Has anyone experienced interference with radio reception due to the static electric field that could build up around magneto type ignitions on Zenoah G23-G26s? I am curious to find out if anyone has lost control of giant scale planes that are powered by these or similar power plants due to this possible phenomenon?


While there are many theories about this does anyone have a solution or comment?

Any object that has air moving past it, whether airborne or on the ground will accumulate a static charge if isolated from Earth ground. Therefore, if this were a problem, all model aircraft would experience the phenomenon, and do, but not to the point that it is problematic.

Whether the engine is equipped with a magneto or not is irrelevant in regard to static charge accumulation.

Motoman, Are you referring to electrostatic interference as opposed to electromagnetic iterference?? As I understand it , static interference is what you get when you have two pieces of metal rubbing together somewhere on you plane. Electromagnetic interference is caused by current flowing through a wire or a coil of wire.

RJ

RJConnet, from the description (electric field that could build up around magneto) he is talking about a magnetic field. The answer to this question is no, electrical interference is typically due to a changing field and I don't think our equipment is susceptible to that type of noise. The type of noise in question is different from RF.

Actually, a changing magnetic field will generate current in a nearby wire. Guess how a generator works and an electric motor. There is also the high secondary voltage in the spark coil to worry about. When the high voltage collapses (when the plug fires), this generates a strong magnetic field radiating from the high tension wire. Ain't electricity and magnetism wonderful.

This is true but the generated current in the wire will be of very low frequency and will not cause trouble with the receiver. When the plug fires the spark creates a noise pulse that contains all frequencies. This is what causes trouble and must be shielded or suppressed.

Hmm, wrong frequency for receiver?
How about inducing a voltage (current) in the signal wire of a servo? Might that be a problem?

Depending on how fast it collapses, it could be a high frequency noise signal.

The problem is that I can't figure out why I would lose signal to my aircraft suddenly after flying 3 great flights and then nothing. Total lose of signal to the receiver.

The model in question is a Hanger 9 Taylorcraft. G23 and a Futaba pcm receiver and computor radio. I have a Robart 1/3 cub scale gear mounted as the landing gear. There are several moving parts on the landing gear. All engine switching is in the cowl. This is the second time around for this phenomenon and subsequent crash. First one was rebuildable. After several great flights with all the airabatics a pilot could ask for. I am wondering if some interference is being caused by the either the engine/coil/ magneto or something else. Possibly the landing gear. Our club has not experienced any radio interference for practically the 12 or so years we have been at the current location. PGRC is a great field for those who know it. I am sending the receiver back to GP for a check. Every one at the field was suprised at the crash who was there. I am an experienced pilot. One second you have it and the next its flying off into the trees. Now, I am the first person to acknowledge pilot error. The first time I thought it was me. But the second time in the exact same set of circumstanses is to coincedental. I appreciate all the imput. It has good to see some real discussion concerning the possibility of this phenomenen.

95% of RFI comes from the Spark plug. Shielding and resistance will greatly help.

This next bit will probably start a food fight but here goes. You should be able to fly an gas engined plane on FM. If you have a "RFI Problem," and you fix it by using PCM. You really didn't fix it, you hid it and sooner or later it will bite you in the b*t.
If your flying FM and want to change to PCM for some of the other functions thats cool.

TKG is right. If it won't work with FM, it is not airworthy.

DITTO!

Does anyone have a solution for sheilding/isolating the receiver from the possible interference from the spark plug? If the fire wall doesn't do it what will?

You don't shield the RX, you shield the spark plug.
If you shielded the RX it would do no good. Because you would still have parts of the radio system outside the shield and they would bring in noise to the RX.

I don't know about you but I don't wrap my servo leads around the mag coil. Since we are talking EMI here you would have to be very close to the source in order to interfere with the servo pulse that is in the order of 4.5 volts in amplitude.
As for RFI, since there is no spark gap in the primary circuit of the mag, the frequency is limited by the inductance and the capicitance in the circuit. It would be too low to get to the receiver.
The secondary of the ignition circuit is another matter. It contains the spark gap and is very high voltage. The spark gap converts the ignition pulse into a square wave. A square wave is defined as an infinite number of odd harmonics. Some of those odd harmonics will be in the range of the receivers RF and IF pass bands. The secondary circuit (spark plug) is the one that must be shielded.
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Any ideas about how to go about sheilding the plug from emitting this type of harmful interference without effecting weight or cooling of the engine?

C&H and others sell the shielding systems.

I suspect your plug lead worked loose.
Last wintwer I was flying a G45 powered Weeks Special when the engine suddenly quit. I landed it deadstick and found the plug lead had came off. I reinstalled it and attempted to take off again. In the taxi out the airplane suddenly turned around and came back at me. I proceeded to range check it with the engine running and found I could not get 10 feet of range. I rechecked the plug lead and found I had not quite got it back on correctly. I reinstalled it as it was supposed to be and it solved the problem.
The engine would run OK but the electrical connection was not complete as it should have been.
I was using a FM receiver. If I had been using a PCM receiver I probably would have got it off the ground and lost it