The ruddervators in a properly rigged V-tail Bonanza aren’t aligned in level flight. As others have noted, it may be that the 180 elevators aren’t supposed to be, either.

Now I’m curious enough to go take a look at the 185. . . .

mtv wrote:And enlarging bolt holes in a torque tube in a control surface would be approved by the FAA?

Whatever winds your watch, I reckon.

MTV

Slap an an970 large area washer over it and it will be fine.[emoji849] Seen it twice on cubs.




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If you haven't already, check the security of the rivets which join the torque tube to the flange which bolts to the bell crank. To do this hold the elevators in each hand and try to gently move them in opposite directions. If there is some play, it could be that the rivet holes in the torque tube have become elongated or out of round from years of stress. If there not too bad, sometimes they can be reamed out and replaced with the next size rivet.

Geez...now I’ll have to go check mine! Troublemakers all...

Since I have not diddled with the elevators recently on a 180 series, but have recently just re-assembled a 206, I will point out one item. If you read the manual of a 206 for example, the elevators are not even and are not supposed to be. There is around a 1.8° split dialed in in the manufacture. This is to compensate for P factor, the air swirling around the fuselage from the prop. It has a slightly different influence on each elevator segment and the twist is to naturally compensate for this. It is there to make it fly straighter.

They may not even point it out in the 180 series manual, since on a 206 you have to rig the trim. This is done by streamlining the elevators and splitting the difference. You accomplish this by making a little jig with two pins pressed on a plate. One pin goes into the hole on the escutcheon on the panel and one on the shaft of the yoke. It puts it in the position, then you rig trim tab travel. There is no tab on the 180 series, but rather a trimable stabilizer. So they may never point this out, except in the drawings.

I checked a couple planes a while back and forgot to reply. My 5500 hr ‘56 182 has uneven elevators, as does a 1800 hr ‘70’s 180. Sure seems like that twist is supposed to be there, and an engineer/pilot I mentioned it to had the same p-factor theory that Dogpilot mentions.

OK...I checked today. My ‘58 182 with 3200 TT and NDH has elevators that are not perfectly aligned. When the right elevator it aligned with the horizontal, the left elevator is raised at the outboard tip about 3/8...maybe 1/2 inch.

After bigrenna's post about post about rigging, Mat (mountainmat) helped me look over my plane. One of the things we found was the elevator issue in this post. It doesn't seem easy to fix as the elevator joint is not adjustable. One of my elevators was either swapped or rebuilt after a ground loop in the 70's. Might be a bent part, might be as designed. When reinstalling the tail after completing the service bulletin my IA noticed the difference. He thought the elevators may be aligned like that to counteract left turning tendencies. If that's the case you would expect the right to be more drooped.

Next time you are at a fly-in check everyone's elevators. My bet is that they're all a little off. Doesn't mean it doesn't bother me until I get it figured out for sure.

dogpilot wrote:Since I have not diddled with the elevators recently on a 180 series, but have recently just re-assembled a 206, I will point out one item. If you read the manual of a 206 for example, the elevators are not even and are not supposed to be. There is around a 1.8° split dialed in in the manufacture.

Are you saying that the manual specifes this split?

I've been through a ton of single engine Cessna manuals and never seen anything like this, but I've never worked on a 206. I just went through a couple here out of curiosity and did not see any mention of this. One thing I did notice is in the elevator rigging section it references that the travel of the elevatorS (as in plural) should meet the spec in section XYZ. They do list a tolerance of +/- 1 degree usually, which would lead me to believe that they could be off as much as 2 degrees relative to each other in either direction and be in spec.

I love being wrong if I get to learn something, so I'd love to see something in a Cessna manual.

Second-hand info, but I did find this:

Per the Cessna Model 206 and T206 Service Manual, chapter, 8 Elevator Control System, figure 8-2, the R/H elevator is slightly in the nose up position with the L/H elevator streamlned. I believe that there are several other aircraft rigged the same way, but this one I'm pretty familiar with. They use this to counteract torque along with the offset of the vertical fin. Probably most of the higher horsepower singles have this feature.

Discussion here: https://www.askbob.aero/content/elevator-rigging

Here is the excerpt for the 206 manual:

Elevator Control Adjustment/Test
A. Rig Elevator (Refer to Figure 202 and Figure 203).
(1) Fabricate a Neutral Rigging Tool from 0.125 inch (3.18 mm) steel plate, 0.209 inch (5.3 mm)
diameter drill rod, and 0.250 inch (6.35 mm) diameter drill rod. (Refer to Detail B).
(2) Remove access plate (310BB) and fairings (340AL and 340AR). Refer to Chapter 6, Access/
Inspection Plates - Description and Operation.
CAUTION: Position a support stand under tail tie-down to prevent the tailcone from dropping while working inside.
(3) Install the neutral rigging tool to lock the elevator control in the neutral position.
(4) Streamline the left elevator to neutral with horizontal stabilizer.
NOTE:
NOTE:
Do not attempt to align the elevator trailing edges as there is a 0 degree 54' twist designed into the connecting torque tube. This twist causes the right elevator to be higher than the left.
Disregard counterweight areas of the elevator when streamlining. These areas are contoured to be streamlined at cruising speed (elevators approximately 3 degrees down).

dogpilot wrote:Here is the excerpt for the 206 manual:

Elevator Control Adjustment/Test
A. Rig Elevator (Refer to Figure 202 and Figure 203).
(1) Fabricate a Neutral Rigging Tool from 0.125 inch (3.18 mm) steel plate, 0.209 inch (5.3 mm)
diameter drill rod, and 0.250 inch (6.35 mm) diameter drill rod. (Refer to Detail B).
(2) Remove access plate (310BB) and fairings (340AL and 340AR). Refer to Chapter 6, Access/
Inspection Plates - Description and Operation.
CAUTION: Position a support stand under tail tie-down to prevent the tailcone from dropping while working inside.
(3) Install the neutral rigging tool to lock the elevator control in the neutral position.
(4) Streamline the left elevator to neutral with horizontal stabilizer.
NOTE:
NOTE:
Do not attempt to align the elevator trailing edges as there is a 0 degree 54' twist designed into the connecting torque tube. This twist causes the right elevator to be higher than the left.
Disregard counterweight areas of the elevator when streamlining. These areas are contoured to be streamlined at cruising speed (elevators approximately 3 degrees down).

WOW that's interesting! Thanks for sharing. I'll be re-reading my skywagon manuals to see if I can find anything like that.

Yes, very interesting discussion. Cessna never mentioned this in any of the C180/185 MM's.

I can understand why it would never be mentioned in the Maintenance Manual, you don't have to rig it, just bolt it together. It would be in the actual engineering drawings that very few, if any people have. It is in the 206 manual, since you do have to rig it and I suppose more than one person asked and they finally put it in there to stop all the questions. The only time I ever saw actual engineering drawings of a Cessna was at Soloy while we where doing the Twin Pac conversion, since it was a sponsored Pratt & Cessna project. They tend to guard those.