An Awful Sound

[Ironflight]

It was a very short flight over to our neighboring airport this evening to attend our monthly “Choir Practice” (no actual singing takes place – it is simply a hangar get-together….), and as luck would have it, someone had parked a truck where I usually put the airplane. In order to give myself an “out” when I wanted to leave, I swung the Val around hard – but misjudged the edge of the pavement just a wee bit….

The sound was sort of a “Bang/Snap/Crunch!” Whatever …. it was loud, and I could tell I wasn’t going anywhere. I shut down and climbed out to see that I had apparently invented the RV retractable tail wheel – the wheel was pointing up at the bottom of the rudder, having spun on the round spring, and there was a fair amount of mud spread around. Both of the cross-bolts that hold the tail wheel “knuckle” to the spring had obviously sheared. I was surprised to see a small muddy hole with no obvious fixed objects – I expected that I had unluckily hit something hard and/or solid, but this was not the case.

Truth be told, I generally change these bolts every other annual since they almost always develop a little bit of play, and when removed, show obvious signs of wear. I didn’t change them this most recent annual, but will now make it a yearly event – they are pretty cheap! Still, better for those to shear than to damage the spring attachment to the fuselage – we did a thorough inspection, and found nothing bent or popped after tonight’s incident.

Fortunately for me, I was broken down next to several hangars full of homebuilding tools and parts – we had it all back together before the party really got going. I had to get a quick ride home to pick up a spare tail wheel link we have on the shelf – the one on the plane was slightly bent and had a broken rod end bearing (repairable) – and everything was back together with about 20 minutes of work.

Memories of that awful sound will probably make me a little less casual about imparting side loads on the tail wheel, and I’m going to makes rue to swap the bolts out annually. Meanwhile, I have some little bits of “bolt shrapnel” to add to my “worn out parts” collection that I keep to remind myself that nothing lasts forever….



So - does anyone know the part number for that rod end? Double male AN3 threads....


Paul

[TX7A]

Glad to hear it wasn't more serious, Paul. Ya' just never know what dangers lurk.
Now, if it was a certain nose gear that hit the hole....well, the outcome may have been different.
Yep, I said it.

[rv9av8tr]

Bummer! One of those good learning experiences. Rod end bearing your looking for is here. Part number depends on left or right hand threads.
http://www.aircraftspruce.com/catalo...s/auroracm.php

Good luck!

[Steve Sampson]

Paul - how many landings would you have done on those bolts?

[f1rocket]

Having those bolts shear is a common problem with RVs that get used a lot. It is very difficult (I say impossible) to drill these holes in such a way as to get a tight fit that won't wallow out over time.

Of course the fix is to install taper pins in these holes after first tapering the hole with a #2 taper pin reamer. Fix it and you can forget it. While you're at it, install one of Vince Fraizer's improved steel tailwheel assemblies to improve your over-nose visibility and to correct the geometry of the Van's assembly.

You might want to consider this. Glad there was no other damage to your bird.

[Ironflight]

Originally Posted by f1rocket

Having those bolts shear is a common problem with RVs that get used a lot. It is very difficult (I say impossible) to drill these holes in such a way as to get a tight fit that won't wallow out over time.

Of course the fix is to install taper pins in these holes after first tapering the hole with a #2 taper pin reamer. Fix it and you can forget it. While you're at it, install one of Vince Fraizer's improved steel tailwheel assemblies to improve your over-nose visibility and to correct the geometry of the Van's assembly.

You might want to consider this. Glad there was no other damage to your bird.

I'm thinking about going back and looking at the taper pins - I have just never taken the energy to research it before, but after shearing the bolts, it might rise to a higer level of awareness!

And I haven't used a Van's tailwheel in years - I am a firm beleiver that the Van's tailwheel is "damage waiting to happen" due to low clearance if you drop it over a lip. The Val has an API (extremely rugged), Louise's -6 has a Bell, and we have one of Alex's "Bell Clones" for the -3. I haven't used Vince's casue I don't (yet) have another plane that needs one.... This little incident, however, could happen with any of them - it is due to side loads and twisting around the spring.

[f1rocket]

Here's the parts list if interested:

AN386-2-9A taper pin (aircraft spruce)
AN975-3 taper pin washer (aircraft spruce)
B&S #2 taper pin reamer (http://www1.mscdirect.com/CGI/GSDRVS...00000142220635) (1/2 the price of AC$)

The taper pin is an odd-sized Browne & Sharpe #2 taper, so don't confuse it with other -2 tapers. I probably will never use mine again so if interested, I can ship it to you for $25. Just let me know.

[Mel]

Originally Posted by Ironflight

I shut down and climbed out to see that I had apparently invented the RV retractable tail wheel ? the wheel was pointing up at the bottom of the rudder, having spun on the round spring,

Sorry Paul, but you didn't invent this. It has happened to the best or us.

[jthocker]

Same thing happened to me about a month ago, except I was lucky enough not to damage my Bell or Silver bullet link!

[apkp777]

I was thinking about the taper pin mod. However, I think it might be a good thing to have the AN3 bolts break under the excess side load. It's possible that the damage would be realized somewhere more significant if it didn't fail where it did (I.E internal bulkhead)

Anyway, it's got me thinking about upgrading my Van's tailwheel.