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Solved Control rod trim.

#1
So I decided to move all the control rods one notch closer to all the control surfaces on my Apprentice S in order to give me more manovorabilty. After this, I trimmed the surfaces as best I could on the ground and then sent the plane up. It was all working fine and I was able to move around a lot more and then I decided to go around at a higher speed. It became apparent that at high speeds, the tail would buffet violently and jerk the plane around. I was guessing that it was an elevator issue so I played around with the trim but no difference so I brought it down, changed the rods to where they were originally and it flew perfect. Does anyone know why this happened or how I can get around it?
 
#2
Likely it is the as3x gains being to high and fighting your pitching moments.

I had a Parkzone Sukhoi Su29, that would do the same thing in 3d mode but flew amazing in pattern mode.
 

Merv

Well-known member
#4
It's the brand name that Spectrum uses for their stability system built into the Rx. It's is what gives you the three flight modes, beginner, intermediate and advanced. It is also makes the recovery button work.

I agree with @SportyModder, if you are using stability, try turning down the gains. If you are in advanced mode, look for the pushrod flexing. If found, you will need to add supports to the pushrod to prevent flexing.
 
#5
It's the brand name that Spectrum uses for their stability system built into the Rx. It's is what gives you the three flight modes, beginner, intermediate and advanced. It is also makes the recovery button work.

I agree with @SportyModder, if you are using stability, try turning down the gains. If you are in advanced mode, look for the pushrod flexing. If found, you will need to add supports to the pushrod to prevent flexing.
I'm in Advanced, there is no flexing, rubbing, dents or faults with anything on the plane. It can't be the stability system because it is completly off in advanced. It also does it in a straight line with no Input from me. When it does it, it looks like there is some kind of break in the airflow on the tail which causes it to bounce around but everything is smooth and I still have no idea what it is.
 

Merv

Well-known member
#6
I'm in Advanced, there is no flexing, rubbing, dents or faults with anything on the plane. It can't be the stability system because it is completly off in advanced. It also does it in a straight line with no Input from me. When it does it, it looks like there is some kind of break in the airflow on the tail which causes it to bounce around but everything is smooth and I still have no idea what it is.
I agree, in advanced mode there is no stability. What about changes in air speed? If the situation only happens at high speed, then it is flutter. You are looking for some kind of slop, could be in the servo, could be in the push rod, could be in the horn, could be in the hinge. Something is allowing unwanted movement of the control surface.
 
#7
I agree, in advanced mode there is no stability. What about changes in air speed? If the situation only happens at high speed, then it is flutter. You are looking for some kind of slop, could be in the servo, could be in the push rod, could be in the horn, could be in the hinge. Something is allowing unwanted movement of the control surface.
As3x is a 3axis gyro.... it removes some buffeting from wind turbulence, and makes the aircraft appear not to be affected by wind.

S.A.F.E. is what recovers the plane and gives you stability. Advanced modes still limits bank angles and pitch angles. The third position allows unlimited aerobatic performance.
 

Merv

Well-known member
#8
As3x is a 3axis gyro.... it removes some buffeting from wind turbulence, and makes the aircraft appear not to be affected by wind.

S.A.F.E. is what recovers the plane and gives you stability. Advanced modes still limits bank angles and pitch angles. The third position allows unlimited aerobatic performance.
So you saying that gains could still be the issue?
 

Bricks

Well-known member
#9
Have you checked to make sure when in advanced mode the AS3X is actually off, plug everything in move your transmitter switch to advanced and move the plane around and if the AS3X responds to the movements. If it does then your transmitter is not set up properly and shutting off stabilization.
 
#10
Have you checked to make sure when in advanced mode the AS3X is actually off, plug everything in move your transmitter switch to advanced and move the plane around and if the AS3X responds to the movements. If it does then your transmitter is not set up properly and shutting off stabilization.
As3x should have quick momentary effects on the control surfaces.when you move the plane violently, it will twitch the controls to counteract the movement.
I suspect when you moved the control linkage, you inadvertently changed the gains, by increasing leverage and movement of the surface.

SAFE will try to level the plane.
 
#11
I agree, in advanced mode there is no stability. What about changes in air speed? If the situation only happens at high speed, then it is flutter. You are looking for some kind of slop, could be in the servo, could be in the push rod, could be in the horn, could be in the hinge. Something is allowing unwanted movement of the control surface.
So there is some kind of weakness in the tail plane that can't cope with higher pressure airflow at high speeds. I'll buy some thicker control rods as the horns are pretty stable it seems to me.
As3x is a 3axis gyro.... it removes some buffeting from wind turbulence, and makes the aircraft appear not to be affected by wind.

S.A.F.E. is what recovers the plane and gives you stability. Advanced modes still limits bank angles and pitch angles. The third position allows unlimited aerobatic performance.
I had it in position 3/Advanced/expert whatever you want to call it. I had unlimited aerobatic performance. Thread on I moved the rods was so that I could knife edge.
 

Bricks

Well-known member
#12
As3x should have quick momentary effects on the control surfaces.when you move the plane violently, it will twitch the controls to counteract the movement.
I suspect when you moved the control linkage, you inadvertently changed the gains, by increasing leverage and movement of the surface.

SAFE will try to level the plane.
If the transmitter is set up it can be turned off many put SAFE on a switch so if you loose orientation or get in a bind you can hit the switch and the plane self rights and stabilizes itself. On Spectrum DX series many use the bind button on the top of the transmitter for the SAFE part.
 
#13
If the transmitter is set up it can be turned off many put SAFE on a switch so if you loose orientation or get in a bind you can hit the switch and the plane self rights and stabilizes itself. On Spectrum DX series many use the bind button on the top of the transmitter for the SAFE part.
I have the DXe. Bind corrects the plane to a straight and level position. Position 1 on the switch does not let the plane hold its bank. Position 2 will bank but only to a certain degree. 3 is off.
 

moret

Active member
#14
You can turn SAFE on - off or mode 1, 2, 3 Advance etc. This has nothing to do with AS3X I think you would have to get into the programming on the receiver in the Apprentice S to turn AS3X on - off
SAFE limits your control of the plane ( no rolls, loops) and levels the plane
AS3X helps with wind gust and makes the plane fly "like a bigger plane"
AS3X will not stop the plane from rolling or looping.
From my book it looks like if SAFE is on it overrides or turns off AS3X

I fly my timber X with SAFE off but AS3X is still on.
SAFE is a spectrum thing,
AS3X on the timber X the throttle needs to go above 25% before it is enabled
 
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#15
You can turn SAFE on - off or mode 1, 2, 3 Advance etc. This has nothing to do with AS3X I think you would have to get into the programming on the receiver in the Apprentice S to turn AS3X on - off
SAFE limits your control of the plane ( no rolls, loops) and levels the plane
AS3X helps with wind gust and makes the plane fly "like a bigger plane"
AS3X will not stop the plane from rolling or looping.
From my book it looks like if SAFE is on it overrides or turns off AS3X

I fly my timber X with SAFE off but AS3X is still on.
SAFE is a spectrum thing,
AS3X on the timber X the throttle needs to go above 25% before it is enabled
That makes sense now. I still think its the control rods because looking at them they are pretty flimsy.
 

quorneng

Well-known member
#16
Also remember that the nearer in a control rod is placed on an arm the higher the load on the rod, the more likely it is to flex and cause control surface flutter!
Not that I like using them but it is one advantage of using a 'snake' as in effect the 'rod' is supported along its entire length so no 'flex' effects.
 
#17
Also remember that the nearer in a control rod is placed on an arm the higher the load on the rod, the more likely it is to flex and cause control surface flutter!
Not that I like using them but it is one advantage of using a 'snake' as in effect the 'rod' is supported along its entire length so no 'flex' effects.
There is already a sought of plastic sleeve over the rod to prevent flexing but its still too weak.
 

FDS

Well-known member
#18
You are also reaching the point where you are trying to make the airframe do things beyond it’s designed limits, I would make something else that’s better suited to acrobatic flying before getting too deep into this “problem.”
You are fighting the limits of the control surface size, deflection and the wing position. There’s a reason real high wing, slow flying planes tend to be used as trainers not sport or acrobatic aircraft.