aileron flutter
 

Aloha from Hawaii.

Today I maidened my super stearman, after 3 weeks of building it. 1st flight, as I applied full throttle the ailerons would flutter, when I chop the throttle to around half, the flutter would stop. Brought the plane down safely, checked the aileron control surfaces, tried second flight, same thing. On the third flight, I disconnected the control rod between the top and bottom ailerons, taped the top aileron and guess what, no flutter!! flies like all the other planes I have flying.
The servos I'm using is, futaba 3152 digital. Is this too weak to handle two ailerons? I'm using a 6 volt battery. Should I install two more servos for the top ailerons? or use a stronger servo? Guys, I need your opinons and help!!
The stearman is from great planes, 71.5" ws, weights in at 13 lbs flying weight and using a saito 150 fs GK for power.

Thank you very much for all your help and responses regarding this problem(1st time for me).

Sincerly and Mahalo

Mike..

RE: aileron flutter
 

There are smarter people than I that will respond, but since I am the first, I will through in my 2 cents worth ...

How far along the length of the aileron is the servo installed and what is that position relative to the push rod going up to the top aileron? My thinking is that there may be some flex going on between the servo in the bottom wing and the top aileron. Adding servos to the top wing is certainly the most direct solution and probably would not require that much surgery. So far, I have not had to do that on one of my bipes, but yah never know. I don't know what I would do with the push rod though. Best left off, but what about scale? Just wouldn't look right.

Good luck finding the right solution.

Bedford

RE: aileron flutter
 

Have you checked to see where the flex or looseness is, if any? You may have a situation of compounded tolerances making for a sloppy connection at the top aileron. Mass balancing may be part of the solution too, since it will actually eliminate the flutter altogether regardless of your linkages' ability to control it.

RE: aileron flutter
 

The servo should be strong enough.

Maybe the control rod between the top and bottom ailerons bends under compression, allowing the top aileron oscillate.

Test it and try a control rod of higher diameter or material strength.

This is good reading about flutter:

http://www.rcuniverse.com/magazine/a...rticle_id=1289

RE: aileron flutter
 

Aloha from Hawaii, E.H.

Thank you very much for that very interesting article.
My friend Paul(expert flyer/test pilot) and I tried different methods to try and eliminate the flutter, to no avail. However, when using only one set of ailerons(super stearman has two sets, top and bottom) the stearman flew with no flutter at all. If I can't cure this problem I'll
have to go the route whereby I'll be using four servos, one for each aileron. Fyi, the super stearman has provisions for using four servos which is not scale looking.

Mahalo from Kauai..

Mike..

RE: aileron flutter
 

enforcer,
I'm not sure, but doesn't the scale Stearman have ailerons on the bottom wing only?
Darrolair

RE: aileron flutter
 

Well actually you can, pretty simple and its up to you.

Read this thread and pay close attention to the pictures and text in post #7, 10 and 19.

http://www.rcuniverse.com/forum/m_10438490/tm.htm

By the way if this is the Great Planes Super Stearman ARF I love mine but it is the PT-17 version and does not have the upper ailerons. It serves a hard working glider tug.

John

RE: aileron flutter
 

Yes, Mike, the mass balancing will definitely solve the problem.

May be balancing only the top ailerons will suffice.

RE: aileron flutter
 

Aloha Darrolair.

The original PT-17 stearman has only two ailerons, you are correct. But, the super stearman as in the real aircraft does have two additional ailerons making it 4 ailerons. In the real world, military pilots who bought the older PT-17 transformed them into what is now a super stearman, by adding two more ailerons and adding wheel pants and changing the original power plant to a pratt & whitney with around 500 HP. The original engine was around 250HP or so.

My set up is; futaba 617 RX, 3152 digital servos and for power a saito 150 GK running an master airscrew 16 X 8 prop.

There is provisions for two additional servos on the top wing, but I kind of wanted it to look more scale like and use the control rods to link the top and bottom ailerons togather.

Regarding the connections between bottom and the top ailerons, there is no slop and everything is as tight as possible.

Mahalo for your imput regarding my situation.

Mike..

RE: aileron flutter
 

Aloha Lnewqban.

I may try that in the next couple of days. Like I mentioned earlier, when I taped the top ailerons, disconnected the connecting rod between top and bottom ailerons and flew my plane at various speeds and attitudes and some slow and full speed passes, no flutter and not even a hint of buzzing.
This is my first expirience with flutter.

Mahalo from Kauai..

Mike..