Tail dragger ground handling

M

monk1

Charter Member
I have a tail dragger that has a wide turn radius on the ground (without using differential braking). I'd like it to turn tighter, more like other tail draggers like the LIC Champ for example. Is there anything in the aircraft cfg I can modify to achieve this? Any help from the flight dynamics gurus would be appreciated.
 
Is it a multi-engined or single-engined aircraft?

Does it have a castoring tailwheel or is it a fixed or a skid type?

Is there a reason you are not using differential braking?
 
Tako_Kichi said:
Is it a multi-engined or single-engined aircraft?

Does it have a castoring tailwheel or is it a fixed or a skid type?

Is there a reason you are not using differential braking?
Click to expand...

The model is Bill Lyon's J3 Cub. I don't use differential braking most of the time because with most of the tail draggers I have it's not necessary they turn so well with a blast of air over the rudder. I'd like Bill's Cub to do the same if possible.
 
Luckily, I still have that one archived.:engel016: (Hey - smilies are back - thanks Ickie!)

The tailwheel is set for 90° steering, which is actually a little too tight. It will turn with positive steering effect (sa if the tailwheel was linked to the rudder), but as is, you have to be very gentle with the inputs. That high a steering angle puts the center of the steering radius between the mains and just ends up dragging the tailwheel sideways. Open the aircraft.cfg and change the "90.0" in the point.0 line to steer at an 80° angle to relocate the steering center to just outside the mains and maintain that positive input. The other option is to set the angle to 180°, which in the Sim is a flag to act as a castoring wheel.

And I thought I'd never have a use for my high school trig...

Edit: I just took another look, and there's no braking section at all in the cfg file. It might be a good idea to copy the one from the default J-3 so that you have something close to the braking power you should have and also activate differential braking via rudder input.
 
Thanks for the input Tom. I understand what you're saying, but my point.0 looks like this:

point.0=1, -19.30, 0.00, -0.50, 5000.0, 0, 0.5124, 47.0, 0.07, 2.5, 2.00, 0.0, 0.0, 0.0, 0.0,0.0

I don't see a 90 in there. What am I missing?

Here's the whole shebang...

point.0=1, -19.30, 0.00, -0.50, 5000.0, 0, 0.5124, 47.0, 0.07, 2.5, 2.00, 0.0, 0.0, 0.0, 0.0,0.0
point.1=1, -2.8, -3.0, -5.2, 1968.50, 1, 0.5124, 0.0, 0.7, 2.5, 0.7, 0.0, 0.0, 1.0, 0.0, 0.0
point.2=1, -2.8, 3.0, -5.2, 1968.50, 2, 0.5124, 0.0, 0.7, 2.5, 0.7, 0.0, 0.0, 2.0, 0.0, 0.0
point.3=2, -4.80, -16.25, 0.20, 1787.40, 0, 0.0000, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 5.0, 0.0, 0.0
point.4=2, -4.80, 16.25, 0.20, 1787.40, 0, 0.0000, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 6.0, 0.0, 0.0
point.5=2, -19.30, 0.00, 3.8, 2787.40, 0, 0.0000, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 9.0, 0.0, 0.0
point.6=2, 1.67, 0.00, -1.83, 1787.40, 0, 0.0000, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 4.0, 0.0, 0.0
point.7=2, -19.30, 0.25, -0.48, 2900, 0, 0.000, 0.0, 0.000, 0.0, 0.000, 0.0, 0.0, 5.0, 0.0, 0.0
point.8=2, -19.30, -0.25, -0.48, 2900, 0, 0.000, 0.0, 0.000, 0.0, 0.000, 0.0, 0.0, 5.0, 0.0, 0.0
 
monk1 said:
Thanks for the input Tom. I understand what you're saying, but my point.0 looks like this:

point.0=1, -19.30, 0.00, -0.50, 5000.0, 0, 0.5124, 47.0, 0.07, 2.5, 2.00, 0.0, 0.0, 0.0, 0.0,0.0

I don't see a 90 in there. What am I missing?

Here's the whole shebang...

point.0=1, -19.30, 0.00, -0.50, 5000.0, 0, 0.5124, 47.0, 0.07, 2.5, 2.00, 0.0, 0.0, 0.0, 0.0,0.0
point.1=1, -2.8, -3.0, -5.2, 1968.50, 1, 0.5124, 0.0, 0.7, 2.5, 0.7, 0.0, 0.0, 1.0, 0.0, 0.0
point.2=1, -2.8, 3.0, -5.2, 1968.50, 2, 0.5124, 0.0, 0.7, 2.5, 0.7, 0.0, 0.0, 2.0, 0.0, 0.0
point.3=2, -4.80, -16.25, 0.20, 1787.40, 0, 0.0000, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 5.0, 0.0, 0.0
point.4=2, -4.80, 16.25, 0.20, 1787.40, 0, 0.0000, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 6.0, 0.0, 0.0
point.5=2, -19.30, 0.00, 3.8, 2787.40, 0, 0.0000, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 9.0, 0.0, 0.0
point.6=2, 1.67, 0.00, -1.83, 1787.40, 0, 0.0000, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 4.0, 0.0, 0.0
point.7=2, -19.30, 0.25, -0.48, 2900, 0, 0.000, 0.0, 0.000, 0.0, 0.000, 0.0, 0.0, 5.0, 0.0, 0.0
point.8=2, -19.30, -0.25, -0.48, 2900, 0, 0.000, 0.0, 0.000, 0.0, 0.000, 0.0, 0.0, 5.0, 0.0, 0.0
Click to expand...
Hmm... No sure why yours doesn't match mine - maybe someone's already tried to make some alteration. The steering angle is the eighth parameter in each line, 47° in your case. Instead of trying to turn too sharply, it's just not turning enough. The same fixes apply - use 80 if you want sharp, positive steering, and 180 if you want genuine castoring action.

EDIT: Your contact points are definitely different from the ones in the original "cub4free.zip" archive on my system. There's a couple of additional scrape points, and the mains have been altered slightly. I also rechecked my math according to your numbers, and I'd go with no more than 75° steering angle for that setup.
 
Tom Clayton said:
Hmm... No sure why yours doesn't match mine - maybe someone's already tried to make some alteration. The steering angle is the eighth parameter in each line, 47° in your case. Instead of trying to turn too sharply, it's just not turning enough. The same fixes apply - use 80 if you want sharp, positive steering, and 180 if you want genuine castoring action.

EDIT: Your contact points are definitely different from the ones in the original "cub4free.zip" archive on my system. There's a couple of additional scrape points, and the mains have been altered slightly. I also rechecked my math according to your numbers, and I'd go with no more than 75° steering angle for that setup.
Click to expand...

Well that's mighty odd, don't know why my numbers would be different than yours. Maybe I was messing with it sometime in the past. I think I'll go back to Avsim and download it again and compare the numbers. Until then, thanks for pointing that out, I'll change that to 75 and see what it does.
 
Heck - yours might be better. I'll reinstall the standard plane and then take it across the grass to see where the dust kick up. It's been a while since I flew that one...
 
I reloaded the Cub package and wound up with an entirely different cfg file. Plus, I had a tundra tire version of Bill's J-3 that has now disappeared and I don't see it in the package. I wonder if I just overwrote some old payware. Do you know where his tundra tired "bush" model is?
 
I seem to remember one from WAY back, but I can't find it listed anywhere. The closest I came was an outdated link to the AvSim forum.
 
Thanks Willy, I posted over there, then found it later. The file name is CubFs9D.zip and is not found in too many places. That's where the cfg file I had came from. So now that I have the tundra tire version back, I can get to work on the ground handling problem. If anyone wants Bill's tundra tire version you can find it here. I hope this is a legit site.

http://wcm.flightxpress.de/files/1106/files1106.html
 
Thanks for the links. One note - you need to right-click and save target as for the Old Hangar links, otherwise you get an error page.
 
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