hey guys, took my plane for a fly a week ago and had 2 perfect flights, then this morning took it out for a fly take off perfect, pulled the throttle back to 1 quarter stick, and PCM kicked in, it locked into a bank and i almost lost the plane, scared the crap out of me ..
any ways i pulled the throttle after about 15 seconds of no responce from the plane, and landed it, Now i have worked it down to be ignition interference... what have i done wrong, i range check the model without motor running and i get heaps and heaps of range, i turn the motor on, at full power range is not reduced but at a little above idle power setting, the reciver locks up, and goes into PCM, and controls are real laggy and they just stop, then respond like 3 seconds later [:@].. What do i do, i think its because i have the throttle and choke servos 1 cm away from the ignition switch? is this causing interference to go into the throttle and choke servo leads from the ignition switch, and it is feedbacking into the reciver? Should i Take the switch out and mount it on the opposite side of the fuse or somthin? What to do...

That would be a good place to start at. Try to keep good separation between radio and ignition componenets. It is easier to relocate a switch than the servos.

Move it around and let us know how things worked out.

Jon

It's highly unlikely that the location of the servos is the problem.

It flew two nice flights that morning with no trouble, this indicates that the basic design or layout is OK. RFI does not suddenly start leaking unless something changes.

You say it loks up just off idle. This points at something loose that is vibrating. Check the ignition ground on the engine, anything else that can come loose. It could also be something has broken loose inside the ignition box.

TF

I had the same thing happen to me..all of a sudden I started getting some glitches..The cause was the lock nuts on the aluminium landing gear plate were loose..they were vibrating at certain rpms enough to cause some RFI..I put some thin washers and tightened them down..just something else to check.

Another culprit for this type of interference is inferior quality switches, or a switch thats malfunctioning.

As a test bypass each switch one at a time.

hey tom, i dint fly 2 flight that morning with it, on the same day, this happened a week after the 2 perfect flights, and i know why they were perfect, because i didnt back the throttle down to below mid stick, i was 3 quarter and over exept for landing but it was close in, so no interferance was encontered, i got interference a week later when i tryed to do a bank at a lower speed setting below midstick, i will phone desert aircraft and ask them, could it be the ignition...

I would bet on the Medal to Medal, and I think you mean the radio is going into Fail Safe not PCM

the throttle and choke servo have the ignition switch right next to it, so im going to put the switch on the other side, im also buying some RF Filters/RF Chokes, to put around the servo leads.. And im buying a servo icolator from i4c hope this should get rid of it, what do u guys think?

Good for a start

not necessary unless you are using them temporarily to troubleshoot.



Waste of money IMO..

why is it a waste of money, it will make sure for 100% clean/non interference running?

The isolator will make sure any RFI that the servos might be picking up are not transferred back to the receiver, however, it won't block any RFI the receiver's antenna might be picking up. It protects against the possiblity of long servo extensions picking up RFI and routing that back to the receiver so it protects against that scenario but if you have a metal to metal vibration the receiver (not the servos) is picking up or if the receiver itself is picking up RFI from the engine, it won't help. A choke on long servo extensions would probably do close to the same thing.

What he said!

I have 2 twisted HD extentions running down the fuse to the 2 servos driving the elevators, then underneath this on the outside of the model is my Futaba reciver antenna, is this ok, shouldnt make any difference? I am going to move the ignition switch to the other side of the fuse away from my Throttle and Choke servos, i will get back to you guys on the results and findings, if this dosnt fix it, could it be a problem with the Ignition Module itself? i have phoned DA Aust and he is getting back to me in the Morning.. So ill have a lil chat with him... Ill see how i go, keep those suggestions flowin

Have you checked the condition of the plug wire to see if it has been rubbed raw by the cowl? That's just one of many things that could be wrong. How old is the ignition battery, and how well is it holding a charge? A weak ignition battery will cause glitches all by itself.

Definentlly check the spark plug cap and wire,i just had all sorts of interferance from the metal shield vibrating some.

I would be very interested in knowing the power system on this airplane. What I am thinking is that at that throttle setting is when the engine vibrates the most. When it does this the servos have a hell of a time trying to keep the surfaces from bouncing around. As a result of this the servos are going to draw lots of power and may be pulling the nominal RX vlotage down below what the RX needs. If the ignition is going to create RF it will do so at all RPM. The suggestions of something being loose causing a problem at a certain harmonic is good too.


Shawn

the ignition cable looks fine as i said its brand new, the spark plug cap is fine to the best of my knowledge...I am running a verry good power system so there should be no problem there, the ignition battery is 1 year old or less... Its a 2000Mah NIMH...
Im running Fromeco 4800Mah Regulated down to 5.98 Volts. So no problem should lie there... I seriously do wonder though, why the interference only happens at just above idle power setting... Its got me stumped? Im more and more leaning towards somthing wrong with the Ignition module itself.. Even though its brand spankin new. And there is nothing vibrating in the plane, reciever is strapped down in foam, so is the regulator, so is the Fromeco battery, all servos are secure, linkages are tight, Im running Carbon fibre tubes with threaded rod inside, with two locknuts on each end, with ballinks on the servo end and platic clevises on the motor end. No RF should be occuring there... Will phone up DA Aust now...

Why dont you try a different RX?

Mabe the excessive vibration at that throttle setting is enough to mess with the rx? bad crystal? cracked filter?

its a brand new reciver but, i will take it down to the field with a spare reciever this saturday, and if it dont improve with the movement of the switch ill try the other RX i have, another Futaba 149dp. I just came up from the garage i wraped the ignition wire (spark wire) in that black swivel plastic tube then i zip tied some fuel tube ontop of that so it dont get interference from touching the muffler...
I have a good fealing about the moving of the switch i want to give it a go now but have to wait till the weekend, peace out guys

Ill let you guys know the verdict as it comes to hand...

Try installing a FM receiver temporarily. They are better at showing up interference, this will help you chase down the problem.

TF

on your spark plug cap,make sure it is tight at the base of the plug were it grounds,this has been the case in some of mine