Wing Heaviness

How to keep the Cessna 170 flying and airworthy.

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Wing Heaviness

Postby flyboy122 » Wed Mar 18, 2020 2:29 am

Hi Folks,

My 170B has a slight left wing heavy tendency. On a glass smooth evening if I let it go it will gently roll left. Usually I just lean my foot on the right rudder pedal and that picks it up, though that does result in the ball slipping out a bit. Before I start messing with rigging I just want to make sure I'm messing with the right things.

The easy thing would be to just tweak the rudder trim tab. Like I said, that does pick the wing up nicely but puts the ball out a bit. Is there something else I should be looking for? Aileron rigging, incidence adjustment, ???

It's got the 180hp/CS prop Avcon conversion if that makes a difference.

Thanks,
Dennis Martin
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Re: Wing Heaviness

Postby dstates » Wed Mar 18, 2020 2:48 am

Are your rudder return springs in good shape?
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Re: Wing Heaviness

Postby DaveF » Wed Mar 18, 2020 2:51 am

I get wing heaviness when fuel draws unevenly from the tanks.
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Re: Wing Heaviness

Postby ghostflyer » Wed Mar 18, 2020 7:59 am

Check your aileron rigging, it’s very easy . Remove the panel under your aileron bell crank quadrant in the wing and it has a rig pin hole in it . You can use a Phillips screw driver [number 2 ] as a rig pin . Be careful that the controls are not moved by any body else . This should lock the aileron control. See if the ailerons are faired and see if the flat bottom of the wing is in line with the flat bottom of the aileron. Use a piece of straight edge timber to see the relationship of the under surfaces of wing and aileron. Have a look,at the control wheels in the cockpit and see if the are in the horizontal position . Now at this stage a lot of people will be jumping up and down saying look at your flap trailing edge [rh wing] it should be lined up as per the book. Ok, But what happens if the RH flap has been rigged up and the aileron was rigged to that. Also the wing tip could have had hangar rash and it’s not perfect. The aileron to quadrant push pull rod can be adjusted if necessary. If adjustment is necessary I would use the help of a A/P .
This advice was for entertainment purposes only and please consult the relevant FAA and manufactures manual .
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Re: Wing Heaviness

Postby gahorn » Wed Mar 18, 2020 10:05 am

The airplane rigging should be checked. An Int’l C-170 Assoc’n Member can get the rigging instructions detailed by our former Parts/Mx Coordinator Tom Hall in the Mx Library: viewtopic.php?f=41&t=8196
Tom placed into fairly simple language the Cessna procedure.

If your rudder is centered and your airplane is “square” (IE, Measured from wingtip trailing edge to top of Vertical Stab is the same, both sides), then the flap trailing edges should be equally level with the fuselage shoulder-fairing. (The flap should be lifted by-hand to simulate air-pressures in-flight, as that will remove slop in the flap/roller/tracks.). The control yokes should be centered/level and the inboard end of the aileron should be level with the flap. The outboard end of the aileron will be 1/2” below the wingtip fairing trailing edge. (The original wingtip fairings are not “handed”, IE, they are interchangeable/identical, therefore the ordinary wingtwist which exists in the A/B models outboard of the station 100/strut-attach places the aileron trailing edges 1/2” below the tip fairing.)

If the flap trailing edges are not “equally-level” with the fuselage shoulder fairing, then check the rear-spar attach eccentrics to see if they are equally adjusted. These rear spar eccentrics are where the wing angle-of-incidence is adjusted to affect “wing heaviness.

Hope this helps.
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Re: Wing Heaviness

Postby ghostflyer » Thu Mar 19, 2020 5:49 am

I was trying to explain a very simple method of checking rigging that could be done on a sand bar on a river etc and not having a flat concrete floor . you can use a iPad for the correct degrees of throw of a control surface also . I told about the iPad trick and thought I would use it on my aeroplane . Shock /horror my Lh aileron was way out . My aircraft always flew with a heavy wing and thought due to extensive repairs to the wings . The eccentric bush was at its max limit in the rear wing attach point. It was ME that fitted the new cables , it was me that fitted the control surfaces and it was ME that rigged the aircraft. It was me that signed the paper work and log book. However we have a independent inspection that has to be carried out by a person not involved in the build up of the flight controls . So what when wrong??. I approached the “independent inspector and asked what did he check. He said he went by the book . Then I told him my issue . My issue got around the workshop and a apprentice approach me and told me he saw the old person that I had bought the wreck from playing around [adjusting the flight controls] with the flight controls . Initially when I purchased the parts and wreck all parties thought it was a good deal. But after a time when the aircraft was going back together , I noticed the person that I had purchased the aircraft from attitude changed and he told a number of people I had ripped him off on the deal. I confronted him and he denied everything. I have replaced all aileron ,elevator cables and rudder cables and checked all rigging since . The “new” cables came part of the deal originally were thrown out as I didn’t trust their integrity.The aircraft now flies hands off for some time even with a ratty looking ,dog chewed Lh aileron .
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Re: Wing Heaviness

Postby Bruce Fenstermacher » Thu Mar 19, 2020 10:09 am

There are so many things to check and a sequence to doing it. For example is your turn and slip indicator perfectly level with the aircraft seat rails? If not the ball will be out when in fact you are in trim. As controls go the rudder is the first thing one would be sure is correct. Then focus on the wing components. But there is much more to it that going straight to the rudder or wing.

But in reality there are so many things to consider. Take an inventory of your aircraft for items that would cause asymmetrical drag. Ever so slightly more drag on the left side would cause what you are seeing. Out of balance fuel is another. How sure are you you didn't have more fuel in the left tank than the right? Where you the only occupant in the left seat of the aircraft? Does this slightly left turn tendency change with airspeed or different power setting? All things to consider.

In reality, if we were all honest, there are very few aircraft, not just 170s, that are always rigged exactly straight and level and in a correct fashion.

Both of my 170s had a tendency to turn slightly left. On the first one I spent hours and hours gong over every adjustment in correct sequence. I finally just ran slightly more fuel in the right tank or rested my foot on the right rudder pedal or my hand on the right side of the yoke. My current 170 does the same thing and my answer to it the same.
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Re: Wing Heaviness

Postby gfeher » Thu Mar 19, 2020 12:35 pm

A well-balanced 170 will be ever so slightly left heavy with equal fuel and flying solo from the left seat, especially if you are a big guy like me. Why, because you are sitting to the left of the center longitudinal axis. My plane is well balanced and flies hands off for long periods in calm air. I have fun sometimes by flying hands off and turning the plane slightly by weight shifting. But it's got to be really calm air. And you can only do it slightly in the B model because the effect of the dihedral takes over. It's one of the things I love about the 170 (at least my 170B). So before you are certain that your plane is slightly left wing heavy, fly it in calm air with equal fuel in both tanks and another person in the right seat who weighs about the same as you do.
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Re: Wing Heaviness

Postby gahorn » Thu Mar 19, 2020 2:27 pm

Bruce and Gene both make excellent points, especially the points about the T&B calibration and the dihedral of the B-model.

I want to point out that in my own B-model I’ve investigated this phenomenon about “hands off” flying, and discovered the airplane to be curiously indifferent to what would ordinarily seem to be major issues.
For example, with myself the only occupant and with the right fuel tank indicating 1/2 and the left full... the airplane flew straight and level. (This might lead you to believe that if completely in-balance it would turn Right... but No... it still flies perfectly straight.)
On the way to the Bardstown convention I had the opportunity to deliberately run the airplane for two hours on the left tank only until it indicated slightly less than 1/2 and the right tank Full. This was with two persons, my wife and I, and 150 lbs of “junk and luggage” in the rear seat and baggage area. The airplane still flew straight-and-level.

About twelve years ago or so I had the flaps re-skinned to correct a distinctly incorrect matter. (The airplane had been rebuilt many years earlier and the flaps had a 1” to 1.5” slope from right-to-left at their trailing edges. The right end of the right flap was exactly matched to the right aileron but it’s left end was 1.5” below the shoulder fairing. The Left flap: The right/inboard end was exactly matched to the shoulder-fairing and the left/outboard end was 1.5” below the aileron. Both ailerons were 1/2” below the wingtip fairing and the yokes were level.). It appeared to me that the flaps had been rebuilt on a table and not in a “jig” and that they were both done by the same repairman in the same sequence, perhaps riveting them from right-to-left, resulting in being exactly wrong in exactly the same manner.
The airplane flew level before ...and AFTER... my favorite sheet metal shop re-jigged and re-riveted those flaps to make them exactly straight. When they were re-installed and rigged to match their respective ailerons, we went out and flew the aircraft and... it STILL FLEW PERFECTLY STRAIGHT, despite that rather large change in rigging and flap-profile! With both flaps having been corrected in the same twist/direction I would have, and did expect that the airplane would need to be re-rigged for a left-turning situation after the flaps left-ends were both “raised”. But it had no effect whatsoever.

I have discovered thru the years that the POWER setting of these airplanes can affect this “turning” personality. If the airplane is flown in smooth air with a power setting of ...say, 2450 RPM.... and it’s straight and level.... a change of power will often influence the directional-stability of the airframe. I attribute this to P-factor. An increase in power will slightly/slowly create a left-turning tendency and a power reduction will create a right turn. (Both changes require a minor pitch-trim change to maintain altitude, of course.)

Summation: In my opinion, fuel imbalance and occupant seating has very little influence on “wing heaviness” of a properly-rigged B-model, and I believe that is a special attribute of B-model dihedral.
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