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So….how do you diagnose poor rigging in a plane ?
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There is a lot of experience among the readers here on BCP, and many of you are building or have built in the past. Whether you are buying a used plane, renting, or building your own, Captain Obvious says making sure a plane is “ properly rigged” is important.

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MTV in two separate posts discussing ACA Scout and Husky Aircraft wrote:
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As I noted, they did have some quality issues some time back. I've also seen some really badly rigged ones (and Super Cubs, as well), so have someone take a good look at it first.
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Pay particular attention to the wing rigging first time you fly it. Start out with some gentle stalls, and gradually work your way into more aggressive stalls. If it rolls off hard anywhere for any reason you can't explain by your control inputs--GET IT RIGGED RIGHT. I've seen a couple of these airplanes brand new which were rigged REALLY badly, and which had really ugly stall characteristics. Find that out on a test flight up high, not on short final to some high DA backcountry strip, and get it fixed. Scouts are easy to rig right.

Here is an interesting link with lots of information:

http://bondline.org/wiki/Rigging_Checks_and_adjustments

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Rigging Checks and adjustments: “Significant performance changes can be obtained by removing the errors and getting the plane correctly rigged. “

Clearly different planes (Bearhawk vs Cessna 180) and different configurations ( Bush wheels, floats, etc. ) will affect the checklist or matrix.

If you look at enough used aircraft for sale you see some projects that are stunning and perfect, while others don’t even mind using duct tape on the dash to cover an out of service instrument. In terms of Certified Aircraft, in 2015 hopefully most manufacturers have cleaned up their quality assurance act and are putting out a decent product. The same goes for the kit guys like Rans, Bearhawk, and Just Aircraft.



So what do you look for to ensure the plane is properly rigged?
What actual flight procedures will help diagnose various shortcoming?
Does anyone have a check list for their particular aircraft?
Does anyone have a Matrix Set up that has Problems vs Solutions listed?

Grab a smart Level and start comparing measurements from opposite sides. You can get the plane relatively level (laterally) on the ground by letting air out of tires and such. Measure dihedral, washout, control surface deflection, etc. Also, once level, check that your ball is centered so when you go flying you at least know it's pretty close.

Also, don't forget that adjusting one thing can change something else. Example: On a cub, adjusting dihedral/washout will change tensions on the aileron cables.

Easy, start in the cockpit, center the stick/yolk, even the rudder pedals, jump out and look at the deflections/differences.

I'm also curious to know if there are things to really check for when getting a say a quick build kit. Weighing each wing, or running a laser level line down the fuselage, etc.

Years ago Lexus used to run this TV ad about how they could roll a marble along the gaps between door panels or where the trunk met the fender line. All was uniform. I look at my Jeep Grand Cherokee and it is anything but.

Reading the many posts on various websites, I have gotten the impression ( false or correct?) that certain planes have that Lexus-like quality of fit and finish, while others are less so. Moreover, it seems a scratch built plane will sometimes sell for less than a kit built, again due to concerns about average scratch vs average kit built quality and consistency. Although clearly we have all seen scratch projects that far exceed any certified or kit built aircraft as well.

We all remember what happened with the Hubble Space Telescope in the beginning. It's the little things that sometimes can mean a lot.

If you're familiar with the make/model, it's not too hard to tell if it's rigged well or not. Most older airplanes which haven't been re-rigged for a long time will be out of rig because of cable stretch, and often we just live with it, unless it's uncomfortable to fly. That's what led me to have mine re-rigged a few years ago--the comfort had gone out of it, because I was having to maintain rudder pressure and opposite aileron during cruise, in order to fly straight and level. After re-rigging, I could (and can still) fly by trimming the elevator for level flight and taking my hands off the yoke and feet off the pedals. That's the essence of a properly trimmed airplane, that it will stay straight and level without any pilot input.

That's not everything, of course. There must be full elevator travel and full rudder travel, and it's entirely possible to be out of rig in such a way that there's more control surface travel one way than the other. That's where proper measurements come in, so that the control surfaces move the way that they should and as far as they should.

It's also possible for an airplane to fly well, but to have both ailerons drooping a little. It'll fly OK, but it will go slower than it should in cruise. My airplane gained a couple knots, because that problem in mine was corrected during the re-rigging. Or perhaps the flaps don't retract quite all the way; that will cause the same excessive drag.

It's less likely that wing washout will be unequal, but that can happen if the airplane was in even a minor ground accident and careful reconstruction wasn't accomplished.

And of course there's the simple issue of a bendable rudder trim tab being bent too far one way or the other, which can make even an otherwise properly rigged airplane seem out of rig.

Way back in ancient times when I was learning to fly, the 150 I flew on my long cross country was horribly out of rig--let it go, and it would go into a pretty steep right bank almost immediately. The easy solution was to hang the hand mic over the left side of the passenger yoke. The weight and tension from the mic cord was exactly right that the airplane would fly straight and level with just me in it. Now that's re-rigging at its cheapest!

Cary

Ref: post #1

In defense of ACA, my little Scout was rigged very well (opinion) from the factory. She is dream to fly straight, stall, etc etc.

Carry on men...good thread.

Some if not most factory airplanes have some sort of rigging procedures, usually spelt out in the shop manual. You can "fix" an out of rig condition, at least to the extent of the airplane flying (pretty much) hands off, by band-aiding the problem (say with a trim tab) but if you have the time patience and ability (or money) it's probably best to start from square one. I will say that a lot of cessnas are out there flying around with the aft spar attach eccentrics dialed all the down on one wing and all the way up on the other, in order to fly straight-- sometimes even with a little droop on one aileron to help.

I usually try to get behind the plane and look at it.... usually differences are easier to spot from wing to wing from behind. I tend to look at flap gaps and aileron positions as well as lining up the vertical and horizontal with the wings to eyeball how square things look, for starters.
Every plane, certified or not, has rigging instructions. Some are more technical than others. I've seen them range from one sentence to a whole book.....
Rigging can range from cables to whole surfaces....and it's all worthwhile.
JH

hardtailjohn wrote:I usually try to get behind the plane and look at it.... usually differences are easier to spot from wing to wing from behind. I tend to look at flap gaps and aileron positions as well as lining up the vertical and horizontal with the wings to eyeball how square things look, for starters.
Every plane, certified or not, has rigging instructions. Some are more technical than others. I've seen them range from one sentence to a whole book.....
Rigging can range from cables to whole surfaces....and it's all worthwhile.
JH

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What he said. There's rigging of the wings on many airplanes, but not all, and then there's rigging of the control surfaces on all airplanes. Get the rigging right and the plane will fly hands off or nearly so, it will stall straight and predictably and it will perform close to the manufacturer's specs.

Some airplanes have fixed wings....no adjustment available. An example is the Found Bush Hawk. That is a one piece wing, essentially....so the dihedral and wash is fixed....no adjustment available. You rig those by re-rigging one flap if necessary. Creates a little drag, but it's all you've got.

MTV

Maybe not "Badly" rigged, but a fixed trim tab on any control surface is a clue something isn't quite right.

CPA has a great writeup on rigging Cessnas, but there is good info in there for everyone.

You have to have a good starting point. The first thing I do is check the ball, level the airplane per the manual, then make sure the ball is centered. All rigging starts from there. Fly it with the ball centered, and you can learn a lot. Does it stall straight ahead? Does it have a heavy wing.

Ailerons are generally not messed with for heavy wings, since they will trail to a neutral position. A trim tab on an aileron on the other hand will help, but I generally consider that a band aid. Cessnas fix heavy wings with the eccentrics, most rag wings I am half familiar with will lengthen or shorten the rear strut (but I'm not much of a rag wing guy, so don't quote me). On Cessnas, if you have to use flap to lift a heavy wing, something else is wrong.

If a Cessna does not stall straight ahead, it can be poorly built wings (or not coordinated, but that isn't the airplane's fault, Right?). There is a simple procedure spelled out in the service manual for measuring wing twist. They are supposed to have no twist between the root and station 100, and 3 degrees of twist between station 100 (the rib at the strut) and the tip (except the 170A, I think it has 1.5 degrees, 140A may be different as well). I've measured A LOT of wings, factory original, wings built in good and bad jigs, wings built on saw horses, and none of them measured 3 degrees. The ones that I considered "perfect" based on my knowledge of their history or repair all measured 2.8 degrees. The fact is, it doesn't matter as long as they are equal. If one has more or less twist, the airplane may not stall straight ahead. That being said, I have flown airplanes with up to 1/2 degree difference in twist left vs. right and they flew well and stalled straight ahead, so there is room for some error, but ideally, they should be equal. Cessna does allow for a bit of slop in this regard, but I can't remember the spec, something like .100" on either end of the measuring rig. I've also heard of guys who wanted to make their Cessna faster so they built wings with no twist, or less than original. In theory it would work, not sure if it did in practice.

Control travel limits should be check as well. It doesn't generally affect flying hands off, but it can significantly affect controllability when you need it most. I was checking out a good friend and good TW pilot in his new to him 180. He had trouble with it darting left on takeoff and I chewed him out repeatedly for it. He let me fly and it did the same thing to me. We finally chased it down to the right rudder travel stop was limiting deflection by a lot. Not obvious on a walk around, but painfully obvious when we flew it and when we measured it per Cessna's book. Aileron travel in a Cessna is not adjustable, at least not via anything in the manual. I suppose you could file out the slot in the bell crank but then you become a test pilot. Elevator travel is adjustable via an eccentric block and up and down travel are adjustable independently.

Sorry if this is a bit random. My world is 180s and 185s, so this mostly applies to them and may or may not apply to others. Rigging a skywagon from scratch can be an all day or more project.

I rig airplanes -Been to and graduated from Cessna Pilots Association Rigging class and have the tools ,knowledge on how to make your airplane fly stright and level at "BOOK SPEED". Some airplanes CANNOT be reset or rigged -mostly from previous damage. Lots of bent wings out there especially on Cessna and piper tail draggers. .Even tri gears can and have been flipped over where vertical fin/rudder is no longer serviceable. 185 owner call me over to do annual and wanted to know why airplane flew all askew with little cheater tabs all flight controls. Stood behind 185 and right wing had been rebuilt ? on pair of saw horse and wrinkle in fuselage -horizontal NOT parallel to trailing edge of wing. Insurance company years before had sold it as scrap after cartwheeling down runway. A&P was told to put nothing in log books or face being fired, simple statement "repainted right wing tip and new plastic on horizontal stab was all we could find. Airplane ended going to Beegles in Colorado for complete rebuild before airplane flew right again .
Rigging take 1 1/2 days to get right and cost $800.00 for single engine up to 210 -210 is additional 600 bucks. Evaluation is $200 bucks if you want to see if we can do anything. If you decide that we can do the job Evaluation is absorbed to rigging. cost. These cost ar at AZ50 if additional travel is required expenses additional.