Rigging Question

[Robert Eilers]

In level flight at 2450 RPM the slip/skid indicator on my 170B is about 1/2 a ball out to the right. I have to continuously apply a little right rudder to center the ball. After tweaking the rudder trim tab I have reduced the ball to 1/4 out to the right - still requires right rudder. I have a descent bend in the trim at this point - not extreme - but descent. I also have noticed that when the aircraft is at rest on the gear with the tailwheel centered the rudder is cocked slightly to the left. I am not sure how far I should go with bending the trim tab, and am curiouse to know if the rudder is purposely rigged to cock left slightly?

By the way I have noticed 170's with a trim tab on the left aileron - some with the trim tab bent significantly up into the slip stream - what is going there?

[tshort]

Having just gone thru a similar problem ... have you checked the rudder return springs? Sounds like the one on the L side of the cockpit might be broken...

Thomas

[doug8082a]

By the way I have noticed 170's with a trim tab on the left aileron - some with the trim tab bent significantly up into the slip stream - what is going there?

170s should not have an aileron trim tab. I they do it's a band-aid fix for a problem that still exists. The trim tab should be removed and the true source of the problem should be found and corrected.

[Bruce Fenstermacher]

Robert

It very well could be the springs.

I've not consulted the service manual but I believe that if your rudder peddals are even your rudder should be straight. Your tail wheel should track pretty closely to the rudder.

The first step in rigging your airplane is to make sure the skid/slip is installed level with the airframe level laterally. If it's not it will give erronious readings.

As for the trim tab one the aileron this is usually an un approved mod that is masking other rigging issues.

There is however an STC'd electric aileron trim system that is available for 170's. My plane has it. It is not effective and I don't recomend it. In order to have any effect at all the tab has to be driven to one extreme or the other and then there is not much effect. This would explain why the tabs you've seen on ailerons have so much deflection in them.

I seem to remember seeing a fair amount of deflection to the left, when looking forward from the back of the rudder, on most 170s. How much is average I don't know.

[tshort]

It's pretty easy to check the springs - pull the cover plate on the underside of the forward fuse and have a peek up in there. Once you've eliminated that start looking at the more complicated stuff.

T.

[Robert Eilers]

Thanks for the help - I'll take a look at the springs.

[GAHorn]

By the way I have noticed 170's with a trim tab on the left aileron - some with the trim tab bent significantly up into the slip stream - what is going there?

170s should not have an aileron trim tab. I they do it's a band-aid fix for a problem that still exists. The trim tab should be removed and the true source of the problem should be found and corrected.

Quite correct, Doug! No aileron tabs are permissible on a 170. (Unless some other basis of approval is provided. The only approved one I've seen is the electric one like Bruce mentions. I've seen that one on two aircraft, and both owners said it was nearly useless.)
I recall seeing a 170 show up at the Tehachapi convention with an (illegal) tab on each aileron... each of which was significantly bent so as to completely counteract each other!

It's probably the rudder circuit problem, like the springs already mentioned.

[blueldr]

There isn't any reason to "look" at the rudder return springs. All you have to do is reach in and pull back on the rudder pedals. If they return forward the springs are intact.

[1SeventyZ]

Does your 170 fly hands off in the roll axis with your little bit of right rudder input? I recently went thru this with rigging my 170. When I bought it, it required constant left aileron pressure and right rudder to fly S&L, and the control wheels were out of level with the ailerons in neutral position.

Through adjusting the eccentric bushings at the rear carrythrough spar connection, and the length of the aileron push-pull rod turnbuckles, we were able to get it pretty damn close to hands off.

[Robert Eilers]

Actually, the C170B flies very well hands off with jsut a little right rudder pressure. I have decided after tweaking the rudder trim tab to the point the ball is about 1/4 out the close is good enough.

[wa4jr]

Sounds like there are a few 170s out there with a heavy left wing as evindenced by the number of them that have an "illegal" aileron tab on the left side deflected in the up position. I had all I can take of my left-wing heavy 170. I flew a long IFR trip down to Florida earlier this month, and when in the clouds I could'nt look away for more that a few seconds at a chart, or else I'm in a left turn 30 degrees off heading To maintain level flight, my control wheels are deflected 20 degrees right....I just hang my arm on the right side to provide the needed counter-weight. All is fine until I need to use two hands for the chart and then woopee here we go into the left turn unless I bring in lots of right rudder to lift the left wing and slip along until my map reading is done. I can look out and see the left aileron down and the right one up....rudder centered and ball centered. Eccentric bolts are frozen and the left wing bolt is in the max down position with the right wing bolt in the max up position...meaning I don't have any more adjustment room to trim out the heavy left wing...even if I could move the bolt What I need is a rigging exorcist....I mean expert that is familiar with the heavy left wing problems. Do older 172s have the heavy left wing? Can anybody suggest someone in the eastern third of the country that knows how to properly rig a 170. At this point, I'll make the special trip and stay in a motel somewhere as long as some can rig the flight controls so that I can fly "hands off" for more than a couple of seconds without my left window filling with green and brown while my right window is all blue

[GAHorn]

John, I'll send you some riggin info, but it's possible you're dealing with a flap or aileron or rudder issues (or a combination.)
If you have a right flap slightly extended...it'll make your left wing heavy.... see what I mean? Check your up-travel and your ailerons.

[tshort]

If you're interested I can send you a list of the CPA (cessna pilots association) approved riggers in your area ... I have heard lots of good things from the CPA guys about getting the rigging done properly.

edit: here is the link to the list - not sure where you are:
http://www.cessna.org/newsite/courses/riggers.html

I have wondered about mine, too - no heavy wing, but when in level cruise the elevator is deflected downward a significant amount...

Thomas

[Bruce Fenstermacher]

John I improved my left heavy wing with careful attention to rigging detail but I didn't eliminate it. In my case I think it's a combination of 50 years of repairs done here and there which could have been done better and the pilot sitting on the left.

I usually adjust it by running the right tank 5 gallons more than the left.

BTW rigging start with your turn/slip indicator. Is it installed level with the aircraft. Then adjust the rudder (don't forget the return springs) and then the wings.

[bradbrady]

Robert,
Lift the tail, if the rudder goes one way or the other, you probaly have a broken return spring. Anything else you have a rigging problem.
brad