Thorp Air Command - T18.net

I have been having an issue making sharp or tight left turns. Another owner said he has the same problem. I can step on right brake and break the tailwheel loose and spin around fine but not so on the left. I swapped out brake cylinders, same, checked the brake pad and it is not glazed and shows signs of brake wear matching the left side, brake is not spongy and has fluid. Any ideas? Thanks

I have the same problem. Seems like Lee said something one time about the inability to get a lot of left brake with full left rudder.

Is it possible that for some reason the tailwheel is not breaking loose when you go full left rudder. I think mine is set up so it breaks about the time the rudder goes to full deflection. I know I adjusted so that would happen with my Maule but I am less certain about the AP tailwheel I have on now

It's about wear on the pin in the breakout mechanism. Take the fork loose from the housing and turn the pin over and reassemble. Note, a small zip tie is used in the reassembly process.

_________________
Bob Highley
N711SH
SN 835
KLAL

Tail wheel issues was my first thought. Just fyi, I have the same tail wheel. I modified it to stay locked out to +/-45 degrees. Works like a champ. These tail wheels do wear. I suggest putting the tail up on a bucket so you can hang the wheel free and see if there is play. I shimmed mine with a lowes nylon washer and it tightened it right up.
Good wheels, but they must be maintained.
Cubes

Thanks Bob and Cubes, it is brand new but i will check it out. Appreciate the input.

Well, Tailwheel brakes the same in either direction of rudder movement. Flipped the pin and problem still persists. Next?

When you swapped the pin, did you look to see the condition of the notch in the tiller bar? Might have a sharp ramp on one side. Also, are you pushing full rudder while trying to turn? Or are you just trying to use the brakes to castor the tail wheel?
Cubes

Pin looks fine, Tried using full rudder and brake at the same time. Wondering if the geometry on that pedal might be an issue.

It is the brake application that causes the unlock function. It is all about side load on the tailwheel assembly. Adding rudder does nothing to breakout the mechanism. Try it with the rudder centered. Low speed and stick back BTW!

_________________
Bob Highley
N711SH
SN 835
KLAL

I disagree Bob. The tail wheel is designed to free caster at 30 degrees. But it can caster early, as you point out, due to side load. However, our rudder is designed for 30 degrees of travel. How many are really 30 degrees? It is very hard to measure precisely. So, if you have 31 degrees available and go full rudder, you will break it free.
But most likely, you are looking at the ability, or not, to get the same rudder travel. Does the issue happen while you are out of the cockpit and pushing the plane?
Cubes

I stand corrected. That points to the fact that Bob's left rudder stop may be limiting full travel.

_________________
Bob Highley
N711SH
SN 835
KLAL

Thanks Bob and Cubes, I 'll check the rudder travel as far as it hindering the break point. But, now my bendix is hanging up so I'm pulling the starter off now.

Because the Thorp flies with the engine slanted down, a weak starter drive spring can allow the drive to engage in rough air or during a wheel landing. Early on, I chased this problem more than I wanted to admit. Bill Williams got tired of propping me to get back from cross-countries. I put a good SkyTech on and solved the issue.

_________________
Bob Highley
N711SH
SN 835
KLAL

I just degreased the drive and shot it with silicone but if that doesn't work I'll go that route Bob.