FMC Stepped Climb - B 737-800

[fireflybob]

You are cruising and considering a stepped climb to a higher level so enter this on the CRZ page which then shows a fuel saving (say) of 200 kg. Does the step take into account (extra) fuel burned in the climb to the new level?

Thanks for any help - would appreciate a reference if possible.

[BOAC]

Not a lot of help, but gut feeling is yes, no reference other than comparing my en-route climb/cruise fuel burn tables with the result of the FMC. Certainly if you input a step with less than the 'rule-of-thumb' 1 hour to go it generally shows a deficit.

[Old Smokey]

BOAC's gut feeling is correct, it does but there is a caveat (as always).

If you enter the "new" level into the FMC without executing it, it shows the Time and Fuel situation as though you were already at the new level. If you insert the appropriate step (2000, ICAO etc.) the FMC then "assumes" that you will step to the new level when it recommends to do so, and considers the incremental Climb and Descent factors for the new level.

Regards,

Old Smokey

[HiFli]

Wind at the higher level is not taken into account. Insert the desired higher level in the CRZ ALT on the INIT page and execute. Leave the ALTSEL on your present level. Upload the wind;it "thinks" you are at the new level. Do the simle arithmetic to see whether you gain by climbing. If so, reset ALTSEL and climb. Works everytime.

[HiFli]

Apologies, should have typed CRZ page, not INIT page.

[BOAC]

HF - I suspect we all know how to do it - the question was are the FMC figures reliable?