User needs help understanding Step Climb

[Mike Ionas 5]

During a flight from KJFK to KLAS with FP: RBV J230 SAAME J6 HVQ PXV VIH ICT PUB DVC GRNPA1 the initial FL was F360. I departed at 1415Z and after reaching cruise level i entered a step climb to F380. It was calculated that the s/c point was approx 1000nm away at 1737Z in the CRZ page and then I changed to the PROG page where the value was also displayed correctly.However, when after a few minutes i selected the CRZ page again the STEP POINT was initially blankand then changed towhile when selecting the PROG page it was showingSelecting the same sequence at a later stage during the flight:The value of the distance to the s/c continue to decrease (negative value) with every new calculation:Finally upon reaching the s/c point the values changed to normal:and after the step climb the t/d point calculation was displayed:This is the NGX with SP1 and 736/7 expansion installed. The installation was clean after removing all old versions.Any ideas?

[Leffe 4]

What I see in CDU is that your max was 367 according to your load.So then you can´t pass the Max value before decending in that flightplan with that load!/ Leffe

[Mike Ionas 5]

Obviously the point of a step climb is to do it when you have burned enough fuel to be able for a higher FL, isn't it?

[Leffe 4]

Obviously the point of a step climb is to do it when you have burned enough fuel to be able for a higher FL, isn't it?

Yes if you can manage to burn that fuel before TOD otherwise not.You are properbly to close to TOD before the fuelburn have gone down enough for a step climbEDIT: The FMC won´t lie, it has your flightplan./ Leffe

[willywonka 36]

I had the same problem with STEP POINT at -10000000nm away. Attempting the change the CRZ ALT or STEP altitude in the FMC crashes the plane.On another flight, the step point was at 2nm, and never actually reaches NOW. The SP1 is a great improvement to the step function since the release, but looks like there are still a few bugs left.

[Mike Ionas 5]

Yes if you can manage to burn that fuel before TOD otherwise not.You are properbly to close to TOD before the fuelburn have gone down enough for a step climbEDIT: The FMC won´t lie, it has your flightplan./ Leffe

This was a 2018nm flight, i.e. aprox 5h:30m. The departure was at 1415Z with the s/c point calculated at 1738Z and the ToD calculated at 1921Z. Therefore there was more than enough time to burn fuel and have an optimal FL of F371 with a max F386 as you can see in the 8th picture after 3 hours in flight (the FMC won't lie, correct? ).

[Leffe 4]

This was a 2018nm flight, i.e. aprox 5h:30m. The departure was at 1415Z with the s/c point calculated at 1738Z and the ToD calculated at 1921Z. Therefore there was more than enough time to burn fuel and have an optimal FL of F371 with a max F386 as you can see in the 8th picture after 3 hours in flight (the FMC won't lie, correct? ).

Ohhps, didn´t looked at that pics. SORRY my bad.Then it´s peculiar you couldn´t make that step. But you could do it manually./ Leffe BTW shouldn´t you put FL020 or 2000 in STEP....because you wanna step from FL360 to FL380 / Leffe

[Mike Ionas 5]

I did it manually as you can see in the final picture.I was under the impression that in the step field we input the FL to which we want to climb, not the difference between the current FL and the next FL. Is that wrong? Additionally the s/c was calculated correctly in the begining (unfortunately no screenshot) however when i visited the CRZ page for a second time the peculiar values you see appeared..

[emvaos 13]

The STEP calculation does not work with simplistic optimal altitude vs weight calculation (only) but mainly with fuel saving. That includes speed scheme, wind and ISA to begin with. The FMC recalculates an entire "test" RTE in parallel to the actual route and compares fuel at arrival. In your pictures the ACTUAL WIND values between STEP inquiries change considerably. Perhaps so does ISA DEV. Different input, different output. It is a solver not a table interpolation method.In case of a MOD RTE or STEP scheme displayed in the CRZ page you can actually edit R3 and enter your own wind forecast. The header will change from ACTUAL WIND to EST WIND.

[Mike Ionas 5]

Could the changes in wind have caused the wrong calculations and the erratic values in PROG page?I was not aware you could edit the R3 line with wind prediction. I will try that in a future flight.

[emvaos 13]

Ναι Mike (yes MIke)

[Leffe 4]

I did it manually as you can see in the final picture.I was under the impression that in the step field we input the FL to which we want to climb, not the difference between the current FL and the next FL. Is that wrong? Additionally the s/c was calculated correctly in the begining (unfortunately no screenshot) however when i visited the CRZ page for a second time the peculiar values you see appeared..

No, step Climb is like 1000, 2000, or whatever how many feet you wanna climb.Do a search in the FCTMAlso Emvaos is right, found that in FCTM/ Leffe

[Mike Ionas 5]

Ναι Mike (yes MIke)

Λογικό αν γίνονται τόσοι υποΛογισμοί από πίσω (logical with so many calculations in the background).Out of curiosity; when inputting the initial values in the PERF page before departure, I always input the wind prediction for the route (as derived by ASE). Shouldn't that be used in the CRZ page calculation as well instead of the actual wind and therefore without having to input the predicted wind value again? At least this would be the logical thing in my humble opinion (obviously i do not know how the actual FMS works).

[Mike Ionas 5]

No, step Climb is like 1000, 2000, or whatever how many feet you wanna climb.Do a search in the FCTMAlso Emvaos is right, found that in FCTM/ Leffe

You are mistaken. Check FCOM Vol.2, page 11.42.22

[Akila 39]

I had/have a different Issue, of FMC suggesting me a Flight Level of FL362 on a 25 Min' route (79nm), totally not realistic to climb that high for such short route.if any one knows how to over come this, it would be amazing.