What's your cost index?

[m80drvr]

Heard a rumor bout a guy at my airline that always put 999 in the bus box. The CP called him and asked why he was using 999 on all his fights. The pilots response was "cause it won't take 1000".

D

 

[Bjammin]

Our index is on the flight plan and can be anything from 80 to 250. On the frieghter if we are behind schedule they plan for a CI of 250 to get important frieght on deck. They encourage captains to go to 25 or 0 if we are ahead.

 

[atldc9]

"Cost Index and how we use it.


With the advent of FMS/PMS, operators gained the ability to make an economic decision regarding speed based on other costs, but including fuel. This was done with the development of a formula called Cost Index. The formula seems simple enough. It is the sum of the Variable Crew Costs (cockpit and cabin) and the Variable Maintenance Costs divided by the fuel costs in cents per pound. Fuel costs seem easy enough to calculate although it can get a little complicated when tankering effects and hook-up fees are considered. Variable crew costs get very complicated when one considers the wide range of pay on any given flight. (Seniority, gaurantees, volunteer flying, trip credit, actual or schedule, minimum daily, reserve status,etc. That is just for the cockpit, the cabin having their own variables.) Variable Maintenance Costs are even more difficult to calculate as some airplanes are under warranty or parts of them are under warranty and many components are on a cycle basis for change or repair rather than hourly.

In consideration of this complexity, it still has been possible to assemble the data that at least captures the spirit of the formula. Our Phoenix Flight Planning program can do this. The computer can generate a Cost Index and when entered into the PMS/FMS will allow a flight to be flown at its most ECONomical speed. (Perf on PMS MD-80s.) The computer will adjust speed in climb, cruise, and descent and should yield a minimum total cost for the flight. If fuel is comparatively cheap, it will fly fast ( have a high CI.) If fuel is expensive, it will fly slow (a CI more toward zero.) The range of speed from fast to slow is from just below MMo to MRC. It normally flies between MRC and LRC. In other words, it tries to capture as much of that 1% of the burn that we talked about earlier.( That 1% being the fuel used between MRC and LRC.)

The following discussion may add a little cloudiness to the subject. Let's examine a flight. STL-LAX. As soon as the flight departs STL and climbs at 320 knots, the CI calculation is invalidated.( The flight is still operating with an economic consideration in mind but the consideration is to help increase the volume of the STL airport and not to minimize the total cost of the flight). As you can see, all flights operating into and out of STL cannot have a correct CI calculated for it because of this speed intervention. The same is true of flights on oceanic where a portion is flown at constant mach.
We do believe with some massaging of the formula that we can get fairly accurate CIs on these flights. Testing is continuing and we hope to have something in the works later in the spring. We do have some flights where CI calculations are correct and we can expect to see that concept implemented before too long.

The way we have been operating is that we have CIs that emulate LRC as closely as possible. That is why you have been seeing a CI of 30 on the MD-80s for example. It is fair to say that with fuel costs rising, the airline should be operating at a slightly lower speed. This decision has to be made very carefully however, as on time performance could be impacted by that decision.

We will be using a concept based on a Boeing recomendation called "Generalized Cost Function". This GFC takes the Cost Index formula and incorporates a consideration for on time arrival. Thus it takes into account all the costs mentioned above plus a cost associated with on time arrival excursions. The number you see will still be expressed as Cost Index and GFC will not be displayed" By AA

As I was reading this, all I could think was, damn, he spit this out of the top of his head?

 

[DougsRule]

Depends on the leg...if its the last leg and I want to make my commute...BALLS TO THE WALLS BOYS and FCUK the Cost Index!!

 

[FL420]

Airbus published an outstanding article in their FAST magazine that has the information you seek. It is a 108 page .pdf file found at:

http://www.airbus.com/store/mm_repository/pdf/att00006418/media_object_file_FAST37_full.pdf

It covers the Honeywell FMS's found in most of the Airbus models as well as in many Boeings.

Here is the real link to the article. Sorry about that.

http://www.iata.org/NR/ContentConnector/CS2000/Siteinterface/sites/whatwedo/file/Airbus_Cost_Index_Material.pdf

 

[(o) (o)]

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