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Mike Ionas

User needs help understanding Step Climb

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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 blank005.jpgand then changed to006.jpgwhile when selecting the PROG page it was showing007.jpgSelecting the same sequence at a later stage during the flight:014.jpg015.jpg016.jpgThe value of the distance to the s/c continue to decrease (negative value) with every new calculation:019.jpgFinally upon reaching the s/c point the values changed to normal:021.jpg022.jpgand after the step climb the t/d point calculation was displayed:023.jpgThis is the NGX with SP1 and 736/7 expansion installed. The installation was clean after removing all old versions.Any ideas?

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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

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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

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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.

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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? Whistle.gif ).

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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? Whistle.gif ).
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

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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..

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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.

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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.

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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

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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).

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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

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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.

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You are mistaken. Check FCOM Vol.2, page 11.42.22
I admitt that I was wrong about this FL380 instead of step of 2000 feet, which i thought.I guess I read it wrong in the other manual then, and that I usually always do my steps manually./ LeffeI´m curious if you got an answer why you couldn´t climb then?Also I understood it had something to do about wind/fuel etc but as you saidyou set up an average of Cruise wind from ASE so I don´t either understand what oneshould change that./ Leffe

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The predicted wind was entered in the PERF page, while the CRZ page was using actual wind for its calculations. I was able to climb when the time came, the calculation was wrong.

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The predicted wind was entered in the PERF page, while the CRZ page was using actual wind for its calculations. I was able to climb when the time came, the calculation was wrong.
Ok, good to know./ Leffe

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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.
The FMC doesn´t calculate it based on the route lenght. Only on weight/fuel consumption etc.

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The FMC doesn´t calculate it based on the route lenght. Only on weight/fuel consumption etc.
that is strange.based on what I was told, it should, I just could never find that "trip" altitude that everyone kept mentioning to me.
Well first of all, it's not called OPT Altitude - but "trip" altitude. And the page I'm speaking of is the INIT REF page 1.
FMC will Calculate it for you. It's called trip altitude, and is shown on the INIT REF page 1 in the FMC. It do however require you to enter basic information: Origin, destination, CI and Weights
Here is from the manual:
Trip altitude is automatically computed and displayed whenever entries have been made for the ORIGIN, DEST, GROSS WT, and COST INDEX. Otherwise, the field is blank.Trip altitude is the predicted minimum cost altitude determined by operator constraints. Provides crew a reference for selecting a planned cruise altitude.

there are flights that short in real life (i do them all the time in real life - as a passenger)example LLBG - OJAI, well Royal Jordanian uses ERJ for that route , but it could easily be an NG.you will see those short distances more often in south east Asia, like Philippines or Indonesia when it's Island hopping,long enough to justify a flight (as cursing it in a ferry would take a long time), but it is actually a very short distance/flight.or in places that there are no roads (crossing the rain forest) and only by flight you may reach there (e.g. Sentani/Jayapura - Papua , Indonesia to the baliem valley, must be done by air, even thoughthe distance is very short) - done by Merpatti commercial Airline & Lion Air, and guess what Lion air were the 1st to have the NG900 in the world at 2006/7.Another example I used to use those flights in the Philippines, when the roads conditions are very bad and a ground ride would take you like 8hr or so, there is an alternative of taking it by Air, e.g. Puerto Princesa <-> El Nido (Palawan).I use those short flight many times in the FSX/NGX. for me it is crucial to have that calculated.

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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.
Dear Vangeli,I tried the step climb using estimated winds instead of actual as you suggested but the problem remains.This time the flight was from LGAV to LHBP following NEVRA UZ507 TSL UL617 MAKED UP36 RAXAD UL617 PARAK UY554 ABONY. Initial FL F360 with a step climb to F380 a little bit later.After reaching cruise level I selected the CRZ page and entered the new FL and the estimated wind:105.jpgThe s/c was calculated correctly and then I selected the PROG page:106.jpgEverything normal again and the s/c was calculated a little bit before MAKED wp:107.jpgHowever, after a few minutes when selecting the CRZ page for a second time, the initial calculations disappeared:109.jpgand the step point changed to NOW:110.jpgand when selecting PROG page the s/c time remained correct while the distance changed to a negative 6 digit value:111.jpgalthough in the ND the s/c was displayed at the same position as before:112.jpgAfterwards I returned to the CRZ page, deleted the STEP CLIMB value and upon re-entering it it was again calculated correctly regardless of actual or estimated winds. However when i visited the CRZ page again after a few minutes the same problem occurred.Therefore the first time the step climb is always calculated correctly. However if after sometime I visit the CRZ page again the problem occurs.Is this only happening to me?MikeP.S. It seems somebody changed the subject of this topic from "step climb problem" to the one displayed now...

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