737 FMC Speed Limits
Bit of a strange one that neither of us could explain.
Having been asked to climb and cruise at .77 by ATC the FO selected .77 on the FMC Limits page (Progress Page 2 IIRC). However, as we climbed higher and the high speed yellow bar reduced to below .77 the aircraft decelerated and the climb speed indicated on the climb page also reduced, we ended up at about .755. However, again, selecting .77 on the climb page was possible and the aircraft then accelerated to .77.
I'm fairly new on type but the FO wasn't and couldn't explain why.
Couldn't find an explanation in the Tech manual, FCOM, or Ops manuals.
Any pointers or explanations about why it would reduce in the first place but then allow you to increase it again? I'm assuming that had we selected the speed on the climb page initially none of that would've happened.