Oskar Speer

Assumed Temp. B747-8 GE nx-2867

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1 hour ago, Oskar Speer said:

   HI! I know that in this forum  there is many intelligent people. There fore I ask for help inside here. I need a accurate T/O Performance Calculator for B747-8 GE nx-2867. The EFB in VC do not have that function yet.

https://flightsafety.org/files/RERR/TakeoffTrainingSafetyAid.pdf

As far as I am aware there is none available at this time.

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In absence of a performance takeoff calculator, we would need the FPPM, but I don't think it is available to public. 😉

Edited by Budbud

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6 hours ago, Oskar Speer said:

There fore I ask for help inside here. I need a accurate T/O Performance Calculator for B747-8 GE nx-2867.

There is a work around but it is not an accurate method.  For simulation purposes why are you requiring an accurate calculation?

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I use real world data, and the assumed temps when applied in the sim don’t really provide a very accurate N1 setting a lot of times. Which is fine, it’s just a sim, but I’ve found that if I try to takeoff in a loaded -8 in the sim using the takeoff data and weights from a real flight it comes pretty close to running off the end of the runway due to not enough power. I just adjust it so that the N1’s match. 

In general though, without a calculator for assumed temp, just the derates is sufficient. For light weights TO-2, moderate TO-1 and heavy TO. That seems to work sufficiently for me in the event that I don’t have data to use. 

Jeffery Williams

 

Edited by Jetlinker
Grammar corrections and name added

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1 hour ago, Jetlinker said:

I’ve found that if I try to takeoff in a loaded -8 in the sim using the takeoff data and weights from a real flight it comes pretty close to running off the end of the runway due to not enough power.

Almost every flight I make in the -8 is at MGTOW only limited by MGLW.  I haven't noticed any problems although I'm not running any assumed temps.  

One suggestion is to do it the ol' fashion way which is create a schedule through trial and error.  That's pretty much how it was done when I went through military test flight school back when everyone was wearing "brown shoes." 🤣

Grace and Peace, 

Edited by Bluestar
typo

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3 hours ago, downscc said:

 For simulation purposes why are you requiring an accurate calculation?

Probably because it‘s PMDG... 😉 „bring facts, not youtube“... do it right, don‘t estimate or fake it... I hardly fly the -8 atm, I prefer the -400 for which I can use a well matching topcat-profile.. 

when I fly PMDG or FSL I want to simulate an as correct as possible operation and there is little room for speculation or abusive power setting 😄  and using TO-50 all the time is getring boring xD

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1 hour ago, Ephedrin said:

Probably because it‘s PMDG... 😉 „bring facts, not youtube“... do it right, don‘t estimate or fake it... I hardly fly the -8 atm, I prefer the -400 for which I can use a well matching topcat-profile.. 

when I fly PMDG or FSL I want to simulate an as correct as possible operation and there is little room for speculation or abusive power setting 😄  and using TO-50 all the time is getring boring xD

Understand.  Same problem as the B77W... no TOPCAT there either.

In this case I use the method mentioned a couple of times here in that I run the takeoff calc with OAT, and then I start using other values for OAT as my assumed temperature... this means sometimes DTO 40C and sometimes DTO 55C are the solution.  One may also add a NOTAM if you have an obstruction you want to clear but i usually drop the assumed temp 5C if I want an allowance.  This at least gives me a process that I use that while it might not be using the same tools at least I'm going through the same steps.

Edited by downscc

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7 minutes ago, downscc said:

Understand.  Same problem as the B77W... no TOPCAT there either.

In this case I use the method mentioned a couple of times here in that I run the takeoff calc with OAT, and then I start using other values for OAT as my assumed temperature... this means sometimes DTO 40C and sometimes DTO 55C are the solution.  One may also add a NOTAM if you have an obstruction you want to clear but i usually drop the assumed temp 5C if I want an allowance.  This at least gives me a process that I use that while it might not be using the same tools at least I'm going through the same steps.

Yes, I do the same.. it‘s a bit weird to think a pilot would do that xD but it works for now. Fingers crossed that the calculation update is on a good way

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5 hours ago, Jetlinker said:

Which is fine, it’s just a sim, but I’ve found that if I try to takeoff in a loaded -8 in the sim using the takeoff data and weights from a real flight it comes pretty close to running off the end of the runway due to not enough power.

Welcome to the real world!  I can think of plenty of airfields where the lift-off point in a 744 can occur relatively close to the end of the paved runway surface.

This is not usually due to a lack of power, but more likely down to carrying out a max weight takeoff on a limiting runway.  There is also the possibility it might be the result of a long line up along the runway where too much concrete is used before takeoff power is set; or perhaps because inaccurate data is used in the takeoff calculations (apparently the performance calculator in the -8 EFB is still a work in progress).  However, without a performance manual to compare the real aircraft data with the performance calculations in the PMDG -8 it is impossible to say exactly how accurate it is. 

For what its worth, I think PMDG has done well to create a fully loaded -8 that gives anyone the impression it comes pretty close to running off the end of the runway!

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1 hour ago, berts said:

This is not usually due to a lack of power, but more likely down to carrying out a max weight takeoff on a limiting runway. 

I can think of a couple runways down in SA where get'n in wasn't the problem, it was getting out.  If the runway had any moisture on it, the T/O  was a no go. 🙂

Grace and Peace, 

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3 hours ago, berts said:

Welcome to the real world!  I can think of plenty of airfields where the lift-off point in a 744 can occur relatively close to the end of the paved runway surface.

This is not usually due to a lack of power, but more likely down to carrying out a max weight takeoff on a limiting runway.  There is also the possibility it might be the result of a long line up along the runway where too much concrete is used before takeoff power is set; or perhaps because inaccurate data is used in the takeoff calculations (apparently the performance calculator in the -8 EFB is still a work in progress).  However, without a performance manual to compare the real aircraft data with the performance calculations in the PMDG -8 it is impossible to say exactly how accurate it is. 

For what its worth, I think PMDG has done well to create a fully loaded -8 that gives anyone the impression it comes pretty close to running off the end of the runway!

Yeah, the -8 is certainly not much of a performance airplane. I’ve flown them out of places like Quito in real life so I know what a hair raising takeoff in one looks like. What I was saying more or less was that the assumed temps that I’ve plugged into the sim from actual flight Aerodata have produced N1’s that are maybe 3-5% less than what the paperwork said it should be, so in a full -8 that small percentage can nearly make the difference as to whether or not you clear the trees at the end  😅

 

 

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Next time I do a flight I’ll try to post an example of the discrepancy. Again, it’s a sim, and a lot of variables go into what determines the actual N1 setting. The realism of the aircraft compared to the real thing is still quite astonishing for a home desktop sim, so by no means am I complaining. I’ve been out of the real thing on medical leave now for over a year, so it’s been nice to be able to use it to stay fresh on things. 

Edited by Jetlinker

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On 11/7/2018 at 9:02 PM, downscc said:

Understand.  Same problem as the B77W... no TOPCAT there either.

My solution was to create a pseudo -300 profile from the -200 base by increasing the maximum TO weight to the -300 value. Seems to work well enough. Same engines, same wings just heavier weights.

Edited by kevinh

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