The International Cessna^® 170 Association

Yesterday I went out with the CFI and went to several grass strips and several other airports for more practice.
On returning home, I had a little more trouble keeping the plane straight ... nothing severe, just seemed like I was working more to maintain directional control on landing. I just figured I was tired.
When I went to pull the plane back in, I found both tailwheel chains dangling in the breeze! The teardrop shaped clips (http://www.aircraftspruce.com/catalog/l ... prings.php) that attach to the horns on the tailwheel had both bent almost straight - not broken, just bent to where they came loose...? Seems like this would be tough to do, the way they are designed an axial load should not really be able to straighten them.
My landings were good - there were no hard landings, no tailwheel first landings, no hard / full rudder deflection in either direction. The only thing we could come up with was that on the grass runways there is a little bit of undulation, so on takeoff the plane would undulate a little before becoming airborne. If this was enough to compress the flat spring of the tailwheel assembly up towards the rudder, then it could have loaded both springs at once and maybe the clips were the weak point...?
I don't think the TW springs are too tight ... any guidelines for this?

Anyway, as Stu said, that just shows that you don't need the tailwheel to fly - the plane is plenty controllable with rudder alone! Good learning experience.

Thomas

Pictures:






Thomas

I have never seen that kind of clip come undone. I would heve to suspect that they were not properly installed to start with. If they were properly installed, I would expect to see the sharp angles of the clip to be pulled straight in order to be pulled out of the steering arm. I don't believe that would be possible without distorting the steering arm or some other part.

I agree with blueldr, those got pulled apart both of those sharp bends should be inside the chain link so they can't get pulled apart.

Thomas, I could not tell form the picture but there is supposed to be a guard on that little clamp about halfway up your spring. Mine did not have one, and I have seen the chain get caught on the clamp resulting in a hard swerve on landing, that could also be what straightened the clip. I made one from a hose clamp that was lying around and solved the problem. Also, I'm not sure it makes a difference, but normally the springs connect to the rudder horn (I believe that is just semantics, though).
David

Yep. I suspect Dacker is right on target. See the IPC for the guard (PN 0442125) which prevents the chain from hanging up on the shackle.

I can't tell for sure from the picture, but the springs look like they might be compression springs and/or too small to me. Are you sure you have the right springs?

I know both of the ends of the clip were properly installed ... the first time I preflighted the plane one was loose and I check them on every preflight now.

Anyone have pictures or a link to a part for the guard? I'm not sure what you're referring to. Not sure how to determine if they are the correct springs - doubt there is a part number anywhere.

Is this what should be used:

http://www.aircraftspruce.com/catalog/l ... prings.php

For 20$ I might just replace them (if that's the correct part) - I need to order some stuff from ACS anyway.

It is bewildering ... especially where the bend is. I posted some pictures on other forums and didn't get any answers - mostly stuff about jamming the rudder pedals around and making rapid / rough control inputs while on the ground. There was definitely none of that, not even a hard landing (not a testament to my skills, we just had a cool spring day with no winds and the flyin' was great!)

Thomas

Thomas,

The springs in the link you posted are compression springs and are not the correct spring for the 170. The 170 uses tension springs, which are simply coils with a hook at each end, as seen at http://www.aircraftspruce.com/catalog/l ... prings.php . I don't know for sure whether Spruce's springs are approved on the 170, but I suspect they are.

Do a search in these forums for previous discussions on compression vs tension springs.

Miles

I hate it when you guy’s do this now I have to ride all the way out to the airport and see if I have the correct springs with guards and I will probably even have to do a test flight to make sure they work correctly on multiple landings.

Interesting reading.
I wonder if the lack of "give" in the compression springs led to the failure of the clips?
Anyone have a part number for tension springs? Might give them a shot. I don't like the idea of the compression springs bottoming out and pulling on stuff back there...

Thomas

cessna170bdriver wrote:Thomas,

The springs in the link you posted are compression springs and are not the correct spring for the 170. The 170 uses tension springs, which are simply coils with a hook at each end, as seen at http://www.aircraftspruce.com/catalog/l ... prings.php . I don't know for sure whether Spruce's springs are approved on the 170, but I suspect they are.

Miles

I believe those springs are for the Scott 2000. I think that Spruce carries the right springs, but does not have them listed in the catalog. They look similar to the ones above. The TCDS requires that the 3200 be installed in accordance with Scott Bulletin I-168 and I think the bulletin has the part # of the springs. I have the bulletin at the hanger and can fax you a copy, but I am out of town until Sunday. One of the other members might have it handy and can get it to you sooner.

That would be great when you get a chance ...
I tried to find it online but can't even find a web site for the manufacturer... ? Anyone?


edit ... never mind, it is scottaviation.com, just well hidden amongst the oxygen stuff. Looks like part #3239-00 spring connector kit. Sound right?


Thomas

In addition to having the wrong type springs installed, it appears that the clips were installed between the springs and the steering arm. The clips are properly installed between the springs and the chain, with the sharp bends of the clip in the chain. This would preclude the clip coming open other than on purpose.

tshort wrote:I tried to find it online but can't even find a web site for the manufacturer... ? Anyone?
edit ... never mind, it is scottaviation.com, just well hidden amongst the oxygen stuff. Looks like part #3239-00 spring connector kit. Sound right?

Thomas

Be careful with the part #'s. Different aircraft use different springs for the 3200. I just had a friend with a Citabria call me yesterday, stuck in Jean Nevada with a broken spring on her 3200 looking for a spare. After looking I realized that Citabrias use a totaly different spring. Asking around I was told that her spring was readily available in the aircraft department of the local hardware store . I understand you can get Cub springs there too. Don't know about 170's.