High cruise alt PFPX on short trips

[JoeDiamond 67]

 

 

I suppose that in the real world you don't have TOD 5min or less after the TOC!

 

It's not uncommon at all on short flights.

[Driver170 42]

I find flights under 300 nm with PFPX the cruise alt is different from the FMC OPT. Anything over its bang on

 

I'm using TOPCAT and wondering do i use the VR V2 speeds from TOPCAT or the FMC? I know to use TOPCATS V1 speed.

 

Thanks.

[wolke85 150]

I find flights under 300 nm with PFPX the cruise alt is different from the FMC OPT. Anything over its bang on

 

I'm using TOPCAT and wondering do i use the VR V2 speeds from TOPCAT or the FMC? I know to use TOPCATS V1 speed.

 

Thanks.

 

Hi Veron!

 

The FMC OPT sure is a valuable reference, but please also remember and bare in mind that the weather may change or other factors may come into play that the FMC may not (be able to) consider that properly at the time it calculates the OPT ALT (in the sim.

PFPX on the other hand for instance does consider weather forecasts and takes it all into account quite properly.

And please do not be surprised if You stay at cruise altitude for just a very short time (as pointed out several times here in this thread).

Real world procedures often differ from the way a scenario/procedure is replicated in the sim - and yet it still can be all set up very close to reality - and PFPX does a good job in doing so. It certainly is a very valuable tool and very reliable.

And it still offers the chance to use the "Altitude Cap" option.

You have mentioned NATS UK in one of Your posts but i would furthermore also suggest to take a look at FlightAware for instance to follow various real world flights - and the altitudes provided there.

http://de.flightaware.com/live/

 

You may then use these altitudes as a reference/orientation in PFPX and eventually "cap" it there.

Maybe You already tried this option, but as i don't know i thought it worth mentioning.

 

And if You also use TOPCAT - better always use all the numbers TOPCAT gives You or all the numbers that the FMC offers You but do not mix them (i.e.: V1 from TOPCAT and V2 from the FMC)

 

Have You been considering watching the tutorial videos from Kyle as i have mentioned in #39 - sorry for repeating myself here, but they are really great and i am just asking, because if i remember correctly, TOPCAT and its interaction with PFPX is also mentioned there.

I also consider Kyle's TOPCAT video here to be very help- and useful:

 

Cheers

[Driver170 42]

Hi chris thanks for the reply dude!

 

You are right i done a short flight and the cruise alt was FL290 on the way back it was 240 with a step climb. Prob PFPX taking into account the weather.

 

I'll stick with PFPX cruise alt always have but was just questioning the such high alt for short flights but i see why

 

I will also cap the alt in PFPX if i have alt rest from NATS UK, ie FL145 - FL245

 

Ok i'll take off the QRH in the FMC and use ALL VSPEEDS from TOPCAT

[wolke85 150]

Hi chris thanks for the reply dude!

 

You are right i done a short flight and the cruise alt was FL290 on the way back it was 240 with a step climb. Prob PFPX taking into account the weather.

 

I'll stick with PFPX cruise alt always have but was just questioning the such high alt for short flights but i see why

 

I will also cap the alt in PFPX if i have alt rest from NATS UK, ie FL145 - FL245

 

Ok i'll take off the QRH in the FMC and use ALL VSPEEDS from TOPCAT

 

Hi Vernon!

 

Great to read that my suggestions were at least a bit help- and useful for You!

In regards to TOPCAT - one more thing though:

You may also consider setting up Your NGX profiles more properly in so far as to mach perfectly with PFPX but based on the weights as used by PMDG's NGX - this thread here is really great for achieving this:

 

http://forum.avsim.net/topic/417842-topcat-pfpx-737ngx-weights-how-to/

 

... sadly - the pictures at page 1 of this thread got lost - but(!) - good luck to everyone interested, they were found again and all the info needed is now available there again at page 5, post #65!

Feel free to check it all out when Your time and interest allows it - i think it is really be worth it:

 

http://forum.avsim.net/topic/417842-topcat-pfpx-737ngx-weights-how-to/page-5

 

Have some great flights and enjoy cruising the skies!

Cheers

[rsvit 16]

I find flights under 300 nm with PFPX the cruise alt is different from the FMC OPT. Anything over its bang on

Thanks.

http://forum.aerosoft.com/index.php?/topic/80454-short-trip-cruise-altitude-problems-still-not-correct/

 

Here is a topic about this calculations. You can also find a table from FPPM for short cruise altitudes and what seems to be used by FMC to calculate optimum altitude.

 

But this table is not programmed into FPPM the same as in some real dispatcher programs.

 

So you can determine by that table minimum trip fuel cruise altitude and insert it into FPPM and check if it uses less fuel. If you want to stay longer in cruise then just choose how many minutes and get the altitude by that table again. Don't forget to do the corrections.