PPRuNe Forums - Boeing FMS "step to" prediction

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Boeing FMS "step to" prediction

Does anyone know exactly which values are taken by the FMS into consideration when calculating a fuel burn prediction for a "step to" level? CDU shows some savings or penalty but does it account for this short climb phase that we need to go through before reaching a new level?

For example we are 50NM from TOD, maintaining FL340. We put a 360 into "step to" field. The calculation shows 0.3% saving. Does this mean we can expect a total of 0.3% save for the remainder of flight, including 2000ft climb, or is it just a calculation of WHAT WOULD HAVE BEEN SAVED if we had found ourselves at FL360 in this very moment?

Thanks

My tech manual says the following:

Quote:

Displays the predicted cost savings or penalty associated with flying the displayed speed/altitude step climb or descent profile, as compared to flying the current cruise speed schedule and maintaining present altitude to top of descent.

I think 'over 50NM' the answer will be academic, but could be useful over longer distances of say 500NM.
Would your climb not move the TOD point 6NM nearer you ? and the fuel you use to climb that 2000ft will be offset by the amount of fuel you save in the corresponding 2000ft descent.
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