737NG and Smiths FMC Climb Calculations
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737NG and Smiths FMC Climb Calculations
Pehaps some of you engineer types could help with this -
I have noticed some interesting anomalies when entering various climb speed schedules in the FMC - this on 737 600 and 700s flying Cost index 13-17.
as an example:
Econ Climb gives speed of 274 Kt/.77 - time at TOC of 1948.3Z -distance to top of climb 105nm.
Max rate gives speed of 256/.77 time at TOC of 1948.5Z distance to TOC 99nm
Climb speed of 320/.77 gives time at TOC 1948.5Z - distance to TOC of 112nm.
My question - why do max rate and high speed climb take the same amount of time to TOC. Would it not make sense to climb at high speed ie gaining an extra 7 miles down range for 12 seconds more at climb thrust? Or is this an FMC error? Or am I missing something blindingly obvious
I have noticed some interesting anomalies when entering various climb speed schedules in the FMC - this on 737 600 and 700s flying Cost index 13-17.
as an example:
Econ Climb gives speed of 274 Kt/.77 - time at TOC of 1948.3Z -distance to top of climb 105nm.
Max rate gives speed of 256/.77 time at TOC of 1948.5Z distance to TOC 99nm
Climb speed of 320/.77 gives time at TOC 1948.5Z - distance to TOC of 112nm.
My question - why do max rate and high speed climb take the same amount of time to TOC. Would it not make sense to climb at high speed ie gaining an extra 7 miles down range for 12 seconds more at climb thrust? Or is this an FMC error? Or am I missing something blindingly obvious
Join Date: Jul 2000
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[guess mode]A 320kt climb will spend much more time at lower altitude, so whilst the climb is only slightly longer, you will spend much more time with a higher fuel burn at a lower altitude. Hence your actual fuel burn will be higher[/guess mode off]
