No Descent Via VNAV

[berts 97]

22 hours ago, scandinavian13 said:

Bob, who used to work at BA, and is remarkably vague about what the position actually was.

This isn't always the case, but I'm curious as to the source...

The comment about the 747-400s, though, supports my point: it's variable, and dependent on the situation.

Kyle, I think I can understand why you say the Bob you apparently know is remarkably vague about this subject..

The main reason for this is because the FMS Cost Index is a potentially sensitve piece of commercial information and is determined using various factors, such as the current price an operator might be paying for their fuel.  In view of the fact that only the Chief Pilot is likely to have this sort of detailed financial information, I very much doubt if any airline or operator will give the flight simming world an up-to-date or accurate CI figure!  The Cost Index is primarily used by the FMS to set the aircraft's performance parameters and it can be either a standard (default) planned Cost Index or one that is calculated for an individual flight. Sometimes a Flight Plan will have no Cost Index recorded at all, in which case the crew has to input a manual speed into the FMS.

[Captain Kevin 586]

5 minutes ago, berts said:

Kyle, I think I can understand why you say the Bob you apparently know is remarkably vague about this subject..

I don't think he actually knows Bob, I think he was just using it as an example. Probably make more sense reading it this way.

23 hours ago, scandinavian13 said:

...and this is why I'm not a member of a single VA out there. This kind of stuff propagates because of VAs, and their assertions of what is, and isn't true, based on some random dispatch they, or their kid picked up off of a flight, or a friend, or something...or Bob, who used to work at BA, and is remarkably vague about what the position actually was.

 

[Jetlinker 13]

24 minutes ago, berts said:

Kyle, I think I can understand why you say the Bob you apparently know is remarkably vague about this subject..

The main reason for this is because the FMS Cost Index is a potentially sensitve piece of commercial information and is determined using various factors, such as the current price an operator might be paying for their fuel.  In view of the fact that only the Chief Pilot is likely to have this sort of detailed financial information, I very much doubt if any airline or operator will give the flight simming world an up-to-date or accurate CI figure!  The Cost Index is primarily used by the FMS to set the aircraft's performance parameters and it can be either a standard (default) planned Cost Index or one that is calculated for an individual flight. Sometimes a Flight Plan will have no Cost Index recorded at all, in which case the crew has to input a manual speed into the FMS.

It could be sensitive, I’m not entirely sure. I know that the regional I used to work for put the fuel prices at each station on their flight releases. The RJ that I flew did not have a CI though. If I’m doing a make believe flight in which I have no real world paperwork to reference I just come up with my own CI. For longer legs that are on time, I’ll use a lower number. For a short leg or one that is time critical, I’ll use a higher number. At the end of the day it’s a sim anyway. Realism can only go so far... 

[vc10man 732]

If I thought CIs was confusing beforehand, now it's even more mind-boggling reading this thread!

Pros/cons/whyfors, etc etc............

[downscc 1,327]

2 hours ago, vc10man said:

If I thought CIs was confusing beforehand, now it's even more mind-boggling reading this thread!

Pros/cons/whyfors, etc etc............

Keep it simple Rick, CI equals cost of aircraft divided by cost of fuel.... don't try to put numbers in this because the units are not real but the concept is this simple.  Higher aircraft costs due to financing costs, labor costs, maintenance costs; and cost of fuel is self explanatory.  The most economical CI is one that balances the cost of aircraft with cost of fuel to achieve lowest total costs.

Edited January 14, 2019 by downscc

[vc10man 732]

53 minutes ago, downscc said:

Keep it simple Rick, CI equals cost of aircraft divided by cost of fuel.... don't try to put numbers in this because the units are not real but the concept is this simple.  Higher aircraft costs due to financing costs, labor costs, maintenance costs; and cost of fuel is self explanatory.  The most economical CI is one that balances the cost of aircraft with cost of fuel to achieve lowest total costs.

Good elucidation there Dan. So, the question begs that as I use the Queen more often than the others, as pointed by Marc, would a high 100s CI be okay for long hops? Dont't want to run out of fuel!

Contemplating getting the -8i, but am sitting on the fence would it be overkill for me being adept at the FSL Airbus, the MD-11, 737,757, 767, 747, and the 777; the Majestic Q8-400, etc.......

[Captain Kevin 586]

1 hour ago, vc10man said:

So, the question begs that as I use the Queen more often than the others, as pointed by Marc, would a high 100s CI be okay for long hops? Dont't want to run out of fuel!

You shouldn't run out of fuel if you do your fuel planning properly. I've always used a CI of 172 and I was fine.

[downscc 1,327]

1 hour ago, vc10man said:

Good elucidation there Dan. So, the question begs that as I use the Queen more often than the others, as pointed by Marc, would a high 100s CI be okay for long hops? Dont't want to run out of fuel!

I'm using CI 120 right now for a BAW -8i trip.  Realistically, you run the fuel requirements with a CI or speed so if you change CI you run a new fuel calculation.  I've seen a cargo company copy of a plan that used 85 and there are probably operators out there using anything from 20 to 300.  I notice the PFPX aircraft template I have for the -8 has one speed in the pull down box of 0.86 so I also use the FMC for fuel planning.  Just be sure to increase the fuel remaining prediction in the FMS to cover start and taxi.  I add 4 T... so if I want to have 12 T remaining I add fuel until the FMC reads 16 T remaining (presuming the winds are close to prediction)

[vc10man 732]

7 minutes ago, Captain Kevin said:

You shouldn't run out of fuel if you do your fuel planning properly. I've always used a CI of 172 and I was fine.

I use PFPX to predict the fuel as per the flightplan it generates and add a few 1000kgs on top for safety margin.

[Captain Kevin 586]

10 minutes ago, vc10man said:

I use PFPX to predict the fuel as per the flightplan it generates and add a few 1000kgs on top for safety margin.

I also use PFPX. You can enter the cost index when you're planning your flight, and it'll take that into consideration.

[skelsey 765]

In amongst all the CI discussion it's worth remembering that ultimately it is what the airline would like one to do...

I recall a story I was told about a time when an airline were planning certain flights at very high speeds to reduce the block time and, I think, get out of having to roster an additional 'heavy' pilot on the sector (or something along those lines).

Naturally the union were quite unhappy about this and so the crews' response was to select the lowest possible speed once in the cruise!

There were two departures out of HKG each night, one leaving an hour or so after the other. One night somewhere over Mongolia, the later departure, being flown by a management pilot somewhat bound to follow what the company wanted, went screaming past the earlier departure which was plodding along on the top of the yellow band at about M0.76.

As the faster aircraft rapidly disappeared in to the distance, a rather indignant voice came crackling over VHF2:

"You're a bloody disgrace flying that aeroplane so fast!" 

[vc10man 732]

3 hours ago, Captain Kevin said:

I also use PFPX. You can enter the cost index when you're planning your flight, and it'll take that into consideration.

Where in PFPX do I enter a CI for it to take into consideration?

[Headley 26]

Flight planning screen => Aircraft tab => Cruise/Cost index window: type in what you want or need ...

[berts 97]

3 hours ago, skelsey said:

One night somewhere over Mongolia, the later departure, being flown by a management pilot somewhat bound to follow what the company wanted, went screaming past the earlier departure which was plodding along on the top of the yellow band at about M0.76.

Tut, tut, Simon.  Where's your respect for your Virtual managers?  😉

Besides, don't you mean the red band - and maybe the slower one was probably stuck at M0.76 because it was being held low and slow behind a Virgin A340?

[Captain Kevin 586]

40 minutes ago, vc10man said:

Where in PFPX do I enter a CI for it to take into consideration?

On the flight planning screen, when you select an aircraft, you'll see Cruise/Cost Index. You can do it there. The profiles I have seem to allow 0 to 500.