Rigging

Big Ed

Big Ed

N50247 - '79 Super D
Joined
Jul 20, 2020
Messages
1,938
Location
Tampa, FL
Spent an hour banging out spins in my Super D yesterday, working on competition entry. Aircraft wants to spin right, and needs aggressive left rudder prior to break to rotate left. Judges will dock for this.

IMO this indicates rigging issues, probably with washout. Aircraft should break cleanly straight ahead, and should spin easier to left because of slipstream.

Is washout something I can monkey with myself?

On separate note, did some departure stalls. Have done plenty in 150hp Decathlon, but these were first in Super D. Had just me and less than half tanks. The climb angle was quite remarkable. I'd guess I was hanging on the prop at 60-plus degrees for a while. Felt like an astronaut.
 
If you hesitate to mess with tachometers, do not mess with rigging. Rigging is not difficult, but is about ten times more important - uh, make that a billion times more critical than a tach installation.

Yeah - even the lowly Super Cub climbs at a 45 degree angle full power full flaps.
 
Bob Turner said:
If you hesitate to mess with tachometers, do not mess with rigging. Rigging is not difficult, but is about ten times more important - uh, make that a billion times more critical than a tach installation.

Yeah - even the lowly Super Cub climbs at a 45 degree angle full power full flaps.
Click to expand...

I don't hesitate to mess with the tach. I've pulled it out about 10 times trying to sort out the issue. I hesitate with the legalities of the paperwork.

The previous owner monkeyed with washout on the right wing. I think he screwed it up. The way I see it, if I mark and record the turns of the adjusting nut on the rear strut, I should be able to backtrack on any adjustment I make.
 
What about the legalities of the paperwork when messing with lift struts? That is definitely an A&P entry.
 
Big Ed said:
I don't hesitate to mess with the tach. I've pulled it out about 10 times trying to sort out the issue. I hesitate with the legalities of the paperwork.

The previous owner monkeyed with washout on the right wing. I think he screwed it up. The way I see it, if I mark and record the turns of the adjusting nut on the rear strut, I should be able to backtrack on any adjustment I make.
Click to expand...
we tweaked my wings with a half-turn turn of the rear strut clevis end on each side. I used a long enough piece of straight wood (enough to bridge the underside camber of the Citabria airfoil, you'll have to do something else for the semi-symmetrical airfoil of the Decathlon) with a level to verify twist in the direction the plane was rolling after it was reassembled. that half turn on each side did the trick.

assess relative to each side and tips relative to the root, you're a smart fella, you'll be fine. :)
 
Big Ed,

I am having the same issue you had with the Super D. Citabria refuses to maintain a spin to the left, spins well to the right, flys like a dart otherwise. Did you ever have you dihedral checked? If so what was the outcome.
 
VaporGlobalAviation said:
Big Ed,

I am having the same issue you had with the Super D. Citabria refuses to maintain a spin to the left, spins well to the right, flys like a dart otherwise. Did you ever have you dihedral checked? If so what was the outcome.
Click to expand...
No, as I got more experience with the aircraft, I found it flew fine. Issues with spin were not getting full elevator ROM and not holding full control deflection.
 
Before you start changing rigging look at your latest weight and balance info. If it's old look into doing an impromptu W&B (you don't have to put it in the logs if you don't want to).
For the Citibrthon type of airplanes you'll want the acro CG located somewhere between the center of the envelope and the rear of it. A nose heavy plane tends to mush out of stalls and refuse to spin or snap roll. Basically the tail is fighting the wing for rotational control.
Sometimes when we remove all the weight we can in the pursuit of acro performance we forget it matters WHERE we remove the weight from!

Chris
 
Hiperbiper said:
Before you start changing rigging look at your latest weight and balance info. If it's old look into doing an impromptu W&B (you don't have to put it in the logs if you don't want to).
For the Citibrthon type of airplanes you'll want the acro CG located somewhere between the center of the envelope and the rear of it. A nose heavy plane tends to mush out of stalls and refuse to spin or snap roll. Basically the tail is fighting the wing for rotational control.
Sometimes when we remove all the weight we can in the pursuit of acro performance we forget it matters WHERE we remove the weight from!

Chris
Click to expand...

I have a 2022 W&B w/CG. I agree, an aft CG is better overall for maneuverability. When I run it for solo ops, I am middle of the aerobatic CG envelope. I have yet to spin with two souls onboard, That may be a game changer for sure!
 
Bartman said:
.... I used a long enough piece of straight wood (enough to bridge the underside camber of the Citabria airfoil, you'll have to do something else for the semi-symmetrical airfoil of the Decathlon) with a level to verify twist in the direction the plane was rolling after it was reassembled. ..... assess relative to each side and tips relative to the root, you're a smart fella, you'll be fine. :)
Click to expand...
I have 2 rigging boards (made from aluminum square tube and an angle) constructed for a Pitts per their drawing and they work fine on a Decathlon. Don't need a level, just comparing any twist between the two.

I like to start with a comparison of left and right wings with the rigging boards positioned over the first rib out. I know there is no adjustment however fuselages can get a little bent and I like to know what I'm working with.

Then each wing - one rigging board inboard and one outboard - just sighting from the tip will show any twist. By all means measure the angles if you like but I don't. Both wings the same - a tad of washout each seems to work the best.

Unfortunately, some people use wing twist to rig for cruise rather than to the specs and checking for behaviour at the stall.

I have some photos I will try to find and add here.
 
Looking from the tip of the left hand wing. Approaching the stall a lot of right stick was required to keep the wings level. At the stall a very aggressive uncommanded left roll and aggressive, fast spin entry. Just that little bit of washin on the left wing was enough to cause that unacceptable behaviour (I don't know why pilots were putting up with it until I came to fly it!).
 

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Because they never stalled it? I find even CFIs that don't do stalls from one flight review to the next. I just did an experienced aerobatic pilot in his new GCAA 160. He couldn't do a partial power turning stall! He had owned One Design, Decathlon, and I think maybe a Pitts prior to the GCAA. Just kept increasing the bank angle. Common.

We have a Super Cub like that - it rather abruptly drops the left wing in a stall. Nobody notices, because recovery starts pretty much before the break. Mis-matched ailerons (not uncommon on a Cub) combined with differential wash = semi-mean behavior when fully stalled.
 
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