Cost Index
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bArt2,
BOAC beat me to it by a few seconds, it's a matter of company policy.
As an example we use a standard CI=65 for our B777 operation, but company policy is to increase to 150 if more than 15 minutes late.
Regards,
Old Smokey
BOAC beat me to it by a few seconds, it's a matter of company policy.
As an example we use a standard CI=65 for our B777 operation, but company policy is to increase to 150 if more than 15 minutes late.
Regards,
Old Smokey
Up to you to decide on sector pay against get-home-quicker
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Good discussion and some thread creep. I'll try and address the issues in the last few posts.
First PDA and understanding weight effect vs. engine/airframe deterioration. If the correct GW is in the FMS then APM type software will derive good PDA values for the cruise phase of flight. If however, extra load is put on and not accounted for in the ZFW and GW then the PDA will be skewed by the weight difference. As discussed previously APM PDA values are not the whole picture and from a flight planning system perspective a PDA value that represents the whole flight is more beneficial. It is important to remember that there are two PDA values; one for the flight planning system and one for the FMS. These two values can be from 0-4% different. It is also important to understand that the flight planning system PDA will also contain a component that matches the flight planning system calculations to the manufacturer's calculations. This is a fixed value and varies based on flight planning system provider, aircraft and engine type.
Next there is the issue of comparing what other operators use for CI values. this is a mugs game. Many variables enter the equation for calculating CI and no two operators have the same cost structure. The next issue is are you operating in metric or imperial units - their CI values are different. lastly comparison would assume that all airlines used the same, robust process to calculate CI. That is the furthest from the truth.
Then the great issue of tactical speed management and use of CI. This is a great theoretical idea, but doing it successfully is very difficult. First, we must realize that just increasing CI while maintaining altitude is a very costly way to reduce flight time. CI was designed to be used in a 2D (altitude and speed) solution. 2D solutions work in flight planning systems that have lots of data on wind profiles and computing power. Current FMS hardware/software does not have this proper 2D capability and was really designed as a system to allow the autoflight system to strategically fly the aircraft efficiently based on a 2D optimized flight plan with a given CI. we must also understand the effect of wind on speedup/slowdown capability and realize that they yield completely different orders of magnitude results in a headwind vs. a tailwind. You also need to clearly understand the cost penalty for the late operation vs. speeding up. I have seen pilots speed up a flight and spend five times as much as what was saved.
In a perfect world the best way to make the speed up decision is to have an in-flight flight plan generated to achieve the desired arrival time. this will adjust the vertical profile as well as the CI value to obtain the most speed up for the least cost. The incremental cost increase should be compared to the delay cost. Modern flight planning systems can do this very easily. LIDO has a module called VSOPs (Variable Speed Operations) that allows entry of a desired arrival time.
The issue of CI and efficient flight planning and operating is a complex multi-layered problem. I have been working in this area and teaching about it for over 10 years and still have only scratched the surface.
First PDA and understanding weight effect vs. engine/airframe deterioration. If the correct GW is in the FMS then APM type software will derive good PDA values for the cruise phase of flight. If however, extra load is put on and not accounted for in the ZFW and GW then the PDA will be skewed by the weight difference. As discussed previously APM PDA values are not the whole picture and from a flight planning system perspective a PDA value that represents the whole flight is more beneficial. It is important to remember that there are two PDA values; one for the flight planning system and one for the FMS. These two values can be from 0-4% different. It is also important to understand that the flight planning system PDA will also contain a component that matches the flight planning system calculations to the manufacturer's calculations. This is a fixed value and varies based on flight planning system provider, aircraft and engine type.
Next there is the issue of comparing what other operators use for CI values. this is a mugs game. Many variables enter the equation for calculating CI and no two operators have the same cost structure. The next issue is are you operating in metric or imperial units - their CI values are different. lastly comparison would assume that all airlines used the same, robust process to calculate CI. That is the furthest from the truth.
Then the great issue of tactical speed management and use of CI. This is a great theoretical idea, but doing it successfully is very difficult. First, we must realize that just increasing CI while maintaining altitude is a very costly way to reduce flight time. CI was designed to be used in a 2D (altitude and speed) solution. 2D solutions work in flight planning systems that have lots of data on wind profiles and computing power. Current FMS hardware/software does not have this proper 2D capability and was really designed as a system to allow the autoflight system to strategically fly the aircraft efficiently based on a 2D optimized flight plan with a given CI. we must also understand the effect of wind on speedup/slowdown capability and realize that they yield completely different orders of magnitude results in a headwind vs. a tailwind. You also need to clearly understand the cost penalty for the late operation vs. speeding up. I have seen pilots speed up a flight and spend five times as much as what was saved.
In a perfect world the best way to make the speed up decision is to have an in-flight flight plan generated to achieve the desired arrival time. this will adjust the vertical profile as well as the CI value to obtain the most speed up for the least cost. The incremental cost increase should be compared to the delay cost. Modern flight planning systems can do this very easily. LIDO has a module called VSOPs (Variable Speed Operations) that allows entry of a desired arrival time.
The issue of CI and efficient flight planning and operating is a complex multi-layered problem. I have been working in this area and teaching about it for over 10 years and still have only scratched the surface.
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Here's the simplest explanation I've seen:
COST INDEX= ratio of FUEL COST ($ per kilogram)/ TIME COST (fixed operating cost $ per minute)
Where TIME COST includes the amortization of the aircraft, crew, maintenance, management, depreciation, etc.
For example, a CI=30 means the cost of 30 kilograms of fuel is equivalent to the cost of 1 minute of time cost.
Therefore, it is management who eventually determines which base reference cost index to use. As flight deck crew, we should initially set the CI according to what management instructs us then revise strategically as required to adjust for time savings bearing in mind the consequential effect on the EFOB or fuel remaining predictions at destination and/or alternate.
COST INDEX= ratio of FUEL COST ($ per kilogram)/ TIME COST (fixed operating cost $ per minute)
Where TIME COST includes the amortization of the aircraft, crew, maintenance, management, depreciation, etc.
For example, a CI=30 means the cost of 30 kilograms of fuel is equivalent to the cost of 1 minute of time cost.
Therefore, it is management who eventually determines which base reference cost index to use. As flight deck crew, we should initially set the CI according to what management instructs us then revise strategically as required to adjust for time savings bearing in mind the consequential effect on the EFOB or fuel remaining predictions at destination and/or alternate.
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St Ex, I agree with flying the company derived CI and following the flight plan lateral and vertical profile, as long as a safe and comfortable flight is maintained.
However, tactical change of CI in flight need to be approached with far more care than just a consideration of the EFOB requirements. Our business runs on very tight margins and speeding up a flight can result in large cost increases for very little measurable commercial gain. The problem is that just staying at a fixed altitude and increasing CI results in smaller changes in time and due to the fact that CI increase vs. fuel/time is non-linear the costs can spiral exponentially.
Unless you know for a fact what the commercial gain is for the speed up and what the cost increment is at the higher CI, you are dancing with the devil. As stated in my previous post the best way to approach this is through the use of 2D profile optimization using an in-flight flight plan from a good flight planning system and an airline specific data set of commercial costs for late arrivals, passenger missed connections etc.
However, tactical change of CI in flight need to be approached with far more care than just a consideration of the EFOB requirements. Our business runs on very tight margins and speeding up a flight can result in large cost increases for very little measurable commercial gain. The problem is that just staying at a fixed altitude and increasing CI results in smaller changes in time and due to the fact that CI increase vs. fuel/time is non-linear the costs can spiral exponentially.
Unless you know for a fact what the commercial gain is for the speed up and what the cost increment is at the higher CI, you are dancing with the devil. As stated in my previous post the best way to approach this is through the use of 2D profile optimization using an in-flight flight plan from a good flight planning system and an airline specific data set of commercial costs for late arrivals, passenger missed connections etc.
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All of which returns us neatly to posts #20 and #21. If they do not specify what to do, you have at least 3 choices.
1) Just do what you want anyway ( or there are often mobiles and HF)
2) Stick with PLOG CI
3) Ask your company for policy
Often 'late' arrivals due to delays are easily absorbed in the programme and 'wasting fuel' to make up time un-necessarily can often, as Cbs says, cost a lorra money.
Obviously if you have an arrival landing slot to make, as at PRN in the 'early days' of KOSFOR, it make sense to adjust rather than have to divert.
1) Just do what you want anyway ( or there are often mobiles and HF)
2) Stick with PLOG CI
3) Ask your company for policy
Often 'late' arrivals due to delays are easily absorbed in the programme and 'wasting fuel' to make up time un-necessarily can often, as Cbs says, cost a lorra money.
Obviously if you have an arrival landing slot to make, as at PRN in the 'early days' of KOSFOR, it make sense to adjust rather than have to divert.
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on the 744; according to the boeing info; LRC figures are based on zero wind, and CI, the winds are taken into account.
Also, operations can "bias" a flight plan for a particular airframe, or route, if they so choose.
Also, operations can "bias" a flight plan for a particular airframe, or route, if they so choose.
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Willit Run, you have identified an important difference between LRC and CI - the inclusion of wind. There are some LRC data sets that have values for different winds.
As for "biasing" for a particular aircraft, this is what PDA does.
As for route specific adjustments, this can be done based on fuel costs and then on a day-of-flight basis if there are specific constraints such as arrival time requirements. Again the caution here is using the right tools to adjust CI and flight profile to achieve an arrival time; slow down to arrive after a morning curfew or arrive before a night curfew, needs to be tempered with what is really possible. This is a complex discussion that really needs a number of graphs and data sets to illustrate. Unfortunately, very difficult to accomplish on a forum.
One of the other issues associated with this is the "planned" departure times and block times in an airline schedule. If not done properly this can lead to far to many operations requiring tactical speed adjustments. The challenge is that block/departure times are hugely influenced by commercial constraints to gain a competitive advantage when attracting customers. Many travel booking engines rank by departure/arrival time and this influences customer choice. Having participated in these discussions it is fascinating.....
As for "biasing" for a particular aircraft, this is what PDA does.
As for route specific adjustments, this can be done based on fuel costs and then on a day-of-flight basis if there are specific constraints such as arrival time requirements. Again the caution here is using the right tools to adjust CI and flight profile to achieve an arrival time; slow down to arrive after a morning curfew or arrive before a night curfew, needs to be tempered with what is really possible. This is a complex discussion that really needs a number of graphs and data sets to illustrate. Unfortunately, very difficult to accomplish on a forum.
One of the other issues associated with this is the "planned" departure times and block times in an airline schedule. If not done properly this can lead to far to many operations requiring tactical speed adjustments. The challenge is that block/departure times are hugely influenced by commercial constraints to gain a competitive advantage when attracting customers. Many travel booking engines rank by departure/arrival time and this influences customer choice. Having participated in these discussions it is fascinating.....
