ignition interference
 

Gents

help a newbie out, I'm getting intermittent interference with my latest project. range checks good at 300' engine on and off. 3w78T with DA ignition. everything isolated and running through an I4C power isolater.

the problem is sometimes in flight in various attitudes the airplane goes into hold for fractions of seconds, i've got the throttle set to high idle.

antenna is in a nyrod running along the fuse then into the turtle deck in an H9 Extra 330S.

I pulled the cowl off and noticed all connections secure but was curious if the shielded spark plug cables could rub against the engine standoffs and create RF? they are routed underneath the engine mount standoffs but have enough slack in them to rub if pressed against.

I slit some tygon tubing and covered that portion of the cable that could potentially come into contact, wrapped it in electrical tape and then zip tied it secure.

any ideas?

thanks

buck

RE: ignition interference
 

Do you have all your RX stuff--like switches, servos, batteries at least 12" or 15" away from your ignition system?

On one of my planes, I had to seperate everything by almost 18" to stop the RF problem.

Try routing your antenna down the side of the fuse and then put a 90 degree bend in it and run it along the LE of the stab. For some reason, putting a bend in the last 25% of the antenna can help out with interference problems.

If you want to run the last part of the antenna along the LE of the stab--just secure it with a few 1" wide strips of monokote or ultracote. Iron the strips on the bottom first and then route the antenna. Fold the strips up and over the LE of the stab and tack them down with an iron. That holds the antenna really nicely.

RE: ignition interference
 

thanks for the tip amigo. I"ll giver a try.

the batts, switches etc are roughly 14" away from the ignition module.

appreciate the help

buck

RE: ignition interference
 

If your system goes into hold you must be using PCM receiver and you have a serious problem. Get and install a PPM receiver for testing purposes. Do a range check with and without the engine running. If you don't have a problem with the PPM receiver installed your PCM receiver is bad.If you don't have a problem with the engine not running and do with the engine running disconnect each servo, one at a time. If the problem goes away when one of the servos is disconnected clean the connections to that servo and try again. If you still have a problem replace the servo. Try replacing the battery and switch.
Check and clean all of the connections of the ignition system especially the spark plug lead. If you still have a problem replace the ignition battery and its switch.
If you have done all of this and you still have a problem find another place to fly.

RE: ignition interference
 

thanks amigo. I will trouble shoot this problem and use your post as a reference to start from. I'm using a brand new JR 955s and Hitech 5645 digitals all around except for the throttle servo

take care

buck

any thoughts on the spark plug cables touching the engine standoffs as a potential source?

RE: ignition interference
 

Since they are both grounded to the engine they should not be a problem. I am assuming the spark plug lead is shielded. If not, the insulation on the spark plug should prevent any problem or you are not likely to get the engine to run very good.

RE: ignition interference
 

thanks for the info regarding the spark plug leads.

I went out and test flew it today after wrapping the leads with electrical tape and tygon tubing. I can only assume that fixed the problem because I couldnt' duplicate any of the problems I've been experiencing with the RX going into hold for fractions of seconds.

I flew the same sequence as yesterday, left-right, vertical to include pointing the antenna directly at it and had no difficulty controlling the plane. I even set the throttle to high idle and it never once blipped in flight.

seems to easy of a fix so I won't let my guard down initially and will have spare receivers and crystals at the ready to see if it was just a fluke.

thanks to all who responded

cheers

buck

RE: ignition interference
 

I seriously doubt that wrapping the spark leads fixed your problem. However it can't hurt and if it makes you feel better---

RE: ignition interference
 

you're probably right bro' but it does make me feel better.

however, I will be monitoring it closely and will use the throttle going to failsafe to provide some heads up that it wasn't a one time fluke. with any luck I'll sneak in a flight or two prior to going to work tomorrow.

I'm getting 300' engine on and engine off (all quadrants) on a range check on deck.

any other possibities you may have thought of aside from the ones you previously posted?

Keep adding water, I'm trying to absorb as much info as I can from as many sources as I can.

Luckily, I've got two very experienced buddies that can check 6 and ensure everything is cool.

thanks again for your inputs

Sun Valley Flyer or Mesa flyer???? I'll be out there in November hopefullly for the jet show. I'd like to say thanks in person.

buck

RE: ignition interference
 

I fly at EVA on Ironwood. I live close to the field where they fly the jets but they have too tight noise restrictions on the gas engines for me.

RE: ignition interference
 

ALL ignition components must be more than 12 inches from any reciever compnent. Batteries , switches servos and servo leads.

Some people get away with thier components closer but I have not seen a reliable setup with compnents close together.

RE: ignition interference
 

right on thanks bro'

put another 4 flights on her today with one of my experienced gas burner buddies watching on.

weird, the only thing I changed thus far is to wrap the spark plug leads with tygon / tape and zip ties to keep from brushing against the engine stand offs.

however, I'm not letting my guard down and will keep my FS set to high idle.

thanks for the inputs.

buck

noise restrictions for gas burners out in the sticks of Mesa? the prop tip noise must reverberate off the desert terrain / hills.

RE: ignition interference
 

I guess you haven't been to Mesa lately. There is not many sticks left.