jester_s1

First, it's really helpful to use the right terms. You do not have a flutter issue. Flutter is what happens in flight when the turbulence on your control surface matches its harmonic frequency and it vibrates in flight.

Second, lets get clear on what's actually happening. Are your control surfaces moving rhythmically with the plane vibration as if they are being shaken by engine vibration, or are they moving somewhat randomly? Can you hear the servos moving when it happens, or are they still? Have you tried holding one of the surfaces so it doesn't move? Could you feel the servo trying to move it anyway or was it all still?

If the servos aren't causing the motion, then you have sloppy control linkages or sloppy servos. If the servos are causing it, then you have a radio issue. FWIW, there is no good reason to put a .60 engine on a .40 size trainer. You don't need the extra power, and the extra weight and stress on the airframe can only do harm.

DRC1

My Feedback: (10)

Jester, I haven't read any statement regarding the actual plane other than an Alpha. Nitro has a 60 Alpha. H9 only has a 40 Alpha, however, the 40 Alpha calls out a 40 - 60 2-stroke. The OP is using an Evolution 60. I am assuming it is an H9 Alpha 40...

I doubt that this issue is a radio problem.

Most likely since it was stated their is no linkage play... There are only two reasons for excess vibration which would cause an illusion of severe crontrol surface deflection (not flutter) at WOT. However, this could lead to and result withflutter in flight.

The reasons are:

1) Out of balance Prop, balance prop.
2) Center hole was offeset during reaming, replace prop and ream with a proper reaming tool from the back side (engine side) of the prop.

I suspect one of the two is the root-cause.

Both just make it harder on a smaller airframe, when a larger displacement is used. Again, the airframe is spec'd for a 60. I would always recommend the upper spec engine. You can always throttle back and a properly balance trainer doesn't fly much different with a 60 vs a 40 on the nose. Now, decrease the wing area and using an other than flat bottom wing, it gets a bit more interesting bytrading weight for displacement. But I just don't seea significant differenceon a trainer if balanced correctly.

byrne1157

While all of the suggestions are good, it is best to eliminate 1 item at a time, working from one end to the other. First, battery. Battery connections. Switch(es). (I would suggest removing the switch from the fuselage for a test run, Vibration could cause intermittent contact opening). Rx power connector. Receiver. (Could have cold solder joints). Xtal in Rx. Servo connectors. Servo extention connectors. Servos. Servo linkages. Hinges. Guarantee you it's one of these!!LOL

sensei

His opening statement as I understand it. There is what appears to be a 1/4" buzz on all the surfaces, this occurrence begins at about 1/2 throttle and continue through full throttle, my first thought is high frequency vibration, back in the day before I moved over to 2.4 this was a typical setup on my 72mhz. stuff, 1/4 thick foam with Zip ties strapping the receiver's down snug and no buzz issues for many years of flying this way, now I have seen prop or bent crank issues cause this surface buzz before, but not in a very long time. Anyway I guess time will tell and I do hope you get everything worked out.

Bob

rgburrill

You say you are using 4-40 rod throughout.  Is it sleved or just fed through bulkheads without sleveing?  I used it on throttle control once because that is that the instructions said - bad instructions [:'(].  The rod going through the firewall created a lot of electical niose much like what you are describing.  A friend in the club suggested putting a grommet on the through hole and that solved the problem.

jester_s1

This is why I asked if we're talking about the surfaces moving on their own without the servos doing anything or if it's actual servo movement causing the jitter. There's no need to check anything electrical if the issue is severe vibration causing the surfaces to flop around. But if the servos are actually moving, he'll know it's radio related. More information is needed before we'll be able to actually diagnose the problem and recommend a solution.

Instructor

My Feedback: (16)

Easy way to check for bent crankshaft is to check the runout of the prop tip, of if he is using a spinner, the runout of the backplate of the spinner. Place something on the floor at the prop tip and rotate the prop 180º. If the prop tip doesn't come around the same every time, then the crankshaft could be bent. Most harmonic viberation that occurs at half throttle is due to out of balance props or off center hole....

Larry

Rodney

It is never wise to run a transmitter with the antenna collapsed for any length of time. This will create a high SWR which will cause the output stage of the transmitter to become very hot and will definitely increase the failure rate sometimes causing a quick failure of the output transistor in the transmitter. The AGC (automatic gain control) which is incorporated into most all good receivers will prevent any problem when the antenna fully is extended on the transmitter as long as the transmitter is a few feet (3 to 5) from the receiver.

straitnickel

72mhz broadcasting how? PPM or SPCM? I had PPM take interference before. The servos would chatter on the ground also. Remedy that with SPCM.

tevans55

I had a Alpha 60 that fluttered and it was the whole tail fluttering because it was only screwed on per the instructions. When I epoxied it on that stopped the flutter. An EVO .60 on a .40 size Alpha is a problem.

Lightspeed1551

My Feedback: (4)

Try clear tape across the bottom gap between the stabilizers and control surfaces. If it's air moving the surface it will be a quick fix. Also those lame CA hinges can cause up and down play (flutter) in surfaces.

jester_s1

No they don't. CA hinges are as strong as anything else you can use. If you don't believe me go try to pull the hinges out of your plane. You'll rip the wood loose with the hinges still holding strong if you do.

The OP does not have a flutter problem at all, but if he did it wouldn't be caused by CA hinges, not sealing the hinge gaps, or having his plane the wrong color. It would be because he was exceeding the speed at which his surfaces had turbulence shaking them at their harmonic frequency.

da Rock

The OP isn't really clear if all the surfaces jittering the same amount is in the air or on runup on the ground. But it would really be strange if it was in the air and he still had the airplane. It'd be odd to have it happen at the same time and equal amounts to all surfaces simultaneously as he describes.

It really does not sound like aerodynamic flutter from his description.

Rudder, elevator, ailerons all reacting in unison at the same time and the same amount of deflection? And he could see all that from the ground?

Sounds like his RX has a problem caused by engine speed (vibrations often have resonance).

sensei

As I understand it the airplane has not flown yet, so this is not a flutter issue. Sealing gaps on the surfaces improves the effectiveness in roll, pitch, and yaw, however it will not stop flutter mode from starting in the first place, at best it will only change the point of when it starts or how violent the flutter may be, the intensity of it could be improved, or it could be a whole lot worse by sealing the gap.

Bob

speedair

Id say its prop balance or the horns may be loose on your control surfaces.

I was also wondering wether it could be the engine low speed mixture. I found with enya engines if the air bleed isnt set right they tend to vibrate a lot on idle

DRC1

My Feedback: (10)

OP implied, "before he flies... yadayada..." in my opinion...Healso stated that the control linkage has no slop. Also using a Evolution 60.

The problem most likely is with the prop, either balance or the center hole isn't centered after reaming...

Evolution 60 should be fine on this plane, albeit a bit on the large side for engine displacement. But a H9 Alpha (OP hasn't confirmed the plane) is still spec'd for a 60 2-stroke. So, the engine size is a non-issue, other than prop issues are a bit more of a concern due to more mass rotating on the nose.

LD

Live Wire

To check the radio flutter or what ever, Just turn off the reciever while you are seeing the flutter, if is still there it is not your radio Just make sure you do this from behind the plane[:@]