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### Cost Index question

Posted: Mon Dec 25, 2017 9:35 pm
Hi folks,

I have a question regarding the cost index. If 1 airline uses pounds to construct their flight plan and uses a cost index of 40 and I wanted to know what cost index 40 (CI40) is in kilos, am I to presume that I would have to just convert the cost index number from pounds to kilos??

i.e.
pounds divide by 2.2 = kilos
40 / 2.2 = 18

Brgds
Wxman11

### Re: Cost Index question

Posted: Mon Dec 25, 2017 11:13 pm
The cost index has nothing to do with the unit you use. It doesn’t matter whether an airline uses kg or lbs, the index equals the same thing. So there’s no need to convert anything.

### Re: Cost Index question

Posted: Mon Dec 25, 2017 11:30 pm
On airbus equipment cost index is either on kg/min or 100 lb/hr. For a A330 with RR engines a cost index of 40 kg/min is equal to 53 (100 lb/hr)

Have a look online for an Airbus publication “Getting to Grips with Cost Index) for more details.

### Re: Cost Index question

Posted: Tue Dec 26, 2017 7:30 am
Here's a good review by Boeing. Cover several aircraft types.

http://www.boeing.com/commercial/aeroma ... _05_1.html

### Re: Cost Index question

Posted: Tue Dec 26, 2017 1:48 pm
Where in that article do they describe the cost index differance between normal SI units and American?

### Re: Cost Index question

Posted: Tue Dec 26, 2017 2:28 pm
zeke wrote:
Where in that article do they describe the cost index differance between normal SI units and American?

Actually Airbus coveres that very briefly in their document, and there is a bit of contradiction:
http://ansperformance.eu/references/lib ... -index.pdf page 7 gives index units as
Units are given in kg/min or alternatively as 100 Ib/h

Strictly speaking, 1 kg/min should translate into 132 lb/hr, not 100. Not sure if that is the overall accuracy of optimization, or there is a unit switch option (that would probably be meaningless, since the way Airbus describes the system, pilots don't have the data for accurate calculation anyway, and should probably use the number provided to them by the company. Calculating proper units on the ground should eliminate some confusion)
Anyway, according to Airbus graphs, 30% difference at high values of cost index can eat up all possible optimization, especially if initial calculation is a bit off from the minimum.

### Re: Cost Index question

Posted: Tue Dec 26, 2017 2:39 pm
Strictly speaking, 1 kg/min should translate into 132 lb/hr, not 100.

No 100 lb/hr is correct, that is why the SI CI=40 (kg/min) is equal to the American CI=53 (100 lb/hr). I think Boeing also factor theirs by around 2 orders of magnitude.

### Re: Cost Index question

Posted: Tue Dec 26, 2017 3:24 pm
zeke wrote:
Strictly speaking, 1 kg/min should translate into 132 lb/hr, not 100.

No 100 lb/hr is correct, that is why the SI CI=40 (kg/min) is equal to the American CI=53 (100 lb/hr). I think Boeing also factor theirs by around 2 orders of magnitude.