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AirEd questions (Read 1379 times)
6th Jul, 2010 at 4:40pm

Eagle_54   Offline
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In the air file setting what could I adjust to help my plane out some.

I have a plane I am trying to tweak out it is a super sonic type of plane and right now the ceiling for the aircraft is around 70,000 ft up and I can get to mach 4.5 but, I am looking for the ceiling to be a little higher up and getting around mach 6. Some of the things in the air file I do not understand to well like EGT and N1 settings. Also I had to put the drag fairly low to get the speeds I have now and slowing down is a problem as well I hit around 500kias with  the engines set to nil only way. I can slow myself down for landings is using the flaps. If I increase the drag then I can not hit mach 4.5 I have been tweaking for many hours and I can not find the right combination or something. Is there something I could do to the engines to increase power other than using thrust? Also another thing from a dead stand still to in the air is a little to quick 0 to 200 in no time, is there a way to slow it down from a dead stop till in the air and still have enough engine to hit mach 6?

I wish some one had a good list of all the data for AirEd for what they do for performance.

Any information would be helpful.
 
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Reply #1 - 8th Jul, 2010 at 11:24am

atc4usaf   Offline
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It sounds like your problem actually exists in the 1503, 1504 and 1506 table.

What happens is that as you increase altitude, the altitude increases, air density decreases which means the engine won't have the air necessary to produce thrust (simply stated).  So you have to set up the tables above to define what the engine is capable of at those altitudes and speeds.

As an example, 1503 is the low mach setting and TBL 1504 is the high mach setting.  I set 1503 for .00 Mach (this is set using the top-left-most cell to set the mach for the table) and TBL 1504 is set at the max mach number fot the aircraft.  Then the left cells under the mach number set the Inverse Air Pressure Ratio.  Pretty much Sea Level density divided by the density at the max operating altitude.  As an Example: Sea Level density is 1.225 kg/m3 and the density at say 98500' is .01841 kg/m3.  So 1.225 / .01841 = 66.53.  This would go in the lower left cell as it defines the max altitude that the aircraft will be operating at.  Now you take the aircraft at Sea Level and set the N2 at throttle positions.  (throttle position is the top row of cells next to the mach number cell in percent of throttle.  idle is 0.000 and full throttle would be 1.  50% throttle would be .500).  Idle thrust lever position would equate to idle N2 speeds... say 24% or .24.  In the rest of the cells below the throttle position, you set N2 turbine speeds in percent of max N2 rotor speeds (75% N2 would be set as .75000)  Just set the sea level IAP line here as we'll set the 98500' IAP line later.

Go to TBL 1504 and set it as whatever max mach you want the aircraft to fly at.  Say 5.00.  That goes in the top left cell again.  (these two cells actually generate a 3D table.)  The IAPs are the same as TBL 1503.  1.00 for sea level and 66.53 for the max altitude.  Increase the thrust scaler in the .cfg to something that will overcome the drag to get you to the speeds you want.  We'll reduce this to 1.00 after we set up the engines and drag.  Now you take the aircraft up to the max altitude and increase the N2 ratings to give you the numbers you want.  I usually use a spreadsheet in excell to make it easy to increase by percentages... say 20% to start, then as I get closer, decrease it to say 2%.  You'll eventually get the N2 numbers where you want them.

What this does is position you to adjust TBL1502, where N2 sets N1.  In TBL1502, you'll set N2 across the top row, then mach in the left lower cells (the top left cell can remain at 0.00).  In this case 0.00 (stopped) and 5.00 (max mach).  Then you set the stopped N1 speeds to what you would like.  Then take your aircraft back up to altitude and max mach and increase this lower row of cells to get your N1 numbers where you want them.

It is important to note that you are actually dealing with CN1 and CN2.  Which are derived from differences in temperatures and density between sea level and operating altitudes.  It is just easier to reserve the last cell in these tables as a higher than rated cell (if sea level max N2 is say 103%, use 108%).  It's hard to explain here but it's trial and error.  Smiley

Now that you've set the N2 / N1 relationships, N1 sets thrust at different speeds in TBL1506 as percentages of max thrust which was set in the .cfg.  Increase the high mach thrust settings until you get your desired cruise speed with the desired N1 settings.  You'll have to come back and tweak this setting as you re-adjust drag.

I'll admit, I'm not perfect in this process as far as being able to calculate absolute numbers.  I've tried with formulas that I've found to estimate calculated N2 and N1 but they were a bit off.

I also have to stress the use of real numbers in the FDE.  I see a lot of FDEs that use 29990 as rated N2 in the .Cfg; but how can we get real results from unreal numbers.  Use TCDS information for engines ( Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to Login or Register ) to get the documented data.

Hope this helps.
 
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Reply #2 - 18th Jul, 2010 at 11:53am

andyjohnston.net   Offline
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Also, what you're asking is not within the limitations of FlightSim, where the max speed is 2666 ground speed, approx mach 4.5.

Hitting mach 6 is essentially impossible.
 
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