Cost index....777 FMC vs PFPX

[RPRIEVER 52]

Greetings all,

 

I have a question regarding the cost index used for the 777, vs what is planned using PFPX. I'm currently in the middle of a PHNL-KATL flight. When I planned the route in PFPX, I couldn't figure out how to add any specific CI. There's a page (speed/altitude) that allows me to adjust the cruise/cost index for each waypoint, but the options (via a drag-down menu) are "initial, AE320, LRC, M.82, M.83, M.84, M.85, M.86". For this flight, I left that parameter blank. On the actual FMC, I randomly chose a CI of 50. I'm currently cruising at M.83. My current TAS is 481, and PFPX seemed to plan for 485.

 

This might be a chicken vs egg question, but do I have to choose a CI in PFPX first (and if so, how do I do that?), or do I create one in the FMC and then adjust the parameters in PFPX?

 

Any help would be appreciated.  Many thanks.
 

[scandinavian13 5,192]

 

 

This might be a chicken vs egg question, but do I have to choose a CI in PFPX first (and if so, how do I do that?), or do I create one in the FMC and then adjust the parameters in PFPX?

 

Place the CI where the Mach number is for the cruise speed.

 

Use the same CI when entering data on the PERF INIT page.

[RPRIEVER 52]

Place the CI where the Mach number is for the cruise speed.

 

Use the same CI when entering data on the PERF INIT page.

Kyle,

 

Can I assume that I would choose the first waypoint AFTER the climb (ie, the first "level/cruising" waypoint? Also, after adding the CI, does it carry over automatically to the following waypoints, or do I have to repeat the CI for each one?  Many thanks.

[scandinavian13 5,192]

 

 

Can I assume that I would choose the first waypoint AFTER the climb (ie, the first "level/cruising" waypoint?

 

No.  When you're planning a flight, they give you a window where you give it the aircraft, your generic route (dep/arr airports only), cruise speed, weights and so on.  Override the cruise speed with a CI by just typing in the CI.

 

This has nothing to do with (and shouldn't have anything to do with) waypoints.

 

 

 

What you're thinking of is something else.  Those are constant speed segments for things like the NATs. Those are automatically entered where applicable by PFPX.

[RPRIEVER 52]

OK.....but my question is this:  when planning my flight in PFPX, where exactly do I enter the CI? My current route (HNL-ATL) obviously doesnt have a NAT, so that wouldn't apply in this case.

[RPRIEVER 52]

Just figured it out (and it was in front of my face this whole time). It's on the "aircraft" page, under "cruise/cost index" (D'OH!!).

 

Funny thing is....I kinda knew the idea behind CI years ago, before I even thought of using it in the flight sim environment. The airline I work for IRL had an article in their employee newspaper, explaining that sometimes getting there faster (and burning more fuel) is a necessity....especially if the alternative is a late arrival, and a large number of busted connections for passengers. The added cost for fuel would more than make up for the cost of pax reprotection, hotel costs, etc.

[Gavin 99]

Thanks for this post.  I missed that little CI thing myself. Doh!

[scandinavian13 5,192]

 

 

The airline I work for IRL had an article in their employee newspaper, explaining that sometimes getting there faster (and burning more fuel) is a necessity....especially if the alternative is a late arrival, and a large number of busted connections for passengers. The added cost for fuel would more than make up for the cost of pax reprotection, hotel costs, etc.

 

Yep.  This is why every time the subject comes up where people are asking all the time about what airline uses X cost index, I always chime in to say it's variable.

 

 

 

It's on the "aircraft" page, under "cruise/cost index" (D'OH!!).

 

 

 

I missed that little CI thing myself. Doh!

 

It's amazing the unnoticed things that wind up being right in front of you the whole time...

[Slayer 190]

Thanks, I couldn't figure out where to put it either.

[JohnsonPBX 8]

Please try it by yourselves guys, I tried planning a flight with the 777 profile in PFPX two days ago, and entered a CI of 20 in the Cruise/Cost Index section of the Aircraft tab. It even showed my selected CI in the OFP. Problem is that, regardless of the CI number entered, PFPX always calculated the same speeds and fuel burn / time figures, which ended up being pretty inaccurate.

 

For instance, for that flight PFPX calculated a cruise speed of ~485 KTAS, while my actual cruise speed, calculated by the plane's FMC, was of ~390KTAS. That's right, nearly a 100 KTAS difference, which isn't certainly acceptable. I tried using different numbers for the CI in PFPX (20, 80, 100, 500), and the OFP still showed the same speeds with any. Can any of you please confirm if it's an issue from PFPX in general or just me?

 

Thanks!

[RPRIEVER 52]

That 390 TAS doesn't seem right. All of my 777 flights have given me a TAS of approx. 490. My flight yesterday was planned for 7:58. The actual time was 8:25, however I did add a hold upon my arrival, and did a missed approach/go around. So, if you eliminate those 2 items, the times were pretty accurate.

 

Disclaimer: the hold and go-around were caused by my forgetting about the sim while the Rays playoff game was starting......ooooops!  :unsure:

[Flamin_Squirrel 71]

Just figured it out (and it was in front of my face this whole time). It's on the "aircraft" page, under "cruise/cost index" (D'OH!!).

 

Is that the aircraft setup page you're talking about? If so, that's just the default setting you've changed. You can change it for each flight during the planning process too.

[phil747fan 14]

Please try it by yourselves guys, I tried planning a flight with the 777 profile in PFPX two days ago, and entered a CI of 20 in the Cruise/Cost Index section of the Aircraft tab. It even showed my selected CI in the OFP. Problem is that, regardless of the CI number entered, PFPX always calculated the same speeds and fuel burn / time figures, which ended up being pretty inaccurate.

 

For instance, for that flight PFPX calculated a cruise speed of ~485 KTAS, while my actual cruise speed, calculated by the plane's FMC, was of ~390KTAS. That's right, nearly a 100 KTAS difference, which isn't certainly acceptable. I tried using different numbers for the CI in PFPX (20, 80, 100, 500), and the OFP still showed the same speeds with any. Can any of you please confirm if it's an issue from PFPX in general or just me?

 

Thanks!

helllo,

 

any chance you post your flightplan.

 

if it s a transatlantic flight there is a fixed mach portion so whatever CI selected the fixed mach will be used over it ...

 

all the best.

 

Phil

[scandinavian13 5,192]

...and this is why we can't have nice things.

 

[RANT]

 

Guys,

 

You really, really need to ensure you know what you're doing before asserting there are problems.  Earlier, we had guys who didn't even know that you could throw CI into PFPX to have it plan using that CI.  In other threads, there have been people who don't understand why PFPX's step climbs don't match the FMC calculated steps, particularly over the NATs (hint: you can't step while on a NAT, and need to fly a constant speed, so the OFP states an altitude and a constant speed for that segment).

 

Aviation is an extremely complicated realm.  This idea that, since you've been using FSX for years and years, and are comfortable with complex add-ons, you know everything you need to know to go barreling into PFPX like a pro needs to go.

 

As I've said hundreds of times already:

If the pictures YOU are handing to PFPX and the aircraft don't match, you can't expect the numbers to match.  If you're using a CI of 20, then the CI of 20 should be both in PFPX and the FMC.  The same goes for any other variable between PFPX and the FMC.

 

Flight planning has many more complexities to it than most people think.  How many of you knew that the NATs are constant altitude - constant speed segments?  Note that when you plan a route across the Atlantic and use a NAT, you'll get a M0830F370 at the beginning and an N0460F390 at the end of it.

 

What just happened there?

 

You just told the oceanic controllers that you plan to fly that segment at Mach .83 at FL370, and then, at the end of the NAT, you plan on resuming your ECON speed and stepping to FL390.

 

Does the FMC know you're on a NAT?  Where did you tell it that it was a NAT, and how did you tell it that it's a constant speed - constant altitude segment?  How do you do that?

 

The FMC has no idea what designates NATs/PACOTs/AUSCOTs/etc.  All it knows is that you're hitting waypoints.  The only way it knows to apply the rules of the NATs is when you tell it by typing in .83/FL370S for that first NAT waypoint, and E/FL390 at the final waypoint.  Note that, after doing so, your planned numbers will start to match up a little more closely.  Add wind via the WIND REQUEST feature and those numbers get better.

 

Since the FMC has no idea what a NAT is, and what rules apply to the NATs, it doesn't know that it can't use its optimal stepping.  If you let it believe that, then the numbers are going to be off.  It doesn't know that it can't use optimal (variable for the flight condition/altitude/weight) speeds, either.  If you let it believe that, then the numbers are going to be off.

 

 

 

It's all about the pictures.  If you're not matching the pictures between the OFP and the FMC, then it's your fault the numbers aren't matching, not PMDG's or PFPX's.  Furthermore, if you believe PFPX's planning is off, then you should go let them know.  Posting here isn't going to get them to change anything.

 

[/RANT]

[Alaaar 34]

Thank you Kyle where can get more information about RFRX and do you recommend it .....because I have Vroute pro + FS Commander ????  will it replace them ?? 

 

Many thanks