How can we calculate the cost index in FMC?

[marwan95 0]

I always add 30 to cost index in the FMC's perf init page. And how many to reserves in perf init?Thank you

[LZaman 0]

your reserves should include the following: Reserve fuel = altn fuel + 30' holding fuelWhen you hit the reserve fuel (you should be at destination by that point otherwise you should've legally diverted!) you have little options left.Either the airfield is a good airfield with multiple non-crossing runways, and the weather is above minima (and you expect to start your approach in a reasonable (do-able) timeframe). Note that at this point you are committed to land at your destination. (this option is changing the FP to a flight plan without destination alternate for fuel planning)If not you will be forced to divert immediately to your alternate and be committed to land over there.If weather all around is too bad to land legally, you have done your homework wrong! (at this stage it would be REALLY wise to ask atc about airfields which are open and have decent enough weather minima...) Cost Index is a very mathematical figure. In airbus they say your cost index is a figure all in f.e. CI = 40 = 40kg/minbut again, it's very mathematical/statistical...there no rule but in general CI = 0 = max range ; CI = 25 = long range ; anything above is considered 'economical'(remember flying fixed Cost Index = NOT fixed speed as this will depend on wind / SAT/weight )

[sho69607 29]

Cost index is programmed based on an airline's preference. The higher the cost index the less effecient the aircraft will be, the lower vice versa. I usually go anywhere from 85-100. Since this is sim it is up to you. Reserves is how much fuel you will have after landing unless you use them to go to an alternate airport or get put in a holding pattern. Hope this helps.

[marwan95 0]

your reserves should include the following: Reserve fuel = altn fuel + 30' holding fuelWhen you hit the reserve fuel (you should be at destination by that point otherwise you should've legally diverted!) you have little options left.Either the airfield is a good airfield with multiple non-crossing runways, and the weather is above minima (and you expect to start your approach in a reasonable (do-able) timeframe). Note that at this point you are committed to land at your destination. (this option is changing the FP to a flight plan without destination alternate for fuel planning)If not you will be forced to divert immediately to your alternate and be committed to land over there.If weather all around is too bad to land legally, you have done your homework wrong! (at this stage it would be REALLY wise to ask atc about airfields which are open and have decent enough weather minima...) Cost Index is a very mathematical figure. In airbus they say your cost index is a figure all in f.e. CI = 40 = 40kg/minbut again, it's very mathematical/statistical...there no rule but in general CI = 0 = max range ; CI = 25 = long range ; anything above is considered 'economical'(remember flying fixed Cost Index = NOT fixed speed as this will depend on wind / SAT/weight )

Oh, Thank you so much for your long reply!:)It is very useful!:)

Cost index is programmed based on an airline's preference. The higher the cost index the less effecient the aircraft will be, the lower vice versa. I usually go anywhere from 85-100. Since this is sim it is up to you. Reserves is how much fuel you will have after landing unless you use them to go to an alternate airport or get put in a holding pattern. Hope this helps.

Yeah it helped!:) thxEven one question: can anybody help me to change the panel lightning in the VC. It is too white. I prefer a bit orange shade in the background lightning.I saw a post about this, but now I cannot find it:(

[MarkW 1,479]

It varies by airline. British Airways sets the cost index to 28 in their older 737's and that is what I am using in the NGX. Mark.

[badderjet 181]

I usually go anywhere from 85-100. Since this is sim it is up to you.

This is what I also do usually, I go for 100. One wants to arrive, no? Although it's highly unrealistic, as per real ops numbers in the 10-50 range are way more likely, especially nowadays.

[Sekstifire 10]

The fuel prices and the general economic shape of the aviation industry have forced the airlines to run at very low cost index. Its normal for many carriers to run a CI below 20. I seriously doubt that anyone runs it in the 80-100 range. We do of course not have to pay for our virtual fuel so one can set whatever CI one like. Personally I like to keep it real, so I usually run a CI of ~15

[raymar 969]

I see 30 and 50 and 80 a lot. In the PMDG NG tutorial Tim Metzinger uses 150 and flatly states the sim at that time totally ignores any number used for CI for any calculations. It just wants a number up to 500. Why don't you fly a flight with a cost Index of 10 and repeat the flight with a CI of 490. That should be enough range to tell if there is any difference. Are you concerned about the virtual cost of fuel or is it the cost of virtual fuel? I can't seem to tell the difference in real costs. Quote - The COST INDEX is not modeled in the sim yet so any number will give the same result. Unquote. Page 45. Fred Clausen used a Cost Index of 100 in his Tutorial for the 737NG. Of course, PMDG might have added some calculations just to make it more realistic. But, should they have done that, wouldn't you think they would have documented it in the 3.000 +pages of pdfs. If you want to stay real, as some posters do, use any number that works. Alter all, noone seems to sweat the additional fuel, some use 2, some use 5, some use a perscent of something. Most of us don't ever run out of fuel so what's the big deal? Ray

[raymar 969]

I found this in an old PMDG AOM. . . " Cost index is calculated as the aircraft operating cost divided by fuel cost. [($/hour aircraft operating cost) / (Fuel Cost in Cents/Pound)] A cost index of 00 will result in the maximum cost economy, with slow climb rates, maximum range cruise and slow descent speeds predicted by the FMC in order to minimize fuel burn. A high cost index will result in higher climb rates, cruise and descent speeds. The cost index is designed to provide a relative index of the cost of aircraft operation vs. time en-route: Note.Cost index is not currently functional in this version, but a basic model has completed development. A fully functioning cost index model will be added to the FMC/CDU at a future update. Cost Index: The cost index number is a scale value from 0 to 1000 that helps to determine a level of economy for aircraft performance calculation. " Notice it could be up to 1000. Interesting. It is a required entry in the CDU/FMC and its has 4 little boxes, so that is most like correct.So maybe you would like to try a 00 and a 1000 and see if you feel better about the flight. EDIT - Looks like the above is out of date. I can enter from 0 - 500, even though the required boxes are 4 digits, it seems to have an upper limit of 500. I changed the CI duing a flight several times from 0 - 499 and then checked all the calculations for the remainder of the flight and couldn't see any changes. Ray

[Guest EJTENC]

Depends on operations back in the office. They come out with the figures based on several factors. Fuel economy as priority, but also delays etc.We have several Cost Indexes: 15 being standard, for all routes, with LGW, SXF, VIE, ORY, DUS being the exceptions, where we use CI 40 (With the standard 15 for returnflights)Routes to and from HRG are flown w CI 40.

[Foghorn 4]

Upper management has instructed me to use a very low CI as the fuel costs are very high and I need to save money after all my upgrades to have the NGX and FSX working smoothly.

[badderjet 181]

and then checked all the calculations for the remainder of the flight and couldn't see any changes.

Huh, not sure what you're missing there, but the changes are most obvious. All speeds change, the whole vertical profile changes basically. Fuel predictions change. Practically every performance number changes. Try a climb at CI 0 and one at CI 500 and you should certainly see where this is going.

[dotChuckles 0]

Somewhere on this forum there was a really useful post linking to a pdf that explains how airlines calculate CI based on the type of flight. It had the formulas and a guide as to when to apply it. If you have a quick search you should come across it... might have been about a week ago I think.

[Tabs 2,790]

40 is a good average value, it's what I use.

[Chrjs 61]

Somewhere on this forum there was a really useful post linking to a pdf that explains how airlines calculate CI based on the type of flight. It had the formulas and a guide as to when to apply it. If you have a quick search you should come across it... might have been about a week ago I think.

I don't know whether you mean this article, but it is officially from Boeing on how to save fuel and explaining the CI in detail: http://www.boeing.co...ticle_05_1.html Btw, the AERO Magazin can be ordered as a Download Verision for free! Regards, Chris Volle