>>Neverthless MSFS seems to be able to model spins quite well.>> Not in my experience. Unless one takes large liberties on>some of the SD tables.>> I don't know if MSFS accounts for 'gyroscopic' coupling>between Ixx, Iyy, and Izz. But, such coupling is one>important factor in spins. >> Missing in MFSF is the ability to vary Yaw derivatives as a>function of Alpha and Beta. They can only be modified wrt>Alpha. My feeling is that both need to be adjustable to get>realistic spins. JSBSim allows that, but it looks like no one>has figured out how to get spins in JSBSim so far.>Regardless of how it's done, I'd say that Rob Young (RealAir Simulations) has got a pretty good imitation of spins, which isn't bad, since all this flight simming is just an imitation anyway. :D I do believe, that he has the best "spins" in flight sim land. They may not be always perfect, but the spins begin for the right reasons, look authentic without an airspeed buildup, stop with normal recovery techniques, and best of all, the break into a spin is quite immediate without dilly dallying around...... so to speak.Spins and slips have been a RealAir specialty for several years.L.Adamson

>>>>Incidentally, the Yaw Damper may work better in FSX than in FS9.<<<

>>>>>Incidentally, the Yaw Damper may work better in FSX than>in FS9.<<<<>>No joy on the FSX yaw damper Ron. I set up yaw_damper_gain =>2.0 and tested 4 A/C between FS9 and FSX; three were stock>FD

Ron,Thanks for the info. I'll spend some time getting better educated on this since this thread has piqued my interest. My background is electrical engineering, not aerodynamic so most of these terms and formulas are a bit foreign to me at this time.Got to say that I have found this thread to be the most informative and interesting discussion that has taken place since the release of FSX. This in my opinion is the root purpose of forums.Thanks for awakening me to this exciting area of FS.Rick.

>>>> My impression was that the FSX YD worked a bit better. Besides looking at the rudder movement, I had a test gauge that showed Yaw, etc. However, the jet I was flying didn't have a 'ball'. If the YD is working the ball should stay more centered in turns. <<<

>>>>Thanks for the info. I'll spend some time getting better educated on this since this thread has piqued my interest. My background is electrical engineering, not aerodynamic so most of these terms and formulas are a bit foreign to me at this time.<<<http://perso.orange.fr/hsors/FS_Soft/index.htmlhas most everything you might need to get started.As he mentions, and something that really helped me, a quick primer on the terms can be found by looking in his AirEd.ini file. It

>Ron,>Thanks for the info. I'll spend some time getting better>educated on this since this thread has piqued my interest. My>background is electrical engineering, not aerodynamic so most>of these terms and formulas are a bit foreign to me at this>time. Heck, I'm an EE. But, no employment for over 20 years. Bruce Artwick's original FS team was composed mostly of EE's with Private Pilot's licenses. No aeronautical engineers. ;) Most everything I know of aerodynamics is due to MSFS. While I used to fly light AC, I didn't have to know many details to make them go up and down. The Engineering Mechanics courses I had to take cover a lot of what is involved in flight dynamics. Though, one really only has to know a bit about moments, forces, etc. The trick is to see things in the simplest way and not go down inappropriate paths. I've spent years on that. >Got to say that I have found this thread to be the most>informative and interesting discussion that has taken place>since the release of FSX. This in my opinion is the root>purpose of forums. A lot of this stuff was worked out years ago in the AIR file forum at avhistory.org. Originally for CFS. The AVSIM Panel/AC Forum has also had threads on this stuff. Some are very long and one has to separate the wheat from the chaff.>Thanks for awakening me to this exciting area of FS.>Rick. I think MFSF is actually useful for engineering analysis. A simple case would be to see how changing the prop on a C172 to a different pitch would affect climb and cruise performance. Of course, one has to have a good drag and powerplant model before he can trust the effects of changes. At least TBL 401 ('Lift Slope') isn't a factor at lower speeds. As far as drags go, it's just a matter of setting Oswald Efficiency' (~0.8) and Cdo (~0.035) correctly. Such info is available from various sources, but in the end I tweak them a bit to best fit AC performance (such as glide slope and max speed). They can't be calculated exactly anyway; good engineers know how to tweak such parameters a bit to fit actual performance. The reciprocating engine has several tables. A general understanding of 'Volumetric Efficiency', 'Friction Torque', etc. helps in shaping the applicable tables. While props are another matter. ;) It's hard to get engineering data on props, but if the other parameters are good, then I can tweak the two prop tables to fit the PoH tables. One can then change the prop pitch (or diameter) and the effect on the FS AC performance should give an idea of what a prop change on a real AC would result in. That worked from me when I calculated the change in prop diameter to load the C172SP powerplant to a lower red line RPM. Power dropped from 180 to 160 HP. Which is really the main difference between the C172SP and the C172R. Lower rated HP mainly because a slightly different prop is used. But, longer powerplant life. The lower HP doesn't affect top speed much, but does have a significant effect on climb rate. Rick, if you wish you can leave an AVSIM message for me by clicking on my name. Ron

>>>>> My impression was that the FSX YD worked a bit better.>Besides looking at the rudder movement, I had a test gauge>that showed Yaw, etc. However, the jet I was flying didn't>have a 'ball'. If the YD is working the ball should stay more>centered in turns. <<<<>>I

>>>>A couple of years ago I learned jet transports can't move the rudder more than a few degrees above 180 kts or so. The hydraulic pressure is purposely limited so only a limited yaw moment can be applied. Note even that was too much for the jet that crashed in NYC near the end of 2001. That probably involved dynamic stresses that damaged the vertical tail/rudder.<<<< Didn

Douglas, You got your revenge and replied to my long message with another long one. ;) I'll try to keep this shorter.>>A couple of years ago I learned jet transports can't move>the rudder more than a few degrees above 180 kts or so. The .. Heck, most of my comments disappeared! Leaving just the bit below:>>>>>PS: Just found 1 GB of DIMM's in my mailbox. 1.5 GB total>should really be enough RAM for FSX.<<<<>>Santa came early! I have 2 GB, and the biggest advantage to>having that much is I can have several programs open at the>same time (including MSFS) and switch between them. .......>Douglas I almost ended up buying a new PC after my current one got messed up when I put in the additional DIMM's. Maybe a cable connection, even after pulling out the new DIMM's I couldn't get into the BIOS setup. Pulling the DVD/CD cable finally got me in. This morning I got the extra 1 GB in, bringing my total to 1.5 GB. The HD no longer flashes as I fly, virtually no stutters or pauses. I still think some of the FSX problems are due to the way XP manages memory. My swap file grew too 850 MB, the same as it had before the new RAM. However, I had 750 MB of HD cache available. Before it had dropped as low as 100 MB. I think the HD cache holds read-ahead scenery so HD access is much reduced. Extra RAM didn't stop FPS from dropping below 10 with 'Thunderstorms'. That's a different thing. A better Video card would likely help some. I doubt more than 1.5 GB would help FSX. Maybe those with heavy graphics could use more, but my Task Manager showed around 750MB 'Available' with FSX running.Ron

>>>>>Thanks for the info. I'll spend some time getting better>educated on this since this thread has piqued my interest. My>background is electrical engineering, not aerodynamic so most>of these terms and formulas are a bit foreign to me at this>time.<<<<>>Rick,>>The website link Ron posted:>>http://perso.orange.fr/hsors/FS_Soft/index.html>>has most everything you might need to get started. Herve's site has a lot of info, but it doesn't have an "A, B, C..." on MSFS. At least my "aircraft.cfg" and info in Aired.ini help. JSBSim has a 'Back of the Envelope' newsletter that has quite a bit that also applies to MSFS. Assuming one understands how to interpret the FS lingo. ;)>As he mentions, and something that really helped me, a quick>primer on the terms can be found by looking in his AirEd.ini>file. It

>>>>You got your revenge and replied to my long message with another long one. I'll try to keep this shorter.<<<

>>>>>You got your revenge and replied to my long message with>another long one. I'll try to keep this shorter.<<<<>>LOL! The only revenge I

>>>>>>It appears there is no simple way (changes in>aircraft.cfg) to fix the fuel flow and still have N1 reading>appropriately.<<<<>>The problem with the fuel flow being higher in the 738 is the>new

>>>>Would you be so kind to describe how I would change the Cdo on the 737 in FSX please.<<<http://perso.orange.fr/hsors/FS_Soft/fsairfile.htmlBe sure to make a backup of the airfile before you begin working on it.Now you