Elevator Fluttering
 

I have the Modeltech Formula 3D and I noticed yesturday during a small flight that the elevator was shacking real bad so I had to back way off on the throttle . I have elevator supports and this obviously didnt help that issue at all , can anyone else give me advice on this issue ? OH to let you know , Its not the elevator parts that move , its the structure of the plane thats doing the shaking from what I can tell .

Thanks :(

RE: Elevator Fluttering
 

Sound like something is loose in the tail or a prop that is out of balance.

Considering you balance issues in the other thread, I'm now wondering if this plane was wrecked at the tail and repaired.

RE: Elevator Fluttering
 

This kind of what I am thinking too. It's not the easiest thing to do but you need to try and look down the fuselage towards the tail and see if there is any evidence of repairs to the plane. You can get an inspection mirror from just about any auto parts store that would make it easier to look down there and see if there is any damage. Also look at the covering on the plane and see if there is any evidence that it's been recovered. On ARF's there should be no seems in the covering along the length of the fuselage. If you can see where covering has been added in along the fuselage that would be a dead giveaway. Also look to see if the color of the covering on the rest of the plane matches the covering on the tail of the plane, if not it's another clue that it's been recovered.

One thing to try would be to have a helper hold the plane up with the engine running and open it up to full throttle. If the tail surfaces shake as you described then you've got issues with bad structure or vibrations from the motor. But if they don't shake then you have issues with flutter occurring while the plane is in the air. Flutter can and will destroy a plane if it's not corrected. A few things to check that could be the cause of flutter are failed hinges, loose or weak connections on the control horn, flexing of your pushrod, loose or weak connections at the servo control arm, failing servo, or stripped or loose control arm on the servo. No matter what, a plane with a known flutter issue shouldn't be flown until the cause of the flutter is determined.

Hope this helps

Ken

RE: Elevator Fluttering
 

Trying to clarify things here. Are you saying the horizontal stabilizer is shaking and it is supported with flying wires?

If the stab is shaking and is built up (not sheet) it may have cracked or broken parts in it.

RE: Elevator Fluttering
 

I looked at the manual online
From the photos it appears the stabilizer is stick built so it could have some bad glue joints.
http://media.hobbypeople.net/manual/123771.pdf
Page 41 mentions sealing hinge gaps. Is that done?
Page 43 mentions the tail bracing but doesn’t go into any detail.

Based on the balance issue post, it does make you think it could be a wreck. This is an ARF and it’s designed to have the elevator servos in the tail. You shouldn’t have to redesign the control system and move the servos up front to balance an ARF. The RCU Magazine review discussed balancing and didn’t report a problem.

RE: Elevator Fluttering
 

Thanks for the reply , I went and got a mirror from the auto store and I see no damages to the plane at all , all the covering is stock...I dont have the gaps sealed though

Soth servo's are good to go and are very solid along with the horns .

I have have to try it tomorrow with a helper holding the pane while i give it full throttle . I honestly dont think it will flutter when I do this , due to the fact it only did it when I was in the air at 1/2 throttle .

RE: Elevator Fluttering
 

More curiousity than anything;
What engine are you using?
And what prop?

RE: Elevator Fluttering
 

lol:D, I just looked at a picture of the airplane...
http://image.rcuniverse.com/forum/up...50/Zx71693.jpg
The elevators are about 3 times as big as the little stabs and the ailerons have almost as much chord as the wing!!. SLOW DOWN! You cant fly very fast with a 3D plane with Gigantic control surfaces like that one has. Flutter can do all sorts of things. With that plane if you are using the correct to slightly oversized engine, unless you taking off, flying vertical or doing a blender or a waterfall or something you dont need much throttle at all, probably only 1/4 throttle or less!...... If you are at any attitiude short of 60 degrees take it easy on the throttle and see what happens. That plane was designed to go pretty slow, seriously, keep the airspeed DOWN.

RE: Elevator Fluttering
 

I agree with MikeEast. In addition, large diameter/low pitch props keep the top speed down and make for better hovering/climb performance. You can also try to mass balance the elevator. Put lead ballast in the part of the elevator that is forward of the hinge line until the elevator's CG is on or slightly ahead of the hinge. This is done on most full scale airplanes.