Hi

 

Been using 777 and PFPX for a while now and there are a couple of things bugging me that I wondered if anyone had any ideas about please?

 

1)

I use PFPX to plan the flight and as a simple example on a flight like HESH to OMDB Sharm el Sheikh to Dubai 1250 NM  it says on my flight plan that when I reach my destination I will have 10 LB fuel left at my destination.

 

When I then enter up all the details into the FMC of the 777 as well as importing wind data etc and matching climb profile to the same as in PFPX the FMC will typically predict a much higher EFOB at destination of something like 15 LB. However as I do my flight the FMC EFOB number gradually decreases over time until when I am near my destination it ends up typically around the same as PFPX predicted in this example 10.

So my questions is what is going on, why does the FMC of my 777 always predict EFOB much higher (15 LB)  before I depart than it will actually be when I arrive (10 LB)?

 

2)

A common flight I do is HESH to OMDB Sharm el Sheik to Dubai . 1250 NM ish

I always set PFX to step climb 2000 and leave the altitude cap the same as the service ceiling

And when I first started using PFPX my flight plans included step climbs which the 777 also did during flight.

Lately however it seems for 3 months or so my flight plans do not include any step climbs and nor is the 777 conducting any

 

Anyone have any ideas why this has happened? I.e PFPX is not creating step climbs anymore?

 

Thanks

 

Lawrence

PFPX is still creating step-climbs, though if you're light on fuel and PAX/Cargo, you probably wouldn't need one (i.e Short Flights).

 

I recently did WSSS-VHHH (3h15m) all the way at FL390. No steps.

 

Today I attempted VIDP-EDDP (~13h) and I had 3 step climbs en-route. It's all variable and dependant on fuel burn, winds aloft, distance, weight, etc. Don't worry about it too much until and unless the plan tells you to step up.

For question #1:

Here a couple of things to check out (which I had to do with my planning).  Is your Cost Index (CI) the same in PFPX and the 777 FMC?  I made that mistake recently.  Someone correct me if I'm wrong, but I thought I read somewhere that you should import winds into the FMC when you get to cruise.  I did PANC-RJAA recently and was blown away that my planning and actual flight were within 100 Ibs.  I don't expect to get that close because of enroute weather changes but I thought it was kind of cool.  

 

I haven't had any problems with step climbs, they have been spot on with PFPX and the FMC.

 

Chris K.

 

 

1)

I use PFPX to plan the flight and as a simple example on a flight like HESH to OMDB Sharm el Sheikh to Dubai 1250 NM it says on my flight plan that when I reach my destination I will have 10 LB fuel left at my destination.

When I then enter up all the details into the FMC of the 777 as well as importing wind data etc and matching climb profile to the same as in PFPX the FMC will typically predict a much higher EFOB at destination of something like 15 LB. However as I do my flight the FMC EFOB number gradually decreases over time until when I am near my destination it ends up typically around the same as PFPX predicted in this example 10.

So my questions is what is going on, why does the FMC of my 777 always predict EFOB much higher (15 LB) before I depart than it will actually be when I arrive (10 LB)?

 

It's very important to ensure that PFPX and your flight have the same data picture.  Most often, people I help end up messing that concept up.

 

This is going to sound stupid, but if you were to plan how much money you were going to need for a trip to the grocery store, and you mapped out everything in US dollars, but everything was in Canadian dollars when you got there, your numbers are going to be off.  Again, that probably sounds pretty obvious, but the concept is this:

You planned on one assumption, but reality was different, so your numbers were off.

 

PFPX is the same way.

If your weights don't match, you'll have bad numbers.  If you're flying with a CI, but PFPX planned using LRC, you'll have bad numbers.  If you planned the flight hours before flying it, your planned weather data will be off, so you'll have bad numbers.

 

My money is on the CI.

 

 

 

2)

A common flight I do is HESH to OMDB Sharm el Sheik to Dubai . 1250 NM ish
I always set PFX to step climb 2000 and leave the altitude cap the same as the service ceiling
And when I first started using PFPX my flight plans included step climbs which the 777 also did during flight.
Lately however it seems for 3 months or so my flight plans do not include any step climbs and nor is the 777 conducting any

Anyone have any ideas why this has happened? I.e PFPX is not creating step climbs anymore?

 

The PMDG 777 will only step climb if you tell it to (or you're using the auto-step feature, which is an unrealistic concession).

 

PFPX always has calculated steps, unless you specifically tell it not to.  My bet is that you changed something, or there's a max altitude restriction on some of those airways.

I think with #1 if you look in the 777bug list the FMC fuel calculation has been fixed. 

Guys thanks for the suggestions. I see what you are saying, and about the CI yes I definitely match it to what I set it at in PFPX, in fact I do this because I originally watched Kyles video that explained to me how to use PFPX which made me buy PFPX and Kyle you emphasised then how important it is to get the same data picture which I took on board and have since applied.

so yes I definitely match the CIs.

Ill also try importing winds during cruise

Interesting comment about the big fix too thanks

Thanks

 

 

I see what you are saying, and about the CI yes I definitely match it to what I set it at in PFPX, in fact I do this because I originally watched Kyles video that explained to me how to use PFPX which made me buy PFPX and Kyle you emphasised then how important it is to get the same data picture which I took on board and have since applied.

 

Thanks for watching (and paying close enough attention to remember the CI thing)!  It may very well be the fuel calc bug, but I thought that was related to something else.  I can't remember what was broken prior to the SP, though, because I've seen seen so many things in the changelogs through testing.