My new to me S-2A came with two thumbs up from excellent sources in terms of the state of rig. Both the owner and the ferry pilot report hands-off or near hands-off behavior. Of course one of the first things I'm likely to do is to grab the rigging boards for a quick look. The fact that there were trim tabs on both ailerons just made me that much more curious.
Turns out the rigging isn't too bad compared to some I've seen. But perfect it is not and I think I see at least one reason why there are tabs on the ailerons. The airplane may have also had a slight tendency to drop the right wing during an upright stall.
Upper left wing tip. I'll guess this is about 3 washers worth of error in the direction of rolling left. Note that you can see the far rigging board in good alignment with the other two height-wise. This tells me the top wing is pretty flat (but with some 'twist').
Upper right wing tip. I'll give this 2 washers worth of right roll. Again, the third rigging board is just visible in the background indicating a flat top wing.
Lower right wing tip. This one earns 3 washers of right roll.
Lower left wing tip. This one is almost perfect. Call it one thin washer rolling right.
When all the errors are added together you get a 2.5 washer error in the direction of right roll. This is a guesstimate at this point but it does show a reason why the aileron tabs were added. Once the wings are true the tabs may not be necessary or maybe a small wedge under one aileron will replace the tabs.
Left aileron trim tab. A fairly significant amount of left roll from this tab.
Right aileron trim tab. I'm not sure how effective this tab is given the direction of the deflection, the small angle and the fact that it is behind the TE and not in clean air. Still, it is deflected in the direction of left roll.
I prefer to use the rigging boards visually. I don't use levels (digital or otherwise) if I can see all the boards. It is fairly easy to see a thin washer's worth of error by eye and since that's the smallest practical amount of adjustment available there's no need to try to measure anything smaller.
Notice I didn't level the airplane. For purposes of a touch-up to the rigging you don't need to have the airplane level. If you want to confirm that the wings are level to the fuselage you will need to go back to square one and level the fuselage, etc.
I did not check the tail surfaces yet. It is possible there's additional roll coming from there.
I have not removed the I-strut fairings yet so I don't know what's there washer-wise. I suspect I'll be adding washers at the front spars which means loosening the wires to allow access. I will also use an Aviat wire tensiometer to measure the existing tensions more out of curiosity than anything else. I normally use the G-meter to adjust wire tensions.
More to come -- after I tweak things..........
Turns out the rigging isn't too bad compared to some I've seen. But perfect it is not and I think I see at least one reason why there are tabs on the ailerons. The airplane may have also had a slight tendency to drop the right wing during an upright stall.
Upper left wing tip. I'll guess this is about 3 washers worth of error in the direction of rolling left. Note that you can see the far rigging board in good alignment with the other two height-wise. This tells me the top wing is pretty flat (but with some 'twist').
Upper right wing tip. I'll give this 2 washers worth of right roll. Again, the third rigging board is just visible in the background indicating a flat top wing.
Lower right wing tip. This one earns 3 washers of right roll.
Lower left wing tip. This one is almost perfect. Call it one thin washer rolling right.
When all the errors are added together you get a 2.5 washer error in the direction of right roll. This is a guesstimate at this point but it does show a reason why the aileron tabs were added. Once the wings are true the tabs may not be necessary or maybe a small wedge under one aileron will replace the tabs.
Left aileron trim tab. A fairly significant amount of left roll from this tab.
Right aileron trim tab. I'm not sure how effective this tab is given the direction of the deflection, the small angle and the fact that it is behind the TE and not in clean air. Still, it is deflected in the direction of left roll.
I prefer to use the rigging boards visually. I don't use levels (digital or otherwise) if I can see all the boards. It is fairly easy to see a thin washer's worth of error by eye and since that's the smallest practical amount of adjustment available there's no need to try to measure anything smaller.
Notice I didn't level the airplane. For purposes of a touch-up to the rigging you don't need to have the airplane level. If you want to confirm that the wings are level to the fuselage you will need to go back to square one and level the fuselage, etc.
I did not check the tail surfaces yet. It is possible there's additional roll coming from there.
I have not removed the I-strut fairings yet so I don't know what's there washer-wise. I suspect I'll be adding washers at the front spars which means loosening the wires to allow access. I will also use an Aviat wire tensiometer to measure the existing tensions more out of curiosity than anything else. I normally use the G-meter to adjust wire tensions.
More to come -- after I tweak things..........
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