Tailwheel Troubleshooting

We’ve compiled a list of common issues that we see with the Van’s type tailwheel assemblies, along with simple solutions.

Before we get started, let’s define a few key pieces of terminology so we’re all using the same words for the same parts. Forgive the crude Sketchup drawing here:

A few common issues and how to address them:

Locking pin jammed in the housing

If debris or burrs inhibit the smooth movement of the locking pin, it may jam inside its housing. This will present different symptoms depending on how it has jammed. If it jams all the way inside the housing, the tailwheel won’t lock properly or will only lock sporadically. You can remove the pin, clean it, dress any burrs you find, and make sure the housing is cleaned before regreasing everything.

If the pin is really stuck, a pin punch can be used to force it out from the backside, though make note of the location of the roll pin which forms the backstop on the square hole. After you reassemble the tailwheel, make sure the pin moves in and out of the housing smoothly and locks smoothly with the control arm.

If the pin jams all the way or partially out, your tailwheel will remain locked and the forces put onto the tailwheel may damage some parts of the assembly. You’ll most commonly see notches form on the locking pin nose and sometimes the bushing can be damaged by a pin forced to turn through the softer bushing material.

Tailwheel unlocking at inappropriate times

Your tailwheel should unlock ONLY when it is turned past the angle at which the locking pin is retracted. It should not unlock by a sideways force alone… so if stepping on the pedal is enough to unlock a tailwheel that is otherwise in trail, something is wrong.

What’s most likely at fault is that the pin is not sufficiently engaged in the control arm notch. Van’s parts cut the notch fairly shallow, meaning that the pin is limited in how far it can extend. In the right circumstances, a propagation of error between a shallow notch, an excessively rounded pin, and worn corners on the control arm can cause a sideways force on the control arm to force the locking pin back into its housing, unlocking the tailwheel.

The solution here is to fix all the little problems that added up to this. Our control arms feature a deeper notch, which means the locking pin can engage more fully and get contact between the straight sides of the notch and the straight sides of the pin.

We also recommend blunting the nose of the locking pin, giving them more of a “bullnose” profile rather than a fully round one. Make sure the corners of the locking pin are still rounded so that they don’t catch on the walls of the groove in the mounting socket.

Tailwheel assembly binds or feels tight

If the tailwheel steering feels tight on assembly, the likely culprit is that the top nut is compressing the wrong parts of the assembly. If you look across the top of the assembly, you’ve got the top surface of the control arm which is probably just about in line with the top surface of what I’ll call the “shoulder” of the tailwheel shaft. For proper function, these two surfaces need to be close to coplanar, but the “shoulder” should stand out “proud” – just above the top surface of the control arm.

If the opposite is true, and the control arm surface sits above the shoulder of the tailwheel shaft, the system will bind, as the washers on top will tighten onto the control arm, which will then compress the outside of the mounting socket to the bottom of the tailwheel fork. You can easily tell if this is the case, as the tailwheel will feel tight and resist swiveling when the top nut is tightened down but will loosen up if the nut is backed off.

You can solve this issue by carefully removing material from the top of the mounting socket using a belt sander, ideally just enough to get the tailwheel shaft shoulder above the top surface of the control arm. Alternatively, you can add a 1/2″ ID shim washer to the top of the tailwheel shaft shoulder (find these shim washers on our website)

Note that if you have the JDAir mounting socket (or tailwheel yoke, as they call it) with the needle bearings in the shaft, you should not sand this unit, as it will likely result in debris from the sanding getting into the needle bearings. Instead, use 1/2″ ID shim washers on top of the tailwheel shaft to configure the assembly.

Tailwheel has too much vertical play

It is possible as parts wear for vertical play or “slop” to develop in the tailwheel. If this play is strictly up and down, it’s generally not a problem unless it’s very severe. If you would like to address vertical play here, you can use a feeler gauge to determine how much play you have and use a 7/8″ ID shim washer to address it. This shim washer can go under the mounting socket or on top of the control arm. Be careful, however, not to shim too much, as this can cause the tailwheel to bind.

My control arm has play

I often get calls from customers concerned about play or slop in the control arm piece on top of the mounting socket. This play can be either up and down or side to side. These parts are made with somewhat loose fit so that they don’t jam and malfunction, so a little bit of play is normal. How much is too much? I wouldn’t necessarily worry too much about this unless it is causing some other tailwheel malfunction. If you are concerned about it, you can check the control arm, tailwheel fork, and locking pin for excessive wear and replace parts as necessary.

Tailwheel has play other than vertical

If the bushing in the mounting socket has become excessively worn, the tailwheel may develop play in directions other than vertical. While it usually would take quite a lot of slop in this system before real problems develop, you can consider replacing the bushings in the mounting socket, or replacing the whole mounting socket altogether.

To do this, you need to determine what type of mounting socket you have.

• The Van’s standard part is easy to identify by the bronze bushing inside the mounting socket. These will usually, but not always, also feature a non-functional grease zerk, which serves as a bushing retainer. You should be able to source replacement bushings at an industrial supply shop. When you’re replacing the bushings, make sure to loosen the grease zerk if present, press the old bushings out, and replace with new bushings. Make sure to reopen the groove in the top mounting socket with a Dremel tool or mill once the bushings are in, as this is important for the function of the locking mechanism
• Our “Screaming Eagle” mounting socket has a dark grey, engineered plastic bushing. You can find replacement bushings on our store.
• JD Air’s tailwheel yoke performs the same function, though its live bearings should not wear over the life of the product. If you have excessive play in this unit, something else is going on.

Tailwheel tire wears unevenly or fork sits crooked

If your mounting socket was not installed vertically the first time, your tailwheel fork will sit crooked and your tire will likely wear unevenly.

This can be addressed by replacing the mounting socket, which involves match drilling a few holes. For more on this process, see our document “Changing a mounting socket” or contact us.

Tailwheel strikes bottom rudder cap

The tapered rod spring that makes up the tailwheel can end up bent over time and occasional hard landings. You should normally have 3 inches or more of clearance between the top of the tailwheel and the bottom of the rudder. If your tailwheel seems too close to your rudder or if you notice damage to the fiberglass from a rudder strike, you may consider replacing the tail spring. See our document “Drilling the tail spring” for more information.

It is also possible to put a downward bend into the spring, as discussed here.

Issues with Steering Link Adjustment

The next three problems are most commonly found in situations where a steering link system has replaced the stock steering chains. If your tailwheel does not unlock on one side, if you notice a “notch” in your locking pin during servicing, or if your tailwheel “bangs” when unlocking on one side, you should check your steering link for proper adjustment. All three issues are indicative that the link needs to be adjusted for length. What’s happening is that the rudder hits the stop before the tailwheel reaches its unlock position, causing the force from the tailwheel to jam against the stop. See our Steering Link installation document for more information.