Sign in to follow this  
CKAJCA

What Cost Index to enter in FMC?

Recommended Posts

I use PFPX for all my flight planning and now I do not seem to get a Cost Index number (I think I did before!!). All I get now is MACH: M.78 or LRC. When I enter the Cost Index into the FMC what figure should I be using. I hope that makes sense.

 

Regards Colin

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

 

 


I use PFPX for all my flight planning and now I do not seem to get a Cost Index number (I think I did before!!). All I get now is MACH: M.78 or LRC. When I enter the Cost Index into the FMC what figure should I be using. I hope that makes sense.

 

CIs change.  While many operators have a value that's a default, it's normally only used in cases where they - either intentionally or accidentally - do not provide a value on the load sheet.
 
-If the flight is delayed on departure and there's still a chance to get there on time, they'll raise the CI to go faster and get there on time.
-If they're expecting delays at the destination, they may dial the CI back to just get there at the end of the rush.
-If the flight has a ton of Premiere Members (or whatever the airline calls them), they may actually dial the CI up to get them there early.
-If the price of gas goes up, the CIs often go down.
-Certain routes will have higher CIs, while others have lower CIs (based on average revenue gained on that segment).
 
There really isn't a standard value for airlines in all cases.  Despite what many will claim here, it's not as static as many would have you believe.

Share this post


Link to post
Share on other sites

This is a PFPX question, and best served in their forum.  Each aircraft in PFPX has it's unique speed table that comes from the templates, note the 737 is different set of options from either 738 or 739.

 

Kyle answered the which is best question. I keep it simple and select a set speed in PFPX that best matches the CI range I'm going to use in the aircraft. Usually it's either .77M or .78M. in the NGX.

Share this post


Link to post
Share on other sites

Depends on the airline. American carriers are big bean counters so you get a different one each flight. Foreign carriers are more set in their plans, Emirates for example recently changed over to a general cost index system. European LLC's also have a set system and some bigger European carriers. I do not have the latest numbers, but

 

http://forum.avsim.net/topic/336375-cost-index-database/

 

that is a start

 

-David Lee

Share this post


Link to post
Share on other sites

 

 


European LLC's also have a set system

 

That just doesn't make any sense to me. Do those operators just not take a basic ECON class to know what an opportunity cost is, or what? It still baffles me why any one operator would want to use a fixed CI. As an LCC, you'd imagine that they'd be even more sensitive to moving the CI around to really squeeze every last bit of revenue out of the aircraft.

 

Then again it also baffles me why any company would use Excel for their "databases," but that happens all the time, and companies waste heaps and heaps of money on the time spent on maintaining them, so I guess it's more of an issue of the human capital an operator has...

 

 

 



that is a start

 

Not only is that 4 years old, it also contains a bunch of stuff that simmers are simply reporting back with. That could be as simple as "oh hey, I saw a dispatch sheet on this one flight with this one airline and it said 42, so they must use 42 all the time!"

Share this post


Link to post
Share on other sites

 

 


Then again it also baffles me why any company would use Excel for their "databases," but that happens all the time, and companies waste heaps and heaps of money on the time spent on maintaining them, so I guess it's more of an issue of the human capital an operator has...

 

LOL I agree... not a fan of flat databases. Excel is a common tool in engineering but I've seen it used from everything from boiler plate forms (without computations) to modelling a petrochemical refinery's crude slate.  It boils down (pun intended) to lack of training by corporations. They only invest what they must in their human capital. People stick to what they know and if they know Excel but are a little shaky in Access or any other relational db then they are going to use Excel.

Share this post


Link to post
Share on other sites

Cost index varies but for us 10-35 is a typical range.  You may see the occasional 100 if you have really strong winds.  A CI of 100 puts you right up against the redline so almost everybody is going to back the speed off a bit anyway.

 

In PFPX you can enter a cost index in the cruise speed box instead of a mach number and it will adjust the speed accordingly.

Share this post


Link to post
Share on other sites

That just doesn't make any sense to me. Do those operators just not take a basic ECON class to know what an opportunity cost is, or what? It still baffles me why any one operator would want to use a fixed CI. As an LCC, you'd imagine that they'd be even more sensitive to moving the CI around to really squeeze every last bit of revenue out of the aircraft.

 

Then again it also baffles me why any company would use Excel for their "databases," but that happens all the time, and companies waste heaps and heaps of money on the time spent on maintaining them, so I guess it's more of an issue of the human capital an operator has...

 

 

 

 

Not only is that 4 years old, it also contains a bunch of stuff that simmers are simply reporting back with. That could be as simple as "oh hey, I saw a dispatch sheet on this one flight with this one airline and it said 42, so they must use 42 all the time!"

 

For short haul LLC flying most numbers are fixed or a certain range each flight, in Europe many times you are at cruise only for 30 minutes, and your climb and descent numbers are fixed differently. For companies like Emirates they have a set standard that most of the time gets followed. Of course I never said the numbers are put in the same each time, and the link I gave is only a "getting started" number for someone to use, of course if you desire 100% realism you'd have to ask the flight planning dept.

 

I don't see the big deal using a database like that, simmers dont have all the complicated planning software that takes into account everything for a flight including overflight costs of each country for long haul. so a database of general numbers is fine for us just simming.

 

David Lee

Share this post


Link to post
Share on other sites

I've got a set of numbers I use, which mainly tailor the IAS speeds more than anything.  I hear SWA was using 30, and maybe
even as low as 20 according the rumors.. But I don't like it quite that low. When artificial SWA, I usually climb out at around 290-

295 or so knots. In order to get this speed, I use 36-38 most of the time with the 700, and probably about the same with the 800.

With that CI, the descent will almost always be 282 IAS once you merge out of mach speed.

When I use the pseudo BBJ's, I usually use a higher number. Usually 45 with the 600, 40-45 with the 700, and 40 or so with

the 800 and 900. With the 600 and 700, the descent  with CI 45 will usually be 290. I'd have to check the larger planes..

Forgot what they do with the 40-45 range. I haven't used over 50 in a long time..  I hardly ever see over 300 knots IAS the

way I fly. As long as a high cruise alt, I find the CI doesn't effect mach cruise a whole lot. All those will cruise at m .78-.79

as long as the alt is high enough. Being I stay under CI 50, I never see a mach cruise speed over  m.79.

Share this post


Link to post
Share on other sites

 

 


For short haul LLC flying most numbers are fixed or a certain range each flight, in Europe many times you are at cruise only for 30 minutes, and your climb and descent numbers are fixed differently. For companies like Emirates they have a set standard that most of the time gets followed. Of course I never said the numbers are put in the same each time, and the link I gave is only a "getting started" number for someone to use, of course if you desire 100% realism you'd have to ask the flight planning dept.
 
I don't see the big deal using a database like that, simmers dont have all the complicated planning software that takes into account everything for a flight including overflight costs of each country for long haul. so a database of general numbers is fine for us just simming.

 

That's just the thing, though. Ask your average simmer (who knows what a CI is) what you should use and they'll likely say "well, Operator X uses 42" (note the specific value, without stating a range). Ask them if it changes and they'll likely say no, even if it does. The very fact that the linked thread simply lists set values without a range lends to this idea. There's enough misinformation in this hobby. I really don't like contributing to it, so I speak up when I see something that can be potentially misleading. In this case, a thread with specific values is potentially misleading, particularly because the other thread does not note that the values may change, and the reasons for why. The amount of confusion on the topic is a clear indicator of this.

 

Moreover, CI doesn't only affect cruise, so saying that it doesn't matter for a short flight is somewhat misleading. Granted, shorter segments mean that the CI has less of an effect on a single flight, but remember that even winglets aren't very effective from a single flight perspective. It's the savings over time that are the issue. For companies like Emirates, CI should be even more of an issue, since their business model is limited to longer haul flights for the most part, which would see even more of a benefit to tailored values. Then again, they may not be as constrained by fuel costs, given their advantage in that market.

Share this post


Link to post
Share on other sites

I've got a set of numbers I use, which mainly tailor the IAS speeds more than anything.  I hear SWA was using 30, and maybe

even as low as 20 according the rumors.. But I don't like it quite that low. When artificial SWA, I usually climb out at around 290-

295 or so knots. In order to get this speed, I use 36-38 most of the time with the 700, and probably about the same with the 800.

With that CI, the descent will almost always be 282 IAS once you merge out of mach speed.

The 20 CI was definitely a thing a few years ago; we're talking about the airline that used to fly 260 knot climbs to save gas. Circa 2010 the went from using 38 to 20, if I remember correctly. I know they were using 20 as recently as last Spring, but WN could have easily changed since. 

 

 

That's just the thing, though. Ask your average simmer (who knows what a CI is) what you should use and they'll likely say "well, Operator X uses 42" (note the specific value, without stating a range). Ask them if it changes and they'll likely say no, even if it does. The very fact that the linked thread simply lists set values without a range lends to this idea. There's enough misinformation in this hobby. I really don't like contributing to it, so I speak up when I see something that can be potentially misleading. In this case, a thread with specific values is potentially misleading, particularly because the other thread does not note that the values may change, and the reasons for why. The amount of confusion on the topic is a clear indicator of this.

 

Moreover, CI doesn't only affect cruise, so saying that it doesn't matter for a short flight is somewhat misleading. Granted, shorter segments mean that the CI has less of an effect on a single flight, but remember that even winglets aren't very effective from a single flight perspective. It's the savings over time that are the issue. For companies like Emirates, CI should be even more of an issue, since their business model is limited to longer haul flights for the most part, which would see even more of a benefit to tailored values. Then again, they may not be as constrained by fuel costs, given their advantage in that market.

This probably stems from simmers having a very limited understanding of what CI actually is and how it fits into the bigger picture of airline operations. When it comes to generating an OFP, there's much more that goes on in the background that is transparent even to most pilots. The thread probably isn't that bad, since it's a nice ballpark for those that want to fly realistically. 

 

Then again it also baffles me why any company would use Excel for their "databases," but that happens all the time, and companies waste heaps and heaps of money on the time spent on maintaining them, so I guess it's more of an issue of the human capital an operator has...

Several of my friends have done internships at US carriers, and the amount of Excel work they did was a bit frightening. 

Share this post


Link to post
Share on other sites

This probably stems from simmers having a very limited understanding of what CI actually is and how it fits into the bigger picture of airline operations. When it comes to generating an OFP, there's much more that goes on in the background that is transparent even to most pilots. The thread probably isn't that bad, since it's a nice ballpark for those that want to fly realistically.

Yeah, I agree. That's also a criticism I've had with the community as well (more with the media, actually). A lot of weight is placed on what a pilot says, when the industry is often better explained by someone else. Pilots don't know a lot of what goes on in ops. Heck, how many times have you heard the pilot say "sorry for the delay ladies and gentlemen - we'll make it up in the air"? Someone from ops would be able to tell the pilot that the delay was predicated on their filed cruise speed, and "making it up in the air" would simply ruin the purpose of the intentional ground hold, causing strain on the system at the destination airport (see page 21 "How Does a GDP Work?": http://www.fly.faa.gov/Products/Training/Traffic_Management_for_Pilots/TFM_in_the_NAS_Booklet_ca10.pdf). The pilot usually doesn't know much about the reasoning behind ground stops or delay programs.

 

Of course, that's not to say "don't trust pilots," but in many cases there's a better info source. A pilot can explain how to fly an approach. The TERPS team can explain why it was designed like that. The Regulatory team can tell what compliance issues need to be evaluated. The operator (and/or Regulatory) can explain what kind of currency needs to take place if the approach requires special certification/equipage. The controller can explain how to clear someone onto that approach. Each of those parties probably won't be able to do much other than explain their own realm in any detail without butchering it at least partially.

 

It helps people get in the ball park, but I think we (as a community) need to be better about putting disclaimers on things of this sort. If they didn't have any ill effect without a disclaimer there wouldn't be a misconception, but there clearly is an information issue here.

 

Several of my friends have done internships at US carriers, and the amount of Excel work they did was a bit frightening.

Definitely. I remember it well. It was pretty frustrating, but trying to explain why things should change to the ramp staff was about as effective as trying to explain quantum physics to the brick wall behind the push tug.

Share this post


Link to post
Share on other sites

Hi,

From the moment I'm becoming older and older and I don't want to wast too time to think I usually use a CI of 30 and I'm happy...jet A1 is not expensive with FSX...

 

Ciao

 

Andrea

Share this post


Link to post
Share on other sites

That's just the thing, though. Ask your average simmer (who knows what a CI is) what you should use and they'll likely say "well, Operator X uses 42" (note the specific value, without stating a range). Ask them if it changes and they'll likely say no, even if it does. The very fact that the linked thread simply lists set values without a range lends to this idea. There's enough misinformation in this hobby. I really don't like contributing to it, so I speak up when I see something that can be potentially misleading. In this case, a thread with specific values is potentially misleading, particularly because the other thread does not note that the values may change, and the reasons for why. The amount of confusion on the topic is a clear indicator of this.

 

Moreover, CI doesn't only affect cruise, so saying that it doesn't matter for a short flight is somewhat misleading. Granted, shorter segments mean that the CI has less of an effect on a single flight, but remember that even winglets aren't very effective from a single flight perspective. It's the savings over time that are the issue. For companies like Emirates, CI should be even more of an issue, since their business model is limited to longer haul flights for the most part, which would see even more of a benefit to tailored values. Then again, they may not be as constrained by fuel costs, given their advantage in that market.

I know CI doesn't only affect cruise but very rarely are you flying vnav descent unless you are the extreme cost cutting like Ryanair. ATC do not like jets descending at 250-260 knots at flight levels. Most of the time you are going down at a set speed like 280 or 300. So in that regard the CI is really only affecting cruise numbers and climb. But not climb much because even at low CI your climb speed is pretty high (above 280-290) - David Lee

Share this post


Link to post
Share on other sites

I know CI doesn't only affect cruise but very rarely are you flying vnav descent unless you are the extreme cost cutting like Ryanair.

I wouldn't quite call this a qualified statement. Might you be able to provide a list of operators who don't use VNAV in the descent? I know some might not, but that seems like a very bold statement without any references provided.

ATC do not like jets descending at 250-260 knots at flight levels. Most of the time you are going down at a set speed like 280 or 300. So in that regard the CI is really only affecting cruise numbers and climb. But not climb much because even at low CI your climb speed is pretty high (above 280-290) - David Lee

This is definitely not a qualified statement. As someone who's spent quite a lot of time working with ATC, and traffic management from the TRACON to the the System Command Center (ATCSCC) here in the United States, the speed predominantly a non-issue. Granted, the speed drives the descent rate for an idle path descent, but unless you're unnecessarily tying up flight levels by descending very slowly (around 500 fpm), it really doesn't matter. For the lateral perspective, aircraft types are highly variable in their operation, so adjusting for closure between an operator descending at a higher speed and an operator using a lower speed is just business as usual. For the vertical perspective, it's a non issue unless you're descending so slowly that you're well outside of the "normal" assumption. A difference of 20 knots isn't going to cause that.

 

Ask most controllers what speed they'd prefer an aircraft to descend at and you'd likely get a blank stare. The only times they really see any issue is when you have a GA aircraft in the mix with large/heavy (GA aircraft climb like pigs, especially in the summer), or you have a military aircraft that climbs so quickly that the ATC automation blanks the value because it assumes the rate is unachievable (see F/A-18 climb rate). ATC isn't here to micromanage the flying of aircraft. They're here because aircraft are different, and operated differently, and need to have someone with a different perspective ensuring that they are separated. If you're not fitting into the mix, they're there to either prompt you to attempt to fit into the mix (usually not until the TRACON, at lower levels), or provide some sort of mitigation (like a "blow-by").

 

As I've mentioned in this thread already, please be very mindful of the information you're putting out there. People who are less knowledgeable will take information from those who appear knowledgeable at face value. There are already enough misconceptions about ATC out there. Let's not add more.

The world's largest 737-800 operator have been using just CI6 for the last three years.....

With no variance at all? One would imagine that such an operator would, well, harp on most efficient practices and cost balancing. Costs are rather variable in this industry. Using a fixed value is almost akin to using a fixed FL. Then again, developing some way of managing and balancing those costs itself is a cost, so maybe it's just resignation?

Share this post


Link to post
Share on other sites

I know CI doesn't only affect cruise but very rarely are you flying vnav descent unless you are the extreme cost cutting like Ryanair. ATC do not like jets descending at 250-260 knots at flight levels. Most of the time you are going down at a set speed like 280 or 300. So in that regard the CI is really only affecting cruise numbers and climb. But not climb much because even at low CI your climb speed is pretty high (above 280-290) - David Lee

We've been using just CI6 for the past 3 years, this gives you a descent of 245 kts on transition. ATC in Europe have absolutely no problem with what speed you descend at. As every operator flies at different speed, either with a fixed or variable CI, you might be asked by ATC to speed up or slow down to maintain separation. We plan to descend at our CI (245kts) and we accelerate if asked to.

 

The ECON CRZ and CLB speed is a function of not just CI but your planned cruise altitude, HW/TW component and Gross Weight and will vary every flight. Your ECON DES Speed is fixed.

 

There is also a common misconception that all we ever use is LNAV and VNAV. For our operator VNAV is the default CLB or DES mode. During DES we'll use it if on profile. As soon as we get a shortcut we'll be high on profile and you have two ways to recapture that profile, accelerate and/or use speed brake. We use what ever mode on the MCP to get the job done.

 

 

With no variance at all? One would imagine that such an operator would, well, harp on most efficient practices and cost balancing. Costs are rather variable in this industry. Using a fixed value is almost akin to using a fixed FL. Then again, developing some way of managing and balancing those costs itself is a cost, so maybe it's just resignation?

 

No variance at all, CI6 and that's it and from what I understand it will be staying that way. It's not all about saving money (although a big part of it!!) With the introduction of CI6 there was a notable decrease in the amount of High Energy Approaches being flown too.

 

Share this post


Link to post
Share on other sites

No variance at all, CI6 and that's it and from what I understand it will be staying that way. It's not all about saving money (although a big part of it!!) With the introduction of CI6 there was a notable decrease in the amount of High Energy Approaches being flown too.

 

That latter part makes sense, I guess. Still, I find it a bit shortsighted. Granted, I'm not running an airline, but fixed behavior is by nature inflexible, but flying by its nature requires flexibility for efficiencies.

 

In any case, interesting bit of info about that op and its fixed CI.

Share this post


Link to post
Share on other sites

This whole conversation is somewhat academic since the cost index is basiclly just a starting point for flight planning.  We usually end up tweaking the speeds in the box to our liking anyway during the flight.  Some pilots input speeds directly into the climb, cruise and descent pages, others just bump the cost index up or down until the speeds are what they want.  Throw in some ATC assigned speed changes along the way and the CI becomes even less relevant.

 

In short I wouldn't spend too much time worrying about the perfect CI to use.


I wouldn't quite call this a qualified statement. Might you be able to provide a list of operators who don't use VNAV in the descent? I know some might not, but that seems like a very bold statement without any references provided.
 

 

I think his statement may have been poorly worded.  A better way to say it that some operators don't use the computed ECON speed during a VNAV descent.

 

Our company standard descent speed is 290.  The FMC will never give us a speed lower than that in ECON, even if the true ECON speed would be lower.  Even then going into places like ORD you are going to end up changing it to at least 300, if not more.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this