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surface flutter - 1/20/2013 1:29 PM   
tazzzz


 

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Status: offline 		I just fired up my ALPHA with an evolution 60..but at WOT all the control surfaces flutter 1/4"or so. Seems to happen from 1/2 throttle to WOT, what causes this,,Id like to resolve this soon. I dont want to take the chance flying it with this going on.

THX-TAZZZZ

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RE: surface flutter - 1/20/2013 1:43 PM   
gene6029


 

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Status: online 		I'm thinking its the addition of slop, or play in every point from the servo arm out thru the control horns to the hinges. That is of course provided you are not talking about an electrical or radio problem. When the motor is not running can you feel any play in the control surfaces by trying to move them back & forth? I'm not sure if we are talking about a mechanical or radio problem here....Gene

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RE: surface flutter - 1/20/2013 1:57 PM   
cap 580


 

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Status: offline 		It is  caused by the control rods giving or bending under stress. This happens alot with a single aeliron servo appplications.    The faster the plane goes the more stress the control rods are under.  Or the clevises are not fitting tight in the horns.  This is caused by drilling the holes in the horns to big.   Antother reason may be the control surfaces may not be glued or hinged tight or close to the plane.  I have had a couple of planes do this also.   One is a 8ft Telemaster.  It sounds terrible at wot. It is because of the single servo for the aelirons.  The wire is just to weak. 

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RE: surface flutter - 1/20/2013 2:01 PM   
cap 580


 

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Status: offline 		I should of read closer.  I thought it was in flight  .Like Gene  I would say excessive play in the controls. 

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RE: surface flutter - 1/20/2013 2:49 PM   
Rodney



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Status: offline 		You do not say what type of system you have. On some systems, if you have any metal to metal contacts that can rub together under vibration, it can create some interference. It is not as likely to happen if you are on 2.4GHZ but will often happen on the lower frequency such as 72MHz, 6 meteres, etc. Of course, if there are any intermittent connections any where, vibrations from the engine could cause such problems.

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RE: surface flutter - 1/20/2013 2:50 PM   
tazzzz


 

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Status: offline 		Th
anks guys,but there is absolutely no play at either end of any of the control surfaces,,,the all seem to flutter simultaniosly at the same time with same amount of distance.

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RE: surface flutter - 1/20/2013 3:33 PM   
gene6029


 

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Status: online 		Since you stated all the control surfaces are ( fluttering ), can you tell us if the servos are moveing or is it just the control surfaces moveing? A low reciever battery voltage can cause the servos to act nervous. Also on 72Mhz, ( you didnt state 72 or 2.4) if you are doing all this with the antenna collapsed on the transmitter or rolled up on the reciever it can cause the servos to act this way. The only thing common to everything ( in the plane) is the reciever battery & switch. Check these for loose or corroded connections. Is there any way you can get help from someone at your local club?....Gene

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RE: surface flutter - 1/20/2013 3:40 PM   
LesUyeda



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Status: offline 		Prop balance???????

Les

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RE: surface flutter - 1/20/2013 3:43 PM   
JohnBuckner



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Status: online 		Are you using a 72mhz system? You need to answer some of these questions or no one can help. If you are using a 72mhz system is there metal to metal contact at the carburator?

For example is the throttle arm itself made of metal combined with a metal clevis. This was a very common reason for for this behavior on 72mhz systems and people forget that metal to metal at this point is a big no/no.

John

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RE: surface flutter - 1/20/2013 3:50 PM   
sensei



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quote:

ORIGINAL: LesUyeda

Prop balance???????

Les


That is what I am thinking as well...

Bob


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RE: surface flutter - 1/20/2013 4:53 PM   
tazzzz


 

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Status: offline 		Yea, its a 72mgz system, all the servos are fluttering,no metal contact to engine at all,,battery is at 5v right now, lots of foam to stave off vibrations,,all surfaces are tight,, and Im using 4-40 rod thru out,,,do you think it may be the receiver acting up?

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RE: surface flutter - 1/20/2013 5:57 PM   
gene6029


 

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Status: online 		Its possible to be the reciever, but could be a whole list of items. I'd try moveing things or pokeing around with the motor not running to see if you can instigate & or isolate the problem. You stated it only happens once the throttle is over 1/2 open, so im guessing it is vibration induced. Can you bypass the switch & plug the battery directly into the reciever, that will rule out the switch. Then try un plugging one servo at a time, looking for bad connection on servo extension. Try replaceing the reciever if you can, i have had loose Xtals, broken antenna wires, even cracked ckt boards on my helicopter recievers from previous crashes. You'll have to become a detective, but at least you decided not to fly until you find it, since it wont heal itsef in the air You'll eventually find it & please let us know what you find.....Gene

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RE: surface flutter - 1/20/2013 7:09 PM   
JohnBuckner



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Status: online 		Definately virbration induced, If after trying what gene listed above and no joy then you need to try another recieiver. Probably the most cited reasons for reciever problems under vibration is a cracked ceramic filter (am not talking about the crystal) and next in line would be a fractured circuit board trace. Both from firm arrivals (crashs) or something as simple as free fall of the receiver from the workbench.


John

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RE: surface flutter - 1/20/2013 8:14 PM   
Instructor



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Status: offline 		quote:

ORIGINAL: LesUyeda

Prop balance???????

Les


That is what I am thinking as well...

Bob


I think theae guys have hit it on the head. Change the prop or check the balance on this one. To see if the receiver is at fault, remove it from the plane, leave the servos connected. Without the engine running, tap the receiver case and watch the servos. If they don't move any, then the problem is in the prop balance....


Larry

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RE: surface flutter - 1/20/2013 8:55 PM   
tazzzz


 

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Status: offline 		OK, guys,,Ill try all of the above,,gonna have to my investigation hat on. Thanks for all the advice,,,,,,,let you know when eraticated.

TAZZZZ

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RE: surface flutter - 1/20/2013 9:42 PM   
RCER88


 

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Status: offline 		I would also look closely at the on/off switch and wiring connections between the battery and the receiver a bad switch or wiring connection will cause the problem also. In the past I have had brand new defective switches. It does happen.

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RE: surface flutter - 1/20/2013 10:05 PM   
tschuy


 

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Status: offline 		The 72Mhz receivers are pretty sensitive to vibration.   Make sure it is padded and protected well.  I like to use 1/2 foam semi-losely wrapped and then using a velcro band to secure it to the airframe.  Some folks like using rubber bands.   The second issue I see and tend to agree with in this string here is prop balance.  Get your prop balanced.  Third thing is antenna routing.  Keep it away from the battery leads and any metal to metal contact.   Even a Z-bend rod with the servo connection to the throttle arm can cause some feedback into the radio with vibration.   Finally try swapping out the reciever and see if that makes a difference.   May have to borrow your field buddies radio for testing to make sure it is not a receiver issue....

Wish you the best with sorting it out.

Please share with all when you figure it out.  We all learn from each other and become better fliers and friends.


< Message edited by tschuy -- 1/21/2013 1:51 AM >


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RE: surface flutter - 1/20/2013 11:05 PM   
Live Wire


 

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Status: offline 		Loose or bad Xtl in RX!

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RE: surface flutter - 1/21/2013 1:48 AM   
zacharyR


 

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quote:

ORIGINAL: Live Wire

Loose or bad Xtl in RX!



WOW man the **** is THICK .... really guys ???[

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RE: surface flutter - 1/21/2013 1:55 AM   
LD24


 

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Status: offline 		You will have many opinions regarding this... Don't take the advice of... "This is normal..." becuase it isn't...
"
I haven't read you experience level, I'm assuming you're just starting out. I'm also assuming you have a H9 Alpha 40 and opted for the 60 size 2- stroke Evolution 60NX...

First thing first to check, and check all...

1/4 inch at any throttle speed seems to be begging for in flight flutter which is a non-recoverable phenomina and will destroy the plan in flight if it occurs. If you used a 40, the risk is lower. But the 60 in this plane is well overpowered even though the Alpha is showing 40 in the specs. No problem with the 60 in the plane... Just less room for errors when flying at faster speeds.

Check the following:

1) Linkage should have minimal slop. If there is more than 1/32' slop at the contol surface, stop and fix the problem. Checked by moving the control surface with you finger.

2) Reeming the prop may have resulted in changing the center hole location causing an severe out of balance prop condition (Meaning center is no longer center). Ditch the prop and ream from the plane side of the prop with a proper size prop reamer.

3) Prop is out of balance. Less of a problem with a smaller prop. With the 60, everything is pronounced in this size plane. Most likely cause of vibration resulting in the appearance of control surface movement. Balance the prop by either sanding the plane side of the prop without taking much material. Not the tip of the prop. Or you could take clear finger nail polish in thin coats to the back side of the light side of the prop near the end of the blade.

Check and fix these three things and you problem should be significantly reduced.

With some vibration the illusion is the control surface will have a lot of slop. When the plane is in the air, there will be less vibration as there is no contact with the ground to reverberate back to the plane...

If anyone of the three things are an issue, fix them before flight. Seek assistance by a qualified pilot at a local RC field to pre-maiden check before attempting to fly...

Good luck...

Larry Diamond

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RE: surface flutter - 1/21/2013 2:05 AM   
LD24


 

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Status: offline 		Do you have the antenna pulled out next to the plane with a fully charged battery? Don't do this... Leave the antenna down when working on the plane in the house... Pull it out when your getting ready to fly...

If you are seeing any kind of movement from the control surfaces with the plane off, the radio could be a problem. Check the plane to make sure where you antenna is routed. Also check to make sure you do not have any metal to metal contact that will rub with vibration.

Take a video and post it. We can look at the video and tell you mre about the problem. However, the best solution is to get help from a seasoned pilot from you area.

Larry

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RE: surface flutter - 1/21/2013 2:14 AM   
thepamster


 

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Status: offline 		Has this radio system ever been used before? Been in a crash? What is the radio system? A lot of unknowns.
If no metal-metal contacts first try a different battery, then, bypass switch with battery directly into receiver, then unplug servos one at a time to see if problem goes away, could be a bad servo, then what is left is receiver.
I am assuming of course you do not have a spare receiver.
Once you eliminate everything else what remains must be the truth.




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RE: surface flutter - 1/21/2013 2:19 AM   
Gray Beard


 

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Status: online 		With large control surfaces and analog servos vibration itself can create the movement. Can you hold an aileron with the engine running and keep it from moving? Vibration with a glow engine is usually caused from an out of balance prop. Glitching usually shows up with just a couple control surfaces moving. With all of them moving it can be a bad RX glitching from a bad pot. Just some ideas to check out. Bypass the battery switch just by plugging the battery plug directly into any open port will tell you if it is a loose wire in the switch.

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RE: surface flutter - 1/21/2013 2:29 AM   
thepamster


 

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quote:

ORIGINAL: LLD

Do you have the antenna pulled out next to the plane with a fully charged battery? Don't do this... Leave the antenna down when working on the plane in the house... Pull it out when your getting ready to fly...


Larry


This is a good point. I had forgotten about this phenomena with some 72mhz radios when both antennas are fairly close together though I don't remember throttle position affecting that. It would do it with engine off.
I think the OP has us all confused by the thread description. Flutter happens while the plane is flying which this plane has not flown.


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RE: surface flutter - 1/21/2013 2:37 AM   
Gray Beard


 

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Status: online 		That brought up another thought, I once had a plane tied up to a chain link fence and the plane was glitching. Removed it from the fence and all was well. That only happened once and it was a while ago.

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