73NG FMC fix radius

[galdian]

Hi all

Just curious - and maybe common to all FMC's - the fix page will accept xxx/511 but will not accept xxx/512.
Any reason why 512nm is the magic cut off point??

Cheers.

[AviatoR21]

The Airbus A320 only accepts up to 256NM fixes as this is all the spare memory it has 256Kb. Lucky for you the Boeing has double - 512Kb. No, this is not a joke!

[Chesty Morgan]

512 bits (computery things) where 0 is the 1st and 511 being the 512th.

[fox niner]

If you write 511 in binary, it is 11111111. (8 digits) for 512, you write 100000000, which is 9 digits. The fmc is an 8-bits computer, which can not handle 9 digit binary numbers.
Apparently this is the case if you have a single fmc configuration in your 737. With a dual fmc, things might be different.
The 8 bits config was chosen because of cpu stability.