Rudder Pedal Return Springs

[bzim140]

Cessna 140, s/n: 14985, N3669V

Thanks for your suggestions on the master cylinders. I am posting this again because I was not sure if the first post was accepted.

We have another issue related to the rudder pedals and cables. The rudder cables are slack and touch the bulkhead holes in the aft fuselage. The maintenance manual says the rudder cables should be tensioned until the cables do not touch the bulkhead holes. We have tightened the turnbuckles fully and the cables still touch the bulkhead holes. We do not see any evidence of cable stretch at the swages on either ends of the cables. The larger 3.5 in diameter pulleys are installed per kit SK4051-1. The turnbuckle barrels are correct: 2.25 in length on the left and 4 in length on the right. If we installed a 2.25 in barrel on the right, we might get the right tension, but not correct per the parts manual.

There is another feature that influences the cable tension. There are springs attached to the rudder torque tube extension levers that run to either side of the center console, see photos. The one on the left is 3.5 in attached to the aft lower bolt on the center console. The right one is 5.25 in and attached to the right forward lower center console bolt, see photo. The springs are not in the parts manual. Any ideas? Perhaps a service bulletin or letter? Are we looking at a new cable or spring adjustment? Thanks B. Zimmerman

[6643]

The maintenance manual says the rudder cables should be tensioned until the cables do not touch the bulkhead holes.

I'm not sure where you found that, but it is not correct. The only thing tensioning the cables is the pedal return springs. The only adjustment is the distance of the pedals from the firewall, six inches, measured from the hinge line of the pedals. If the cables are rubbing because they are too loose then I'd suspect the springs.

[6277]

The rudder return springs are in the parts manual. 0411837-1 for the left and -2 for the one on the right. They are not the same size.

[6643]

Yes, the rudder bars are offset so the loop on one spring is longer to compensate. (Yours look to be the same.) If you use the same spring on both sides the rudder will be pulled off center and you'll fly uncoordinated.

[bzim140]

Thanks for the responses.
The place in the maintenance manual where the rudder cables should be tensioned to not have them touch the side holes in the aft fuselage bulkheads is page 2700/27. Rereading your suggestions about the springs, we realize someone attached the springs to the cable attachment lever, instead of the brake master linkage and also attached to the wrong center console bolt. We will try the correct orientation tomorrow. B. Zimmerman

[6643]

"pilot spring.jpg" appears to show the spring attached correctly, to a small hole in the rudder bar cable horn.

[6643]

Here are some good pictures from the old forum. The first one shows the spring where it attaches to the rudder control horn.

[bzim140]

Thanks all who contributed. Without your photos and advice, we could not have figured it all out. Changes made: Springs were installed on the wrong side and attached to the incorrect points on the center console structure. After correcting those items, the cables were retensioned and do not touch the holes in the aft fuselage bulkheads. The cable tension came out to be 10-12 lbs. The tailwheel chains were slack on arrival. The Scott tailwheel manual had us set them at 25 lbs. The result of all of this is positive rudder control. Thanks so much for your help. The membership was well worth it!!

[8474]

Thanks all who contributed. Without your photos and advice, we could not have figured it all out. Changes made: Springs were installed on the wrong side and attached to the incorrect points on the center console structure. After correcting those items, the cables were retensioned and do not touch the holes in the aft fuselage bulkheads. The cable tension came out to be 10-12 lbs. The tailwheel chains were slack on arrival. The Scott tailwheel manual had us set them at 25 lbs. The result of all of this is positive rudder control. Thanks so much for your help. The membership was well worth it!!

The Scott installation instructions that are posted on the association website says there should not be any tension on the chains, just no slack.

John, what is the correct tension on the chains?

[6643]

Which tailwheel? The 3200 should have just enough tension to eliminate slack. The springs are very heavy. Scott P/N 3239 spring kit. For the 2000, stretch the springs approximately one inch when installed, (this will produce a tension of approximately 25 - 30 lbs.) The correct springs are Scott P/N 2134.