RANS aircraft: Check your rudder

Bill Scott · Post by **Bill Scott** » Mon Oct 25, 2010 3:43 pm

Folks, I thought I should share this for safety sake.
(My aircraft is an S6 ESD-XL, but I suspect this may well apply to the S4/S5 in addition to the S6 family.)
Whilst doing a pre flight check on Sunday, I found a problem with the lower rudder mount / eye bolt.
Normally I make a visual inspection first and then check the various bits for physical security including ensuring the split pins etc are in place. Today was no different and all looked fine. I usually check the vertical stabiliser for stiffness on its mounts and then hold the rudder and apply up & down pressure on it to see that all is well with the top and bottom pivot mounts.
This time I did it differently and I'm glad I did. I stood behind the aircraft and put the fingers of my right hand around the base of the rudder at its leading edge and pressed my thumb against the aluminium tail channel. The rudder moved outwards to the rear together with the eye bolt !! The movement was roughly 8mm and I repeat that an initial visual inspection looked perfect.
The most likely cause is loosened rivets on the nut plate. This plate is fitted to the vertical stabiliser spar and the eye bolt goes through the tail channel into the nut plate. The eye bolt then provides the lower pivot for the rudder.
I will be having a good look at it through the week, armed with a decent light and will report my findings.

When conducting pre flight checks it would be a good idea to be in the habit of applying an outward pull to the base of the rudder to check that the eye bolt is secure.

Steve Brown · Post by **Steve Brown** » Mon Oct 25, 2010 7:17 pm

Hi Bill
I'm sure Malcolm McBride would be pleased to hear of this for his Safety Spot!

Bill Scott · Post by **Bill Scott** » Mon Oct 25, 2010 10:43 pm

Hi Steve,
Yes it might well be of interest. I'm going up to the strip tomorrow and intend to find out exactly what is moving in relation to what. Will try to get a couple of decent pictures also.
Rectification ought to be simple enough, once the exact problem is identified.

Bill Scott · Post by **Bill Scott** » Tue Oct 26, 2010 5:56 pm

I've had a good look at her with a decent light today. I Undid the skin and poked my head up into the fuselage to get a close look at the nut plate, expecting to find two loose rivets, but not so.
So, with my head in the fuselage I stretched around & managed to move the base of the rudder only to see that the movement was the tube itself. The rear spar of the vertical stabiliser (stern post) wasn't quite fully home against the panel across the rear of the fuselage. The post is a very tight fit between the two bottom longerons.
It seems that when I fitted the eye bolt & tightened it until it didn't want to turn any more, it was at the point of interference with the other two tubes and just needed that bit extra. I had stopped at the point where I felt I had been in danger of stripping the threads.
It had been firmly in place and looked perfectly ok to the eye. The actual movement of the eye bolt was about 3mm and that is what now shows through the nut plate, with
the tube firmly in place.
Anyone re-skinning or building a Rans might have the same experience, but forewarned is forearmed and it is easy to check, once you know.
All it cost me was a new split pin.

Sandy Hutton LAA372 · Post by **Sandy Hutton LAA372** » Wed Oct 27, 2010 5:08 pm

Are you saying this all came loose between your Permit Renewal Inspection earlier this month and Sunday? It sounds to me like it should have been covered by the Mandatory Inspection MOD/204/013, at that time.

Bill Scott · Post by **Bill Scott** » Wed Oct 27, 2010 6:36 pm

Sandy,
No, MOD/204/013 applies to earlier S6 aircraft tailplane attachment points.
Although that one isn't showing on the TADS sheets on the LAA website, my Inspector has just confirmed that it's not applicable to my darling Rans.

Regards,
Bill

Sandy Hutton LAA372 · Post by **Sandy Hutton LAA372** » Wed Oct 27, 2010 8:05 pm

Maybe there's a case for an Issue 2 of this inspection leaflet now.

Glad you found it and no harm done.

Bill Scott · Post by **Bill Scott** » Wed Oct 27, 2010 8:36 pm

Yes Sandy,

I'm inclined to agree as it isn't on the website and I didn't notice it on the Skycraft site either, although I only had a quick glance there.

The little glitch on mine is relevant to anybody who is fitting the vertical stabiliser into the airframe at build time or after removal of it for any other reason.

I also checked with my inspector and he agrees with my thoughts on how it came about.

Cheers
Bill

Light Aircraft Association

RANS aircraft: Check your rudder

RANS aircraft: Check your rudder

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Inspection