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Flight dynamics discovery

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Guest Ron Freimuth

>Roger, >>Ironically, I just found this out a couple weeks ago. >Annoying, isn't it? ;-) >>One other thing I've seen with 2K2 is that all the trims >reset when loading another aircraft or reloading the current >one. This makes it really easy to fix broken aircraft.cfg >files. I load up a model - say a 767 - then trim it to >level flight, ten reload it, and BAM! nose dive. I change >the aircraft.cfg file to fix the horizontal stabilizer, >reload, and it now flies right. I suspect MS figured some obscure formula to set the pitch trim when an AC is loaded. Often it's way off the the correct cruise value when I have about 2 degrees of H. Stab angle which forces the tail down. Maybe they assume the H. Stab moment is zero, as most of their FS2K2 AIR files have, but I always set it in proportion to the elevator moment. That is, I use about the same ratio of Elevator_Lift/Elevator_Moment as H_Stab_Lift/H_Stab_Moment. And, make the H. Stab about 3X the values for the elevator, depending on the area ratio. Sometimes an AC will load with the trim not being far from cruise value, other times it's several degrees negative. In any case, Aileron and Rudder trim are not saved, so they also have to be adjusted (many AC don't have Aileron Trim). >I originally thought having the trims all reset was a >problem until I realized the potential to fix things. ;-) >Then I saw the negative negative. ;-) Makes life a lot >easier now to get things flying right. I just automatically >change the HS incidence when I convert from 2K to 2K2. I had the impression the H. Stab angle was set from the AIR file on the first run. So, a good FS2K AIR file should come out correct in FS2K2. But for the Oswald Efficiency, which appears to be set based on Aspect Ratio and Taper. And, who knows what else. I always set it to a reasonable value, such as 0.80 for big jets and possibly higher for SEL's. To make it consistent with the Induced Drag Constant set in the AIR file (but, not used in setting that Oswald Efficiency in aircraft.cfg).>But then again, I still to this day have problems knowing >whether to use plus or minus for wing incidence and twist! >:-lol As I mentioned to Roger, and he verified: Changing either in aircraft.cfg without resetting that SEC 1101 parameter messes up the Induced Drag. Roger stated the effect per degree. When the SEC 1101 parameter is reset after changing Wing Incidence, Twist, or TBL 401 there is no change. I'd estimate that CFS people spent 1000 hours over a long time to figure out that SEC 1101:50 parameter.Ron

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Guest Ron Freimuth

>Ron, >>I don't know if you remember me emailing you to ask about >excessive use of trim about a year and a half ago as I >trained in a 1979 172N , with a follow up email of >excitement about my first solo, but your original 172 with >the bugs program in FS2k (don't remember the name), helped >me out immensely!!!Christopher, I'm going to save your testimonial. >evenings after he got off of work), I began with a new >instructor who, as best I can describe it, was all business. >He recognized instantaneously that I was more than ready for >my cross countrys, etc. And we proceeded to crank out the >remainder of my license in under 3 weeks. I got my PPL in >40.9 hours and I can honestly say that flying around your >flight model saved me A LOT OF TIME AND MONEY!!!!! Took me 51 hours in a C172 to get my PPL. Back in 1964. ;)>dollars!!! And that's coming from my CFI! I flew Roger's >flight model over and over during my PPL training, and sure >enough, last July I got my PPL in .9 over the minimum 40 >hours and soloed at 8 hours at a Part 61 school (so it >wasn't a "crank you out with minimum time" school -141, it >was a get your certificate when you have proficiency >school). I am now working on the Instrument, Multi(at the >end of this month), and commercial. To anyone that is >looking for a great airfile, Ron's for FS2k2 is great!, But, >keep an eye out for Roger's, if it can be integrated into >the FS2k2 VC!!! I have a C172N version that I use with Roger's C172 panel. I don't remember if I offset the engine yet. That reduces the need for rudder trim, similar to what is done in real AC. Setting the engine location in aircraft.cfg to about -0.2 ft laterally (normally 0.0) works well for small AC and one then needs to adjust the rudder less with power setting. However, the prop sliders should be at 50% or higher so the offset has something to compensate for. It's partly Roger's fault that I got so much into doing MS Flight dynamics. While I had been doing AIR files since FS98, Roger and I spent a lot of time on the C172 about three years ago. Seems I got to working more and more on flight dynamics after that.>Roger you have a done a great deal to advance the training >realm of the hobby. I don't just like flying around in eye >candy! And you ahve solved that, along with the great Rob >Young and Ron Freimuth. >Thanks again!!! >Christopher Braun There is a big organization that is very interested in using MSFS for training. I won't say more now, but I did the flight dynamics for a particular trainer that appears to have met the requirements. However, any future contributations depend a lot on MS patching FS2K2. There are some serious bugs that make it impossible to get appropriate autopilot control. Mainly for jets.Ron

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Guest Ron Freimuth

>> To anyone that is >>looking for a great airfile, Ron's for FS2k2 is great!, >>Is there a "Ron's" airfile out there? I hear nearly >everybody want's one !! I also heard the same over at >Flightsim com. Wouldn't be that 172 file that's >"temporarily" not available ( but I have) would it? :) Funny how the value of something increases when it's hard to get. ;) You probably already have my FS2K2 C172SP 'fix'. Feel free to share (but not UL) it. I should offset the engine, something I thought of a couple of months ago. Too bad I didn't think of that for FS2K, which had really excessive "P-Factor". Actually, it was the 'prop helix effect' that was too strong. That can be reduced in the AIR file. Something else I only thought of recently.>Sure would be nice to tell everybody where to get >it.......... instead of they CAN'T have it!! >Ron?????????? >L.Adamson I think I just did. ;) Let me know if you don't have my C172SP. A lot of people have the few AC files I took off AVSIM's library. I still email many of my AC to people I know. Including an improved C208 amphibian. Ron

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Guest Scott Campbell

Thanks Ron, I'll keep that all in mind as I fidget with this stuff.BTW -- I am currently woring on ACLoader 4.0. If you'd like a preview copy, please em me and let me know.

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Guest

Ron,You're right. I just did a glide test on the C172R model and it is now way, way off. I ended up at 5000 feet when I should have been at 0 (Starting from 10,000). This is a big setback as the this took alone time to get right, the test takes a long time, and has been the stable baseline for my 172 aircraft since the first FS2K upload.Later:Ron, I've really got to hand it to you. I just did the glide test on the last SP air / cfg combination you sent me last fall and it is perfect, didn't stray out of the wide shaded line on the Cessna graph once. I'm going to go back to those as a base for just tweaking the handling, deck angles, and views to be a little closer to what I see in the real plane. The best contribution to the FD part of the hobby I can think of at this point would be a comprehensive listing of which air file variables are not superceeded by the cfg file. It's much easier to fiddle with the cfg as letting the air file rewrite things has all sorts of unexpected effects. Perhaps and AirEdit ini file with the vital fields tagged and a template cfg file showing what should be there. I notice that not all fields are copied unless you start with a really blank cfg.

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Thanks for the info Ron............ & I do have the SP file.L.Adamson

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Guest Ron Freimuth

>Ron, >>You're right. I just did a glide test on the C172R model >and it is now way, way off. I ended up at 5000 feet when I >should have been at 0 (Starting from 10,000). This is a big >setback as the this took alone time to get right, the test >takes a long time, and has been the stable baseline for my >172 aircraft since the first FS2K upload. Did you change the wing incidence or twist? Or, was that after the H. Stab incidence was set to give the flight model you had in FS2000? Your FS2K C172 should be identical in FS2K2 but for the autopilot and LG effects. Assuming you let FS2K2 set aircraft.cfg. THEN: adjust the LG, if necessary. AND, reset the Oswald Efficiency to be the same that was included in the Induced Drag Constant in the AIR file. I think you said the prop type also required a change for your AIR file. FS2K2 probably set it for CS since some of your AIR file settings were for CS.>Later: >>Ron, I've really got to hand it to you. I just did the >glide test on the last SP air / cfg combination you sent me >last fall and it is perfect, didn't stray out of the wide >shaded line on the Cessna graph once. That C172SP I fixed? Or, the one based on my version of the C172N done a couple of years ago? The H. Stab incidence has more effect on drag at lower speeds. Since it increases the force on the wing, Induced Drag is more critical at 'best glide' speed and below. But, as you found, also has a significant effect on top speed. All these things became more clear to me by using Herve Sors' FS Test App. Which shows all these drags during flight tests. Now the H. Stab is set for a down force on the tail to improve static pitch stability. It's a matter of the effective Angle of Attack of the Wing minus the AoA of the H. Stab. There is a French word for this that I can never remember. I have found that setting the H. Stab at 2 degrees (to produce a down force) is about right, but due to the effect on drag, I've not always made it as large as it might be. I think it's 3 degrees or more in the MS Cessna 182's. Flight Dynamics I think they got some years ago -- probably from someone else. Since the 182's have pretty good flight dynamics. Then, MS screwed up the C172SP -- apparently 'good flight dynamics' weren't considered appropriate for FS2K2 AC so they messed up the 172SP. Maybe they didn't know it's the same airframe as the 182 uses. Or, that the 182 is the 172 airframe (with limited changes). ;) > I'm going to go back >to those as a base for just tweaking the handling, deck >angles, and views to be a little closer to what I see in the >real plane. My C172N (which I use with your panel) is about my best AC. I haven't tested it in detail for some time, but this is the one that had a rather good match to the PoH engine tables. > I notice that not all fields are copied unless you start >with a really blank cfg. I comment out the 'wing_apex_location', or anything else I want to be reset after a change in the Reference_Datum, etc. Then, see what FS2K2 sets there after it is again loaded. Ron

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Guest

It's the air file dated 10-23-01 and October 2001 cfg file.

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