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Author Topic: Cost Index feature  (Read 941 times)

Offline Andre

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Cost Index feature
« on: December 06, 2013, 09:21:25 PM »
I would like to see a Cost Index feature added to the "Open New Route" page. Most of you probably know what Cost Index is, but here is a brief explanation:

"Many jet aircraft are equipped with various performance computers for the purpose of determining the best speed at which to travel (ie the economy speed) in order to minimize the total operating cost of the flight. To do this the FMC needs information about time-related costs and fuel cost. Fuel costs are based on the price and amount of fuel needed to complete the flight (legally, with reserves etc). Rather than enter all of these individual factors into the onoard FMC, most airlines use a ratio of the two costs to determine the economy speed for a given flight on a given day. This ratio is called the Cost Index, and it determines the economy speed for a flight by minimizing the total cost of operation."

Cost Index = Cost of Time / Cost of Fuel

Source:
JetPlanner manual. www.Jeppesen.com

http://www.airliners.net/aviation-forums/tech_ops/read.main/45399/

The point is, the Cost Index affects the speed of the aircraft, how much fuel it burns, maintenance and other things.

Scenarios where this would be a benefit in Airwaysim:

- Economy / Fuel burn / Maintenance.
- Flight time.
- Easier to fit a route inside the schedule.
- Easier to target available slots by adjusting the CI which results in the aircraft flying faster or slower.
- Easier to make the route fit when flying to slot restricted airports and/or airports with limited operative times.
- Easier to make routes fit when phasing out an old fleet and transitioning to a different aircraft type.
- Makes it easier to differentiate between an LCC and a Legacy Carrier.
- Currently you can delay a turn-around to use available slots, but you can't speed up the aircraft. CI would let you do that at a cost of more fuel burn.

I'm not a programmer, so I don't know how this can be implemented. But I imagine it would have to be simplified down to a 0-100 CI for all aircraft types, regardless if that aircraft actually has a Flight Management Computer or not. Maybe it could also only affect speed and fuel burn, and not maintenance to make it a bit simpler. I also think that you should be able to set a default Cost Index setting for each aircraft type in the Settings page, just like you can set default registration and turn-around time. Below is an example of how I visualize it in the Open New Route page:



« Last Edit: December 07, 2013, 09:59:27 PM by [SC] Andre »

Offline NovemberCharlie

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Re: Cost Index feature
« Reply #1 on: December 08, 2013, 12:01:05 AM »
This is genious! Sometimes wheni am scheduling I can not fit in a flight because of mere minutes, but i'd be happy to lose some to win utilization!

Big fat +1

Offline JumboShrimp

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Re: Cost Index feature
« Reply #2 on: December 08, 2013, 12:20:29 AM »
I think Sami mentioned this in the past as a possible feature.

BD

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Re: Cost Index feature
« Reply #3 on: December 08, 2013, 02:23:20 AM »
Ok...so this is all about being able to change the flight time between airports for any specific aircraft (presumably within a set range).  Kind of got lost in the Cost Index terminology.  :laugh:

Doing so would affect the cost of that flight (probably mostly fuel consumption), so that there is a tradeoff a player must make. 

Makes sense, and I see the rationale.  There are time when playing with the turn time just won't bridge the gap, and it would be nice to have another tool to fit schedules together.

Similar discussion here:  http://www.airwaysim.com/forum/index.php/topic,46727.msg257927.html#msg257927

The challenge then would be knowing the "default/at par" cost of operating the aircraft and what the multiplier would be (e.g. 3 to 1, as in 10% faster = 30% more cost) to make the outcome of the decision estimatable / predictable ahead of time.

Offline Sami

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Re: Cost Index feature
« Reply #4 on: December 27, 2013, 02:54:02 PM »
Who's going to supply a list of CI vs. speed for all aircraft then? ;)

For A320 series the normal Mach range for cruise is between .76 and .80, but for ATR for example there's no such thing as CI and the cruise speed is always standard. For Tu-214 for example I have no idea what the speed range could be and so on.  .. so using any math to calculate the speed range from the current nominal cruise speed is difficult and will lead to errors. And add the fuel consumption math there ...

But some simplification could work, where you just choose "slow-normal-fast" cruise speed target (not available for props), and system would assume that for example 'fast' is then 1.02x standard speed and 'slow' is 0.98x standard speed (these are from A320 speeds). For fuel usage it's much more complicated though as you need to carry more fuel which in turn needs more fuel etc. (generally speaking CI100/M80 for A320 on a 2.5hr leg needs some 300-400kg more, and CI200 (M80 but lower FL) needs then 600+kg more, with flight time savings being about 3-8 minutes on such leg, depending on winds ...roughly)   ...so all in all, there's not much difference in flight times really on shorter legs; adding 0.02 mach (.78->.80) starts to show really on flights longer than 3-3,5hrs.

But another major difference is the climb/descent speed - standard CI20 for A320 series gives about 280-290 in climb (depending on weight/winds) and something between 270-285 in desc (anything below 300kts is a real granny speed ... blah these fuel prices and the resulting economy speeds :P).. While CI100 puts 340 kts to both. Again this data for all planes is rather impossible to be sourced from.  (and for props again, their climb/cruise/descent speeds are always roughly the same .. in ATR you'd have 170 kts or 190 kts ias climb only and that's it, all other speeds were standard)


However it is true that some flights are planned with a high CI to begin with due to crew rest or scheduling constraints. But in AWS managing that would be difficult - when you think of possible future features like automated conversions of routes between fleet types and so on.

..so to make it short; since the flight time and fuel calculations in AWS are extremely accurate, I'd hate to spoil them with some additions that are not based on any real/proper data, and having such speed range data for all planes isn't really something that's available easily anywhere.
« Last Edit: December 27, 2013, 03:05:24 PM by sami »

Offline JumboShrimp

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Re: Cost Index feature
« Reply #5 on: December 27, 2013, 03:03:00 PM »
How about taking info from one jet with known figures, such as A320, and scaling all other jets proportionally.

3 speeds of slow, normal, fast sounds like great compromise, with normal being default.

Offline [SC] - King Kong

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Re: Cost Index feature
« Reply #6 on: December 27, 2013, 03:59:09 PM »
could come in usefull if i need a few extra minutes for my schedules or just lack the flight time to finish a red eye

Offline Andre

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Re: Cost Index feature
« Reply #7 on: February 18, 2014, 06:47:13 PM »
..so to make it short; since the flight time and fuel calculations in AWS are extremely accurate, I'd hate to spoil them with some additions that are not based on any real/proper data, and having such speed range data for all planes isn't really something that's available easily anywhere.

That's understandable, but I still would like a simplified CI feature for all jets. Turboprops and piston pounders could be left out.

The possible benefits are so many. :)

Offline LemonButt

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Re: Cost Index feature
« Reply #8 on: February 18, 2014, 07:32:12 PM »
Since the problem is turnaround time and not slots (we don't buy landing slots--only takeoff), why not just have more expensive turnarounds?

Instead of flying the jet at Mach .80 instead of Mach 0.79, why not just keep everything flying at Mach 0.79 and then add a staff component for a rushed turnaround?  This would be as simple as adding an overtime labor component to the flight.

It can take you a month to build a house or it can take 1 day--it just depends on how much your willing to spend on labor and overtime.  Overtime costs could just rise exponentially.  Shaving 5 minutes off a turnaround without penalty costs 125% of what it would normally to pay the appropriate employee groups for that time period.  10 minutes would be (125%)^2 = 156%, 15 minutes would be (125%)^3 = 195% to (1.25)^(n/5).  Thus, you could reduce a B777 turnaround time from 165 minutes @ ~1% to 100 minutes @ ~1% at a cost of (1.25)^(65/5) = 1818%.

The listed turnaround is 100 minutes with a high chance of delay, but if you had 10 employees cleaning 10 lavatories instead of just 1 employee cleaning all 10, you can get it turned around with a very low probability of delays.

Offline Andre

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Re: Cost Index feature
« Reply #9 on: February 20, 2014, 07:53:03 AM »
Yes the faster turn-around idea is a good one. I've previously suggested a system where we choose ground handling companies just like we choose fuel providers. The more expensive ground handling companies would turn around the aircraft faster. But having this feature in the same page where you set up the flight would be best, so that we could choose different turn-around speeds  for every flight.

Offline LemonButt

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Re: Cost Index feature
« Reply #10 on: February 20, 2014, 03:15:17 PM »
I see this being a huge benefit for airlines in the ultra-long game worlds with multiple fleet replacements.  You could easily replace a BAC 1-11 with an MD-90 without having to worry about delays from going from a 60min to a 70min turnaround--you could keep it 60min and pay extra.  Genius.

Offline dmoose42

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Re: Cost Index feature
« Reply #11 on: February 20, 2014, 03:20:08 PM »
That's a great point lemonbutt...

 

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