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So I have an interesting dilemma. I have a rolling tendency that I can’t explain. More specifically an aileron deflection tendency. The ailerons are trying to deflect into a left roll. If I let go of the stick from neutral it just goes to the left. I’ve checked the rigging and it looks good. Proper deflection in each direction on both sides. I can’t tell what would cause this. I tried putting washers under the upper part of the mounts of the “up” aileron with no noticeable changes to the behavior. Maybe a trim tab is next.
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Almost flying! -
A lot of people are seeing this condition, where the ailerons don't fly exactly straight. It may or may not result in a rolling tendency - mine does this, but does not want to roll. If it does want to roll, then I think there's plenty of information on how to fix that.
I don't fully understand the cause of ailerons not flying true, but not causing a roll. I guess one aileron is producing more lift than the other, but other unbalanced forces must cancel out the roll. I suspect it's not that simple
An aside, the plane is being driven by a prop which only rotates one way, counteracted by a vertical stabilizer which has an offset the other way, employing an ad hoc aerofoil shape (in the case of earlier kits not supplied with aerofoil tail surfaces). The wings and trailing surfaces have been attached with a measure-drill approach, by hand, either by factory or builder. The fuselage and wings themselves are assembled in jigs, but are not perfect. To my mind, if would be more surprising if everything flew perfectly straight, a slight offset in the controls is unsurprising. The rudder flies with a slight offset too. -
Thanks Battson, maybe I should post in one of the heavy wing threads but I’m not sure it’s the same issue. It seems most posts indicate a slightly heavy wing with a slight offset in ailerons when flying level. Which seems to imply that the heaviness may not really result from aileron offset. What I’m seeing is the ailerons wanting to not just sit a little bit off but deflecting almost completely when I release the pressure on the control stick. I can’t be sure if they would hit the stops or not because I’m not willing to let it go that far.
So, when others are seeing this aileron offset do the ailerons want to deflect further if you try to fly hands off? Or do they find a neutral position with some offset and sit there regardless of roll tendency? I didn’t see a real detailed description of how the ailerons behaved in others cases so I don’t know whether it’s the same or if mine have a different issue.
my rolling (heavy wing) issue seems directly related to the position of the ailerons but I don’t know why they want to keep deflecting as much as I allow them.
Does that make sense or am I missing something?
Almost flying!Comment
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Thanks for the extra information. That doesn't sound like a heavy wing to my mind, that sounds like a control imbalance.
A heavy wing just lazily lists to one side, gradually. It should require a little input force on the stick to keep it level. The ailerons should not keep deflecting if the stick is released, they should fly somewhere close to straight without a hand on the stick. The plane will just tend to roll slowly (depending on how heavy).
If you cannot take your hand off the stick, something is seriously wrong.
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Do you by chance have more weight in the left wing? For example a landing light, magnetometer etc? What were the individual main wheel weights when you weighed the aircraft?Nev Bailey
Christchurch, NZ
BearhawkBlog.com - Safety & Maintenance Notes
YouTube - Build and flying channel
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The aircraft is substantially heavier on the right side actually. 18 pounds or so. Magnetometer and pitot are there too. Do you think an airframe weight imbalance would cause aileron deflection? Maybe I’m trying to come at this problem from the wrong direction but my impression from my last flight was that the aileron deflection correlated with the rolling action directly. When they appeared neutral there was no roll. So I think… maybe incorrectly… that the roll is following the ailerons and not some other cause. So the issue is whatever is causing the deflection. Maybe. My confidence is pretty low on this.
Almost flying!Comment
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I'm definitely not an expert - Kev D is the man for this.
But from what you're saying, I expect for level flight the left aileron will be down, the right aileron will be up, and the rudder will be slightly to the right. The rudder is a tricky one because you can't see it, and you'll be pressing just enough to center the ball. However it is possibly holding a small "steady heading side slip". If the ball is truly centred a small constant turn may occur, or if a steady heading is held then one wing may be slightly low. It's also correlated with a small amount of fuel transfer over several hours which can be another way to diagnose the issue.
Check the alignment of the flaps in the UP position. They tend to act like ailerons, so a flap alignment issue could be a factor. For initial test flying, it's good to ensure that they are fully up against the stops with the cables ever so slight slack (so asymmetric cable tension is not inducing a rolling tendancy). Then use the rod end bearings to adjust up or down as required until symmetrical and on the up stops. Eyeball against the fuselage, or the wing rigging template to set both flaps the same. Later they can be set to deploy evenly by adjusting cable tension.
More info on a heavy wing here https://www.bearhawkblog.com/post/heavy-wing
Some info on how I rigged mine here (best results were from eyeballing it)
Last edited by Nev; 02-21-2023, 01:19 PM.Nev Bailey
Christchurch, NZ
BearhawkBlog.com - Safety & Maintenance Notes
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Like Nev said, check your flaps. If they are even using a digital level, turn the flap rod end out one rotation on the wing that wants to drop. It won’t take much to correct. If it needs a lot of adjustment then I’d look at the elevators to see if both surfaces are parallel and not in a “twisting” position. The ailerons are basically neutral in flight, hands off, reacting to what the rest of the aircraft is doing.Comment
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Originally posted by AKKen07 View PostOriginally posted by AKKen07 View Post
Is the data below right?Originally posted by AKKen07 View Post
1) when ailerons are physically held neutral by sight so they are fared with the airstream and flap, you have no roll.
2) it requires a force on the stick to hold the ailerons in the neutral position.
3) when you let go of the stick, the stick does not find a neutral position rather the stick moves and does not stop moving as far as you know because you have not yet let go all the way to the stop.
4) no other post has yet has described that their ailerons move all the way to the stop if they let go of them.
An idea to ponder: Airflow is applying a force to move those ailerons out of the neutral position all the way to the stop. Just an idea, not a fact. Any other ideas where the force is coming from?
I suppose the aircraft could be rigged spot on but If the top of the left aileron hinges are installed so that it sits proud of the top of the wing (or maybe the right so it sits proud of the bottom of its wing) then airflow over the proud surface could apply that force and it draw the aileron away from neutral?
Brooks Cone
Southeast Michigan
Patrol #303, Kit buildComment
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Thanks guys, I will certainly look into and check all the mentioned items. Brooks is seeing the problem more the way I see it. It seems that the aileron deflection is the cause of the roll but I can’t figure the direct cause of the deflection. I don’t think flap evenness, or uneven weight in the wings, etc.would cause aileron deflection.
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The washer under the hinge trick is primarily a vertical adjustment of the hinge line. The vertical location of the hinge line is a big factor and something you can check. With the ailerons neutral, rest a 4' straight edge parallel to the chord, with one end even with the trailing edge of the aileron. Check to see how the aileron aligns with the wing skin on each side. Whatever the arrangement is, whether a gap under the skin, a gap under the aileron, etc, see if it is the same on both sides. Have you already called Bob? He knows a lot about this kind of thing.Comment
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Interesting, Trying to absorb the observations of roll left when releasing the stick, the stick moves left.......... Aircraft rolls left.
This is suggestive of an imbalance of aerodynamic forces on the "aileron system" and something that is a bit self reinforcing as the movement happens.
Is this new? Initial phase one testing?
I think that a really good sanity check would start with Jared setup up of a straight edge under both ailerons at the same time.
How are the ailerons located in the aileron pocket?
Are the slots at the front and the top surfaces the same side to side?
Lock the stick in neutral and see if the cable tension is equal on the run stick to aileron bellcrank in wing.
Has a nico press slipped?
Does one aileron have more play than the other?
Look closely at the rigging and position of the aileron cable to pushrod bellcrank in the wings.
Are they set up with the same angular relationship?
Are the arms that point aft both square to the rear spar? And parallel to each other?
Is it possible that the aileron hinge point on the left is located closer to the aileron spar than the one on the right?
Is there any significant difference in the thickness of the aileron airfoil profile side to side?
Are the trailing edges similar in shape and thickness? One more rounded, one more square?
If all the above seems OK in concept and symmetry.
See Below.
As the aircraft rolls left, where does the nose go?
Does it take a notable force in flight to maintain the wing level with the stick at neutral?
If the nose tracks left, look toward the horizontal tail as the source of the roll.
Kevin D
#272
KCHD
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Thanks for pitching in Kevin, I was likely going to ask your opinion here soon
Yup it’s initial phase 1. Three flights down. I will take some measurements and report back. I can say that when the stick is released it moves left until I stop it and without complimentary rudder input the nose behaves in a manner that I would expect with Adverse yaw demonstrated with a nose-right movement.
To hold the wings level it takes a good amount of force on the stick. The controls seem so naturally light that just two to three pounds seems like a lot, relatively. And that’s my guess for how much I’m holding at around 140 mph - though it is directly related to airspeed. The faster I go the more force is required and vice versa.
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Okay, so I went through the ailerons and double checked, then made some small adjustments to the rigging.
I also remeasured the H. Stabs to make sure they hadn't changed magically since I set them nearly a year ago. And naturally, they had! The left side was both out of square at the back tube and per my digital level had .3 degrees less incidence than the right side. Since I had added washers to decrease the incidence at the mount, that was easy to fix. I'm guessing that contributed to my roll but I still don't know why the ailerons deflected so much. More notes to take on the next flight - should the weather gods ever smile at me again.
I didn't change anything very significant in the ailerons so I'll answer the questions despite having not checked the flight behavior since tweaking.
With control stick in the middle, the left aileron nose sticks down below the lower skin of the wing just a bit. Along the aileron I'd say an average of 1/8". The right aileron is just flush, except the inboard 8-10 inches or so which seem to angle upwards just a touch - so the edge is above the wing 1/8". The trailing edges of both sit just about 1/8" higher than the tip of the flaps. I don't see any shape anomalies from aileron to aileron. There is no significant play in either aileron.
The bell cranks are square to the surrounding structure as drawn in the plans. As square as I can determine anyway.
In the pocket the ailerons fit pretty tightly. Depending on the deflection they use up all the available space and are the same left and right.
I don't see any evidence of a nicopress slipping but Interestingly during my adjustments it seemed the tension had decreased a smidge to 21 lbs or so. I set it back to about 25 lbs. I measured 25 at the crossover cable above/behind the pilots head. I also measured where the cable comes out of the strut and enters the wing. There it only measures around 18 lbs for some reason. Same left and right. I wiggled the controls a bunch and tested a few times, same result.
Flaps seem to match the wing bottom on both sides, I see no difference left to right.
The adjustments I made are:
-removed the washers I had installed under the left aileron bracket upper mounts.
-tensioned the aileron cables to get 25 lbs in the crossover cable and exactly square the bell cranks (they were very slightly out of square prior, but the same side to side)
-adjusted aileron pushrods to position trailing edges 1/8" over flap trailing edges. Unlike the A model, the B model doesn't have a simple reference for where the trailing edge should be. My wingtips are not perfect and would be a poor reference and there is no wing section inboard of the flaps to reference. So the flaps should be about right.Almost flying!Comment
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You commented:- So do you think that if the plane has other factors causing the roll, the ailerons could be just fine and react with near full deflection as a result? Maybe if I straighten the outside factors first the ailerons will jump into line??
- I just saw your comment and "yes" the outside factors are influencing what is happening. You cannot use ailerons to correct your problem other than lifting or lowering the hinge point with the washers. If they are just close to being rigged correctly, the aircraft should fly reasonably true. They will just go to a point of equal load just like the flaps do when they are deployed.
- Good that you picked up a discrepancy in the tail. These things are so fast that it doesn't take much to knock them out of stabile flight.
- When you set up your ailerons initially, did you use a template of the cord at the end of your wing to set the small trailing end tip rib into position? If so, then set the flaps as close to the profile of the aileron. Then ensure both flaps are exactly at the same angle when their mechanisms are up against their stops. You can later adjust the aileron trailing edges up a bit to reduce force pressures.
- I can't emphasize what a tiny difference between the flaps will make in relation to a heavy wing.
- I am puzzled as to why the roll is so excessive. Normally it will just drop a wing a couple of feet and stay there. For it to continue to roll to need correction suggests something should be obviously out of wack.
- I'm not familiar with your build whether you built from scratch or a kit. If from scratch I'd get the aircraft into a level flight position in the hangar and go over every surface for trueness- dihedral, check for roll out on the wing ends etc.
- Good Luck
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It’s a kit, so I expect things should be reasonably true.
The tip rib had some predrilled holes that I used to locate it, so I didn’t use the airfoil profile. Imperfections there could have affected the tip alignment. But I’m not referencing the tip because it’s visually imperfect.
The flaps were installed with a wing profile that came with the kit, so that’s my reference. Adjusting the flaps is on the short list of things that I’ll try if recent changes don’t do it. But I want to test my latest adjustments next. -
The tail will probably make a noticeable difference and that would provide a continuous rolling force if not true. I think what Steve is suggesting with the tip rib is just to use that one rib to true the ailerons against. On mine, the wing tips were out there doing their own thing, but the ribs were pretty true, so initially I was able to align the ailerons against them. Later, I added reflex to the ailerons once I had a reference. For the flaps I also used the profile board, and checked that they aligned with the ailerons. Once you've got this little gremlin mostly resolved, the flaps can be used to really fine tune it - like a 1/2 turn on the rod end. It makes a barely perceptible visual difference, but a noticeable roll input.
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Personally, I think this is the area where you should focus first. You can rig deflection into the flaps and it will make the plane roll, and you might even get it to be balanced in roll at one speed. But unless the flaps are unevenly zeroed, changing their zero doesn't fix the problem, it only masks it and creates a wedge to push through the air. If you speed up or slow down from that speed it will probably still be out of roll trim.Originally posted by AKKen07 View Post
When we adjust the roll by adding washers under the aileron hinge, we are adjusting the vertical position of the aileron, very slightly. If you have 1/8"-1/4" of difference of aileron height, your first washer probably didn't seem to be doing anything because it took the problem from level 9 to level 8. I'd call Bob and see what he says, he's really wise about these kinds of things.
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It’s common to lower a flap to correct a heavy wing - this has been done on certified airplanes from way back because they’re allowed to do so . You can’t legally attach an aileron trim tab with the certified plane but it’s Much less drag. You can attach this at first with gorilla tape to find what works . Then use a couple blind rivets to mount it. I have one on my f-10 that is one wing from tip to tip . To set wing incidence, use the profile and bubble level out in the aileron region-not in near the fuselage- you may have a small twist in one of your wings.Comment
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That sounds highly concerning!Originally posted by AKKen07 View Post
If I read that right, this sounds like a serious problem.
This must be resulting in a serious rolling tendency.
I would be seeking advice from an experienced professional to resolve that, before conducting further flights (assuming I have understood the situation correctly)
Originally posted by Steve W View Post
^ I totally agree with this.
Originally posted by AKKen07 View Post
^ I think this could be the problem, but there's a lot of room for misinterpretation with doing this via a forum!! Suggest finding a local expert.
It sounds like the aileron hinge points are at different heights on the port and starboard wings (at least). That alone would cause a lot of rolling force.
It also sounds like at least one of the ailerons may have some accidental dihedral - in other words it isn't exactly square to the wing, or to put it another way, the axis of the wing may not be parallel with the axis of the aileron. I may have misunderstood that part, the bold part sounded like you're saying it's not installed parallel.Last edited by Battson; 02-19-2023, 07:54 PM.Comment
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