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Plane rolls at different rates left and right?

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Plane rolls at different rates left and right?

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Old 11-13-2005, 08:56 PM
  #1  
Grelker
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Default Plane rolls at different rates left and right?

I have a 90 size Extra 300. The plane is set up with aileron differential on both sides. When I roll to the right, the roll is axial and fast. when I roll to the left, the roll is noticeably slower and the plane corkscrews thru the roll. I have measured the aileron deflection and differential on both sides and they are the same, linkages are the same, etc. The differential is controlled by end point adjustment on the radio.

Anybody have an idea?
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Old 11-13-2005, 09:56 PM
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Default RE: Plane rolls at different rates left and right?

I think what you are describing is called P-factor. Something to do with engine torque and the spinning prop.

I don't know anything about aerodynamics. So, I could be dead wrong.
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Old 11-13-2005, 11:10 PM
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Default RE: Plane rolls at different rates left and right?

Well honestly i would'nt think you would need much differential in a extra 300.
#1 do you have rudder mixed in with the ailerons? or any other mixing?
#2 I don't mean to offend you so don't take this wrong. are you sure you have the ailerons moving the same amount. not just percentagewise on the transmitter but true measurement taken at the control surface?
#3 Possibly you will need opposite differential for the left aileron roll. i have seen this needed in a pattern plane before.
#4How much differential do you have a thirty second of an inch a quarter of an inch?
Now i have seen planes do this that usually have one aileron that goes up more than the other due to the geometry being wrong such as one control horn being longer than the other. the control horn being farther back on the aileron than the other side. Now the control horn being farther back on one side does'nt sound like a big problem. because you can program the total rates the same on your endpoints. The problem occurs at less then full surface throw because the two sides will not move the same.
#5 Do you have both ailerons sealed at the hinge gap?
Hopefully one or more of these will be able to help you out
Dennis
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Old 11-13-2005, 11:12 PM
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Default RE: Plane rolls at different rates left and right?

ORIGINAL: Rcpilet
I think what you are describing is called P-factor. Something to do with engine torque and the spinning prop.
I don't know anything about aerodynamics. So, I could be dead wrong.
There are several parts to your answer. "P"-factor, torque, spiral airflow, and prop precession are all parts of the puzzle. I don't think it is well understood, though. Could be part of the problem except that airplanes with left hand prop rotation generally roll to the left easier than the right. I think the fact that the rolls aren't axial in one direction suggests an airframe issue like a warp or a difference in incidence between the wing panels. I would recheck the airframe alignment and weight and balance first. It ought to roll fine either direction.
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Old 11-14-2005, 11:36 AM
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Default RE: Plane rolls at different rates left and right?

A plane with a symetrical airfoil needs no diff. Also make sure there is no down or sidethrust in the motor.
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Old 11-14-2005, 12:36 PM
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Default RE: Plane rolls at different rates left and right?

a corkscrew type roll suggest some engine side thrust or a rudder deflection other wise could be called a barrel roll
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Old 11-14-2005, 03:31 PM
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Default RE: Plane rolls at different rates left and right?

Sound like the engine torque is rolling ya faster to the right then the left. AS mentioned before measure the acual throws and check for control rods beding on the rudder. Pull pull stsems will remedy this.

other wise to see if it is really the engine try useing a smaller diameter prop with a larger pitch. carefull because the plane may travel faster though it won't have the pulling power. if the roll rate if affected less than its youe engine doing it. Oh and put the original prop back on. the planes ment for aerobatics not speed
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Old 11-14-2005, 03:52 PM
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Default RE: Plane rolls at different rates left and right?

ORIGINAL: Rcpilet

I think what you are describing is called P-factor. Something to do with engine torque and the spinning prop.

I don't know anything about aerodynamics. So, I could be dead wrong.

You are dead wrong. P-factor is only a "factor" at significant angles of attack. In level flight it doesn't exist. [&:]

ORIGINAL: redfox435cat

Sound like the engine torque is rolling ya faster to the right then the left.

So --- how is this happening when torque makes a plane want to roll left?
[sm=spinnyeyes.gif]
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Old 11-14-2005, 03:54 PM
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Default RE: Plane rolls at different rates left and right?

I suspect that one aileron servo is a bit weaker than the other & is not slewing at the same rate -- maybe a bit more friction in one direction.

---or maybe the airframe isn't quite straight.
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Old 11-14-2005, 04:02 PM
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Default RE: Plane rolls at different rates left and right?

Assuming an engine with standard rotation, torque would roll you faster to the left, not the right, so I doubt it is engine torque. There might be something funny going on with slipstream. You can check this by repropping and/or flying the rolls at a different speed. But my gut reaction is the engine is not the problem unless you have too much side thrust.

As others have posted, an Extra shouldn't need much if any aileron diff. I'd suggest taking all the diff out. Double check alignment of airframe, wing, stab, rudder, engine, etc. Be sure you are not carrying rudder trim, wing isn't warped, etc. Check hinge gaps, seal if necessary. Check that not only your total throw left/right is symmetrical, but that it is symmetrical across the sticks. I.E., your endpoints match, now check 1/2 stick throw. Does that match left/right?

Once satisfied with airframe and throws, fly and retrim if necessary. Land and check where your trims are set. If you had to put a lot of aileron trim in and the ailerons are not level with the trailing edge of the wing, something is still out of wack, i.e. warped wing, etc. Once happy with the trim you carry, very carefully perform rolls taking care not to impart any other stick movement, i.e. elevator, etc. I have often seen rolling issue do to the pilot pushing/pulling elevator as they roll. Once everything is set properly, any yaw from roll should be so small it will be difficult to detect.

Cheers
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Old 11-14-2005, 06:47 PM
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Default RE: Plane rolls at different rates left and right?

Three things I saw in the above posts are probably combining to create what you are seeing.
1-engine torque will tend to roll you faster in the direction of engine rotation.
2-Spiral airflow probably has the flow pushing down on top of the right wing and underside of the left wing as it travels the length of the airframe from the prop.
3- the uneven roll to the left is probably due to either side and/or down thrust in the engine, or a secondary effect of the spiral airflow. It is also there in a right roll when caused by thrust angles, but less noticeable because of the faster roll rate to the right.
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Old 11-14-2005, 09:32 PM
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Default RE: Plane rolls at different rates left and right?

Thanks everyone for the suggestions. the hinge gap is already sealed so I'm thinking John W is on the right track. I'll start checking.....
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Old 11-15-2005, 04:21 PM
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Default RE: Plane rolls at different rates left and right?

I ran into a similar situation with some of my planes and I literally went crazy trying to find out what was wrong. If everything is mechanically ok on your airplane, look at your hand and how you hold the stick of the radio. I hold the radio in my fingers and have my thumb on the stick. When I was rolling right I was "pulling" the stick towards my palm. But when I rolled left I would "push" the stick away and that was where the problem was. I would push it, but not a straight push so I was also adding in some elevator without even knowing it.

Since I wear a neck strap on my radio I just quit holding the radio in the fingers of my right hand, actually raising my hand up a bit so then I could push the stick away easier and I quit having the problems.

Ken
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Old 11-15-2005, 04:45 PM
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Default RE: Plane rolls at different rates left and right?

Had the same problem but I didn't even know it. Flying an indoor Pizza Box type plane and noticed left elevon up when I thought I was flying level and automatically using right rudder to compensate. Tightened up the aileron spring in the transmitter, no more problems.
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