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Other threads were getting too long. Yes, there is an "IAS" problem in FS9. I flew my 727 in FS2K2. At FL 350, Mach =0.742, IAS was 250+/-0.3 kts. What I'd adjusted it for in the AIR file. I got a new AFSD that works in FS9 so could check very closely in both FS2K2 and FS2K4. Of course, I checked AFSD's 'environment' window to be sure the environment was ISA. In FS2K4, at Mach = 0.742, IAS read 254.7 kts. That's just about what it wouild read in earlier FS versions without correctly adjusting REC 1101 "Airspeed Weight Factor". The correct IAS is 250 kts, assuming the standard tables for compressability effect on IAS are used. That's how I calibrated the above factor originally. Further, the 727 FM says the IAS indicator should have virtually no error around 250 kts in cruise conditions. It may be that the new airspeed indicator in aircraft.cfg can fix this, but the lines in the C208 were not added to the 727 when imported into FS9. This will also mess up IAS a bit in my SEL's. Probably not as significant.-RAF

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Thanks for opening up this new thread, Ron. It is needed because I suspect we have just begun to scratch the surface on this buggy sim.I am having considerable difficulty with CG on older imported aircraft. There is an incositency in the way FS9 handles weight and balance data when the reference daum is zero. I noticed this inconcistency in FS02 but only in the values read by my CG gauge (which reads the FS CG value that is always displayed in %chord. (I used to presume this was percent mac.) In FS02 it made no difference to the flight mechanics. But in FS9 it makes a big difference.The values with zero refence datum are clustered around zero. But that should really mean they are clustered around 25%. In some aircraft such as the default King Air 350, this is shown correctly. In fact I added the missing seats and filled them with average people and found a CG at 40%. That made flying very difficult with poor stability. But in my imported aircraft, it just gives me a value like -8%, shows the CG well ahead of the wing on the dumb diagram and makes me fly with considerable aft trim. This messes up the stability and the performance if I try to remedy it with adjustment of the htail_incidence.It seems there must be a key parameter hiding somewhere that determines how a zero reference datum set is to be treated.

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>Thanks for opening up this new thread, Ron. It is needed>because I suspect we have just begun to scratch the surface on>this buggy sim.>>I am having considerable difficulty with CG on older imported>aircraft. There is an incositency in the way FS9 handles>weight and balance data when the reference daum is zero. I>noticed this inconcistency in FS02 but only in the values read>by my CG gauge (which reads the FS CG value that is always>displayed in %chord. (I used to presume this was percent mac.)>In FS02 it made no difference to the flight mechanics. But in>FS9 it makes a big difference. Check my commented aircraft.cfg at Herve' Sors' site. It explains how I set up the wing. As engineers do it: with MAC, Area, and span. The LE should normally be 25% of the MAC length ahead of the CG. Thought, some AC apparently use airfoils where the CoL is a small distance from the 25% MAC line. There is a record in the AIR file that can offset the wing's CoL. I think that is away from MAC/4. I think the Lear 45 is like that, it's official CG range is something like 10% to 30% MAC. I always set 'wing_root_distance' to MAC. MAC=Area/span. I think Sim1.dll calculates it the same way for internal use. The CFS3 SDK implied that. I know quite a few freeware AC displayed CG as a negative number, meaning the CoL was forward of the LE of the wing. Probably aircraft.cfg was set up according to MS names, such as "Wing Apex". I got so confused with just what the CG gauge and distances set in aircraft.cfg did that I tested the real CG of a couple of AC by moving it to just over the main wheels. To check that the AC would be ready to tip on its tail. Or, move the mains to the CG and set payload to the same place. At least my 727 shows the same CG:%MAC flying in FS2K2 and FS2K4. While elevator trim changes from -0.12 to -0.18 degrees. Neglible. This is after I fixed TBL 404 and increased Incidence from 1.0 to 1.7 degrees so it would be compatable in FS2K2. Twist was set to -3.4 deg so I set Incidence to -1/2 Twist so they added to zero. They still have an effect in FS2K2, and I want the FD compatable with it. Note REC 1101:50, "AoAw for Cdi = min" is at the point CL=0. With twist and incidence out of the equation, that means TBL404 should be shifted so CL=0 at the value set in 1101:50. This assumes that parameter was set correctly in FS2K2. If the Lift Slope is correct, flight pitch should come out correctly. I figure 2Pi * (AR/AR+1) * COS (Sweep). Then start squeezing down the lift curve around 0.20 radians so it reaches stall CL around 0.27 radians. Conversly, if CLmax is set from Stall Speed it should occure around 0.27 radians. Then, one can more or less work backwards to get a nominal lift slope. The most important values to set in TB404 are (AoA at CL=0 [usually negative]) and the Lift Slope. That sets appropriate CL at AoA=0, and the AC will fly at the correct pitch. Typically 2 degrees; in FS9 AoA is equal to pitch in level flight. Regardless of loading and CG (H Stab Lift will change that a bit if the tail is set to some incidence) ----------------- >>The values with zero refence datum are clustered around zero.>But that should really mean they are clustered around 25%. In>some aircraft such as the default King Air 350, this is shown>correctly. Again, the %MAC may be be correct over some range other than the typical 15% to 35% MAC IF the CoL is offset in an AIR file table. Howver, this shouldn't be too much. One exception is the Concorde. I found Delta Wings are referenced from the APEX. CoL is 2/3 of the way back from the Apex. The CoL offset is set to -63.0 ft in the Concorde Air file. This is very close to some real number I ran into. Further, supersonic AC are usually balanced at 50% MAC, not 25%. The Concorde has to be close to -53% MAC for TO, but as Mach number increases, the CoL moves to -58%. The CG also has to move back, so fuel is pumped rearward. MS did do a good job on the Concorde CG gauge and fuel pump. Though one can't pump fuel between enough tanks.> In fact I added the missing seats and filled them>with average people and found a CG at 40%. That made flying>very difficult with poor stability. But in my imported>aircraft, it just gives me a value like -8%, shows the CG well>ahead of the wing on the dumb diagram and makes me fly with>considerable aft trim. This messes up the stability and the>performance if I try to remedy it with adjustment of the>htail_incidence. I use TCDS values when possible. Tank locations are often given directly. The problem is to figure where the Reference Datum is relative to the .mdl. At 11'th bulkhead' doesn't help much unless one is working on the real AC. I've also calculated moments and expected trim to be close to zero in cruise. It was the one or two times I did that. Usually I set up the wing, tanks, and payload so CG is at 25% MAC, and screw around with 'Cmo' to get trim close to 0 in cruise. A few times I've changed the 'horiz_tail_angle' and calculated how much I needed to change Cmo to keep trim the same. It comes out when calculated correctly. Usually I just experiment. But like to check mathematically now and then. That is the only way to really tell if things are working as they should.>It seems there must be a key parameter hiding somewhere that>determines how a zero reference datum set is to be treated. Maybe that CoL parameter in TBL 1534 (there is an identical table for FSEdit modifed AIR files). I always set the Reference Datum to the official value. Which is often at the 'front jack point' in jet tranports. If one is lucky, it is at the tip of the AC. But often it is not. However, the simple drawings I see never show where the MAC is. Not even the wings LE. All they show is span, lenght, etc. so one can figure if the AC will fit in a hanger. Milton sent me some engineering drawings of the AC510 and with some difficulty, I was able to figure out all the important aerodynamic distances. The LE distance was given, but the CoL of the wing was not exactly 25% MAC aft. I put that offset in the CoL parameter in the AIR file. Herve sent me a Release Candidate of AFSD that works with FS9. It displays CG, also CG offset in x, y, and z directions. Dowson managed to find the offset of 'dynamic pressure' so Herve' could get something working to me.Ron

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As Ron mentionned, I have now finalized a new version of AFSD which is working fine on both FS2002 and FS2004 (only for jet, reciprocating and turboprop aicrafts by now). For correctly working, it requires a beta interim version of FSUIPC (3.045) is installed in the FS2004modules directory..this version will expire on 31-Aug-2003 but next 3.05 FSUIPC version (that will include the 3.045 changes) will be available before this dateAs far, as I do not have a mailing list of designers who used AFSD before and do not want to upload yet AFSD RC1 to my web page (along with the beta Pete Dowson provided), I will be glad to send you privately this new version if you want it and email me athsors-public@wanadoo.frHerv

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Hi Herve,I'll wait until Pete releases the next version, since I already have a registered version.I haven't been using FS as much since I took up flying. I have about 23hrs in C172SP to date.W. Sieffert

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Yes, a real Cessna 172SP is always more compelling -- and rewarding -- than even a simulated F-15.:-)

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