# Thread: What is the Cost Index?

1. Junior Member
Join Date
Feb 2011
Location
Amsterdam
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## What is the Cost Index?

Can someone explain me in normal english what the Cost Index is? thanks

2. Hi Mathijs:

Cost index (CI) is a made up figure, which when input into the FMC is used to calculate ECON (minium operational cost) speed. The higher the cost index number, the faster the aircraft flies. Basically, the company decides on the cost of keeping the aircraft in the air, and includes all sorts of costs such as crew, aircraft operating costs, fuel etc.. They then decide whether they want the aircraft to fly faster or slower and adjust the cost index as needed.

.. "For example, on the 744s at Cathay, it is normally use CI-80. On certain flights, where the connection time is tight in Hong Kong for passengers, they might flight plan a CI of 250, or 500. This makes the aircraft fly faster. On the other end of the scale, CX255 leaves HKG at 00:45ish, and cannot arrive before 6am due to curfews at Heathrow. a CI-0 is used to make the aircraft fly slower...."

The airline cannot tell an aircraft to fly a certain high or low speed, because that speed will always be different at different altitudes etc.. By giving the FMC a CI, it works out the best fast or slow speed to fly based on the conditions at the time.

NB.- These are data from Delta for the B767:

Aircraft ..............ECON...SL1...OT1
B-767-200............81......54....243
B-767-300............94......63....377
B-767-300ER.......113.....75....377
B-767-400ER.......107.....71.....---

*ECON -- for minimum operational costs
*SL1 around 2/3 of ECON and is use when ther is tail wind or the flight schedule is forwarded. SLI allows to save more gas than ECON
*OT1 is used when there is a headwind or flight schedule is delayed

It's a little hard to understand, and hopefully I have not confused you too much!!
Last edited by pivek; 04-22-2012 at 07:55 AM.

3. Junior Member
Join Date
Feb 2011
Location
Amsterdam
Posts
8
Thank you VERY much! now I finally understand it!