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Guest Boaz

Step CLB ICAO...

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Guest Boaz

Hello there.Been using ICAO as step profile, but only on west bound flights...When I fly East bound I use even FLs and if I have set my FMC to ICAO the FMC wants me to step first to an odd number then plus 4000ft...EXAMPLE:My initial CRZ ALT is FL320 and Step is set to ICAO, my next step alt will be listed as FL350?? Then FL390Shouldn't it be like FL320 to FL360? Thence FL400 if feasable.Thanks.Boaz.

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i never use the given FLs in the FMC. My initial climb usually gets me to FL330 then the FMC gives me a step climb to FL390? I presume this is because im light enough to get there but i prefer to overwrite that with FL350 then FL370 and then FL390. A gradual climb up. also in the legs page you can set a waypoint as a step climb by using an "s" after the alititude e.g .845/FL350S in the legs page and so on.


Paul McMahon

Ireland

747400.jpg

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Guest Boaz

wow I did not know that!Well I am trying to mimic real world operations, the rule of East and West bound traffic.Boaz.

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Guest Skedflyer

Or just overwrite ICAO in the FMC with 2000.

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Gents,(A) Seems first we need to explain what ICAO airspace is.For westbound traffic : (a) Up to FL280 (inclusive) EVEN flight levels increasing by 2000 ft (:( Above FL300 ODD flight levels increasing by 4000 ft starting at FL310. FL300 is NOT available.E.g. FL220, FL240,..,FL280, FL310, FL350, FL390, FL430For eastbound traffic : (a) Up to FL290 (inclusive) ODD flight levels increasing by 2000 ft (:( Above FL300 ODD flight levels increasing by 4000 ft starting at FL330E.g. FL210, FL230,..,FL290, FL330, FL370, FL410, FL450Hence, in ICAO airspace even flight levels above FL300 are NOT allowed and stepsize is 4000.(:( The next step altitude suggested by the FMC will always be ABOVE the optimum altitude at that point. Hence, if for example you select FL260 as your initial cruise altitude, and say stepsize 2000, the first step altitude will be FL3xx and NOT FL280. Explanation : even at MTOW the optimum FL is above FL290...© Unless you are on a very short trip then you better follow the FMC advice. This is not a mickey-mouse implementation of the step system to impress uninitiated users but we ventured to model the real big Boeing system with all its advantages (and drawbacks) to the letter. Trust me (it) it knows better than you since it has already performed a virtual trip at the suggested flight level(s) and calculated fuel (even as you are standing still at the gate).(D) If for any reason you want to fly at another FL than the one suggested by auto-stepping you can always set manually the first step altitude by entering it at 1R in VNAV CRZ page. In this case observe that the font size of the next target altitude increases. Hope this helps,Vangelis===================================== E. M. Vaos Precision Manuals Development Group www.precisionmanuals.com=====================================


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E M V

Precision Manuals Development Group

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For westbound traffic : (a) Up to FL280 (inclusive) EVEN flight levels increasing by 2000 ft (:( Above FL300 ODD flight levels increasing by 4000 ft starting at FL310. FL300 is NOT available.what about your OPT in the FMC? say im cruizing at FL330 and my opt is FL340 do i have to wait for the opt to be 4000ft above my current alt before step climbing? im having trouble following


Paul McMahon

Ireland

747400.jpg

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Vangelis,I don't think anyone is challenging the FMC calculations per se, but the fact is that most of the airspace we fly in is RVSM as of Jan last year, which changes the rules for valid FL's.


Regards,

Brian Doney

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Guest wisborg

As far as I know (Radar Contact as the source) in North America and Europe (maybe other places as well) additional flight levels have been taken into use (RVSM), so there's a 1000 ft separation all the way up to FL410.What I do, if I fly in RVSM space is to set the step climb parameter in the FMC to 2000 ft, and everything works as it should.Of course if you have access to wind aloft data, it might be desirable to choose a higher or lower flight level than the weight wise optimal./ Jesper

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Yep, just make sure you choose a vaild FL initially, and then you will still have to enter either 2000 or 4000 ft steps, and NOT leave it as ICAO, to remain valid if flying RVSM.


Regards,

Brian Doney

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Guest Boaz

So that would explain why it did what it did.But there was no reason to get all defensive about the FMC:-D Nobody would dare out calculate its predictions don't worry...Boaz.

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Brian,Thanks. This should be clarified also. The default stepping scheme is ICAO (i.e. essentially variable step size) with rules explained above. The step size entry in VNAV CRZ page is however editable and you can enter steps between 1000-9000 (use 2000 for RVSM). Note that whole numbers (in terms of thousands must be entered). I.e entering 1543 will result in an INVALID ENTRY message. Enter 0 (zero) for suppressing step predictions completely. DELeting the step size entry will result in ICAO (default as noted above).Finally to answer the other question : If current cruise altitude is FL330 and a step size of type ICAO is defined then the next cruise altitude is FL370 (there is a provision for this, skipped here in order not to complicate matters :)). The FMC will calculate a step point such that at the predicted time/position of stepping UP the gross weight of the aircraft corresponds to an optimum altitude half-way between current and next cruise level. In this example the next step will be predicted at the position where the gross weight corresponds to an optimum altitude of FL350. In fact slightly above that (e.g. 35050-35100) since it also takes into account the extra fuelburn required to climb up. As I said, we ventured to model a rather sophisticated system.In other words the FMC is always trying to "bracket" the optimum flight level by constructing a vertical path for the aircraft to fly a little time below and little time above the optimum altitude by a half the defined step size. This is a very fuel efficient way to fly on fixed flight levels (not withstanding wind/altitude trades). The most fuel efficient alternative is what Concordes used to do and that is to continuously drift up (and sometimes down) based on current weight and ISA deviations i.e. sort of ballistic flight at non fixed flight levels. The latter is ofcourse prohibited for normal jet operation.Best,VangelisPS. Brian : January last year....You're late mate :) In Europe a long time ago.===================================== E. M. Vaos Precision Manuals Development Group www.precisionmanuals.com=====================================


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E M V

Precision Manuals Development Group

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"PS. Brian : January last year....You're late mate :) In Europe a long time ago."Hmm, and over the NAT, PACIFIC, WATRS and Australian regions even before Europe, but, I didn't think that was the point of this thread ? :-hmmm


Regards,

Brian Doney

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Brian,No offence.All,Another piece of semi-useless infromation for those interested : RVSM airspace extends to FL410 (inclusive). Therefore if you intend to travel west, FL's 420/440 are NOT available. Above FL410 one therefore reverts to good old ICAO schemes (430 west and 450 east).Furthermore, for those, flying online in VATSIM or IVAO note that in Italian airspace the west/east convention is turned by 90 degrees to north/south (even/odd FL's respectively) and in Spanish airspace on most airways I checked the west/east FL rule is reversed (west odd, east even...don't ask why, I have no clue). Correct me if I am wrong anywhere here.Finally, in Russia, Belarus and Ukraine available FL's are METRIC as follows :WEST : 1200m, 1800m, 2400m,..., 7800m (i.e. 600 meter/~1000ft steps to FL256) and then 8600m, 9600m, 10600m etc (i.e. 1000 meter/~3300 ft above FL256)EAST : 900m, 1500m, 2100m,..., 8100m (i.e. again 600 meter steps till FL266) and then 9100m, 10100m, 11100m, etc (i.e. 1000m separation above)If the latter sounds confusing you now know why there is this MTRS button on the EFIS display control panel.Best,Vangelis===================================== E. M. Vaos Precision Manuals Development Group www.precisionmanuals.com=====================================


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E M V

Precision Manuals Development Group

====================================

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Guest SKireyev

>Finally, in Russia, Belarus and Ukraine available FL's are>METRIC as follows :>>WEST : 1200m, 1800m, 2400m,..., 7800m (i.e. 600 meter/~1000ft>steps to FL256) and then 8600m, 9600m, 10600m etc (i.e. 1000>meter/~3300 ft above FL256)>>EAST : 900m, 1500m, 2100m,..., 8100m (i.e. again 600 meter>steps till FL266) and then 9100m, 10100m, 11100m, etc (i.e.>1000m separation above)>>If the latter sounds confusing you now know why there is this>MTRS button on the EFIS display control panel.Mr. Vangelis knows his stuff. I thought me using this button to utilize appropriate flight levels over (former) Soviet airspace was just a quirk of mine. I didn't know it was designed for it. Interesting stuff! Another interesting factoid for airplane trivia buffs out there: Russian term for "flight level" is "echelon" [эшелон]Cheers,

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Guest D17S

Whoah! Yet another, entire world to explore! Will it ever end? Hope not.

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