trublesome tailwheels, ground looping
 

It seems that tail draggers are giving many flyers a bad time on the take off roll. We set up the planes for a large rudder throw, for knife edge, 3D, and other aerobatics. Thats fine in the air, but on the ground, we suffer with over control. often with terrible consequences. Many new Tx's do not allow dual rates on the rudder. These planes seem to be much more manageable after the tail wheel leaves the ground and we begin to steer with the air flow over the rudder. Whats a pilot to do? I was thinking of allowing the tail wheel to simply hang limp, like a caster wheel on a shopping cart. The steering would then be done solely by air flow over the rudder, since the tail wheel is just dragging and following along, and not being actuated by the rudder servo. It seems that this would allow pilots to enjoy a gradual increase of throttle and achieve a more scale like take off, instead of the "punch the throttle and pray" scenario that we see so often. Admittedly, ground handling may be much more mushy, but it may be a good trade off. Any comments? Thanks

trublesome tailwheels, ground looping
 

I had a 1/4 scale J-3 Cub that would ground loop if a bug walked in front of it. I have other tail dragger airplanes that you just power it up and they track beautifully with no messing around. I think I know all the rules but in my own experience it is a hit or miss luck thing. Not very scientific.

The basic tail dragger is an unstable system. The problems are that the CG is aft of the main wheel contact point and at low speeds as the tail horizontal tail unloads the wheel to the point that it is not making any side force as the tail tries to swing around. The horizontal tail seems to lift sooner that the vertical tail gives directional stability. If there is any misalignment in the main gear wheels it will show up in the ground loop.

Grass takeoffs work better sometimes as the grass gives more drag on the tail wheel holding things straight.

A tail skid instead of a freewheeling wheel will add drag aft and help.

Lots of prop thrust that can get the vertical working before the tail lifts will help.

Holding up elevator will help with down force at the tail will increase the effectiveness of the tail wheel.

I think that toe in of the main gear is supposed to help also.

I don't think that the castering tail wheel is supposed to help. I believe at least one of the fighters in WWII had a tail wheel lock for takeoff.

Toe In!
 

Definitely try toeing-in the mains first. On all my taildraggers that had control problems during take-off, toe-in of the mains solved the problem. All you need is 1-2 degrees each side and that should do it. Trust me - it works! :)

Ted

trublesome tailwheels, ground looping
 

A lot of guys go to using a seperate control linkage from the rudder servos to a tail wheel stearing arm. That way you can set the wheel for less travel than the rudder itself is using.

trublesome tailwheels, ground looping
 

An easy way to de-sensitize the tailwheel is shown in the photo. This is a 40 size airplane and the pivot point of the tailwheel bracket is 1 inch fwd of the rudder hinge line and the rudder attach point of the tiller arm is 1 inch aft of the rudder hingeline; this ratio allows the tailwheel to deflect 1/2 the number of degrees that the rudder deflects. The steering is compromized in that you now have a larger turning radius, but still practical.

The key to a gradual increase of throttle to attain a scale like takeoff lies in Ben's reply above of holding up elevator to keep the tailwheel in contact with the ground until you have aerodynamic control with the rudder.

The Cessna 170 had a tailwheel lock. as well as Cessna AT-!0, the UC-78, the Beech DS-18, the DC-3/C47, and the C-46, and the B-17; these are the ones I know of.

trublesome tailwheels, ground looping
 

If the wheels are parallel when the plane is in level attitude, then the wheels toe-out when the tail is down. This makes the plane very squirrely. Toe-in of the wheels in level position corrects this. On the Luscomb 8E I used to fly, the tail wheel had a lock that could be overcome when swinging the plane around with a brake applied. This lock did not seem to help as the plane was very squirrely on the ground. One got used to it, and learned to anticipate the wiggles and prevent them.

trublesome tailwheels, ground looping
 

Put a higher rear carriage, you'll decrease the P-factor and have a much simpler take off....

trublesome tailwheels, ground looping
 

use some toe in, and use a castoring tailwheel. I have a 5lb tiger 2, and this setup rocks. I can lift the tail at a standstill and use the rudder to pivot on either wheel. On takeoff, its not squirrely at all, even less so than a full scale cessna 170

speaking of tailwheels...
 

I'm wondering what the best way is to fix a tailwheel to the fuse that I'm building- fuse is formers and stringers, but the rudder doesn't extend below the elevator- (I'm hoping to post a pic tonight, but I've got a slow connection at home- if it doesn't work, will post in the morning on the good 'ol T1 at work-)
The options I'm considering are- 1) castoring tailwheel; 2) tailskid; 3)different tailfeathers
Opinions are appreciated-
Cheers,
Brett

view 2
 

the plane is basically an LT-40-

tailfeathers-
 

I'm aware that the LT-25 has a pull-pull tailwheel, but I'm not sure how it's done- is the same servo used for the rudder along with the pull-pull tailwheel?

last one
 

pic of wings, just for grins-
thanks, and cheers-
Brett

trublesome tailwheels, ground looping
 

Another consideration related to ground handling on tail draggers is the location of the axles relative to the CG. On the typical constant chord wing, axles set right at the leading edge works best. In many cases, gear that was set too far ahead of the wing was the problem. Groundlooping went away with the gear relocated to the leading edge and no toe in OR camber was required. But, this sometimes isn't enough and some camber and toe in is required.

trublesome tailwheels, ground looping
 

imo i would use a castoring tailwheel mounted on the former, with enough rudder throw, they work great, and even in x-winds my castoring tailwheel works better than when my tiger was tri gear, probably partially due to the nosewheel being slightly sloppy

trublesome tailwheels, ground looping
 

thanks mullenc525-
I probably should have posted this in a different forum, but I thought that since the tailwheel issue was here, what the heck... anybody have ideas about a pull-pull set-up for this? Never done it, but I assume that the rudder servo somehow drives the pull-pull for the tailwheel as well?
Cheers,
Brett