David_Moen

I was out to the airfield tonight to try out my Ultra Sport 40+ after moving the battery to change the CG.

While flying in what I thought was dead calm air, I noticed the airplane "twitching" a fair bit. I scanned the trees in the area, leaves were not moving, yet the plane seemed to have developed a nervous tic. I beleve I saw it yawing as if the rudder servo was jittering.

I landed right away and looked things over. On the ground nothing seems amis, yet after taking off, the bumpy ride continued.

After a couple of flights I decided to call it an evening, when I took my wing off I noticed that my receiver wire was right up against the throttle servo, I beleive I should secure it to the fuse to keep it away from other electronics.

I am using a FUtaba 9C radio, the receiver that came with it (sorry, don't know the model) and the 3004 servos that came with the radio.

How do I figure out if I do in fact have a problem with my radio set up? There was nobody else at the field tonight to ask.

WreckRman2

My Feedback: (5)

Do you get a good range test on the ground?

KJohn

David to begin with great work on your part by observing something unusual and your interest in finding out what is different.

You say you made a change to the battery position. Apparently before the change you either had not noticed this same problem or it did not exist in the past. If it did not exist then it is possible that the change (or changes) you made introduced the problem you noticed, probably unintentionally.

The range check (mentioned above) on the ground should be made. And it might be best to try the range test from different angles to the plane. You can stand in one place and make changes to the orientation of the plane. This would be similar to (but not exactly the same as) placing the plane in one orientation and staying a given distance away from the plane as you walk around the plane (walking in a large circle).

Even if this does not point out a problem you will then have an idea what kind of distance you had on the day you performed the test (a 'standard'). It might be helpful to know in the future.

You might want to stake the plane down and do that test with the engine off and then with the engine on.

Next, when the plane is in the air there are generally vibrations that are not experienced on the ground. It is possible that something is loose on the plane and causing radio reception problems or glitchs when the plane is in the air and the engine is running. This could be tested by turning off the engine in the air when you are at a safe altitude near the field and see if the glitching goes away. A deadstick landing will be required (careful: you might get interested in R/C sailplanes). Or sometimes simply changing the throttle setting when flying will eliminate a problem because it changes the resonance in the plane parts. But these changes might help zero in on the actual problem. It might be that your muffler is loose and causing radio reception problems, or that other metal-to-metal connections (engine to metal motor mount for example) are causing problems.

High power lines nearby could cause glitching on humid days that might not be a problem on dry days. High power radio systems in trucks passing by the field might cause problems that eventually subside.

If you pinpoint the actual cause of the 'symptom' you observed I would appreciate knowing what you found out.

David_Moen

I did the standard range check from about 50 yards, but as I was the only one at the field, I could only see that the control surfaces were moving in the appropriate directions, I did not observe any unintended movement, either during my range check or later when I was closer to the airplane. As soon as I can I'll get someone to help me with a better range check. Probably won't be this weekend as everyone is out at the first big "Float Fly" of the season.

David_Moen

Come to think of it, I may have a problem with my TX. It just occurred to me that I've seen the same thing happen when flying G2 with my 9C. Plugged it in this monrning, calibrated it, and let it sit there on the "Contol Options" screen. my rudder, aileron and throttle channels are constantly bouncing +/- 2 to 3% woth occasional bounces in the 10% range. Has anyone seen similar behavior in computer flight sims? This happens wiht the TX module in and out.

WreckRman2

My Feedback: (5)

I'm in the process of sending my 9C back to Futaba. I can't get 15 paces away during a range check before the servos go nuts...

David_Moen

I called Futaba, and from my description they think that there is something wrong with the TX, and they want me to send it to them. Unfortunatley, with an international border between me and them, this could mean that I am without my radio for 3 weeks or so! Not happy about that at this time of year!

Unfortunatley, I did note this when I got the radio originally and was just using it for flying the simulator. I wrote it off as a problem with my cable/sound card.

KJohn

David if the problem is in the transmitter I would think that you would see the symptom when the plane is on the ground. I would think the symptom would not be noticed ONLY in the air. Strange.

If you could borrow the same type transmitter and found you had no problems flying that would also be of interest. But you risk finding that the problem is in the receiver (maybe a crash would take place so this is a little risky).

And what would be really bad is if the repair shop looked over your transmitter and it was returned in 3 weeks with a note that said 'We did not find anything wrong with the transmitter. Now please send the receiver!' Ouch! Maybe you should send the receiver along with the transmitter.

Also, if you have to send in the equipment do it real soon. Hopefully it will be returned in perfect condition. And your plane will still be in working order (that is a huge savings and worth the three weeks of withdrawal symptoms).

David_Moen

I plan to do some more range checking before I put anything in the mail! One of the fellows at the field has an Eclipse on the same channel as me so I think I could bum a memory slot from him.....

SilverEagle2

My Feedback: (9)

This is wierd, I had a 3001 servo go bad on the rudder on the my US40+. Made for interesting flight as the plane would yaw back and forth. Mine turned out to be the servo itself. Check the wiring. I moved the servo lead side to side and it made the rudder servo act like I was switching the power on and off. Turns out that the servo lead had a bad solder joint to the PC board. Mine would be fine until I ran the throttle to full on my Saito 72 and the vibration connected and disconnected the solder joint. Just a thought.

Make sure that the linkage is tight as well. That new rudder design has a lot of area in the counter balance ahead of the hinge line and if any slop is in the rudder linkage, the rudder will hunt side to side while you are flying. That would also make it look jittery.

Jason

David_Moen

It certainly does make life interesting...there's no way I could be moving the stick fast enough to cause the behaviour I'm seeing. Reminds me of my 8 year old after he's had too much sugar!