Flight Dynamics - Faith

[LAdamson 240]

>I agree that flight dynamics are extremely important, and I>hope that FSX has improved flight modelling over FS9.>Yes, restore airflow over the horizontal tail surfaces while wheels are still touching the ground.L.Adamson

[slashed2 53]

Well said. I think one can go from real flight to the sim and recognize vfr objects, but going from the sim to real flight is another story, though that in my opinion is hopefully where FS will improve over the next few years. What really got me during flight training is the motion, the forces pulling on the plane that you just can't replicate in FS, the noise of a slip or skid was shocking in the 152 I was in not to mention the age of the darn thing.Anyway, I agree, for all those sim pilots who think they can land a real plane remember, you screw up in the sim you reload, you screw up in real life, well it won't be pretty, and to me that was the biggest difference. No way could I land a real 152 or 172 without practice in the real world no matter the length of time simming. No matter how good the FM or FD or whatever, the physical sensation is just not there no matter how well you fly by the numbers.Ian.

[LAdamson 240]

>>As a 15 simmer, I assumed I could land on my first C172 lesson>- no way! If the dynamics were accurate, then surely I COULD>have landed a real C172? So, the dynamics need improvement.This is a touchy subject. :DWithin the sim, it's usually a compromise when it comes to peripheral vision, thanks to most having one screen monitors, and feel of hardware such as control sticks and yokes. Yet, once you've made landings in numerous real aircraft, then the feel and look transfers to the sim, with your mind filling in the gaps. At that point, many landings within the sim seem amazingly real!Even the default 172 can do a rather realistic job of the landing phase and is farther enhanced with good use of the V/C cockpit. Some 3rd party aircraft are "sensational" when it comes to landings.Will I ever feel comfortable landing a real 737, Lear, or a WWII Spitfire, just because I can at a desktop.................no. I'd have to have a multi-million dollar sim just to get the actual feel of it all.L.Adamson

[Mace 1,938]

>>Since you mention real pilots-for me the non fluid avionics>are more of a problem right now than the flight dynamics which>for some aircraft that exist now are excellent-and this is>directly related to how a fm feels/acts.If I can't get a>precise airspeed,climb rate,or power setting because of jerky>instruments-reality is lost. (this is one area that is on the>top of my list of improvements). Geof,Incidentally, (I may have missed it), has there been any mention that stock gauges in FSX will be a little more fluid?Rhett

[Reset XPDR 1,300]

>Anyway, I agree, for all those sim pilots who think they can>land a real plane remember, you screw up in the sim you>reload, you screw up in real life, well it won't be pretty,>and to me that was the biggest difference. No way could I>land a real 152 or 172 without practice in the real world no>matter the length of time simming. No matter how good the FM>or FD or whatever, the physical sensation is just not there no>matter how well you fly by the numbers.>>Ian.Although I have thousands of hours FS time in just about everything flyable on the planet, past and present, I've only handled a real aircraft a couple of times (C130, cessna 172) for a few minutes in cruise (supervised of course) and a couple of sessions on a level 5 sim (C130).To be honest, I was amazed to find how much smoother and easier it was to control the real aircraft. Trim response certainly has a way to go in FS!As for the sim, I was set up on the rwy with full motion 'n all and managed to takeoff, do a couple of circuits with a touch and go and a full stop land to finish up. It all came off quite smoothly in fact, much to the amazement of myself and the sim operators (including a RW pilot).Certainly the feel was much different than FS (real rudder pedals on large aircraft are a lot stiffer than my CH pedals LOL) but all the instruments did their thing as expected and the scenery was pretty comparable (FS2000-like vintage actually). The hardest bit was finding the switches and knobs to do what I wanted to do, but thankfully the sim operators helped me out there. If I was doing it by myself, I just would have set up a bigger circuit to give myself enough famil time for the controls and panels.I guess what I am trying to say is that real flight shouldn't be that daunting if you have a stack of FS experience and you appreciate the limitations of that experience, especially the lack of pucker factor. Gary

[GHarrall 494]

May I refer you all to this thread from 'FSAviator' in Jan 2003 when some experiments were done to compare FS8 to FS9 regarding flight dynamics.I'm not sure if this problem was addressed in the FS9.1 patch, or even if it has been looked at for FSX. Maybe someone knows....."Normally I would agree with that attitude ablut moving forward, but the conclusion to this very important thread- which I can't believe hasn't gotten more press over at the general forum- seems to be that this is a major step backward. Essentially MS has made our sim much more of a game, and prevented payware and freeware developers from even attempting to improve it as they were able to do in FS2002.Here's the relevant post from that thread, word for word (long, but well worth the read):Thanks to all of you for re-testing and to all others who have contributed.I believe we have all reached the same conclusion now with everyone eventually confirming my finding that both incidence and twist, together with their pitch and drag consequentials, default to zero at all times in FS2004. After giving this some thought I now conclude that this is not a mistake. It looks more like a a design time decision. I find it unlikely that the different variables relating to incidence and twist could go missing from the different equations in the flight model unless someone was instructed to go through the code and remove them everywhere they occur. Someone has. If this was an error some of the variables would still be working.Since the terms often get confused let me explain that FS2002 had an excellent flight model but dreadful default flight dynamics. The flight model is in the binary code of the product and is used by every aircraft. The flight dynamics belong to a particular aircraft and are coded in each aircraft.cfg and air file. The people who wrote the original flight model for Microsoft understood aerodynamics. The people who wrote their flight dynamics did not.Since there was nothing significantly wrong with the flight model and it had the capability to support realistic flight dynamics some of us who understand real world flight dynamics set about writing flight dynamics files for MSFS which exploited the capabilities of the flight model better than the proprietary default flight dynamics. By the middle of this year tens of thousands of Microsoft customers were downloading our work for free and enjoying the additional realism which we were able to unlock. Increasingly consumers were also buying payware aircraft because they were obviously superior to the aircraft delivered by Microsoft.What those who have contributed to this thread have just proved is that Microsoft have degraded the internal flight model equations just enough to ensure that realistic flight dynamics will no longer work in FS2004. We have been very careful to test with their SDK compliant default aircraft and at full realism. By carefully altering their proprietary code Microsoft have ensured that their commercial competitors, however small and insignificant, can no longer deliver products which are superior to their own. Some of you will have noticed for instance that Rob Young has posted elsewhere that Microsoft have removed the ability of the SF260 to spin in FS2004, whilst enabling spin within the Extra and Jenny FDE.This is entirely consistent with US law and entirely in accordance with the long term competition strategy of Microsoft as a corporation. Microsoft are perfectly entitled to react to competition by altering their proprietary code in ways which disadvantage others and make Microsoft look good.Opportunity, motive and modus operandi? You decide.The destruction of the pitch attitude and drag equations within the internal flight model stands in stark contrast to the impression which Microsoft conveyed prior to the release of FS2004. We have just proved that FS2004 is not compatible with any existing aircraft flight dynamics, even when they were fully compliant with all Microsoft SDKs. Destruction of the realistic pitch equation has ensured that FS2004 displays such aircraft at fake nose up pitch angles which preclude an appropriate view over the panel or VC. By removing the ability to process the drag correction from air file Section 1101-50h Microsoft have ensured that such aircraft suffer degraded performance in FS2004 because they always have excess drag. They become visually and dynamically incompatible with FS2004.FS2004 does not have an FDE converter. It just ignores key aerodynamic data from earlier SDK compliant FDE, degrading them so that they are no better than the new default FDE. Third party aircraft produced by experienced FDE authors, whether freeware or payware, always had significantly more realistic flight dynamics than MS default aircraft and are therefore degraded more. The Microsoft default FDE were so unrealistic that removal of the chosen aerodynamic variables from the flight model has hardly changed their attributes. I believe this points to careful selection and beta testing of the variables removed from the flight model equations.The implications for payware publishers whose expertise lay in producing realistic aircraft which exploited the internal flight model to the full are obviously grave, but they are not the only ones who suffer. The vast majority of MSFS consumers could never tell that the default aircraft had faulty flight dynamics and are therefore no worse off. The minority who could tell, including aviation practitioners and those who have invested hundreds of hours using the product to learn how to operate aircraft realistically from scratch, have been slapped in the face. The equations in question did not have to be destroyed for the eye candy aspects of FS2004 to work. Microsoft could have ensured that your favourite FS2002 freeware aircraft and your collections of FS2002 payware aircraft continued to work in FS2004, just by doing nothing at all to the flight model. Instead they made changes which ensure that all your FS2002 aircraft are degraded. We have proved that Microsoft have removed key aerodynamic variables from the flight model equations. Accident or design? You decide.Now I need to address a 'what if' that have come up in this thread suggesting that there is an FDE work around which can overcome removal of the variables.Ron, Bob and Douglas are talking about how substituting variation of AoA for AoI still 'works' and will have to be employed instead. Whilst this could restore realistic pitch it cannot restore realistic drag and will make the drag result even worse.Since Microsoft have ensured that FS2004 cannot process the drag data correction from Section 1101-50h the result of using an AoA rotation to substitute for an AoI rotation is a cartoon rotation which produces the wrong induced drag and a very distorted performance envelope. The drag consequences of +4dAoA and +4dAoI are very different. Picture a wing meeting the air and the bottom of the fuselage meeting the air in an aircraft where incidence = 4 and AoA = 4. The fuselage is level (aircraft has zero pitch) but the wing is four degrees nose up and is inducing substantial drag at 4dAOA. In FS2002 we could code the pitch and the drag for that aircraft differently and correctly. Now if we use an AoA rotation to remove the incorrect value of zero AoI which Microsoft have imposed for all aircraft in FS2004 we must make the wing have zero AoA to show the fuselage level again (zero aircraft pitch). Having reduced the AoA by 4 degrees to force the fuselage to zero pitch there is now also zero angle of attack and zero induced drag, producing a huge drag error.The proposal that AoA rotation substitute for AoI rotation ignores the fact that we have just proved that Microsoft have destroyed the drag equation as well as the pitch equation. The induced drag error cannot be corrected even though the pitch error can be corrected by the means proposed. This thread was never about data loading and reloading bugs in FS2004 real as they seem to be for some people. This is about the extent to which FS2004 is still a flight simulator at all.An FDE author can force FS2004 to display aircraft at the correct pitch but not with realistic drag. In FS2004 there is still a link between AoA and drag, but Microsoft have destroyed the link between pitch and drag. To make an MDL 'fly' at the right visual pitch it now has to be 'animated' like a cartoon. The MDLs are no longer 'flying' because in FS2004 as we have just proved they are not following the laws of flight. The consequence is that those who choose to produce FS2004 aircraft and updates will have to invoke a solution which is part video game and part flight simulator. Part cartoon animation and part dynamics code. The implications of this internal code change extend far beyond the world of FDE authors. Would be FS2004 MDL authors and painters of quality products have not understood yet. flight dynamics authors will have to explain it to them.When an aircraft is produced for use in any flight simulator, not just this one, the net flight incidence component of the flight dynamics equations is used by the FDE author to rotate the MDL to allow for wing incidence after it has been produced by the MDL maker. This FDE code also controls what can be seen over the panel or VC at run time. The FDE author then corrects any consequential drag error separately. That the FDE author can no longer do any of this in FS2004 is what this thread proved. For use in a video game which lacks wing incidence as a flight dynamic variable the MDLs have to be produced with their incidence rotation built in by the MDL maker at design time. We have just proved that the incidence variable is absent in FS2004.Let that sink in now and get ready to explain it to your project collaborators. That is what I mean by a *serious* bug in FS2004. The other new bugs are inconsequential by comparison.If producers have the goal of releasing FS2004 aircraft with even somewhat realistic performance envelopes which also fly at the correct displayed pitch attitude the only solution is as follows. 1) MDLs have to be rotated nose down by the net incidence of the real aircraft at design time to display correctly. 2) The MDL animations have to be prepared to match that nose down rotation.3) The textures also have to be rotated nose down in the paint package. 4) The FDE then have to be prepared with an 'overstiff' nose oleo which 'corrects' the nose down sit of the rotated MDL on the runway. Mainwheel oleos of tailwheel aircraft may be stiff enough already. I have tested and this works well.5) The MDL oleo animation may have to be written accordingly and not accurately. 6) The rest of the FDE then have to be written to match an 'equivalent aircraft' of zero incidence and zero twist but retaining the real world lift slope and consequential induced drag. Drag errors can then be 'somewhat corrected' using other data fields in Section 1101 which FS2004 can still process.If AoA rotations are used in lieu of the MDL rotation, as some have proposed, there is no way to correct the induced drag, (consider the zero case to understand why), and FS2004 is just a video game with animated cartoon aircraft. That seems to be the way this product is developing and I acknowledge that the majority of consumers who only use the product as virtual airport spectators and virtual passengers will be quite happy with that. The compromise above will therefore satisfy most FS2004 users, including most payware customers, but it is still a compromise with less accurate flight dynamics than FS2002. The comprise is largest for the fastest aircraft. Consequently I doubt that FDE authors whose expertise lies in creating realistic flight models will choose to spend hundreds of hours over the next couple of years producing or updating 'compromised' FDE for FS2004. They may decide to write payware FDE for FS2004 if the price is right, but their more demanding customers will always expect more realism than we now know is possible in FS2004. Those who have promised to produce FS2004 updates have a larger problem. Rotating pre existing MDLs is simple enough, but rotating all the animations and all the textures of a pre existing MDL may not be at all simple. It depends on the package used to create the aircraft originally. The FDE have to be rewritten anyway. All the other new FS2004 bugs also have to be taken on board and if possible fixed. The most important of these are the CoG bugs. Since I think I have now decoded them I will try to explain them later in a different thread. If anyone wants to design a Whitley for use in FS2004 the only choice will be an MDL rotated at design time, but I expect that most FS2004 third party aircraft will be displayed at fake pitch angles within the video game and most users will not notice. However since the fake pitch angles are always nose high you cannot obtain the correct view over the panel and you will wind up having to cheat in various ways to see where you are going, by scrolling the panel, or using a video game zoom factor, or some other video game cheat, to control the game. This has never been a requirement when flying with realistic flight dynamics.Due to removal of the incidence and twist variables the VIEW_FORWARD_DIR and SIZE_Y variables within panel.cfg, cannot always be used solve the view on approach problem in FS2004 in cockpit view due to ground / air mismatches previously solved by FDE code. There are no equivalents for the VC anyway. Setting the correct view over the VC 'panel' has to be resolved by MDL rotation in FS2004. All of which leads to my position on updating my own 'realistic' FS2002 freeware flight dynamics.My finding that FS2004 is unable to process three key aerodynamic variables essential to realistic flight simulation has now been confirmed by a range of experts. It is therefore not a question of how long it would take to produce FDE updates. FDE which are realistic in FS2002 cannot be updated to be realistic in FS2004. It cannot process the variables and equations which would allow real world inputs from flight manuals to cause the real world outputs. I cannot update my FDE for realistic first person flight simulation use in FS2004. The necessary code has been removed by Microsoft. Of course if the key variables were removed by mistake all Microsoft have to do is restore the old equations. They know where to find them. FSAviator"

[tgibson 11]

Hi,For people that don't know, there was a solution found that avoided having to create "nose down" MDL files - shift the values in section 404 of the AIR file. However, the corresponding drag adjustment is still made by altering other (active) drag variables, resulting in only an approximation of the real flight model as compared to FS2002.Hope this helps,--Tom GibsonCal Classic Propliner Page: http://www.calclassic.comFreeflight Design Shop: http://www.freeflightdesign.comDrop by! ___x_x_(")_x_x___

[GHarrall 494]

Tom,Thanks for that. I had always had this old thread in the back of my mind and was hoping that the FS2002 variables would return in FSX.Maybe tdragger or someone from MS can comment?Glenn

[=Hollywood= 0]

The fact that the team has kept so quiet about this area of FS makes me wonder what they're about to spring on us... :-rotor I am sure we're in for some pleasant surprises... :)

[Guest tdragger]

Actually it's probably because the people who post more regularly (myself and Jason) don't know a heck of a lot about the flight models. I know we have them and we pay a guy to work on them but that's about it. It's all 1's and 2's to me...

[Guest Jimbofly]

You couldn't ask the guy you referred to for any info regarding any flight model enhancements over FS2004, could you?:)James

[Cloud9 0]

>Actually it's probably because the people who post more>regularly (myself and Jason) don't know a heck of a lot about>the flight models. I know we have them and we pay a guy to>work on them but that's about it. It's all 1's and 2's to>me...ah-ha! So there are changes to the flight model in FSX: It went from 1's and 0's to 1's and 2's. It will be interesting to see what improvements these 1's and 2's will bring. :-hah David

[Guest tdragger]

This forum posting thing is all done in our spare time. If he feels compelled to post I'm sure he will.