I started up the engine on my just finished quarter scale Waco today for the initial check before flying it for the first time. The plane range checked just fine with the engine off, but when we started the range check with the engine running, all the servos started to jump when the receiver was in front of the plane at 10-15'. The G62 has RCIGN's ignition conversion which never gave an oz of problem on the plane it came off of. I found by touching the rigging wires for the top center wing, the interference stopped, and would restart as soon as I let go. Any suggestions as where to start with trying to solve this issue would be greatly appreciated.

Notes:
The rigging wires do cross and touch in the fuselage.
Hitec 5645 with Futaba S3004 on the throttle
Futaba PPM receiver
Ignition battery 8-10" from receiver

[8D] exact same problem with the same engine and ignition. I moved the antenna out of the fuse and away from the the control rods going to the tail plane.. Range was then great and the Giant Aeromaster and Ralph g62 is a superb combo...

Don//

Don,

I was just thinking the same thing regarding the antenna, and will try your suggestion tomorrow. The antenna runs right between the two elevator control rods and real close to their corresponding servos.

Thanks,

Chuck

You have already solved the problem. If touching the rigging wires makes it go away, moving the antenna most likely will not fix it because the RF still exists. On pull pull systems for Giant scale rudders I always place one wire inside a section of push rod tubing, that way the wires cannot rub on each other.

So I would take a piece of tubing and cover one wire right where they touch inside the fuselage.

Plastic soda straws work well also

An easy way to install the tube is to slit it then "snap" it over the wire. It must be long enough so that if the tube slides on the wire it does not slide enough to allow the wire to rub again

Spray the wires with WD-40.

Chuck, which Waco is it?


Bob

Well, antenna location is the problem, I moved it out of the fuselage and the problem still exists. I'll try putting some space between the rigging wires tomorrow and see what happens.

Bob,
The Waco is a Peter Barth kit. Proctor Enterprises sells it here in the US. If you are interested in the plane, PM me with your email address and I'll send you some construction pictures.

http://www.proctor-enterprises.com/p.../waco/waco.htm

Looks like turn buckles on the rigging wires. Put lock tite on the threads.

Well, I'm not having much success, just lots of frustration. I epoxied the rigging wires on the top center section so they wouldn't rub and the interference is still there. It was 20 degrees out yesterday and prop wash on the hands was a killer, so testing was short. Removing the antenna from the fuselage didn't help either. The interference does increase with engine speed. I've done a little searching and found several comments regarding the rigging acting as an antenna creating interference on a biplane, and that a PCM receiver should be used. The supplier of the plane also said to use PCM. I've always tried to eliminate interference and fly a plane with PPM before switching to PCM, but it's starting to sound like that might not be possible. Does any one know much about flying wires causing interference on biplanes?

I've got a few more things to try yet as the process of elimination continues.

Chuck

" all the servos started to jump when the receiver was in front of the plane at 10-15'. " Did you mean to say, " when the transmitter was in front of the plane " ? How does it perform with the transmitter behind, or off to the side of the plane. The flying wires could be blocking the signal from the front. I had this same problem with some complex wire landing gear. I had to run the Rx antenna up to the fin. Try running it out to a wing tip.

> Jim

Jim,

Yes you are correct about the transmitter, not the receiver. I really haven't noticed any interference from the side or back now that you mention it, but really haven't checked it enough. I'm going to check out it thoroughly tomorrow even if it is 20 degrees out.

Thanks for the suggestion.

Chuck

Example of RFI vs Vibration
Antenna down, engine off range check 200 ft
Antenna down, engine running, range check 100 ft... classic case of RFI this is a 50% reduction in range. Max reduction is 15%
Antenna down, engine running, range check 10 ft..... classic case of vibration induced funnies. Problem areas, bad RX, bad switch, bad battery, bad servo(s), metal to metal contact

Kevlar rigging?......lot of re-work but.............

----------------


Switch out the conductive rigging wires for Kevlar rigging wires.

Running metal, or other conductive material, rigging wires is asking for trouble. The radio waves and the RFI from the engine will be reradiated by the wires.

Also, the original signal from your Tx will be reflected multiple times (multipath in radio jargon) and will confuse the decoder in your receiver.


Ed Cregger

Chuck, tkg may have diagnosed the problem as vibration induced funnies. When you say that you can touch the rigging wires and the noise stops, are you using your bare hand. If so, try using a non conducting object such as a towel or stick. Can you remove the rigging wires?

With my G-62 on a Giant Aeromaster I have a lot of interference from the engine unless I do a little bit of shielding. Here is a photo of the shielding and it would be real easy for you to try in the event that the noise is coming from the ignition and not from vibration. I used aluminum foil. I got this shielding hint from Terry or Bill at CH Electronics.

I've been flying a 1/3 scale Bucker Jungmeister for several years with a full set of functional flying and brace wires and have never had a bit of RF interference from these. All joints must be kept tight. I also am running a PPM receiver. I think it would be a big mistake for you to mask the problem with a PCM receiver. Receiver lock up and crash is not a pretty picture.

I was at an IMAA fly in where a modeler had the same trouble with a 1/3 scale Sopwith Pup. He had changed to a PCM receiver and claimed he solved the problem.
On his first flight the receiver went into PCM hold and he lost the airplane.
If you want to fix the problem change to non conductive wires.

Chuck, if you have solid contact with the aircraft from the rear or sides, then it's not RFI or vibration related. Your flying wires are simply shielding the incoming signal when you stand in front. You have got to get your Rx antenna reoriented. Try it out to a wing tip, or go to non conductive wires.

> Jim

Well, I'm frozen, 20 degrees out and prop wash on the hands is a bear. Anyway, I get interference from all side of the plane, front, rear, and sides with the antenna inside the fuselage and outside attached to the fin. However, I did notice something, the interference is affected by the location of the radio. Standing in a given spot where the interference is real active, moving the radio a couple of feet up, down, sideways will stop the interference. From the side of the fuselage, the radio has a clear view of the antenna without the flying wires blocking the signal. Any comments on this?

Chuck

Well, I'm frozen, 20 degrees out and prop wash on the hands is a bear. Anyway, I get interference from all side of the plane, front, rear, and sides with the antenna inside the fuselage and outside attached to the fin. However, I did notice something, the interference is affected by the location of the radio. Standing in a given spot where the interference is real active, moving the radio a couple of feet up, down, sideways will stop the interference.
That is pretty normal with an interference problem. However, you need to be interference free at least 150' in any direction from the plane with a collapsed transmitter antenna.

From the side of the fuselage, the radio has a clear view of the antenna without the flying wires blocking the signal. Any comments on this?
The flying wires don't in any way shield the antenna at the frequencies (72 or 50 mhz) that we use for our planes. If you were using 2.4 Ghz this might be a different answer. My Jungmeister has flying wires, landing wires, and brace wires all over it and there is no sign of interference. Not to mention a big landing gear wire set.

You need to, once in for all, determine if the interference is ignition related or vibration related or........

You can temporarily shield the complete ignition wire with a piece of aluminum foil wadded around the wire and cap. Ground the foil to the plug with a clamp or tie wrap. Are you using a resistor plug such as a Champion RCJ-7Y?

Bill,

I don't believe it is the engine causing the interference because I have quite a few hours on it, and has never been a problem. However, as you say, the ignition has to be eliminated so I will try your aluminum foil suggestion. The conversion is a RCIGN which are a better on interference. The plug is a resistor type, most definitely.

I got thinking over lunch and realized I used a metal clevis to connect to the tailwheel metal control arm on the pull-pull steering system. Could this be a contribrutor? I don't know why I did that, and it's buried inside tail.

Chuck

I don't believe it is the engine causing the interference because I have quite a few hours on it, and has never been a problem. However, as you say, the ignition has to be eliminated so I will try your aluminum foil suggestion. The conversion is a RCIGN which are a better on interference. The plug is a resistor type, most definitely.
You are correct, it may not be the ignition. Where is the ignition battery located? Is the receiver, servos, switches and battery at least 10" back from the ignition and it's battery? Is the ignition switch located near the engine? Is the throttle push rod non metallic?

I got thinking over lunch and realized I used a metal clevis to connect to the tail wheel metal control arm on the pull-pull steering system. Could this be a contributor? I don't know why I did that, and it's buried inside tail.
If the pull pull system is in a little tension then the metal to metal contact should ok. I doubt that this is your problem.
Are you testing with only the top center wing section mounted and the rest of the wing sections not on? Do the center section wing braces connect to wood or metal inside the plane?

On my plane all of the braces and flying wires use DuBro rigging ends with 4-40 screws to clamp onto the strut fittings thereby providing solid electrical contact.

My name is not Bill.

Good Luck

Check your spark plug and make sure you do not have a carbon ball on the bottom. Make sure that your spark plug wire is not loose were it goes into the coil. Try changing your ignition/kill switch. Typically these are the culprets. As far as rigging goes any complete circuit of wire can block a signal. Example: tail wires all being metal. I will take 1 metal clevis and make it plastic. Any way try the above mentioned on the engine side and I bet you find your problem. And these days PCM always helps!!!!!!!

Yes PCM can help. The trouble is you never know if it will help enough. If it don't then you have a real problem. its better to eliminate the problem if you can. Then use PCM.
The problem with flying wires is not shielding or reflections or multipath usually. They can be a problem but very unlikely.
The problem is vibration on the wires cause buildup of static electricity on the wires. This is the same thing as rubbing your shoes on a carpet. This causes a difference in potential between the wire and other metal parts. If this wire and the other metal parts are in intermittent contact there will be sparking at the contact area. You will not see it but your receiver can hear it.
The cure is to isolate the parts with plastic connectors, or bond the wire securely to the other metal part, or use non conductive flying wires.
This problem can come and go depending on the humidity.

Well, my frustrations continue. The source of the interference is still eluding me and any more suggestions would be appreciated. Below is a list of what I have done to date none of which corrected the problem. Yesterday, I remove the engine and put it in a test stand. With the engine running, and the plane held a foot from the engine, there was no interference! This leads me to believe it is a vibration-induced problem in the remaining components of the plane, which there aren’t many.

Big Bird asked the question “Is the throttle push rod non metallic?” No it is metallic 6” long rod, but there is plastic clevis/ball socket on the throttle and a plastic control arm on the servo. Shouldn’t that be ok or could the metal rod by itself be a problem?

Chuck

By passed the switches for both the ignition and radio
Tried different batteries for both the receiver and ignition
Moved the ignition battery about 2’ from the receiver
Moved the receiver five feet away from the plane; this lessened the interference, but not much
Disconnected all the servos except the throttle
Disconnected all the servos except the rudder and manually adjusted the throttle
Switched receiver
Took off tail feathers metal bracing
Removed center upper wing section and rigging wires
Cursed

I would get rid of the 6" metallic rod. I noticed that you never mentioned shielding the spark plug cap and ignition wire and grounding the shield to the engine. This is the first thing I wound have tried. It is about the easiest thing that you can try and it can be very effective. Using aluminum foil is only temporary to see if you need to go with a fully shielded ignition wire. Ralph puts together a really good ignition system but you will never know unless you try it. If you are slow, it should take you 5 minutes to do it.