In classic Internet fashion, I've been told that only a very few experts can be trusted to examine and adjust the flight and ground rigging of a Skywagon.

I know of Del in Mena, but he's 500 miles from Indianapolis, in a hard-to-get-to place to boot. Who else is there who'll put the thing on grease plates, etc.?

niente qui

I was going to type out a lot of stuff but Dogpilot nailed it. The idea that this stuff is rocket surgery is hilarious. RTFI will cover it, that and make sure you don't have a bunch of dished corrugations on the control surfaces. I've fixed a heavy wing on several birds just by drilling out 6-8 rivets on the trailing edge of an aileron/flap/rudder and straightening out the corrugations.

The toad won't hurt though...

Just to tag on - following the MM to the letter achieves good results. That said, I will add that the later MMs added some helpful details/clarifications to the process missing from the earlier (esp. 100 series) MMs. Finally, the old CPA had some rigging technotes that filled in whatever missing bits there were.

What could go wrong? First off, how many APs have had their tensiometers calibrated recently? Second, safety-wiring turnbuckles with 0.040" wire sucks. And, the turnbuckles have such a coarse thread that a tiny inadvertent turn results in a 10 lb tension change. Oh yeah, some homemade tools make the whole process go better - aileron bellcrank rig pins, for example.

C180_guy wrote:Just to tag on - following the MM to the letter achieves good results. That said, I will add that the later MMs added some helpful details/clarifications to the process missing from the earlier (esp. 100 series) MMs. Finally, the old CPA had some rigging technotes that filled in whatever missing bits there were.

What could go wrong? First off, how many APs have had their tensiometers calibrated recently? Second, safety-wiring turnbuckles with 0.040" wire sucks. And, the turnbuckles have such a coarse thread that a tiny inadvertent turn results in a 10 lb tension change. Oh yeah, some homemade tools make the whole process go better - aileron bellcrank rig pins, for example.

Maybe not the most technically challenging work but based on the above comments I would think having expertise and a passion for rigging would be beneficial. I have this weird aileron trim that was installed back in 1992/93 for god knows why. Probably because the plane was not flying straight. I plan on painting the airplane this winter and will remove the device but I have a feeling I should also check the rigging. When I was a CPA member I heard positive comments about John Efinger. Of course he is in Texas. A long haul for some of us.

http://www.cessnarigging.com



Josh

John is highly regarded in the Cessna community. By the way, a lot of the former CPA folks, including John, are now over at Cessna Pilots Society. CPS is free and fairly active.

Thanks for the input, guys. Sounds like my local guy could do it. Maybe I should read the manual out loud, just in case.

Assuming he’s never done a Skywagon before, any guesses on how long it would take to do the gear?

And thanks again for the input. BCP is a rare bastion of common sense on the Internet.

Re rigging wings & flight controls-- I believe that Cessna Owner Assn (CPA?) used to offer specialized rigging courses,
an A&P could take them & thus be a "certified Cessna rigger".
Years ago, a guy on my airport took his C182 to such a rigger, in Monroe WA,
and had nothing but good to say about how much better his airplane flew afterwards.
YMMV

niente qui

Dogpilot, any chance you could show a picture or sketch of what the shims look like properly installed? I don’t have any darting problems, but the outside of the tire wears faster than the inside, requiring tire flipping every 100 hrs or so. Thx!

niente qui

I wrote this a few years ago...I think it covers gear alignment pretty well

I've been working on these airplanes for a long time and one thing that I believe causes more ground loops than anything else (besides pilots) is bad wheel alignment. Any of us who have flown multiple 170s, 180s, or 185s have experienced different ground handling characteristics between seemingly identical aircraft. Some are just squirrelly on the ground. Whenever I fly one that is like this, I look 3 places, the first of which is the main gear alignment. Second and third, just so you don't have to ask are tailwheel steering and rudder rigging, but that's for another day. I sat down to write this so hopefully more folks can keep from wrinkling up their airplane and their ego. I hope it helps.
The first thing I do when leveling an airplane is lock the gear leg in the gear box. This is done with a pair of shim/wedge assemblies on top of the gear at the outer gear leg bracket. These 2 wedges are loose on about 20-25% of the airplanes that I work on. You'll notice them being loose when your taxiing around and you hear a clunking noise coming from the gearbox. Sometimes you can hear it after lift off with an unbalanced tire/wheel shaking the gear leg as they slow down. The way to check for a loose gear leg is to have your helper shine a light from outside UNDER the gear leg into the gear box. You take a mirror and look UNDER the gearleg from inside the gearbox. If you see light coming through between the gear leg and the outer bracket, itʼs not tight enough.
To tighten the gear leg in the bracket, you need to lift that side of the airplane somewhere besides the gear leg since you need the gear leg dangling in the breeze. There are a few ways to do this. You can use a cherry picker and lift on one side of the engine mount where it meets the firewall, donʼt use a chain, youʼll screw up your engine mount and who knows what else. The other easy way is a screwjack/stiffleg under the wing just outside of the strut. I suppose you could use the float lifting rings if you have them as well.
Once the gear leg is dangling in the breeze, you can tighten it up. This is done by tapping the wedges in a touch further or adding shims. You can only push the wedges in so far before a thicker or additional shim is needed. You donʼt want the shim riding up into the radius of the bend in the wedge. If it gets this far, take it apart and add a thicker or second shim. The installation should have the shim(s) pushed inboard as far as possible and then the wedged tapped in to where it gets tight. DO NOT use the bolts to draw the wedge in to place, they are there just to hold the wedge once it is installed. I usually put the bolt in place just to maintain alignment of the wedge/shim while I tap the wedge into place on either side of the bolt. Once it is seated, I tighten the bolt to the appropriate torque spec.
A couple notes on this step.
You donʼt pound the wedge in with a 2 lb. sledge hammer and your biggest swing. I use my smallest ball peen and a brass punch with medium tap taps. When it seats, youʼll feel it get solid.
The gear leg probably has some room to pivot fore and aft in the slot of the outer bracket. One of the most reputable shops in the rebuild business usually sets the gear at the front limit of the travel. I have no idea why or why not. I like to set it at the aft end for 2 reasons. The first is the majority of the loads the gear sees will be up (landing) or aft (hitting bumps and braking). If the gear is already as far aft as it can go, these forces wonʼt move it. The second reason I like to set it at the aft end is, if the gear moves, it will move forward and change the alignment to more toe in. Toe out is bad news and unexpected toe out is real bad news. Toe in leads to tire wear, toe out leads to insurance claims.
The shims that you use with the wedge should be steel. I like to use 4130 since I usually have that around the hangar. Iʼve heard that the ones you buy from Cessna are aluminum, but I donʼt know because I usually donʼt buy what I can make in 5-10 minutes. Iʼve removed aluminum shims from a loose gear box and found them deformed and smashed, so I prefer steel.
On to leveling...
Now that both gear legs are locked in place in the gear box, we can level the airframe. Cessna specifies 3” as the max difference between the left and right wing tips. With a little effort, you can get much closer than that.
The first thing you do is level the axles. 99% of the hangar floors out there are not level, so itʼs worthless to use that as a reference. To do this, I start with rolling both mains on to a pair of grease plates. You may or may not need to do this until you start aligning, but Iʼm a picky bastard and it canʼt hurt.
I am quite fond of a water level. This can be crafted at your local home improvement store (blue or orange store, it doesnʼt matter unless you have a preference who is going to frustrate you that particular day). Buy yourself 30 ft of 1/2-3/4” ID clear plastic hose and fill it with water. The beauty of water is it is damn near always level when left alone. Accuracy can be improved with the use of “Organic Leveling Water”, but it is hard to find a good source and Iʼm not sharing mine.
Take the ends of the hose and hold them up by the inside of the gear legs where the axle bolts are. Using a matching pair of left and right bolts (top front, bottom rear, it doesnʼt matter, just use the same on both sides) in comparison to the water in the hose, you can see which side is higher. Pick the high side and let some air out of the tire. Keep bleeding air until the two bolts you picked are level according to your water level. Check your water level for kinks because they can throw a wrench in the works. Then grab a strut and shake the airplane side to side 3-4 times to make sure it is settled. Now check the axles and make sure they are level again. Once you are confident that they are level, we can move on.
Move the ends of the hose to the tie down rings at each strut. You can wire them in place if you are working alone. Measure from the bottom of the wing to the water level

in the hose on both sides. If you want to be real picky, you can buy 40-50 feet of tubing and do this same trick at the wingtips, but unless your wings are tweaked, we can assume that they are straight between the strut and the tip, right?
Now that youʼve measured between the bottom of the wing and the water level, measure again. Once you are confident that your numbers are right, you can decide which wing needs to be raised, if any. Whichever side has a smaller measurement is lower, so we need to raise it. We raise it by adding shims under the inboard end of the gear leg. I donʼt remember how much shim will lead to how much change at the tip/strut so I just experiment. This is another shim I prefer to make out of steel. I usually have some .025” and .040” 4130 around, so I just cut it in the shape of the end of the gear leg, drill a 7/16” hole, and slide it into place. Then check the tightness of the outer wedges again. Set the airplane down and repeat everything above. Repeat until the measurements are within whatever tolerance you set for yourself. If youʼre happy with Cessnaʼs 3” at the tip, go for it. My dad taught me to fly and he was a hardass, so if I couldnʼt maintain 1/2 of PTS standards, I did it again. I guess that carries over to my wrenching most days. The 170B I did last night I had within 1/16” at the strut. For what itʼs worth, most airplanes I work on are pretty close with NO shims. Unless 1 gear leg has been changed somewhere along the line, they tend to be equally sprung.
Now that the airframe is level in relation to the axles, we can align it. Personally I like to load the airplane to whatever the typical load is for that particular user. For my airplanes, I load them with full tanks and 2 people up front. This is a good middle ground for my operations. Some folks say the change in toe is so slight that loading it is unnecessary so last night I checked the alignment on a 170B with 180 legs before and after I loaded it with 400 lbs in the front seats. The toe on each gear leg changed around 1/16” so a total of 1/8” difference loaded vs. unloaded. Factor in 240 lbs of gas and the change could have been even more. If I recall correctly, the Cessna Manual even states that loading it to “typical” weight is necessary prior to alignment.
So now it is loaded to a normal operating weight and back on the grease plates. Give the strut a couple of good shakes to let the gear “settle” in to a happy place. Now take an 8ʼ straightedge and set it on a couple of coffee cans in front of the main gear tires. You want the straightedge to touch the tires. Take your friendly square and place it up against the straightedge just inboard of the tires. The perpendicular edge should be placed against the brake disc. It may (probably will) touch either the front or aft edge of the disc.
It should be noted here, or maybe earlier, that the wheel bearings must be snug and the brake discs should have minimal runout. It either is in questions, Iʼll address that when the wheel is in the air back during the tightening of the gear leg in the box.
Make note of where there is a gap between the edge of the square and the disc. If the gap is behind the axle, the wheel is toed in. If the gap is ahead of the axle, the wheel is toed out and the aircraft has likely scared you at some point. Now that youʼve noted the toe, take a look at the camber. The camber is a secondary priority to toe for me when I

set up an airplane, but you can usually get it very close to book specs as well. Now that you have an idea what needs to be changed (or not messed with), you can adjust as necessary. Between the axle and the gear leg are the shims for adjusting the toe/ camber. They are tapered on a diagonal so they adjust toe and camber at the same time. You may need to simply adjust the position of one of the existing shims, or change or add shims. I think the Cessna manual allows for up to 3 shims, but you rarely need more than 2. My manual is at the hangar as I write this, so forgive the ambiguity in referencing it. Now the manuals (parts and service) both give a real neat chart that tells which part number shim affects camber and toe and in what way. Iʼve never found this chart to be useful because I have never had a new shim with a part number on it so I could tell which one I had in my hand. Iʼve had much better luck looking at what change needs to be made and then saying “I need more camber and a touch of toe in, which of these shims in what position will give me that?” Then I bolt it together and repeat the measuring step. You may need several tries to find the sweet spot. Once you find it, take it all apart and replace the axle bolts and nuts. Since they have probably been in there since Clyde put it all together back in Wichita.
One note on the axle bolts, The 170 and 180 originally specified AN5 and AN6 bolts, with NAS145 and NAS146 as optional for ski applications. The NAS are significantly stronger, but Iʼm not sure you need it. Clevelandʼs double puck, 6 bolt wheel STC allows for the NAS bolts on 185s to be replaced with AN bolts. Personally, I think on the average airplane is probably fine with AN bolts, and since the NAS bolts are spendy (~ $20 each), plus you need the special washers, most airplanes seem to end up with AN. Now you know, make your own decision.
Now Cessna lists the toe in spec as 0-.12” per wheel measure at the wheel flange, which is pretty close to the diameter of the disc, so I like the disc. Like I said before, I like to get it down to half that, so 0-.06”. If I have to settle with the camber at the extremes of the spec, but get the toe in nailed, Iʼll take that over the other way around.
Once you get it all bolted back together, youʼll notice immediately that the airplane is easier to push in and out of the hangar. It will taxi with less power and your tires will last longer. It will be easier to handle on takeoff and landing roll and be less likely to jump up and bite you, but donʼt get too comfortable...

Tony, will that process make our airplanes bespoke?

Excellent post, Aeropod! Very comprehensive.
Thanks for taking the time to write that all up.

jrc111 wrote:Dogpilot, any chance you could show a picture or sketch of what the shims look like properly installed? I don’t have any darting problems, but the outside of the tire wears faster than the inside, requiring tire flipping every 100 hrs or so. Thx!

My last two airplanes were both set up with quite a lot of positive camber--
in other words, the wheel "leaned out" at the top.
They tracked just fine, so the toe-in was right,
but the outboard side of each tire wore faster than the inboard side.
No big deal, I just flipped them on the wheel at every annual.
I actually kinda liked it, seems like you'd get more life out of the tires that way.
Plus, that way it seems like you had more tire on the ground when the gear deflected.
My current airplane is set up with the camber pretty much neutral--
I've thought about tweaking in a bit more camber,
but it handles so well I don't want to mess with it.

Thanks, Aeropod!

The rest of you, too!

StuBob wrote:Thanks for the input, guys. Sounds like my local guy could do it. Maybe I should read the manual out loud, just in case.

Assuming he’s never done a Skywagon before, any guesses on how long it would take to do the gear?

And thanks again for the input. BCP is a rare bastion of common sense on the Internet.

I would like to know the difference in rigging a skywagon and a 182 through 182D. I would say none.

asa wrote:Tony, will that process make our airplanes bespoke?

Not this process alone, but it's a good start.

qmdv wrote:

StuBob wrote:Thanks for the input, guys. Sounds like my local guy could do it. Maybe I should read the manual out loud, just in case.

Assuming he’s never done a Skywagon before, any guesses on how long it would take to do the gear?

And thanks again for the input. BCP is a rare bastion of common sense on the Internet.

I would like to know the difference in rigging a skywagon and a 182 through 182D. I would say none.

Not much, the C and D models got a different rudder, I know nothing about the specs on that. I honestly don't know if the rudder travel specs were the same between 180 and 182 during those years either. Rudder travel is a hot button on these things. It's almost always not right. You can imagine how insufficient rudder travel on a 180 could interfere with ground handling. I've rigged a few 180/185s in the last new years that were a handful on takeoff and landing. They were ALL short 1-1.5" of rudder travel. It blew my mind that someone would let it out the door like that.

qmdv wrote:I would like to know the difference in rigging a skywagon and a 182 through 182D. I would say none.

Except for rudder. There are some big nuances. Rudder trim, tailwheel tension, etc.

Aeropod....Thanks for your very comprehensive description of rigging of Cessna gear.

I have had a few folks call me for some instruction in a Cessna taildragger, because they were really struggling. Without fail, those wound up being badly rigged gear.

And, frankly, most mechanics HATE rigging Cessna gear, it's messy and takes time and patience. BUT, properly rigged gear is absolutely vital for safety.

Frankly, any more, I'm pleasantly surprised when I fly a new to me Cessna taildragger that has really well rigged gear.

With regard to the wings and Dogpilot's comments on damage and new: I picked up a brand new Cessna 185 in 1986..a 85 model with a total of 22 hours on it. Before I flew it, doing a pre-flight, I noted that the inboard ends of the flap and aileron on one side didn't fair.....the inboard end of the aileron was a good inch higher than the flap end. So, I pointed this out to our Chief of Maintenance, who called their check airman, who'd done the acceptance flight. That guy (who shall remain nameless) said the plane flew just fine. I argued the point for a while, but got outvoted in the end.

So, I headed north with the plane, and indeed, it flew just fine, stalled straight, etc, etc. In fact, it was rigged very well.

Flew that airplane for four or five years. We got a new Chief of Maintenance, and I took the plane in for it's annual at the shop in ANC. The new Chief looked at that aileron and told me that was going to get fixed. They did. This airplane was equipped with a Robertson STOL kit, which requires significant additional balance weights to be installed inside the ailerons. It seems that in the process of putting that aileron back together, the RSTOL folks had effectively straightened the trailing edge of the left aileron.....and only the left.

While I was waiting for the plane, I looked at a bunch of 185s, and found two others that had the same issue with left aileron. Both were 1985 models, both had RSTOL kits installed.

Only thing we could figure was that Robertson's left aileron jig got tweaked, or????

Anyway, it flew just fine after the mechanics re-rigged it properly to factory specs.

MTV