Comments on aircraft.cfg

[Guest Ron Freimuth]

>Hi. > I had a few days where my total dedication, undivided >attention and involvement was required, and I am glad to >see that this discussion continues. > A lot of good information. I am at different stages, most > elements are at rote or understood, some applied. The >problem I have is that I cannot correlate all the available >information. This is compounded by the fact that some >elements need to be adjusted based on experience and >empirical engineering rather than real data. One problem is understanding what's important, and what only confuses things. I made a copy of my aircraft.cfg message so I can send it out now and then. I still need to comment on props, etc. "Aerodynamics For Naval Aviators" is an inexpensive reprint (~$20) of a Navy manual that covers various AC types. CG, Balance, etc. There are various sites on the WEB, I scan them now and then and generally learn from even the most basic ones. Further, thank's to Herve's AFSD, I can have people actually look at many of the effects I mention. > I ended up wit about 3 .air, .cfg file combinations that I >can do some of the things that I need. The problem is that I >have to interrupt the flight, load another aircraft, rename >/ copy the combo files and reload the aircraft that I use >every time I want to take advantage of the modifications. I >was hoping that there maybe a way to simplify this process, >maybe a background task? If I have two variations of one AC I put each in a different AIRCRAFT folder. And, name them appropriately. One can set different AIR files for one aircraft.cfg, but the main parameters are now in aircraft.cfg, so they are common to all the AIR files it has set. I normally edit aircraft.cfg and/or the AIR file DURING flight tests. Just Reload the AC in flight and the changes are implemented! Be careful, the pitch trim has to be changed back to the value it last had before reloading the AC. Further, this doesn't work for changes to panel.cfg. One has to load a different panel, then go back to the one modificed to get the changes.> As far as the Forward view / attitude, I am more interested >to

[Avcomware 1]

Hi, Ron.Thank you for reminding me of the ability to have a more efficient change over, this will save some time. Have you herd of a way to load any parameters

[Guest]

That's interesting, using the speech to command interface to work VC controls. Good idea. Well, when I had bad carpal tunnel I tried to do my work using one of those I downloaded and found that within a few hours of saying, open, open, copy, paste my throat was about as hoarse as my hands were limp.I don't know that Fly influenced the VC, but Battle of Britain (and probalby some other games) uses a VC with mouseable controls, so I think a 3D view is becoming a standard for gaming.Steve

[Guest]

I hate to make this thread any longer. :-) But you were right. Reducing MOI for Roll took that 'rubber band' effect out of my attempts to align with the runway. I reduced MOI from 3000 to 1500 for a 750lb aircraft.I still run out of elevator authority when flaps are extended 30 degrees. I really do not know how to size the tail surfaces given there was no three view plan to base them on. Just a side view. I might use a photo by measuring relative the man next to the plane.Steve

[Avcomware 1]

Hi, Steve and everyone.Sorry, to deviate from the subject, but this information may be of some help to some here. SpBdy2 is an intelligent way, has the ability to use FSUIPC, for feedback and control, to output commands / keystrokes to your active application. You can output / set radios, read the data and make decisions based on the data read, to go on to the next level. If you have your gear down already, for example, and you issue

[Guest Ron Freimuth]

>Hi, Ron. >Thank you for reminding me of the ability to have a more >efficient change over, this will save some time. > Have you herd of a way to load any parameters

[Avcomware 1]

TV

[Guest]

Pitch Attitude, Landing View Et Al.Ron,Some thoughts on your last two messages:I don't have FS2000 installed at the moment, but if memory serves the 737-400 pitch attitude on final with flaps 30 was around +4 degrees at 140 KIAS and 130,000 lbs. With +4 degrees over the fence, and then a 3 degree flare (per the A/C handbook) that would put you up around +7 degrees and with the very poor pitch stability of that model (greatly improved in FS2002) pilot induced pitch oscillations in the landing flare could easily put you above 9 degrees (I seem to remember that 9 or 10 degrees would put the tail on the runway). Especially if you raised the nose even further to reduce the descent rate (poor technique on my behalf, but at the time, I didn't know any better). At any event, +7 degrees is too much, 4-5 degrees is more like it. As an aside, since you mentioned the 727's tendency to strike the tail if you overrotate or if your rotatation rate is too fast, I found the FS2002 737 to suffer from the same problem if the "aircraft handbook" Vr speed recommended by Microsoft is used in conjuction with the standard rotation rate of 3 degrees per second, the aircraft would not climb away but would drag the tail along before eventually breaking away from the runway and staggering upwards. Funny thing is, I didn't catch on to this until viewing a takeoff on instant replay using spot plane view. To compound this comedy of errors, I was using the Vr speed of 143 KIAS found in the 737-400 flight simulator pilots handbook -clearly too low- and I increased this after finding the real numbers on the internet, only to find the nearly correct speed for Vr at max weight was on the kneeboard reference section all the time! To say the absolute least, I am completely unable to understand why a REDUCTION in flaps lift would be desirable on this aircraft!Forgive my thickheadedness, but I am completely unable to understand your explanation of this variable (via e-mail 12/15/02) or any effect it may have on unaccelerated pitch attitude. I did find that the Abacus FDE utility calls this variable "vertical inertia" -which is perhaps more desciptive- but I cannot discover any noticeable difference in flight dynamics after changing the value of this entry EXCEPT in elevator effectiveness during the roundout or in the landing flare, or what seems more to me like the amount of lift generated close to the runway rather than anything to do with the elevators (ground effect???). Indeed, with my recent discovery that TBLDB 400 Ground Effect? will control the coefficient of lift at altitudes other than the traditional one wingspan above the earths surface, perhaps this entry "lift due to elevator " SHOULD be renamed to "Ground Effect" as I have found that changing this value to a higher negative number will have a profound impact on the aircrafts tendency to "balloon" and float before touchdown, while the reverse is equally true, a lower negative number will eliminate any tendency to balloon or float. Further on this, there is already an entry for "Pitch Moment Due To Elevator" which directly increases or decreases the effective elevator control authority at all points of the flight envelope, so lo, what have we here? Or perhaps this may be another example of "she can"t see the forest for the trees" and therefore related to my particular form of blindness. This one also has me puzzled, I am guilty of using the horizontal stabilizer angle of incidence to adjust the pitch trim to approximately the neutral position (0 degrees) in cruise flight, but I always have it set to a negative value as I understand that a downforce is necessary to counteract the nosedown pitching moment around the C.G produced by the wing CL at the center of pressure (combined pitching moments from the wing and horizontal stabilizer should equal 0, I hope!). If the preceding is correct, then how can this effect be negligible without the aircraft nosing down? Or is Flight Simulator modeled differently from real aircraft physics and if so, in what way? Also, how does this affect the landing pitch attitude? As I understand it, the factors that affect aircraft pitch attitude would be weight, lift produced at any given airspeed, angle of wing incidence, and the resulting angle of attack necessary to produce the lift required to support a given weight. All else being equal, a lower angle of wing incidence will result in a greater positive aircraft pitch attitude and vice versa. Greater aircraft weights or lower wing lift from various causes also result in greater positive aircraft pitch attitudes as the nose MUST be raised to increase the angle of attack and generate the additional lift required. Also, an aircraft in a glide needs less lift than in level flight, it needs only enough lift to maintain the pilot selected rate of descent, and a lower pitch attitude will occur as a result of the decreased angle of attack, and for light aircraft this means a pitch attitude slightly below the level flight position. Using flaps to lower the stall speed, steepen the glidepath, and increase the drag for a shorter landing, will INCREASE the amount of lift generated and lower the pitch attitude even more, to as much as several degrees negative or nose down depending on the type of flaps and their amount of deflection, and the angle of wing incidence. The Earth's gravitational force, as far as I know, remains constant from day to day. The atmospheric pressure does not vary significantly as far as wing lift is concerned, except at higher altitudes (say above 10,000'). Now, the preceding is a reasonably accurate and simple explanation, with the only exception being thrust which I have left out to avoid complicating matters even further (think GLIDER!!), of how real world aircraft go about the business of defying gravity, so what then is causing flight simulator aircraft to approach the runway in a nose level or nose high attitude if everything is accurately modeled after real world physics?I further assert, that this lack of lift at lower airspeeds is the cause of the "landing view problem" in flight simulator, you do not need a monitor with a different shape or two monitors,or just the right panel CFG view tweaks, you need a computer modeled aircraft that approaches the runway in the landing configuration in a realistic fashion. With the aircraft pitch attitude in conformance with its real world counterpart (after increasing the low speed lift), NO adjustment is necessary to see the runway on final approach, it is in fact quite authentic aside from the zoom factor which I will not go into here. (Possible exceptions to this, the heavy transport category aircraft which DO approach with positive pitch attitudes) This bit provided me with an idea, namely, why is there a LOW end to TBLDB 400? Surely one value would suffice for all aircraft by increasing the CL by a specific amount to simulate ground effect, the only variable between aircraft types being the wingspan which would determine the altitude at which the extra lift was applied. Then I remembered that in the real world induced drag is reduced in ground effect, and decided that I was oversimplifying things, it HAD to be more complicated than that if it were to be modeled correctly, and how else to account for all those X & Y values in TBLDB 400?. However, I dutifully began playing around with the numbers in TBLDB 400 by increasing them, and found that they had a profound effect at altitudes other than the traditional one wingspan or so, and that the KingAir pitch attitude for landing could be reduced to negative (-1 to-3 degrees) values depending on how high the y value was set. This result was accomplished after setting TBLDB 401 back to it's original pristine self, and a very short period of testing revealed no nasty side effects. I did notice that only the XY pair 1.0 had the desired effect of dropping the nose at the 109 knot approach speed I used, after increasing the Y value to 1.75. (by the way I found the Vref speed of 109 KIAS at 15000 lb weight on the KingAir kneeboard reference tab I have no idea if its applicable to the real aircraft) I also tried this out on the C-172 since that was one of the aircraft that remained unresponsive to my earlier TBLDB 401 tweaking. And this aircraft responded well after setting the Y value of XY pair 1.0 to a value of 1.3. The pitch attitude with 30 degrees flaps at 65 KIAS and a 500 FPM descent rate went from -0.8 to -2.6! I'm sure everyone will be glad to hear the end of my babbling on about the merits of butchering TBLDB 401, of course it occurs to me that my trespasses into TBLDB 400 may seem equally ridiculous to those exalted beings who know what they are doing, (I am beginning to feel like the ultimate computer flight dynamics heretic) and of course these results are preliminary pending a time when I can spend many uninterrupted hours mapping, understanding and refining the variables of TBLDB 400 and flight testing for undesirable symptoms, but I already know that the Skyhawk's stall speed is lower after the change to TBL 400 by about 6 knots - down to a ridiculous 28 KIAS and I believe it was already too low at the default 34 KIAS- (I think I've seen 47 knots somewhere and the CFG file says 43 @ Vso) and I'm hoping for an educated evaluation from someone like yourself. But I have to tell you, I really LIKE the way the aircraft behaves on approach now! So much so that I shot more than half a dozen landings, everything from no flaps to full flaps, short field & soft field, the landing view forward is excellent and it felt very natural and real and is one of the best times I've had with FS2002 since I installed it. (Until my recent C-172 rental checkout - found some differences in the landing characteristics- see below)Yaw Moment-Prop Effect On RudderI have been using this airfile entry to increase the nosewheel steering effect on several different aircraft, on the smaller Cessnas it provides a much more realistic steering effect at very low speeds and greatly decreases the turning radius without resorting to increasing the steering angle in the CFG file. Increasing the CFG file steering angle value can sometimes lead to unacceptable steering sensitivities on takeoff without having too much effect on the low speed turning radius. In fact, if you enter a value of greater than 60 degrees there, the turning radius can actually DECREASE at full nosewheel deflection - the aircraft seems to slide forward a bit instead of turning tighter. For the smaller aircraft a slight increase to this airfile entry is all thats necessary, for example change the original value 0.002048 to 0.006048. The larger models might need values in the hundreds or more (1450 for one notably reluctant to turn twin turboprop freeware A/C) to see a significant change here. With torque and p-factor sliders set to different positions I have noticed NO effect in flight from increasing this value, and have been using it as a band-aid for aircraft that don't turn well on the ground. Some aircraft turn very well indeed with this value at default, so I wonder what variables are at work here that are present in the right combination in some aircraft and absent in others?I finally broke down and visited my local FBO today, I was tired of relying on memory to evaluate the Microsoft Cessna's, and I am not current in any Cessna type (its been a long time), nor had I ever rented from this FBO before, so it cost me about $140 (signing that credit card receipt reminded me why I want to use FS2002 for IFR recurrent training, flying is so expensive! Even just paying for the fuel for your own airplane) for a one hour checkride with an instructor. I wasn't able to give my full attention to the many nagging questions I have about the performance differences between the real airplane and the virtual as I was somewhat busy trying to convince this man that this mere slip of a girl was competent enough to entrust with their vintage 1986 172P. I did manage to be convincing though, or at any rate to fool him, and can now rent from them Monday through Saturday 6:00am - 8:00pm, Sundays 1:00pm - 7:00pm (they either sleep late Sundays after partying Saturday night or are regular churchgoers - I sincerely hope it's the latter!) for the bargain price of only $95/HR wet. Wow! have things ever changed since we bought our own plane and stopped renting!! Not being able to take notes, or fill out an improvised "test card" and thus aquire some useful data for flight simulator purposes I only brought back some general impressions that confirmed my recollections of how this airplane flies. The real airplane seems heavier and a little more sluggish on the controls than I remembered or than the way it is modeled in flight simulator (and like all small airplanes most especially at low airspeeds). This was a well worn example however and I'm sure it flew differently today than when it left the factory, (they have almost new 172SP models for rent at $125/HR! nearly what I paid for the older airplane AND the instructor! so I passed on the SP) in their defense however, the airplane was clean and had fairly new King avionics and a low time Lycoming, even so the rate of climb is positively less (about 600 FPM) than the computer aircraft although I hear the SP climbs much better than its older siblings possibly accounting for the difference, I did notice that the landing pitch angle (read directly off the artificial horizon no AFSD here) was between 2 and 3 degrees nose down at 65 KIAS or so, it was windy today (winds were 10 at 234 with gusts to 16) and we were getting bounced around a little producing some instrument fluctuation but definitely NOSE DOWN with 30 degrees flaps. And also, completely UNLIKE FS2002'S Skyhawk and perhaps because of it, I had forgotten how it is something of a struggle to get the nose up for touchdown and avoid wrinkling the firewall from a "wheelbarrow landing" and my first landing was almost three point -except we weren't in a taildragger- so my CFI for hire recommended carrying 1500 rpm through the flare to help the elevators out which worked really well. One glaring discontinuity with Flight Simulator is the exaggerated "Dihedral Effect" that Microsoft builds into its flight models, in the real aicraft I found it necessary to hold off bank with a little opposite aileron in steep turns as the airplane tended to increase the bank angle rather than reduce it, and there was little if any tendency to return to wings level from shallower bank angles either. Of course I well remembered this difference, but I didn't remember the tendency for the bank angle to increase at 45 degrees or more.(Wonder if this might pertain to this airplane alone for some reason?) Anyway, I intend to return and go solo to take notes without any raised eyebrows from CFI types as soon as I work up a test card format and justify the expense somehow to my significant other.Also Ron, thank you for the files, I haven't gotten around to trying and evaluating them yet but I look forward to doing so soon.