Nose wheel sinks into ground

[hjwalter 25]

Hello all FS9 aircraft experts,I'm flying a Douglas DC-7 and it behaves very well except for one issue. When I apply power while e.g. on the runway with the brakes set, the nose wheel sinks into the ground after the suspension has been fully compressed. Most probably something in the first line of the contact points but what ?Can anyone help ..... please.GreetingsHans

[Guest napamule]

Sure. Make change, as per 'sample' below, and then do 'SAVE' of cfg. Go look at behaviour. Re-adjust as needed. Do 'SAVE' (NOT 'Save AS'). Done.(contact_points)// 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15point.0=1, -56.00, 0.00, -2.30, 1200.0, 0, 0.60, 40.0, 0.200, 2.5, 0.695, 0.0, 0.0, 0.0, 0.0, 0.0------------------------------------------------------------------------------------------------------------------------NOTE:VALUES ARE FOR DC3 (as I don't have the DC-7) and are 'for example'.----------------------------------------------------------------------------------------------------------------------(1).The '8' value effects nose wheel 'stiffness'. The lower it is, the siffer it will be.So if '8' is '0.500', make it '0.350', or '0.400' or '0.200' (as needed-varies with model) to not have nose wheel bury on braking. ('SAVE'.)(You MAY have to adjust '3' to more negative if nose wheel is off ground after change. This is done with 'trial and error' (no other way) due to 'interaction').You should see results. Of course the model is what determines how much it will 'take' and you MAY have to change value of 8 (ie: 2.5 to 4.5) for the wheel not to bounce on landing due to being 'too stiff' a compression. Trial and error yourself silly to 'get it right'. Only way.Chuck BNapamule

[John Hinson 22]

Hello all FS9 aircraft experts,I'm flying a Douglas DC-7 and it behaves very well except for one issue. When I apply power while e.g. on the runway with the brakes set, the nose wheel sinks into the ground after the suspension has been fully compressed. Most probably something in the first line of the contact points but what ?Can anyone help ..... please.GreetingsHans

Not an expert . . . but the changes I made to mine are:point.1=1.000, -2.400, -12.400, -10.000, 1500.000, 1.000, 2.000, 0.000, 1.000, 1.300, 0.898, 4.000, 10.000, 2.000, 174, 174point.2=1.000, -2.400, 12.400, -10.000, 1500.000, 2.000, 2.000, 0.000, 1.000, 1.300, 0.898, 4.000, 11.000, 3.000, 174, 174topoint.1=1.000, -4.400, -12.400, -10.000, 1500.000, 1.000, 2.000, 0.000, 1.000, 1.300, 0.898, 4.000, 10.000, 2.000, 174, 185point.2=1.000, -4.400, 12.400, -10.000, 1500.000, 2.000, 2.000, 0.000, 1.000, 1.300, 0.898, 4.000, 11.000, 3.000, 174, 185That just puts the theoretical position of the main gear a couple of feet back and makes the aircraft sit more solidly on the ground rather than rocking back and forth excessively when you brake during taxi. I didn't touch the nosewheel settings.I have just run some tests and the nosewheel definitely does not sink into the ground with handbrake on and full throttle.Hope that sorts it.John

[Guest belga1]

Hello,You can have some good explainations in this tutorial available in the Avsim library They will be a complement of the good one already given by napamule.

Category: Flight Simulator 2004 - Miscellaneous Files Flight Dynamics Tutorial File Description:This pdf file is for people who want to learn, or learn more, about updating the flight dynamics of FS2004 aircraft. It won't tell you everything, but it will tell you some things the majority of flight simmers don't know about updating flight dynamics. Filename: how_to_tweak_the_flight_dynamics_of_fs2004_aircraft_172187.zip License: Freeware Added: 2nd September 2005 Downloads: 2244 Author: Bob Chicilo Size: 46kb

For the contacts points meaning and tweaks ... check from the page N

[Guest napamule]

Man. I must be going senile. We are talking about NOSE WHEEL and I go using a tail dragger as an example. Cheesh. Must get more sleep. Or take more Vitamin E? Unbelieveable snaffu. Sorry about that. The 'principle' is the same? NOT.So John would have it hands down no matter what I said. Ha. I suppose the balance gets worked on with wheels going back a bit. Practical (mechanical) solution, I suppose. I should of gone and got the DC7 and looked. What a dummy. 1st mistake I made all year. Hehe.Chuck BNapamule

[hjwalter 25]

Hi guys,Thanks to your reactions I now seem to have found at least the begining of a solution by copying the most complicated looking first [Contact_points] "point.0=" line (the nose wheel) from another aircraft and replacing the existing DC-7 one with it. After that I re-worked it's three static tyre co-ordinates and the maximum steering angle somewhat, and that seemed to do the trick, ..... well, sort of.However, as correctly pointed out by Napamule, the 9th value (Static Compression) can then be tweaked in order to stop or at least lessen this "dynamic-wheel-sinking-into-the-ground" thing. So I re-installed the original "point.0=" line and by "trial and error" eventually managed to correct my problem.Thanks again for pointing my nose in the right direction.Hans

[Guest napamule]

Hans,Glad to hear you worked it out. Contact Points 'work' is a science, and an art, all to itself (as Opa might agree). I have worked on hundreds of all types of models (since FS98) and I can attest that no two models are alike, as far as contact points are concerned. Even the same model from different authors will be different. So therein lies the rub-depends on the model (and/or modeler).I am sure you got a taste of how time consuming and perplexing the up-side down concept of the wheel's vertical cnt pt positioning is. And the forward & backward position of main wheels and how it effects looks (like the tire smoke shows before the wheels touch-ha). The 'old stuff from FS2k2' (DC7?) are the worst. FS9 got better and better over the years (due to modeler 'skills' improving? Probably). All day 'cnt pt session' used to be common occurance for me. Now it's less (maybe I learned what not to fool with so as to not 'mess it ALL up'?). I do vehicle cnt pts too, and THAT is what gave me gray hair. Ha. Cheers.Chuck BNapamule

[John Hinson 22]

I am sure you got a taste of how time consuming and perplexing the up-side down concept of the wheel's vertical cnt pt positioning is. And the forward & backward position of main wheels and how it effects looks (like the tire smoke shows before the wheels touch-ha). The 'old stuff from FS2k2' (DC7?) are the worst. FS9 got better and better over the years (due to modeler 'skills' improving? Probably). All day 'cnt pt session' used to be common occurance for me. Now it's less (maybe I learned what not to fool with so as to not 'mess it ALL up'?). I do vehicle cnt pts too, and THAT is what gave me gray hair. Ha. Cheers.

Hi Hans and Chuck,There is a curious difference between "perfect" Flight Dynamics in FS2002 and FS2004. I once had a formula for converting one to the other (I'm sure I have lost it now), and it entailed a lot of work and mathematics. But my personal observation is that the FS2004 dynamics do tend to leave the centre of gravity very close to the main undercarriage, giving that forward/back rocking motion when on the ground that I have seen others mention in discussion about aircraft I don't have, too. This sometimes has other side effects, like difficulty steering and, the source of this discussion, very bouncy. sinking nose-wheels.I have found the moving of the wheels back a couple of feet solves the problem nine times out of ten, but there is no disputing this is a bodge - as Chuck says, if you like to admire yourself landing (I prefer to look where I'm going :o) ) the little puffs of smoke will be in the wrong place.Best wishes,John

[Guest belga1]

Hello,Interesting article(s) about suspensions parameters in aircraft design (by Milton Shupe)http://www.sim-outhouse.com/sohforums/showthread.php?t=944Regards.Gus.

[Guest napamule]

That advice is FOR THE MODELER who is doing the design of the wheel suspension. My bet is that it don't get implimented by 95% of the modelers because they don't have any MECHANICAL APTITUDE to wrap their head around the concept. You and I may be able to 'visualize' the concept. But some people just can't do it. Don't ask me why/how, but I've seen it in my travels 'around the block'. They couldn't learn to tie their shoes if their job depended on it! But they could draw a pretty picture, with 'cherry red' or 'metal flake paint' and all the trimmings. But they couldn't drive a wheelborrow- that 'machinery' is just too complicated for them. Ha.Chuck BNapamule