck so far...
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Old 27th Oct 2018, 02:35
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Maybe the number of dashes the software engineer went for gave that number of random miles 🤔
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Old 30th Oct 2018, 01:37
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An excerpt from a manual I trust regarding some FMC logic.

"Max is 511nm. (511.9 divided by 2 equals 256. Computer architecture)"

256 divided by 18 equals 14.2.

Can any computer folks comment on the significance of 18 in computer architecture?
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Old 10th Nov 2018, 17:46
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What Max is 511nm 🤔
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Old 10th Nov 2018, 18:07
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Range rings.
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Old 10th Nov 2018, 22:35
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From B787 FCOM

Range Selector​ (Outer)​
Selects the desired ND nautical mile range scale:​
•​ increment/decrement knob​
•​ rotating clockwise/counter-clockwise increases/decreases ND range​ ​
respectively​
•​ between 0.5nm to 1280nm

Havent found a 511 nm range
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Old 10th Nov 2018, 22:48
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744 or 757/767 Fix page.
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Old 11th Nov 2018, 16:00
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Originally Posted by victorpapa
From B787 FCOM

Range Selector​ (Outer)​
Selects the desired ND nautical mile range scale:​
•​ increment/decrement knob​
•​ rotating clockwise/counter-clockwise increases/decreases ND range​ ​
respectively​
•​ between 0.5nm to 1280nm

Havent found a 511 nm range
As extreme p has hinted at It’s the max value radius you can enter for range rings around any fixes in the FMC fix pages...it’s the same on the T7 so looks like it’s standard Boeing “thing”

no idea about the reason for the max runwa6 extension length.
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Old 11th Nov 2018, 16:31
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Wiggy

B777 FCOM Fix Info Page 11.42.34
distance (up to 9999nm) only entries must start with a slash (/
B787 FCOM Fix Info Page 11.42.39
distance only entries (up to 5400 nm) must start with a slash (/
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Old 11th Nov 2018, 18:10
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I regularly use 800nm rings on the 787
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Old 11th Nov 2018, 22:00
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511 is the max in the 737. It’s to do with bits or bites or whatever you computery lot call them. Zero counts as one and 511 others - 512 bites.
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Old 12th Nov 2018, 07:07
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Originally Posted by victorpapa
B777 FCOM Fix Info Page 11.42.34

"distance (up to 9999nm) only entries must start with a slash (/ "


Sounds odd but maybe you have different software.

On our T7's at least the maximum radius circle you can “draw” on the ND around a fix using the FMC fix page is 511miles (at least on the software we have, last tested a couple of days ago )....

Let me check what our current FCOM says, it certainly used to specify the max of 511, funnily enough...
....
Just checked up to date FCOM and at that reference we still have "..distance (up to 511nm) only entries must start with a slash (/..........."

Last edited by wiggy; 12th Nov 2018 at 07:23.
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