Cost Index 737 in your Company.
Joined: Aug 2003
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From: At work
733 We used to run CI 35, and 20 for long range ETOPS flights. Unfortunately because we now have to accommodate the lowest common denominator with competitors, we now fly 28 to give a 280kt descent speed on indicated. I much preferred 35 as it gave 293kts and seemed a bit more stable in speed.
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
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From: UK
I assume so - it may have changed, but CI used to be based on company assessed costs and I believe the FMC 'reacted' to the CI in a chosen way - it is after all just a number and depending on what factors the FMC has to run the index, speeds for a given number could vary. It may well be that nowadays the Boeing FMC has just one fixed scale - I don't know, but the other factor which renders the information abenk requests of little value is that any particular company will have different reasons for choosing a particular speed profile - eg maintenance v fuel weighting/wages etc, so unless abenks company has the same 'running costs' it is of little interest for Company A what Company B does. I guess all airlines now operate to a lower CI than they did.
As 737ng said, in a well-run airline CI should reflect the sectors involved and be provided to crews for that sector, but some companies just have a fixed CI which is a fairly blunt instrument.
As 737ng said, in a well-run airline CI should reflect the sectors involved and be provided to crews for that sector, but some companies just have a fixed CI which is a fairly blunt instrument.
Last edited by BOAC; 19th December 2009 at 08:00.
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Hawk, this is theoretically possible. There are companies which never change the basic parameters in the FMC, others do this on a monthly basis with the latest analyses from the fleet.
There are plenty of factors which all feed in to the system and calculate the individual parameters, using an optimization tool will provide a cost index which is not (!) reflecting the present optimum, but the one based on the last calculation data.
Worked for a company which was very particular about the CI, however, as per directive of the DO, during climb and descend we used a fixed speed setting.....makes the whole game a farce.
Presently using 34 for all classic flights and in during all stages.
There are plenty of factors which all feed in to the system and calculate the individual parameters, using an optimization tool will provide a cost index which is not (!) reflecting the present optimum, but the one based on the last calculation data.
Worked for a company which was very particular about the CI, however, as per directive of the DO, during climb and descend we used a fixed speed setting.....makes the whole game a farce.
Presently using 34 for all classic flights and in during all stages.
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
Likes: 4
From: UK
abenk - I do not understand the question! Higher CI = fly faster = get there quicker. If the scheduled time is less than the 'normal' actual time required you will be 'normally' be late. Company choice then to increase CI for that sector or just accept late arrival.
When you have a tailwind or the resulting arrival is too early for airfield slot for whatever reason, then you can reduce CI. Is that what you ask?
When you have a tailwind or the resulting arrival is too early for airfield slot for whatever reason, then you can reduce CI. Is that what you ask?