# Airbus cost index and LRC

Thread Starter

Join Date: Feb 2002

Location: Australia

Posts: 368

**Airbus cost index and LRC**

Can someone confirm that setting LRC in the A320 /321 requires reference to the LRC tables and manual setting of a specific Mach number that will vary as the weight decreases, rather than setting of a specific Cost Index.

I understand cost index 0 is max range and cost index 999 is min time but we never refer to LRC in our company documents except for some non normal ops.

The 2008 “Getting to grips with Cost Index” doesn’t appear to discuss LRC at all.

Thanks in advance.

I understand cost index 0 is max range and cost index 999 is min time but we never refer to LRC in our company documents except for some non normal ops.

The 2008 “Getting to grips with Cost Index” doesn’t appear to discuss LRC at all.

Thanks in advance.

Join Date: Dec 2010

Location: MC80 Home One type Star Cruiser

Posts: 187

Does this help? PRO-NOR-SRP-01-50 P 15/16

COST INDEX FOR LONG-RANGE CRUISE

The flight crew can use the table below to find an approximate Cost Index value that is calculated for cruise at long-range cruise speed. This value is valid for CRZ FL = OPT ALT ± 1 000 ft.

ENGINE / CILRC kg/min / CILRC 100 lb/h

CFM 56-5-A1/A3 45 60

CFM 56-5-A4/A5 40 55

CFM 56-5-B1/B2/B3 65 85

CFM 56-5-B4 (A321) 65 85

CFM 56-5-B4 (A320) 55 75

CFM 56-5-B4/P 25 35

CFM 56-5-B5/B6/B7 25 35

CFM 56-5-B5/2P CFM 56-5-B6/2P CFM 56-5-B7/2P 30 40

CFM 56-5-B8/B9 15 20

CFM LEAP-1A 40 55

PW6122/PW6124 20 30

PW1100G-JM 40 55

V2500-A1 45 60

V2522-A5/V2524-A5/ V2527M-A5 50 70

V2530-A5/V2533-A5 50 70

V2527-A5/V2527E-A5 40 55

COST INDEX FOR LONG-RANGE CRUISE

The flight crew can use the table below to find an approximate Cost Index value that is calculated for cruise at long-range cruise speed. This value is valid for CRZ FL = OPT ALT ± 1 000 ft.

ENGINE / CILRC kg/min / CILRC 100 lb/h

CFM 56-5-A1/A3 45 60

CFM 56-5-A4/A5 40 55

CFM 56-5-B1/B2/B3 65 85

CFM 56-5-B4 (A321) 65 85

CFM 56-5-B4 (A320) 55 75

CFM 56-5-B4/P 25 35

CFM 56-5-B5/B6/B7 25 35

CFM 56-5-B5/2P CFM 56-5-B6/2P CFM 56-5-B7/2P 30 40

CFM 56-5-B8/B9 15 20

CFM LEAP-1A 40 55

PW6122/PW6124 20 30

PW1100G-JM 40 55

V2500-A1 45 60

V2522-A5/V2524-A5/ V2527M-A5 50 70

V2530-A5/V2533-A5 50 70

V2527-A5/V2527E-A5 40 55

Join Date: Oct 2018

Location: Ferrara

Posts: 2,501

Thread Starter

Join Date: Feb 2002

Location: Australia

Posts: 368

Ive never understood this table even though I have seen it. Tthey're not saying, as far as I can understand, that we set a cost index 40 for LRC because from what I can see in my case using the IAE 2527 engines the value of 40 is representative of 40 kg/hour not a cost index of 40. I’m obviously missing something.

Thread Starter

Join Date: Feb 2002

Location: Australia

Posts: 368

So I've looked at that graph but it still doesn't make sense to me (I'm looking at the version II 1998 appendix 6) it shows at the bottom of that graph that "Cost Index = KG per minute" and that we would potentially have 8 kg per minute burn for LRC which is clearly not correct aws that would only be 480 kgs per hour. Obviously I am missing something in the interpetation of this chart but I don't know what it is.

Join Date: Dec 2017

Location: St. Petersburg

Posts: 5

CI is price of kg of fuel devided by price of minute of flight. Setting CI 25 you say to an aircraft "Hay man, price of 1 minute is the same as price of 25 kg of fuel. Set such speed to save as mach money as you can". CI is not about fuel, it is about money.

Join Date: Apr 2004

Location: United States of Europe

Age: 37

Posts: 477

No.

What you see in the table is the approximate CI that equates to LRC.

The unit of CI being kg/hr (metric) or 100 lb/hr (imperial).

Agreed that adding the unit only leads to confusion.

ref: GTG a/c perf

What you see in the table is the approximate CI that equates to LRC.

The unit of CI being kg/hr (metric) or 100 lb/hr (imperial).

Agreed that adding the unit only leads to confusion.

ref: GTG a/c perf

*Last edited by OPEN DES; 3rd Mar 2020 at 06:29.*

Join Date: Apr 2004

Location: United States of Europe

Age: 37

Posts: 477

Simple: just insert the CI of the LRC.

Most airlines fly a CI lower than the one associated to LRC, somewhere between LRC and MRC. LRC is actually a speed increase and range reduction in many cases.

Otherwise LRC continues to be a concept used in planning stage for driftdown, decompression, ETOPS/EDTO.

Most airlines fly a CI lower than the one associated to LRC, somewhere between LRC and MRC. LRC is actually a speed increase and range reduction in many cases.

Otherwise LRC continues to be a concept used in planning stage for driftdown, decompression, ETOPS/EDTO.

Join Date: May 2006

Location: Sydney

Age: 41

Posts: 23

Ok cool, our company’s A320’s have the VA2527-5A engines and from my understanding of that table, as long as we are 1000 feet +/- from the optimum level we can adjust and find an approximate cost index value for LRC which in turn will give us 40kg/min for this engine type, correct?