We have had two of these planes flutter their ailerons very badly at our club field. One plane crashed and the second one was nursed backed to the field an safely landed. On inspection of this second plane it was discovered that the gears in both aileron servos (JR4131) were stripped, several of the hinges were starting to detach from the wing, and the engine / firewall mount was damaged and loose.

The plane was repaired and new servo gears were installed. The plane was flown again and once again it fluttered and stripped out both aileron servo gears. No other damage has been observed. All linkages are very solid. Prior to this flutter problem the plane has had many successful flights with no hint of flutter. The plane is powered with a Moki 180.

Any comments on what may have caused the failure and has anyone else had flutter problems with this plane?

I have to ask what was the linkage setup like? Unless you have really strong digitals, I hope that the clevis at the surface was attached at the end of the horn and the linkage at the servo was attached towards the middle of the horn. Leverage plays a big part in how much a servo will take. You have to be careful not to overload the servos. With such big emphasis on 3D type throws, a common thing I see is to have the servos installed with horns set up for the most throw. THis will most likely give the servo the least amount of mechanical advantage and will contribute to rapid failure of nylon geared servos. I had a Sig CAP and installed metal gear 645 hi tecs running on 6v instead of 4.8. The tourque rating was around 75 oz in. These were on my ailerons, rudder, and elevator halves. I did not have a problem with flutter on any of my surfaces. The Cap had a Saito 180 up front. All I am saying is to examine the geometry of your setup and make sure to give the servo as much mechanical advantage as possilbe.


Baretta92 :stupid:

Baretta is right-on.

Also be sure that the hinge gaps are sealed.

Jim

Thanks, guys. I'm pretty sure that the linkages and clevis set up is good on this plane, but I'll pass on your comments.

I had both aileron servos strip out on my Sig Cap231EX/Saito 180 plane. I had good strong Sullivan metal horns, 4/40 hardware, sealed joints and 9202s @ 6V(90oz). The weak link was the servo gear train. I have since replaced all the servos with Futaba S9451's and have not had a problem since. Those light airframes with big motors and large control surfaces need a HD gear train.

Mike

are you flying at scale speeds ????

if you are using any prop with more than 8 pitch...you are most likely flying much faster than scale!!


if you fly the full size plane 3 or 4 times faster than it was designed for ....it will start fluttering apart also