Brakes activated with rudder input
I recently purchased a 1949 Stinson 108-3 Flying Station Wagon. I am a new student pilot and intend to use my Stinson to earn my pilot's licence. My instructor has pointed out that the brakes (Cleveland) are being activated with the application of rudder. Not a good thing, as it makes taxiing difficult and landing on paved runways dangerous at best! I / we assume that this is not a "normal" condition. I have tried adjusting the brake clevis downward (shorter) 2.5 turns which was all that I could get out of it with very little improvement. Has anyone out there had experience with this issue? More importantly, does anyone out there have a fix? I would appreciate any advice that may help.
If that is your name? This is a somewhat common situation. You may have gone the wrong way on the adjustment as that would, if I am understanding correctly what adjustment you made, it would seem to shorten the distance between the brake pedal and the master cylinder.
I have experienced this thing myself. I finally realized that I was getting my feet too high on the pedals and inadvertently tilting the top of the pedal as I came in with more rudder. I seem to have solved my problem by consiously keeping my feet low on the pedals with just my toes on the bottom portion of the pedals.
The Cleveland brakes are very good brakes, so much better than the originals, but sometimes they are too good.
Try adjusting the other way and activate the rudder pedals by hand to see if the brake portion of the pedal is tilting and activating or could it be that both you and your instructor are putting your feet too high on the pedals.
Is this your instructor's first Stinson experience?
Some 108-3s used different master cylinders than some of the other dash numbers so that may enter into the picture too.
Larry Wheelock, A&P/IA Owned, flown, maintained my 108 N584LW for 48 years now.
I had a lot of problems with my brakes being activated by the rudder. It turned out I had a mixture of -1 master cylinders and a -3 cable mechanism. I deactivated the park brake which has solved the problem until I get the master cylinders replaced. I would recommend you try deactivating the park brake and see if that fixes your problem. Not a great fan of park brakes anyway.. Does your park brake cable come horizontally through the firewall, or vertically from a standoff welded to the frame..?
As Larry says, it's very easy to inadvertently apply brake if your feet are too high on the pedals.
First, I'd like to thank you both for your prompt replies. Secondly by way of introduction, my name is Jim Duncan, and my Stinson is N4059C. I am based at Indiana County Pennsylvania's "Jimmy Stewart Airport." Please forgive me, I am new to the forum, new to full scale aviation, and although new; very much in love with my Stinson. Then to the heart of the matter. We too originally thought that it was a matter of foot placement being too high on the rudder pedals. So we were then careful to keep both heals on the floor and just use "tippy toes" on the very bottom of the pedals. The results were the same. Then after landing (a dicey affair) we carefully inspected the situation. Using just finger pressure on the very bottom of the rudder pedals (and it did not matter whether we used the left hand or right hand rudder pedals) we noticed that any rudder pedal movement, however slight, caused the "plunger" on the wheel cylinders to begin to move to apply the brakes. A little pedal movement resulted in a corresponding amount of brake application. Full deflection resulted in "locking up" the brakes. Left rudder, left brake and vice versa. We decided to try to "shorten" the linkage thinking that it would provide a little "free play" in the linkage. The theory was that since the brakes were being activated with subtle pressure, to lengthen the linkage would cause the actuation process to just begin sooner. To answer the question about the "parking brake" linkage, the knob is on the lower left side of my panel and it moves horizontally through the panel. I will look at the parking brake situation tomorrow evening and let you know what i find with regard to disconnecting it. Thanks again for your consideration!
Welcome to the wonderful world of Stinsons... My wife and I have had ours for about six months now and really enjoy it - a great aeroplane.
One other thing I discovered, the floorboards had been replaced and there was insufficient clearance between them and the brake cylinder. When you applied rudder, the floorboard pushed the bottom of the cylinder up and applied the brake... Something else to check.
I had the same issue, though left rudder pedal/brake only, and only towards the end of rudder pedal (forward) travel.
The rudder pedal arm would make contact with the bottom (front side) of the pedal and pivot it so that it would apply left brake. More left rudder; more left brake.
The solution was to shorten the linkage. I shortened all of them the same.
...so you know you're not alone...
@n168c I know this is an old thread, but I just got checked out in my new -2 and we noticed the exact same problem. That last inch adds some brake. We joked that its a design feature, rather than a flaw, so the right seat pilot could use the brakes. Definitely more on the left than right, didn't notice on the right, but thats where most of XW was from today.