On Thursday, May 10, 2012 5:54:15 PM UTC-7, JJ Sinclair wrote:
There seems to be a fair amount of confusion about the springs used in almost all modern sailplane rudder cables. The springs are there to keep the pedals upright (pulling forward) and to facilitate rudder pedal adjustment through the use of an 'S' tube. Each rudder cable enters the top rear of its 'S' tube and exitsthe lower forward portion of the 'S' tube, then extends on forward another foot or so and is bolted to the square tube that both pedals slide on when adjusting the pedals forward and aft. One can simulate a broken cable by simply grasping one rudder pedal and pulling it aft about 6 inches. The spring on that side will expand and the rudder cable will go slack. The spring on the other side will slam the rudder hard over...........I just did this on my ship. The same is true for Schleicher, Schempp-Hirth, DG, LS and most all sailplanes!

Some things to check on annual inspection:

1. Nylon inner sleeve in place on both 'S' tubes and extending about an inch out both ends of the 'S'tube.(the nylon sleeve keeps the cable from rubbing metel to metal during normal rudder operation and during pedal adjustment.

2. Springs in place and pulling equal (I measured 9# spring tension on my Genesis)

3. Adjust the rudder pedals full forward and inspect the cable at the top rear 'S' tube. (this is the most likely place to find cable wear)

4. Adjust the rudder pedals full aft and inspect for cable wear at the point where it exits the lower forward 'S' tube.

5. Inspect the weld that attaches the rudder pedal to the rotating tube at the bottom. In an accident, the pilot may have ended up standing on both rudder pedals as the ship came to an abrupt stop. I have found cracked welds due to this and several AD's have been issued on this problem.

6.Inspect the Nicopress sleeve and inner protective eye (thimble) and the bolt that attaches the cable to the rudder assembly. It must have lock-nut or castlenated nut & carter pin.

7. Inspect as much of the cable runs as you can see and don't forget to check the other end where the cable attaches to the rudder, sleeve/bolt nut or pin.

8. Check rudder stops. They may be at the rudder or on the pedals, but must stop full rudder movement before rudder strikes fin or pedals hit fuselage sides.

Most manufactures recommend not using lube on the rudder cables because it attracts dirt and can lead to unnecessary cable wear, but do lube the rudder pedals and rudder hinges. One more little tid-bit, you can adjust the angle at which the rudder pedals sit by simply making the rudder cables longer..........OK, JJ just how the hell do I do that? By inserting two 1" steel carobeaners in the cable run at the forward attach point. This will make both rudder pedals rotate forward about 30 degrees. Some pilots object to the straight up angle of the pedals in ships like the Duo-Discus. Make sure you still have full rudder movement before rudder pedals hit fuselage side..
Cheers,
JJ A&P for 40 years + owner/operator of glider repair station.

Thanks JJ!
Can rust be also an issue ? After all we can't inspect most of the rudder cable.

Ramy