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strange altitude assignments when using OPT ALT


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Hi there

 

I sometimes get strange altitude assignments when using OPT ALT with the PMDG 777 profile. For example, for VHHH-WADD initial FL is 350, then about 20% into the flight it wants me to descent to FL300 before i climb again to FL370. I checked if there are any airways restrictions that wouldnt allow FL's above a certain altitude but couldnt spot anything. I also tried 'upper airspace only' when editing the route, no difference. Same goes for weather, nothing on my route that would require me to descent like that. Its definitely not something you would see in real world and it also confuses the hell out of the FMC as it would usually expect "Climb - Cruise - Descend", and not "Climb - Cruise - Descent - Cruise - Climb - Cruise - Descent"

 

On other occasions it calculated step climbs with 1000 feet steps, just to give me another 1000 feet step a few waypoints later, even though i set 2000 feet step climbs in PFPX. 

 

Anyone else seeing these issues? I'm using PFPX v1.28 including latest hotfix. I didnt see it when using the 737 but that might be due to fact that the flights are usually too short for step climbs anyways

 

Thanks

Lars

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Although i cant find an OFP with those mini step climbs (cant even remember on what route this was), they also show in the VHHHWADD flight i described above. 

 

See attachement for the OFP: VHHHWADD_example.pdf

 

In a nutshell, this is my ATC routing:

 

N0482F350 PECA1A PECAN DCT DUMOL M771 DULOP/N0480F360 M772
ASOBA/N0472F300 M772 LAXOR/N0479F370 L649 BRU/N0477F380 R223
ELANG/N0474F370 M522 GALKO GALK3D

 

FL350 is the initial altitude, then it wants me to step-climb to FL360, immediately followed by a descent to FL300, then we go up to FL370 again, perform a quick step to FL380, go back to FL370 before we descent into the destination :blink:

 

My dispatcher must be drunk...

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The 'step' climb from FL350 to FL360 is actually an RVSM climb most probably caused by the lack of a defined direct in PFPX.

 

Was the route generated by PFPX or pasted from another source ?

 

Adding a direct to the database creates available levels based on the cruise table:

 

 

Please login to display this image.

 

 

this results in:

 

ATC ROUTE: N0491F350 PECA1A PECAN DCT DUMOL M771 DULOP/N0489F360 M772 ASOBA/N0487F380 M772 LAXOR DCT GALKO GALK3D

 

 

 

 


 

 

 

 

 

 

 

 

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Check that a direct does not already exist, possibly with an incorrect cruise table in use.

 

Without adding the direct PFPX generates:

 

-N0484F370 SKAT3C SKATE V4 GRUPA/N0485F380 V5 SABNO/N0483F370 A583
 AKOTA/N0486F380 M754 VINIK M522 MAMOK/N0483F400 M522 ELANG/N0478F390 M522
 GALKO GALK3C

 

The 1000ft level changes are RVSM.

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Only thing i know is that i didn't add any manual directs to the DB. Whats strange is that it doesnt give you the FL300 descent inbetween like it did for me. 

 

 

 

 

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Stephen,

 

i added the DCT exactly as shown in your screenshot, recreated the route, got the plan calculated again and i'm still getting this strange drop to FL300

 

ATC ROUTE:

N0482F350 PECA1A PECAN  DUMOL M771 DULOP/N0480F360 M772
ASOBA/N0472F300 M772 LAXOR/N0479F370 L649 BRU/N0477F380 R223
ELANG/N0474F370 M522 GALKO GALK3D

 

Could this be an issue with my 777 profile? Perhaps something wrong with the underlying performance data?

 

EDIT: Just switched from my 77W profile to a 772 one, now it doesnt drop to 300 anymore, but the ALT profile is still strange, all those small climbs and then it wants me to drop from 380 to 370 just to climb back to 380 again

 

ATC ROUTE: N0494F350 PECA1A PECAN/N0493F370  DUMOL M771 DULOP/N0486F380 M772
           LAXOR/N0485F370 L649 BRU/N0488F380 R223 ELANG/N0485F390 M522 GALKO
           GALK3D

 

thanks again for your help, appreciate it!

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Just out of real world planning:

 

Stepclimbs with a descent to a lower altitude is farely common in real world. Does not mean you have to descend. Its more to be applicable to RADs.

Regarding the 300ER profile, i am just writing a "new" one, based on the original by Judith Blaschegg. Adapting some values to real values, as found in FPPMs for the 300ER.

 

Greetings

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17 hours ago, woozie77 said:

Stephen,

 

i added the DCT exactly as shown in your screenshot, recreated the route, got the plan calculated again and i'm still getting this strange drop to FL300

 

ATC ROUTE:

N0482F350 PECA1A PECAN  DUMOL M771 DULOP/N0480F360 M772
ASOBA/N0472F300 M772 LAXOR/N0479F370 L649 BRU/N0477F380 R223
ELANG/N0474F370 M522 GALKO GALK3D

 

Could this be an issue with my 777 profile? Perhaps something wrong with the underlying performance data?

 

EDIT: Just switched from my 77W profile to a 772 one, now it doesnt drop to 300 anymore, but the ALT profile is still strange, all those small climbs and then it wants me to drop from 380 to 370 just to climb back to 380 again

 

ATC ROUTE: N0494F350 PECA1A PECAN/N0493F370  DUMOL M771 DULOP/N0486F380 M772
           LAXOR/N0485F370 L649 BRU/N0488F380 R223 ELANG/N0485F390 M522 GALKO
           GALK3D

 

thanks again for your help, appreciate it!

 

Hi,

Is it possibly also a Navdata issue? Strange that PFPX would generate the above routing via airways M771 and M772 as these are one-way, northbound only, at least as per the latest AIRAC cycle 1701, and thus shouldn't be chosen for a southbound flight. If you look at a few recent tracks of VHHH-WADD flights (ie on Flightaware) you will see they initially track more south-easterly out of VHHH to SABNO and then via A583, etc, in line with the routing in Stephen's email (#6) above.

 

Cheers,

Michael.  

 

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Yeah that might be possible, if i remember correctly i had this route in my DB already. It might have been created with an older AIRAC/RAD. Guess its time to run a route DB check again ;)

 

Just tried VHHHWADD again, this time with a new route created by PFPX. Still a bit of a nervous profile but no crazy descends anymore

 

N0476F370 SKAT3A SKATE V4 GRUPA/N0477F360 V5 SABNO/N0479F370 A583
AKOTA/N0477F360 M754 TENON/N0478F380 M754 VINIK M522 ELANG/N0476F390
M522 GALKO GALK3D

 

vallevip, looking forward to your 77W profile


 

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And there lies the most probable reason for the direct between PECAN and DUMOL also, an airway was removed between those two points

 

The flight levels you have now posted are optimal and RVSM changes plus the step climb.

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55 minutes ago, srcooke said:

And there lies the most probable reason for the direct between PECAN and DUMOL also, an airway was removed between those two points

 

The flight levels you have now posted are optimal and RVSM changes plus the step climb.

 

Yeah, makes absolutely sense now. Thanks again to all you chaps for helping out, appreciate it

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