Flight Dynamics - Realisim ?

[MarkRey 16]

>Word "compromise" suggests that someone spent weeks fine>tuning their aircraft dynamics. That simply doesn't apply to>Microsoft's shoddy work "in the box". Others designers work is>the biggest testimony of that.>>Michael J.>Michael,Assuming the default a/c are easier to handle than their addon counterparts, is it possible that MS does indeed deliberately make their defaults this shoddy way to make the product more 'user friendly' to the mass market?After all, is'nt bottom line for them not realism which satisfies the relatively few(thousand) of us who care but a product that is as profitable as possible?I'm not siding with or against them - its just a thought that popped when I read your posts:)regards,Mark

[Guest Digital_Flight]

I'm not really sure that this is a pure inertia problem because in many ways, MSFS has that well in hand. Where I seem to notice this the most is during landings in small aircraft like the RealAir SF 260 or the new Decathlon. As you make small changes in pitch and roll on short final the resulting movement just isn't fluid. It's as if the movement rate goes from zero to full speed and then back to zero again with no visible ramping up or down at the ends. Aircraft just don't move like this no matter how light they are and in anycase you can see it in a heavy jet too. I frame lock at 30 and everything is smooth so it's not an FPS problem. This is something that's bothered me for a long time so I'm glad to see that other folks are picking up on it.TonyDigital-Flight

[Guest Dennis_F4i]

I wonder how much of this is a function of the control sensitivity rather than the aircraft model. It may also be a function of limited feedback to the "pilot"; when in a real airplane there are many sensory inputs contributing to the sensation of roll than simply what is viewed on a 17" screen. I find that it is easy to over-control roll in the sim. The minor corrections that happen almost subconsciously in the real world are harder to detect in the sim and result in larger than intended corrections.The other thing absent in the sim the the modeling of turbulent wind gusts on approach. The sim tends to over-exagerate airspeed swings and understates the effect on roll that a gusty crosswind can have on light aircraft. It is not uncommon in the RW to have near full control deflections in adverse approach conditions. The real pilot can go from neutral aileron to near full left or right and back to neutral in a repeately in fractions of a second, something that I have not seen duplicated in MSFS.The bigger gripe that I have is the modeling of pitch trim. In the real world, you use trim to hold the control in position, not to allow the control to return to neutral (unless you're in a 'bus, but then you don't have to trim either!).

[KERNEL32 496]

Wow- this is one of the best threads I have read in a long time! Thanks for the story above Dennis sounds like it was a hair-raiser! Y'all have it together upstairs here and it shows, makes for good reading and intellectual response. I am too very interested in seeing how others observe this FS

[Guest Digital_Flight]

I don't think it's the control hardware simply because I don't see this happening in X Plane while using the exact same input hardware.I also don't think it's a perception problem because it doesn't look right in outside views as well. Not everyone has flown a small plane but most of us have watched them land. The movement I'm seeing looks very wrong no matter how I view it. I think that wahtever the cause is, it's happing in the flight modeling.On trim, in a real aircarft trim tunes out control forces. In other words, if you're holding 2 lbs. of back pressure on the yoke to maintain a certain rate of climb you can adjust the pitch trim to bring that force to zero at that stick postion. Unlike a joystick, the zero force postion of a stick or yoke in a real aircraft is always changing depending on trim setting and airspeed. Functionally though, trim is used the same way in both the sim and in real life. In this case to maintain a pitch attitude for rate of climb without having to constantly hold back pressure on the control. TonyDigital-Flight

[rickalty 0]

David:>>I would expect a plane to come out of a turn virtually immediately if you neutralize the control the surfaces. The planes inertia will cause it to go in a straight line unless forces are applied that cause it to do otherwise.Sorry, David, not at all.In a real world aircraft, if you neutralize the controls in a gentle turn, the plane will gradually straighten up. If you neutralize the controls in a standard turn, the plane will remain in the same turn and go round and round in circles - you will have to apply opposite control to straighten up. And in a severe turn, the turn angle will actually continue to steepen if you neutralize the controls.While intertia does keep an object moving in a stright line, the inertia of an aircraft is a tiny fraction of the lift and drag forces. >>To demonstrate that FS9 aircraft do have inertia maintain level flight and deflect the rudder fairly hard. The planes nose will point quickly in the direction of deflection but the plane will sideslip in the direction it was going due to inertia.That's nothing to do with inertia, it's an airflow issue. That is why aircraft are turned not with the rudder, but with the ailerons. The sole function of the rudder in a turn is to counter the adverse yaw caused by the imbalanced drag the ailerons produce.Incidentally, if you like flying a Cessna 172, download the RealAir one from the library here - it's a VERY good flight model. (And doesn't have the horrible taxiing characteristics of the default plane.) Be warned though... the FS Cessna 172 is a lot more forgiving than the RealAir one - slow speed boo-boos in that will put you into the ground. (Which brings up one of my favourite MSFS bugs - If you crash a plane within the airport boundary, the ATC controller will say "Contact ground when able" :-) Umm, I already "contacted the ground!" Richard

[Guest allcott]

>I wonder how much of this is a function of the control>sensitivity rather than the aircraft model. It may also be a>function of limited feedback to the "pilot"; when in a real>airplane there are many sensory inputs contributing to the>sensation of roll than simply what is viewed on a 17" screen. >I find that it is easy to over-control roll in the sim. The>minor corrections that happen almost subconsciously in the>real world are harder to detect in the sim and result in>larger than intended corrections.>>The other thing absent in the sim the the modeling of>turbulent wind gusts on approach. The sim tends to>over-exagerate airspeed swings and understates the effect on>roll that a gusty crosswind can have on light aircraft. It is>not uncommon in the RW to have near full control deflections>in adverse approach conditions. The real pilot can go from>neutral aileron to near full left or right and back to neutral>in a repeately in fractions of a second, something that I have>not seen duplicated in MSFS.I took on board the advice that was given by a respected expert on sim matters a long time ago - it might even have been for FS2002, but the advice is just as valid for FS9. Always calibrate the controller in VC, and watch the virtual equivalent. The problem is that the short `throw` of most joytsicks makes things seem over-sensitive, leading to massive over-compensations. The solution was the opposite of what you might expect - make the sensitivity HIGHER, then use tiny controller movements. Just as in a real aircraft there is almost never a need to use full control deflections in normal flight so it is with the sim. If you increase the sensitivity you get more movement of the virtual surfaces early on in the movement of the controller. Manage the controller and you manage the aircraft. In those situations where full deflection is needed, then you notice the extra stick or yoke movement immediately and register it as `much greater` than `normal` which is a similar feeling to real flight.I hope that's clear - I just re-read it and I'm not sure I'm making myself understood!Allcott

[barryward12345 0]

>>The bigger gripe that I have is the modeling of pitch trim. >In the real world, you use trim to hold the control in>position, not to allow the control to return to neutral>(unless you're in a 'bus, but then you don't have to trim>either!).This is very well stated!! I only use a MS Joystick and it returns to the neutral position when you let go of it -- so this is not how a real a/c controls work. I don't really worry about threads like this -- I believe that the Sim is only meant to be used for either a visual simulation of flight ( as in a game) -- or as an intellectual simulation. In this latter case, you are using much the same intellectual energy that you do when actually flying - so it is valuable in that sense as a training tool -- but anybody who seeks so called "realism" is delucing themselves!Barry

[rickalty 0]

Bazza:>>This is very well stated!! I only use a MS Joystick and it returns to the neutral position when you let go of it -- so this is not how a real a/c controls work. The feel is pretty good with a decent yoke though. In the sim, as you dial in up pitch, you gradually release the amount of force on the yoke. The fact that the yoke is returning to the neutral position really doesn't feel that different - to me anyway - from releasing up pressure on the yoke in the RW, even though there the yoke doesn't go back toward the panel as you do so. Unless you're a really heavy handed driver, the physical deflections in most of the situations that you'd be dialing out with trim aren't that large anyway.Richard

[Guest Dennis_F4i]

I don't think it's hardware per-se either, but I my guess (and it's only a guess) is that the control acceleration algorithm is as much of a factor as is the inertia model.You're correct in the function of trim, however take the extreme example of slow-flight: at 55 KIAS in a 172 the yoke is nearly in your lap and will stay there (assuming level flight). This is because that is the amount of control deflection required to offset the nose-down CG moment at that specific airspeed. In FS, the yoke would be centered. This isn't a huge "playability" issue, but it does bug me.

[Guest DanielBu]

I'm not a real world pilot but I'd say that the wind would create quite a stopping force when the aircraft is turning - I have a wooden RC model without ailerons, and once as I rolled using the rudder/elevator the wings ripped off because of the pressure that was on them - kamikaze! :D ...just image that with a faster moving aircraft, the increased air flow will also keep the wings from rolling. I dunno, I've got other gripes about FS' flight dynamics...-Daniel

[nudata 10]

I view the trim function in a manner similar to the bandspread of a shortwave radio or fine tuning on an older TV. The objective is to keep the primary operating values as much in the center of the main dial (trim) as possible. If you find that you cannot get enough deflection of the control surfaces with an extreme position of the yoke then start trimming to add "permanent" control surface deflection and thus permit variable deflections more in the center operating realm of the yoke. In other words you are using the trim as the main tuning input and then you do fine tuning (flying) more from the central position of the yoke. Where you can get into trouble quickly is in the preset of trim for takeoff. Too little and the yoke does not have sufficient travel to get you off the ground. Too much preset trim and you can take off like a rocket, loose speed and spin out 500ft above the ground. I really do not know how takeoff trim is actually set on some aircraft where a trim gauge is not available. You can't step outside the aircraft and see any difference in elevator position, at least I can't. So you give it a shot and remember the next time to preset trim by an estimate in the proper direction to effect a more controlled takeoff.Dick 5G8Dick Boley KLBE

[Guest Digital_Flight]

It's not the CG but simply the high angle of attack needed to generate enough lift to keep flying at that low speed but that's another thread. I agree with what you're saying about yoke position in the real aircraft but you're not going to be able to replicate that with the hardware must of us have.TonyDigital-Flight

[Guest Dennis_F4i]

You're right about the hardware; spring-loaded controls don't have any ability to simulate dynamic loads.However, I'm not sure that I agree with your CG statement. You're correct that the a/c is flying at a higher AOA at slow speeds, but I believe that the elevator is working to offset the nose-down momement created by the forward CG. As I'm sure you're aware, even at the aft CG limit, all standard aircraft have a CG that is forward of the center of lift which results in a very deliberate nose-down moment which the elevator must overcome. During slow-flight, the elevator must have a greater deflection to create the same amount of "negative" lift achieved at cruise. So the elevator isn't working any harder because of the higher AOA (nor is it really producing any more downforce than normal), but rather it is slower speed that requires the greater deflection. My CG statement was only meant to explain the need for the offsetting tail force.

[Rudi 0]

Dick, consider how much mass a 172's wings have, and I suspect that you will come up with the answer "not much"! The wings are made of aluminum, and most of the volume in the 172's wing is just empty space. Even considering fuel, which at 6 lbs / gal is pretty heavy, doesn't influence the rolling moment too much because the tanks are located relatively close to the aircraft's C.G. I am a pilot and I flew yesterday and I assure you there is no perception of inertia when rolling into or out of a turn.Dick, I've seen posts from you about flight dynamics for so many years now. Go get some flying lessons! You'll love it!