Step Climbs, FMC and RVSM

[dolin 0]

Hi to everyoneWhen it comes to Step climbs I have some questions:The FMC is programmed to follow the ICAO profile, which is FL310-350-390 etcHowever now there is RVSM, which requires 2000 feet steps.Ok here's the question: My initial cruise altitude is always FL310, then I perform step climbs. I would like them to be according to RVSM, so I enter as a step climb value 2000. But the FMC gives me even flight levels, this means FL320-340-360 etc. How can I tell the FMC to calculate odd altitudes (330-350-370 etc) without modifying them myself? Maybe it depends on the direction of the flight? (eastbound-westbound)Thanks for your help!

[El padrino 2]

Are you sure you've set the initial cruise altitude in the FMC? If I'm not mistaken it's somewhere in the VNAV pages...

[dolin 0]

Are you sure you've set the initial cruise altitude in the FMC? If I'm not mistaken it's somewhere in the VNAV pages...

Yes, otherwise it wouldn't calculate takeof performance, fuel estimates etc.It's in the PERF INIT page, top right. I always type 310 in the scratchpad and press LSK 1R. Then I see the boxes filled with FL310

[rX 1]

It is on the Performance Initialization page (PERF INIT) in preflight setup and there at LSK 5R: STEP: ICAO. Change that to STEP: 2000.

[dolin 0]

It is on the Performance Initialization page (PERF INIT) in preflight setup and there at LSK 5R: STEP: ICAO. Change that to STEP: 2000.

Yes, but as I said it gives me even altitudes only: My initial altitude is FL310, the FMC tells me to climb to FL320 then 340, 360 and so onI would like odd altitudes, because I think that's the way they fly in real life

[rX 1]

Hmm. That isn't right. If you had 310 the next step should be 330. The rule in most countries (mostly except those that have a strong North-South airway orientation) is Eastbound ODD, Westbound EVEN. So you would fly FL310 only if you were flying From the westcoast to the eastcoast for example. Also note (since B744 is a long hauler) when flying on NATs (North Atlantic Tracks) those actually are one directional and occupy Flight Levels. So over the ocean you would use 1000 feet step climbs (if ATC would be able to approve it due to traffic).Anyway, can you try the flight again starting with FL330 now? It might have been a one time thing. I remember clearly using RVSM step climbs on eastbound flights too.PS. Sorry I hadn't read your full post before replying.

[dolin 0]

Hmm. That isn't right. If you had 310 the next step should be 330. The rule in most countries (mostly except those that have a strong North-South airway orientation) is Eastbound ODD, Westbound EVEN. So you would fly FL310 only if you were flying From the westcoast to the eastcoast for example. Also note (since B744 is a long hauler) when flying on NATs (North Atlantic Tracks) those actually are one directional and occupy Flight Levels. So over the ocean you would use 1000 feet step climbs (if ATC would be able to approve it due to traffic).Anyway, can you try the flight again starting with FL330 now? It might have been a one time thing. I remember clearly using RVSM step climbs on eastbound flights too.PS. Sorry I hadn't read your full post before replying.

I think I've found the problem during today's flight EGLL-KLAXIt's related to ATC. When I get closer to my assigned altitude (1000 ft range) they tell me to contact another controller and then they give me the new altitude. But as I climb in 2x sim speed (to save some time) there is little time for this switch and I input the new altitude when I'm very close to the previous altitude (300 ft range). This disengages VNAV and switchs on V/STo engage VNAV again I developed this trick: Change the cruise altitude (FL310) to a new value and then changing it back to 310.It's this trick that messes up Step Climbs: before departure I paid attention to VNAV CRZ page and the next step was at FL330 (with 2000 increments selected instead of ICAO) and after using my trick the step climb was FL320Ok now I'll just have to adjust sim speed better to allow a smooth change of MCP ALT. Thanks for your help!Regards from Italy

[martybuzz 2]

I think I've found the problem during today's flight EGLL-KLAXIt's related to ATC. When I get closer to my assigned altitude (1000 ft range) they tell me to contact another controller and then they give me the new altitude. But as I climb in 2x sim speed (to save some time) there is little time for this switch and I input the new altitude when I'm very close to the previous altitude (300 ft range). This disengages VNAV and switchs on V/STo engage VNAV again I developed this trick: Change the cruise altitude (FL310) to a new value and then changing it back to 310.It's this trick that messes up Step Climbs: before departure I paid attention to VNAV CRZ page and the next step was at FL330 (with 2000 increments selected instead of ICAO) and after using my trick the step climb was FL320Ok now I'll just have to adjust sim speed better to allow a smooth change of MCP ALT. Thanks for your help!Regards from Italy

Just curious, when you say input the new altitude, do you mean on the MCP? By turning the ALT knob to select a new altitude in the climb, it will delete the constraint, if set at the next waypoint, but will not reset the cruise altitude set in the FMC. If the altitude set on the MCP is above what is set in the FMC, then it will reset the FMC to that cruise altitude.Martin Buzzell

[dolin 0]

Just curious, when you say input the new altitude, do you mean on the MCP? By turning the ALT knob to select a new altitude in the climb, it will delete the constraint, if set at the next waypoint, but will not reset the cruise altitude set in the FMC. If the altitude set on the MCP is above what is set in the FMC, then it will reset the FMC to that cruise altitude.Martin Buzzell

Yes I input the new altitude on the MCP, and yes I know it won't change MCP cruise alt. That i do it manually via the FMC, usually inputing a 1000 ft lower value and then re-inputing the original value.When I use this trick I am always above 15000, so I have no altitude restrictions to worry about.

[martybuzz 2]

Yes I input the new altitude on the MCP, and yes I know it won't change MCP cruise alt. That i do it manually via the FMC, usually inputing a 1000 ft lower value and then re-inputing the original value.When I use this trick I am always above 15000, so I have no altitude restrictions to worry about.

I'm still a bit confused. Why are you going into the FMC and changing the cruise altitude? When you set it as part of your pre-flight, you never touch it again. Once the FMC gets to it's S/C (Step Climb) point, you just dial up the new Altitude and press. That will update the Cruise Altitude in the FMC. It will then climb in VNAV mode. Your FMA (Flight Mode Annunciations) on the PFD will change from SPD, LNAV, VNAV PTH to CLB, LNAV, VNAV SPD.Martin Buzzell

[dolin 0]

I'm still a bit confused. Why are you going into the FMC and changing the cruise altitude? When you set it as part of your pre-flight, you never touch it again. Once the FMC gets to it's S/C (Step Climb) point, you just dial up the new Altitude and press. That will update the Cruise Altitude in the FMC. It will then climb in VNAV mode. Your FMA (Flight Mode Annunciations) on the PFD will change from SPD, LNAV, VNAV PTH to CLB, LNAV, VNAV SPD.Martin Buzzell

I'll try to explain myself better.I don't have problems with cruise altitude and step altitudes themselves, my problems are related to ATC and simulation rate (2x, 4x etc.): during late climb Atc tells me the NeXT altitude to get to a bit too late, so I find myself very close to the old MCP altitude and as I input the new value given me VNAV suddenly disengages. Don't know why.The FMC messing-around is not in any procedure or manual, it's something I've made up. For some reason this little trick works, but affects FMC step-climb procedure.Of course the issue is far from an epic failure, but I was just asking if others knew about this and could tell me if it is a resl mechanism of the 747 or a bug.If there are any other questions, I'm here

[pramodrai 0]

Interesting details, Thank you !  :rolleyes:

[kevinh 409]

Yes I input the new altitude on the MCP, and yes I know it won't change MCP cruise alt. That i do it manually via the FMC, usually inputing a 1000 ft lower value and then re-inputing the original value.When I use this trick I am always above 15000, so I have no altitude restrictions to worry about.

Why are you using any "tricks"? If you dial in the new altitude on the MCP and then press the altitude knob (ALT INTV) it will update the VNAV cruise altitude for you and initiate the step climb.

 

If you do the step climb in this way you may still be able to use 2x acceleration.