The Cessna 120-140 Association Forum

New owner of a Cessna 140 so a lot to learn. Sorry if this is an obvious problem, but I couldn't find a description of my issue on the forum or Google.

I noticed on my last flight that it took a fair amount of persuasion with the brake to get the tailwheel to free caster when making a tight turn. When pushing it back to tie it down, the tailwheel swung and got stuck and wouldn't break to free caster (so it was just dragging at about the break angle).

Is this a simple fix of just pumping some grease into the fitting, or will I need an A&P to pull the tailwheel apart and fix something internal.

Any help or guidance would be appreciated.

PS I am currently working on my tailwheel endorsement so there has been a lot of landings. Also it had the wrong springs on it when I purchased it, and I had the correct springs installed. I used the Neil Wright article as a guide for that. The chains don't have a lot of slack, but the springs aren't stretch when on the ground. Would too much tension in the chain cause an issue with breakout force?

What tail wheel do you have? They all work differently.

Sorry I have a Scott 3200. Should have put that in the post.

Did it suddenly stop working? You can try greasing it. (#2 grease) There shouldn't be any tension on the springs and chains. OTOH, if they're too loose you may not get enough angle to get to the release point.

Try lifting the tailwheel off the ground and see if it releases when you turn the tire. You can put a 4x4 under the tailwheel bracket just aft of the tailcone skin and rest it on a milk crate or something. Otherwise you'll probably have to take it apart and do some adjusting.

Some of them do seem to take a bit of "shock" to get them to break free.

I've taken to rebuilding my Scott TW annually. There's a pretty good video here:
https://www.youtube.com/watch?v=S-0i2MT ... eveJohnson

The grease zerk really only pushes grease into the bearing, not into the friction plates.

There is also 3 or 5 springs inside, 5 are used for more friction applications like larger aircraft and 3 are used for lower friction applications like our light 140s. The caster friction is set by the number of springs and how much the castle nut on the bottom is torqued. When you lift it off the ground you should be able to rotate it back an forth with a enough resistance that it stays where you leave it. The break from control is done by a set of spring tabs that are forced to disengaged by a piece called the Pawl. I found that the housing that captures the spring tabs had worn groves that were holding the tabs out and making the pawls job of disengaging the tabs harder. The result was more force required to disengage.

At some point you're gonna have to take a look or get someone to take a look.

There is alot of info here on tailwheel springs, tailwheel chain tension and tailwheel angles. Its worth printing it off and seeing what you have verses what is recommended.

Marshall

Thank you John and Marshall for your replies! I will first try jacking it up and see how it behaves. If a little grease doesn't make it happy, then I will have to get it torn down and addressed.

I'm sure I got the right springs on there now, but I will play with adding a link or two on the chain for tension. I think the angle of the king pin is ok, but I will take a level out there and do a more thorough check than the mark I eyeball inspection.

Thank you again.

The info Marshall wrote is quite good in my opinion and since the airplane is new to you it wouldn’t hurt to jack it up and take it apart to inspect it. Mine also has a 3200 and it wasn’t behaving like others I’ve flown with the Scott 3200. When I disassembled it I found the fork casting to be broken at the slot that holds the spring that controls castering. I found that someone had assembled it wrong by resulting in the outer portion of the casting breaking off and they tried to repair it on such a way as it just couldn’t work right. To fix it would require a new fork casting and pretty much all the other parts because the whole assembly was very worn so, although not desirable due to cost, I opted for a completely new 3200 from Alaska Airframes. It’s PMA’d for the Scott and it appears to be built much more robust and with higher precision. If the casting wasn’t broken I would have rebuilt the old one though.

Anyhow, best to inspect it and make sure it’s not broken or worn out.

So just to follow up. I got the tailwheel to free caster by adding an extra link on one side. I don't have a lot of authority when taxiing no so I have to do a fair amount of brake application. No direction issues when taking off so not a big deal.

I do think a tear down and inspection is on order, but I sure hope I have better luck and don't have to buy a new one.

nickw wrote: ↑Sat Jul 15, 2023 8:26 pm So just to follow up. I got the tailwheel to free caster by adding an extra link on one side. I don't have a lot of authority when taxiing no so I have to do a fair amount of brake application. No direction issues when taking off so not a big deal.

I do think a tear down and inspection is on order, but I sure hope I have better luck and don't have to buy a new one.

If your sleuthing proves inadequate to provide the performance you want, I have a decent condition 3200 off my 120 that would let go for a reasonable amount. Opted for a brand new AB clone last year.