StanP

A bunch of questions about the Queen

23 posts in this topic

Hey folks, 

Like everybody else, I have been enjoying my flying with the Queen since day 1 :-)

I just have a few things which bother me (and I hope you can help me on this)

1) Idle taxi: After applying breakaway power, I find myself obliged to keep my engines at around 29-30% N1 to keep the plane moving (not even at MTOW).. I remember Mr Randazzo mentioning something about some magic being done in P3D to help with that? I re-installed the lua Friction module in FSUIPC, but it does not seem to help. Should I remove it? Everybody else is having no problem with idle taxi speeds? 

2) PFPX profile: I am struggling as well with the planning in PFPX.. The flight I am doing right now had FL330 as an initial FL in PFPX and FL350 planned as a step.. I jump in the plane, FL304 as OPT initial level and no step planned from FL330 to FL350... Fuel wise, I almost spot on so can't complain. I load the winds in the FMC, etc etc.. can't really see what's wrong. If somebody has a profile they could share that has been spot on, altitude planning wise, would be grateful.

3) Hydraulics: with hydraulics off, elevator and ailerons are down, but for some reasons, the rudder does not move with the wind. Is that normal? 

That's all I have! 

 

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3) Hydraulics: with hydraulics off, elevator and ailerons are down, but for some reasons, the rudder does not move with the wind. Is that normal? 

Gravity is always there, but is the wind blowing in the right direction and is it strong enough? The rudder surfaces are pretty large and the hydraulic fluid provides some dampening. Usually a "stiff breeze" is required :tongue:

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5 hours ago, StanP said:

1)

1) I don't have that installed and able to move it nicely.....she is smooth like butter...

2). I believe regardless what FMC said, you have to enter dispatched FL if properly created. Meaning, when you created FPLN you entered all correct data for chosen FIN. After you finish your loading, fueling, thank compare and make adjustments. In other words if initial is FL330 you enter that, compare with FMC data and it should be ok. If not check where step climb should be and enter it....At least that's how I do it...   :biggrin:

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PFPX has an option to select cruise altitude based on lowest cost, lowest time or lowest fuel. Use the lowest fuel option since it doesn't have cost information.  PFPX and FMS may disagree at times, such as when to step, always go with the FMS.  There is a better set of B747 aircraft profiles done by a gentleman in Ukraine that includes all variants and the increased thrust engines for the -400ER/F.... I'm using those.  Available in the PFPX forum download section.  Also, I am a loyal fan of AS16 but if you want see how accurate the fuel predictions are in PFPX you need to rule out winds and use no weather for testing.

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7 hours ago, StanP said:

2) PFPX profile: I am struggling as well with the planning in PFPX.. The flight I am doing right now had FL330 as an initial FL in PFPX and FL350 planned as a step.. I jump in the plane, FL304 as OPT initial level and no step planned from FL330 to FL350.

I hate to state the obvious, but did you ensure your payload in the airplane matched that of PFPX? It's little big things like these that trip me up sometimes.

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6 hours ago, Qavion2 said:

Gravity is always there, but is the wind blowing in the right direction and is it strong enough? The rudder surfaces are pretty large and the hydraulic fluid provides some dampening. Usually a "stiff breeze" is required :tongue:

Yes, a stiff 19 knots breeze, and nothing moving... anyway, details :laugh:

2 hours ago, RW23 said:

1) I don't have that installed and able to move it nicely.....she is smooth like butter...

2). I believe regardless what FMC said, you have to enter dispatched FL if properly created. Meaning, when you created FPLN you entered all correct data for chosen FIN. After you finish your loading, fueling, thank compare and make adjustments. In other words if initial is FL330 you enter that, compare with FMC data and it should be ok. If not check where step climb should be and enter it....At least that's how I do it...   :biggrin:

1) ok.. interesting. I'll try again without it. 

2) That's what I am saying.. there's quite a bit of difference between the initial pfpx proposed altitude and the calculated optimal altitude by the FMC.. I tend to believe the FMC more, but then that would mean PFPX does not cut it anymore ;)

2 hours ago, downscc said:

PFPX has an option to select cruise altitude based on lowest cost, lowest time or lowest fuel. Use the lowest fuel option since it doesn't have cost information.  PFPX and FMS may disagree at times, such as when to step, always go with the FMS.  There is a better set of B747 aircraft profiles done by a gentleman in Ukraine that includes all variants and the increased thrust engines for the -400ER/F.... I'm using those.  Available in the PFPX forum download section.  Also, I am a loyal fan of AS16 but if you want see how accurate the fuel predictions are in PFPX you need to rule out winds and use no weather for testing.

Yes indeed, for step climbs, I always go with the FMC, but 2000 feet difference between the PFPX plan and the optimal alt by the FMC concerns me.. 

I.e. I could have started cruising at FL310 and then step climb at 330. 

1 hour ago, pcubine said:

The profiles that Dan Downs refer to were done by Mykyta Demyduik and his user name for the PFPX forum is inlovewithboeing. This link is to the profiles - http://forum.aerosoft.com/index.php?/files/file/3514-pfpx-boeing-747-400-performance-profiles-pack/.

Alright. I think I have those, I'll check again. 

1 hour ago, wsmeier said:

I hate to state the obvious, but did you ensure your payload in the airplane matched that of PFPX? It's little big things like these that trip me up sometimes.

Of course! 

ZFW the same, and gross weight is the same :-) 

 

Thanks guys!

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3 hours ago, StanP said:

I could have started cruising at FL310 and then step climb at 330. 

Agree, I always have a look at the VNAV CRZ page to see when the first step is and if it is less than 300 nm I will dial my initial up one step to avoid that.  Also, I gave you a suggestion and you didn't acknowledge if that is what you are already doing...ie. using lowest fuel altitude optimization in PFPX.  Again, always pick the FMS over the PFPX data.  PMDG stuck very close to Boeing data in such areas.

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also something to keep in mind... i'm fairly certain that PFPX takes wind into account for efficiency so if the winds are more favorable at a different flight level, it may assign that altitude even if the gross weight of the aircraft might allow for a higher level. 

i had a flight a few days ago that PFPX planned for FL320 for half of the way even though the FMC wanted FL340 fairly soon after reaching cruise. But, the headwinds at that FL340 were about 20knots higher. when i got to the point where PFPX had suggested the step climb, the winds were much lower and from a crossways direction instead of headwind.

Cheers, -andy crosby

 

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Dan is right re using the Minimum Fuel option.  Avoid the minimum cost option as it can give funny figures and I doubt any of us have any information to plug into that feature that makes it worthwhile using.

Cheers,

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4 hours ago, downscc said:

Agree, I always have a look at the VNAV CRZ page to see when the first step is and if it is less than 300 nm I will dial my initial up one step to avoid that.  Also, I gave you a suggestion and you didn't acknowledge if that is what you are already doing...ie. using lowest fuel altitude optimization in PFPX.  Again, always pick the FMS over the PFPX data.  PMDG stuck very close to Boeing data in such areas.

Oh yes indeed. Missed that part! 

I will give a shot right away.

Thanks a million. 

2 hours ago, spesimen said:

also something to keep in mind... i'm fairly certain that PFPX takes wind into account for efficiency so if the winds are more favorable at a different flight level, it may assign that altitude even if the gross weight of the aircraft might allow for a higher level. 

i had a flight a few days ago that PFPX planned for FL320 for half of the way even though the FMC wanted FL340 fairly soon after reaching cruise. But, the headwinds at that FL340 were about 20knots higher. when i got to the point where PFPX had suggested the step climb, the winds were much lower and from a crossways direction instead of headwind.

Cheers, -andy crosby

 

Hey Andy,

Sure I get the point. But in the end, winds for PFPX and the FMC are coming from the same source, and I tend to trust the FMC more than anything else. 

1 hour ago, VHOJT said:

Dan is right re using the Minimum Fuel option.  Avoid the minimum cost option as it can give funny figures and I doubt any of us have any information to plug into that feature that makes it worthwhile using.

Cheers,

Agreed, very good suggestion! 

Trying it right away.

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32 minutes ago, StanP said:

 

Sure I get the point. But in the end, winds for PFPX and the FMC are coming from the same source, and I tend to trust the FMC more than anything else. 

 

yep, but trusting the FMC in this case is a possible source of your discrepancy. PFPX has more information about the wind than the FMC does. and ,more importantly,  the FMC is not considering anything other than the GW when it suggests it is time to climb! and thus may not necessarily match the optimal one suggested by PFPX. the FMC uses the wind data simply to make more accurate predictions en route, not for optimization. you might want to try in PFPX to set FL to "optimization=none" it may be closer to the result you are seeking. good luck! :)

cheers!,- andy crosby

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14 hours ago, spesimen said:

yep, but trusting the FMC in this case is a possible source of your discrepancy. PFPX has more information about the wind than the FMC does. and ,more importantly,  the FMC is not considering anything other than the GW when it suggests it is time to climb! and thus may not necessarily match the optimal one suggested by PFPX. the FMC uses the wind data simply to make more accurate predictions en route, not for optimization. you might want to try in PFPX to set FL to "optimization=none" it may be closer to the result you are seeking. good luck! :)

cheers!,- andy crosby

 

Very interesting! 

I thought the FMC worked a la Triple Seven, taking winds into account in the equation. But now that you mention it, the triple seven works exactly the same, + the recommended FL which does what I am looking for! 

So very well then, I'll make sure to follow PFPX from now, with "Lowest Fuel" Optimisation selected. 

 

Thanks guys! 

 

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52 minutes ago, StanP said:

I'll make sure to follow PFPX from now

On more than several occasions PFPX's recommended initial altitude has been above the maximum altitude of the airplane be it the NGX, 777, or 744. The PFPX step climbs in their OFP package are done earlier than what the FMC recommends. PFPX has a tendency to fly right below the maximum altitude rather than the optimum altitude. I have never paid any attention to PFPX's initial altitude or step climb schedule. Two members from the PFPX forum got into this issue back in January hot and heavy and them dropped it like a hot potato and disappeared into the woodwork. I can't even get them to reply to PMs anymore. I would go with the recommendations in the FMC. I trust PMDG more than FlightSimSoft.

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Hi,

Using the profiles from Flyprecisely, I found the initial cruise level to be pretty spot on.
For the climb steps, there may be some small discrepancies (without being completely off though) but I'm tempted to put that on the small discrepancies being expected winds aloft and experienced ones that I can notice when comparing the values throughout the flight.

In PFPX, I always select optimization=none.

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