Rudder cracking

[Mark B]

I have an Arcus M with steerable tail wheel mounted in the bottom of the rudder. When I first saw this design (copied from the Antares 20E) I worried about possible damage to the rudder or its fixing from shocks on the tail wheel. I was assured that both were extremely strong.

I experienced cracking around the rudder horn - clearly visible on the surface, and also significantly structural. I then learned that at least a couple of other owners have had the same experience, and the rudder has been redesigned to strengthen it in this area. Mine has been rapidly and efficiently repaired by the UK agent Steve Jones, and he assures me it is now much stronger.

My aircraft is Arcus M s/no 24.

[D.J. van den Berg]

Hello Mark,

I am interested to know what your experience is with the steerable tail wheel since the repair. Do you know whether the redesigning has been succesful?

In a couple of weeks we have to confirm the options to Schempp-Hirth. I have heard more negative opinions on the steerable tail wheel and I intend to choose for a fixed one, but I am open for all information on this item.

Kind regards from The Netherlands,

Dirk



Op zondag 5 mei 2013 00:27:25 UTC+2 schreef Mark B:

[Wolfgang Joschko]

Hello Dirk,

I have ARCUS M serial number 8 since 4 Years. I have no problems with the steerable wheel. For me is this feature very important because it gives me the freedom to operate on the airfield as I like.

 

On the other hand you have to operate your aircraft carefully. Pushing the throttle to full power during start on a soft ground brings your ARCUS on the nose wheel. If you then reduce power to much and to fast, your tail will fall down. If you do that too much and too often, I can imagine that the tail wheel will be damaged.

 

Best regards from Germany Wolfgang 8F

[Mark B]

I have had no further problems with the rudder since the repair. My repaired rudder will not be the same as a new design rudder but mine is apparently much stronger than it was, and clearly they have changed the design of new ones to make them much stronger.

 

I also think a steering tail wheel is very useful. At the beginning of the flight it means you can start the engine and do your checks before entering the runway or lining up at the front of the grid. At the end of the flight I often taxi back to my parking place. When I needed a relight in a competition it was a real advantage to be able to taxi back to the launch point.

 

I agree about the difficulty of operating on soft ground. I operate on a grass airfield. I had no problems of the tail lifting when power was applied during the summer. However, during the winter with soft ground it is difficult to apply power without the tail lifting - and as mentioned if that happens you have to take power off very carefully in order to avoid the tail banging down on the ground. It is possible that this is what caused the damage to my rudder.

 

I suspect the steerable tail wheel may help with cross wind take-offs and landings, but I am not sure about this. What do others think?

 

I would definitely choose a steerable tail wheel again.

 

Mark Burton, Arcus M s/no 24

[cernauta]

Unfortunately I'm at the second rudder damage.

 

First time it happened in Rieti. We take off from a runway extension, in facts. There's a concrete bump at the official threshold, which never gave me problems with other gliders (maybe 2-3 cm tall and a rounded surface extending horizontally for maybe 60cm). You usually run over it at good speed, the glider running on the main wheel only. It was occasionally helpful for leaving the ground.

With the ArcusM I didn't follow the prescribed stick-backward technique, preferring a classic mainwheel attitude.

That day, the tailwheel touched the concrete bump at speed, moments before rotation was possible. I felt a terrible bang, and the glider hit the ground with the nose. I now understand how the Arezzo accident (Arcus resting inverted) was probably possible.

There was damage at the lower part of the rudder. Control travel was limited as the steering horns had been moved about 1cm higher, so the horns were struck in the horns fairings.

not a big deal and the repair cost at the factory was reasonable, below my insurance minimum.

Second time, now. I was allowing the glider to run a long landing roll as instructed by the airport manager. There was a very strong headwind (30kts, no cross component). I was keeping the tail off the ground (stick forward). At already a very slow speed, I decided it was time to vacate the narrow tarmac runway.

At the first control input, the right wing impacted the soft, sandy ground. the Wing wheel just couldn't do its job, the wingtip stopped and the glider turned around the wingtip by about 150°.

The tail impacted the ground while the glider was still turning. It all seemed very different from an elegant landing, but I was surprised to find that the rudder was damaged due to the lateral forces. Surely the soft ground made everything worse by stopping the wing and the tail too quickly.

As we removed the rudder, we found that the lower mounting bracket had the main bolt slightly bent. It seems that it's just the bolt and some unknown fittings or bushes that need replacement, not the whole mounting bracket.

The unit is designed to have free play in all but the vertical axis. Rigid mounting of the rudder is provided by the other two pins, which were not damaged.

The rudder itself needs, in my case, a simple repair. Of course, it seems that the junction between the sturdy lower part (which holds the wheel) and the very light remaining rudder surface is designed to be the weak point in case of excessive side loads.

this time, I shoud have kept the tail on the ground; and/or I should have landed on grass, maybe allowing for the wingtip wheel to eventually find the tarmac. Then, I shouldn't probably have tried a turn to the side to vacate the runway, eventually using the engine after a full straight stop to taxy away.

My comment is: don't treat the steerable tailwheel with lightness. It is different from what I was used to. It allows autonomous taxying but it may not be the best option if you fly in remote places, where a workshop is really far away.

aldo

sn37