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Emi

DragCorrection and FFCorrection in aircraft.ini file?

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I found these two values in the aircrafts.ini file of my livery, but I couldn't find any documentation on them:

DragCorrection=0.00

FFCorrection=0.00

 

I assume they are used to adjust the FMC predictions, but can anyone tell me whether they also alter the actual drag and fuel consumption of the aircraft in the simulator or just the FMC predictions?
This would be really cool if we could simulate older aircraft using up more fuel with this option!

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No it wouldn't. Don't meddle with things unless you have PMDG's permission and guidance to do so.

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This probably has to do with the 'Service Based Failure' - Option.

 

As aircraft get older they tend to wear out and respectively Fuel consumption (Engines wear out too; ergo use more fuel) and Drag may increase.

 

I'm guessing these values are increased over time the longer you fly the same airframe.

 

EDIT: Best not to mess with them and mess up the simulation by accident.

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The 747 is a true masterpiece, but if they even modelled the FF in relation to the service based failures... that would really be impressive!

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Hence my answer, pal.

 

This probably has to do with the 'Service Based Failure' - Option.

 

As aircraft get older they tend to wear out and respectively Fuel consumption (Engines wear out too; ergo use more fuel) and Drag may increase.

 

I'm guessing these values are increased over time the longer you fly the same airframe.

 

EDIT: Best not to mess with them and mess up the simulation by accident.

great answer!

 

The 747 is a true masterpiece, but if they even modelled the FF in relation to the service based failures... that would really be impressive!

That would be very impressive and obviously open the potential for customers to align their pmdg 747 to their actual 747 they emulate, fuel consumption wise.

 

Not sure if adding this is a good thing or a bad thing :) I'm kind of on the fence about it. Judging by the posts and videos on YouTube, customers have bigger things to concern themselves with over the performance factors. I.e. Landing/flare and takeoff rotation techniques. Pmdg have also given some very cool features that even I am yet to discover and explore.

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I am not talking about the aircraft.cfg file btw, I am talking about the .ini files that includes the company options for your liveries located in P3D\PMDG\PMDG 747 QOTS II\Aircraft

This one we are allowed to edit according to PMDG and most options are documented in the introduction manual. Just these two are missing.

Any chance someone from PMDG can comment here what these two lines actually do?

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Those lines look like they have something to do with the FMC prediction biases. On the page where you see what airframe and engine you are using, there are adjustments for drag factor and fuel burn. I guess maintenance would get readings as the airplane ages and deviates from manufacturers specification, forward that to dispatch to plug those biases into the flight planning and the pilot would enter those biases in the FMC to get the accurate predictions

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Emanuel, the QOTSII really is cool!

 

The Drag/Fuel Flow Factor line on the FMC IDENT page displays the drag and fuel flow correction factor for each individual aircraft's performance data base. These two readings in the FMC on a real B744 are checked pre-flight for accuracy against the figures on the Flight Plan, but are not normally altered by the Flight Crew because they will have been set correctly by Engineering.

 

You can alter the Drag and Fuel Flow corrections in each individual PMDG Aircraft's .ini file if you want to and the figures you enter will appear correctly in the FMC's Drag/Fuel Flow Factor line the next time you load it. Drag should be a positive value and Fuel Flow negative. Use something sensible, such as DragCorrection=1.10 and FFCorrection=-2.5 (note the minus) and see what happens! Who knows, perhaps time and wear after many years of happy flying will give you the answer!

 

Bertie Goddard

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"Just these two are missing." for a reason?

 

"I guess" good guess. You're close, but not quite there.

 

"Drag should be a positive value and Fuel Flow negative." How sure are you about that?

 

The past comments show just how little is known about the performance factors and how they are derived and handled... If PMDG wanted you changing these, they would've implemented the code in the QotS2 software to correctly change these using the fmc/cdu. They haven't... yet.

 

But "Any chance someone from PMDG can comment here" the haven't yet, and so you might be waiting a while.

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You got some good points there Brian.

 

"Just these two are missing." for a reason?

 

Probably, then again why would they put it in the ini file and not hardcode it somewhere not accessible to the user?
If something is in the otherwise customisable ini that also has to have a reason.

 

 

"Drag should be a positive value and Fuel Flow negative." How sure are you about that?

 

Drag being positive would be logic, if the 747 could be build with less drag Boeing would most likely advertise with the lower values, don't you think so?

I would have said fuel flow should also be positive though, isn't the correction value a value you multiply the performance database with?
This is assuming that the above theory on Boeings published numbers is correct of course.

 

 

code in the QotS2 software to correctly change these using the fmc/cdu. They haven't... yet.

 

I see a "yet" there... you do not by any chance have some insight information? :P

 

 

But "Any chance someone from PMDG can comment here" the haven't yet, and so you might be waiting a while.

 

If they don't want us to fiddle with it they just should say so... then no one needs to speculate.
Rest assured, the moment PMDG tells us we should not play with these values I won't ask again.


Who knows, perhaps time and wear after many years of happy flying will give you the answer! Bertie Goddard

 

Looks like I need to do one of these really, really crappy landings to find out if my drag changes then ;)

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