Hello,
Can anyone explain in what situation you would use the "UPDATE ARM" selection on FMC POS REF Page 2? I'm guessing that it would be used in a situation where you were in an area with no GPS or Radio reception and wanted to update the position, for instance just prior to coast-in? Wouldn't the FMC automatically do this, though, as soon as radio or GPS reception was again available? Is it a defense against GPS spoofing?
Thanks in advance. I wasn't able to decipher the meaning of the selection from the FCOM.
