Taxi Dynamics

[rwdriver]

My apologies if this is an old post - I can't believe I'm the only one dealing with this...but I have some aircraft (Mostly POSKY 747 and 767) that no matter how slow I taxi.... still slide around like they are on ice making it almost impossible to make a 90 degree turn within a taxiway.

Any clues on how to modify these ill tempered taxi monsters?
Thank you so much in advance.

[xxmikexx]

Hi and welcome. I'm not really familiar with this stuff but I'll ask some questions anyway, if only to kill some time till somebody knowledgeable comes along ...

I wonder whether there's enough weight on the nosewheels? And are the turning radii realistically narrow? And might the pitch MOIs be too low?

These are guesses about the possibilities, but they are quasi-educated hacker guesses.

[rwdriver]

MOI's were adjusted to no avail... radius is consistent with other models....other than loading --- how would you add weight to front of aircraft. Basically unsuccessful thusfar.

[copperpen]

I have looked at a few Posky 747 and 767 cfg files. They all have a steering angle of 70 or higher in the contact points. I am currently running an FFX 737-200 that has 68 in the dterring angle and that turns very nicely under 13 kts taxi speed.

Could you be a bit more specific with the model/s.

[rwdriver]

Here is one of the files from FlightSim. Thank you so much for your interest. Sorry it took so long to get back to you!
th7444nc.zip

[copperpen]

Thanks. I'll have a look and see how it performs.

[plainsman]

I am not a fan of POSKY air files. They tend to do some hokie fudges to try to create some specific characteristics rather than really getting the files right in detail. I think one of the fudges they use in the 747s, is to make the yaw way too great, and alter the yaw damper?? At least that was true of some early versions.

[copperpen]

rwdriver

In its original configuration this aircraft would not turn during taxi unless the speed was below 1kt. I had a look at the cfg file in Airwrench ( non edit mode) and modified the MOI to those suggested by the program. Next I had a look at contact points using the time honoured add a light method. The contact points have now been corrected and the aircraft will now turn during taxi. I have spent 30 minutes taxi-ing around the islands at Schipol. It will now allow steering corrections at speeds as high as 30kts along a straight or gently curving taxiway. At 20kts it will take sharper turns, and at speeds below 15kts it will start into a 90 or even a 180 degree turn. You will need to apply a small amount of power to keep the momentum up in these sharper turns.

As I am unable to upload anything apart from pictures or small text files here is a link to the amended cfg file. http://www.humyo.com/4642181/Thai744cfg.zip Let me know if this file works for you.

I forgot to clean up the file after my fiddling. Just delete lights 18 and 19.

[rwdriver]

Thank you so much for your interest, time and effort. It works extremely well - you are a tremendous resource and again, I thank you so much for your help and your contributions to making the community better.

Absolutely fantastic!