Glitch Busting Help
 

I have been fighting a glitch in my plane all summer. It's a 29% AW Edge with a BME 44. Futuba 148 FM Fx and 9C radio. Two batteries with separate switches into a y harness. dual aileron servos (channel 1-7) dual elevator servos (2-6). All except the throttle are Hitec digitals. I've got my engine battery and switch in front of the firewall and the rest of the radio as far back as I can get. Sullivan smoke pump in channel 5. The glitch is very intermittent. The plane will fly along and all of a sudden the plane will spasm. I thought it was RF interference or vibration related interference, but today I observed this:
I set up the plane (Channel 43). My son flies on Channel 46. My Tx was on, about ten feet from the plane. The Rx batteries were on, but the engine was not. I watched as the control surfaces occasional moved, with no input from me. It did not happen with any regularity, just sat there and twitched - ailerons, rudder, elevator, throttle, smoke pump. I have changed the Rx out, and the problem remains. I fly the same Tx in a smaller glow powered Edge with zero problems, so I know it is in the wiring/servos/ switches. The small Edge is on the same channel with no glitches.
So, I'm asking for some advice on finding the glitch - causing culprit. I've jiggled wires, had the plane idling in my driveway for an hour, but it's very intermittent, but consistently appears once or twice per flight, even if there have been no indications of a glitch on the ground. I'm prepared to install new wires to every servo, switch, battery, and the smoke pump, but if there is something obvious I'm over looking I'd like to know about it.
Thanks in advance,
Sam

RE: Glitch Busting Help
 

What are the Hitec digitals type?

RE: Glitch Busting Help
 

Cause is often simple, but finding the cause can be time consuming.
Best Glitch Busting Tips & Techniques gleaned from various newsgroups and elsewhere over many years are under "Radio Systems, Accessories, Alterations and FAQ" sub section "Glitches & Jitter in RX & Servo - causes and cures " on my web page. Another section, "Giant Scale, Large RC models, Twins & Multi Engines" which may also be of interest to you.
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links

RE: Glitch Busting Help
 

G'day Mate,
Where does your antenna run, I bet it's through the fuselage, & it ends up close to a servo or multiple servos, move your antenna away from the inside of the plane, & see if that helps, I had trouble like that with one of my planes, so I ran the antenna out to the end of the horizontal stab, or tailplane, as we call it, & the problem went away.

RE: Glitch Busting Help
 

The aiilerons and elevators are Hitec 5645 and the rudder is s 5745. Alan, you're right about the antenna placement. I fed a tube through the turtle deck and I just pulled out the antenna wire to check how far from the twin elevator servos, and it was about two inches from them. I'll be checking out your glitch busting pages.
Thanks a bunch,
Sam

RE: Glitch Busting Help
 

My experience with the 56xx series of Hitec digital servos is they are prone to glitches. They have never caused a crash for me but will sometimes move off center then return. The first two I had I returned to Hitec and they were replaced. The new one did the same thing. I then put them in a new airplane with new electrics and got the same funnies. I no longer use them in critical applications.
The electronics in the servos will also reboot if the voltage gets too low. Using 6 volts will help this problem.

RE: Glitch Busting Help
 

DaddySam,
I am fairly new to gasoline engine powered airplanes and had glitch problems for some time. The causes were:
1. Intermittent RF noise from the switch in the ignition circuit. It was found by jumpering by the switches one at a time. It took a long time to figure that out.
2. The second, widely intermittent, glitch was caused by the 4mm bolts, which thread into the wing root to secure the wing, vibrating a little loose in flight and rattling against their washers. That little bit of metal-to-metal contact was generating RF noise. The plane has Hitec digitals also. When all metal-to-metal noise is eliminated, the glitches are gone.
Good luck with your glitch-hunting.

RE: Glitch Busting Help
 

Here's an update:
Today I was going through all of my wiring and found some connections that could have been tighter. I started re-wiring all of my servos with new wire and connectors. The only pigtails I'll need now will be for the ailerons to plug in. But the big news (to me that is) is that when I started to take the smoke pump out the controls went crazy. I rewired the pump with new battery and control leads, and the pump still caused some interference. Needless to say, I'm sure it's the problem. Other than the pump, the setup is pretty close to what I have in the small Edge. I'm going to finish rewiring the rest of the servos and give it a test flight this weekend.
Thanks for all of your help. If the glitch persists, I'll let you know.
Thanks
Sam