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Two RV-12iS flight issues

psalys

Member
Patron
Hi all,

1. On takeoff I am adding right rudder to keep the ball centered, but then I notice the plane's nose is yawed to the right. I thought this was my imagination but after over 150 take offs, I'm convinced it is real. My instructor in the right seat agreed yesterday. I have the Dynon Skyview HDX system. During cruise flight or descents the inclinometer and yaw both behave normally.

2. During stall practice, I get a fairly significant right wing drop. The inclinometer is centered but the wing drop is always to the right. Recovery is normal by dropping the nose and adding left rudder. My instructor found this amount of wing drop concerning.

Any thoughts?

Thanks,

Patrick
Eugene, OR
 
I have early SN RV-12 with Dynon D-180 Dual Displays. I have to hold significant right rudder in climb... perhaps 2-3 lbs foot pressure. I have never noticed yaw when holding rudder in a climb.

Conversely, I notice ball is slightly left in a glide with engine at idle.

Cruise is hands/feet-off ball centered with installation of the Van's rudder fixed trim tab at prescribed angle.
 
I would agree that the RV-12, if you are at full throttle for the first few minutes, and climbing out at 75 kt's requires a good amount of depth and pressure on the right rudder to keep the ball centered in a Skyview 1000 Touch, too. Since where I fly is controlled by nearby Class C airspace, KBRB, I have to keep it below 3000 ft for about 4 or 5 miles to get out of that controlled airspace.

There's just no way to relax your foot on the right rudder while climbing out, it is what it is, if you don't want the nose yawing to the left.

Did a climb out from a runway at 980 ft elev to 9500 feet a week or so ago, to catch a 30 kt tailwind, and I was on the right rudder probably 20 minutes, once I slowed up to a 400 -500 ft rate of climb at 85 to 90 kts. :eek:
 
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I have the exact same deal,right rudder on take off and climb out...normal P factor.
RV12 2018 100ULS Rotax dynon skyview touch.
Tony
 
Hi all,

1. On takeoff I am adding right rudder to keep the ball centered, but then I notice the plane's nose is yawed to the right. I thought this was my imagination but after over 150 take offs, I'm convinced it is real. My instructor in the right seat agreed yesterday. I have the Dynon Skyview HDX system. During cruise flight or descents the inclinometer and yaw both behave normally.

2. During stall practice, I get a fairly significant right wing drop. The inclinometer is centered but the wing drop is always to the right. Recovery is normal by dropping the nose and adding left rudder. My instructor found this amount of wing drop concerning.

Any thoughts?

Thanks,

Patrick
Eugene, OR

Since you're close to the mothership, try to get a ride in the factory plane to compare to yours? Or check with Mike Seager who knows these airplanes very well....
 
The climb out sounds normal, except I don't notice a significant yaw, but stall does not sound normal.... if you center the ball with the rudder, take your hands off the control stick does the plane drop to the left or right ? If it does follow vans advice for fixing a heavy wing.

If you power off stall an RV12 and with a centered ball it will stall flat and not drop off - in addition to mine I have flown three others and this is how they all behave.

I suspect that you have a heavy wing
 
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Yaw and drop doesn't sound normal. Is there a possibility that the ADHRS bracket or alignment is a bit off (twisted to the left). Maybe someone has a old style slip indicator to try out

10-06984.jpg
 
thanks for the suggestions

I checked the flapperon setup and they were both 1/8" down per the KAI. I'm leaning towards the heavy wing hypothesis. I notice when I'm in a full power climb, I do have to hold left aileron but not in cruise.

I'll try squeezing the left flapperon and see if the symptoms improve.

I also like the idea of getting an old school inclinometer to confirm that the digital dynon one is correct.

Thanks
Patrick
 
Really tiny amounts and work along the wing......

We had a heavy wing on the first 12, but the second flew hands off from new.

Both drop a wing in the stall but not a huge amount and you can pick it up with aileron - the rudder thing can be a bit of a myth on most well designed, 'normal' airplanes. I do annual flight tests on a lot of airplanes and they usually say to demonstrate wing recovery on aileron and rudder after stall. As with all things, in moderation :D
 
I'll try squeezing the left flapperon and see if the symptoms improve.

I did the flaperon trailing edge squeeze and wasn't happy with result. What works really good is to raise/lower entire flaperon with the rod end pivot bearings. Try 1/2 turn in/out and see if it affects heavy wing.
 
That's an interesting idea Jim

I had to get out my KAI to see what you were talking about.

Thanks for the suggestion.

Patrick
 
I always suggest people keep in mind that there are a lot off different things that can cause a roll imbalance.
Arbitrarily choosing one (adjusting rod ends) without investigating whether the adjustment they are about to make is actually causing the problem, may solve the problem, but only by inducing an additional problem the happens to counter the first one.
 
Adjusting the rod end bearings will start you chasing your tail. Ask me how I know. Haha.
Smashing the trailing edge of the flaperons will absolutely have an effect, but tread lightly because it takes very little to make a lot of difference especially the further outboard you are.
On my RV-12 I?ve noticed that it matters how much fuel is on board or whether or not I have a passenger or luggage (tools). So, be sure all of your observations are correct before you start changing things. These are great little aircraft so have fun!

Good luck.
 
Adjusting the rod end bearings will start you chasing your tail. Ask me how I know. Haha.
Smashing the trailing edge of the flaperons will absolutely have an effect, but tread lightly because it takes very little to make a lot of difference especially the further outboard you are.
On my RV-12 I?ve noticed that it matters how much fuel is on board or whether or not I have a passenger or luggage (tools). So, be sure all of your observations are correct before you start changing things. These are great little aircraft so have fun!

Good luck.

/\ this, Absolutely. I can take my friends RV-12 while sitting in the passenger side at 255# to a heavy right wing, just by shifting my upper body over to the right 3 or 4 inches.
 
Ditto what Dennis and Scott said. I'm a card caring member of the "chasing your tail club".

Changing any dimension of the control linkage is a risky and probably futile proposition. Changing push rod lengths (one side) only changes to relationship of stick position to neutral flaperon position, changing both sides only raises or lowers the flap positions at neutral. Then there are the interference issues: control stick interference with the nuts on the electrical cable run hold down block, push-rod interference with the electronic fuel pump. You might also end up with an over-center (or less than optimum) orientation of the flaperon torque tube arms. Changing the rodend bearings out on the flaperons to raise or lower them will certainly change something, but will also change the alignment of the flaperon with the torque tube attachment point.

I'd ensure all your dimensions are per plans, then focus on the trailing edge. Takes some patience. Some people have also had luck with ensuring the flatness of the top wing skin aft of the aft spar where it meets the flaperon.
 
Thanks for the suggestions

I have been checking and adjusting the flapperons and the upper wing skin trailing edge. Now the other wing (left) is slightly heavy and my right wing drop with stalls is much less severe. I will continue to make small adjustments and try to get it tuned just right.

Thank you all.

Patrick
 
Try taping a piece of string to your canopy to act as a yaw string. If it is straight along the longitudinal axis and the ball is centered in flight it is rigged properly.

I wish I could claim I figured that out for myself, but my old CAP cadet friend became an F-4 pilot. He got his glider license in CAP and learned about yaw strings. When he had to test an F-4 out of maintenance he would tape one on the wind screen. He said they were good up to about 200 knots after which they were gone with the wind!
 
Back to right wing drop upon stall: What are everyone's thoughts on the contribution of the landing light to the issue??
 
Hadn?t thought about the prop wash effect, Carl. I?ll have to try it this weekend and see how much it affects the string. I wonder if putting one on the wing would be far enough out of the prop wash. The geek in me is looking forward to the experiment.🤓
 
Landing light theory

Hi Tacco,

My 12iS has bilateral landing lights.

Thanks for the thought.

Patrick
 
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