PMDG Fuel cost Index

[EHM-1343 Jonathan]

from the PMDG Manual

Insert the value 100 into the scratchpad and click on LSK6L(This value represents the cost index and is probably way too high for a real aviation company, but for now it will do)

This is from the text about the introductory flight....can anybody tell me:
 
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• What a real airline would use on this value?
• Does this have any effect on cruise speeds, optimum flight levels, clim rates and so on....?
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thanks in advance

[EHM-1281 Cyriel]

a quick look on the internet gave me this
http://www.iata.org/NR/ContentConnector/CS2000/Siteinterface/sites/whatwedo/file/Airbus_Cost_Index_Material.pdf

Although it is for airbus the idea will be the same. All I know myself about it that it is highly complicated and depends on a number of factors including the age of the engines etc. I always put 200 in there.

[EHM-1001 Robert]

Cost index is a realtive number for the FMC which tells how much fuel you want to burn, how economically you want to fly. 100 is the maximum, which means you fly full throttle, at all cost! 0 is the minimum, which means you fly very smoothly. The FMC calculates the optimal flight level, optimal climbing and descending rates, optimal takeoff power... everything that is related to fuel burn. The lowest the cost index, the cheapest the flight for the airline

I have red it in the FMC manual...somewhere.

[EHM-1358 Tim]

For Boeings I normally use 40-50.

[EHM-1343 Jonathan]

Originally posted by SirRoberto
The lowest the cost index, the cheapest the flight for the airline

Hmmm...we'll have it on about 50 then...best of both, bit of speed, and economy.

[EHM-1539 Pierre]

The airlines modify it too depending on the current fuel price.
50 is okay. If you are in a hurry and want to forget the price of kerosen someday enter 99
I do it often, after all, the advantage of the virtual world : fuel is free, maintenance too  

[EHM-1343 Jonathan]

yeah...good idea...(not like the Boss will complain with all passangers arriving ahead of schedule:P)

[EHM-0654 Murray]

Originally posted by SirRoberto
100 is the maximum...

Oh no it isn't! (Oh yes it is... Rinse. Repeat.) Least ways, not on the real Boeing 737NG Smiths FMC (and best I can tell, the PM FMC behaves the same)!

The Boeing 737NG FMC Cost Index field will take any integer value from 0 to 500 (inclusive).

500 is least flying time [MAX CRZ] (fuel no object), 0 is least fuel used [MAX ECON] (time no object).

My "Big Boys Fun Book of 737NG FMC's" has at least two pages devoted to Cost Index.

[EHM-1365 Benjamin]

Originally posted by Murray Crane
The Boeing-type FMC Cost Index field will take any integer value from 0 to 500 (inclusive).

Note, Murray's editted his original post since this post was made

I thought the 767's went up to 9999, no? or was it 999 :s

[EHM-0654 Murray]

Originally posted by EHM-1365
I thought the 767's went up to 9999, no? or was it 999 :s

Probably, the current crop of 747-400 FMCs will take a figure up to 9999. When I say 500 above I'm quoting from memory for my 737NG FMC Users Guide (which I was doing my best to commit to memory prior to moving house).

I'll dig it out of the box it's in tonight (I know exactly where it is, unlike my contact lenses and post a full quote tommorow.

[EHM-1343 Jonathan]

ok....thanks. When i got this, i din't realise how accurate things were, everything down to fuel comsumption, its amazing:o

[EHM-0654 Murray]

Originally posted by Razza
ok....thanks. When i got this, i din't realise how accurate things were, everything down to fuel comsumption, its amazing:o

In that case...

Hey kids! Don't forget to enter the cruise temp and wind forecasts (temp on PERF INIT, winds on LEGS), as they have a *huge* bearing on the fuel usage calculations... The PMDG FMC doesn't model either of these as well as the PM FMC, but does take them into account when doing it's fuel usage calcs.

[EHM-1539 Pierre]

99 or 999 ? Both.
Depending on the FMC version and manufacturer the cost index is usually 0-99 OR 0-999.

[EHM-0654 Murray]

Well, to quote from my 737NG FMC User's Guide, COST INDEX is the:

• Ratio of other crew and maintenance costs compared to the cost of fuel. The lower the index, the more influence fuel price has on the speed schedule. The higher the index, the greater influence time related costs (i.e. maintenance and crew) have on the equation.
• 0 causes ECON speed to be approximately Max Range Cruise in zero winds. 500 results in minimum flight time.
• Adjusting CI to meet operational schedule or ATC requirement defeats cost studies if computed by your engineering department.
• RTA function adjusts Cost Index to meet arrival times. Ed: PMDG FMC doesn't do RTA. Don't know about PM FMC.
  
• Ref: Cost Index, CRZ section.

Hence my assertion that for the 737NG CI can be 0-500. :) And as far as usage goes, on the same page, a little further down, it gives this nugget of wisdom:

Technique For a quick set-up to prioritize fuel conservation, enter a CI of 36 to shorten climb phase and for a 280kt descent. Then select LRC on CRZ page.

[EHM-1343 Jonathan]

This will come in very handy...when you say PM FMC, what do you mean...which manufacturer

[EHM-1365 Benjamin]

I just assumed Project Magenta, but now you mention it I could be wrong :|

[EHM-0654 Murray]

Indeed I do refer to Project Magenta. Their FMC simulation seems a little fuller than the PMDG, but I must stress that I haven't actually flown with it yet (have to get a PC to run the MCP on first...), so far I've only been in a position to do solo "induction" on it.

And in case any of you are wondering, RTA is Required Time of Arrival - you set a waypoint and a time to get there by, and the FMC does it's damnedest to get you there by then...