I'm trying to edit the file .air 747 rfp so that the value of the EPR for a certain amount and a certain weight corresponds to a certain speed as the Matt Zagoren manual . What values ​​should I change? I tried with airwrench, but the values ​​come out completely different and the engines increase power very slowly.

 

Sorry for my english

If your manual has the engine specifications such as intake area and static thrust, enter these and any others into the aircraft.cfg file BEFORE using Airwrench. Then in the Engine tab, set the correct Vmax altitude for the 747 and then adjust the RAM Air Gain figure. Go to the Specs tab and check the air speeds - adjust the RAM Air Gain until you achieve the correct Vmax, Vmo, Mmo and Cruise TRUE AIR SPEEDS, not Indicated, for the 747 at Vmax altitude. You will need to use an indicated to true air speed converter, there are a few online which are very useful. If your 747 panel has an FMC, be VERY careful about adjusting aircraft.cfg and .air file weights, fuel capacities and engine specs as the FMC will be calibrated exactly to those specs. 

I can not test the changes because the engine power increase very slowly after using airwrench.

(P.s.: what is the spool-up?)

The slow power increase will be due to Airwrench applying its own figures for any settings which are missing from the .cfg or .air files for your aircraft.

That is why you must check and amend your Aircraft.cfg figures before opening Airwrench, as the .cfg figures will override the .air file figures. When you open the .air file in Airwrench, it will then adjust and synchronise both .cfg and .air file figures for you, but you need to know exactly what you are doing with them and read the manual very carefully.

Spool-up is the jet engine spinning up to speed before ignition.

Hi A32!

 

I too am adjusting a jet engine with Air Wrench.  Thanks for you info here that is helpful.  What I need to do is lower the N2.  During flight N2 is way too high and it actually goes off of N2 Guage.  96% is the MAX N2 for the Beechjet.  Yet in FS9 N2 goes up to 106.7 percent.

 

Can you push me in the right direction to get the proper adjustments?  Thanks!

To adjust spool up time set "fuel_flow_gain= 1" under [TurbineEngineData] in the aircraft cfg. then adjust table 1505 in the air file. Start with the ignition n2% and finish with max allowed n2%. Look for a concave curve that increases rapidly after about 80%.

Record: 1505 

Points: 10

0.000000 0.000000

0.002940 10.000000

0.011800 30.000000

0.020660 40.000000

0.033970 50.000000

0.053170 60.000000

0.133910 70.000000

0.290000 80.000000

0.440000 90.000000

0.570000 96.000000

 

I did what think you meant for me to do.  The very last number right hand side is 96.00000 which is the limit of the N2 per the aircraft.  

 

I just did an engine run and the n2 still goes to 106.7  the number that WAS in the 96.000000 was 108.000000

 

I used airupdate to extract the numbers from the airfile.  That part was rather cool.  Now I can enter them into a spreadsheet if need be.

 

You keep mentioning curves.  Not following you.

I think you keep assuming I have a vast amount of developing and programming experience.  LOL  As I stated I am a newb at this.  

From what I have been able to gather from reading.  Isn't 1503 and 1504 supposed to  be where you would change the N2 parameters?

 

If so I think if I knew what the numbers mean to each other it would make more sense to me.  I see there are formulas to calc new numbers etc and I dont understand that yet.

 

Too bad someone hasn't written an airfile for dummies yet.  LOL

X                     Y
0                    24.1
250               29.4
509              36.153
623.44        40.6865
688.37        44.9067
753.3          51.0682
816.23       60.4256
879.16       72.9981
942.09       88.0401
1005.02    104.9997

 

These are the spool up numbers for the RR Conway 550.  zero x represents the n2 rotation percent at the fuel ignition point which in this case is just above 24%. 105% is extreme engine limited n2. You'll see the graph represents time to n2. Or how long from ignition to max allowed n2. Somewhere along the line will be your idle percent.  In this case idle at ISA is 56%

Look at the curve and yours should be similar-ish.  But bear in mind that the engines for the 747 are different so their spool up time will also be different.