I am running the Smart-Fly Sport Plus set up on all 2 Giant Scale Airplanes. One is a 50cc size and one is a new Aero Works YAK 54 with a DA 85CC engine. From the very first flight, I have experienced throttle problems. On the first landing the throttle began to surge and we used the Ignition Cut-Off to get it on the ground safely. The Throttle Servo was replaced and it did the same thing on the next flight. Again, cut off the ignition and dead stick it in. I then took the aircraft home and worked on the bench, thinking I had isolated it to the white control wire on the Smart Fly "A" lead which feeds the throttle (if wiggled, it was loose and caused the servo to glitch) and is one of the leads furnishing battery also.

Yesterday when I was preparing to fly and started the engine, it went to full throttle and stayed there. I again used the ignition cut-off to stop the engine. This morning I removed the servo which would not operate at all in the Aircraft and then plugged it in, just for fun, into the Smart-Fly board "A" slot, it's normal position. It worked fine!

So basically I am fighting an intermittent problem that cause multiple symptoms. I have a spare Smart Fly board from a now retired aircraft and could substitute it for the current board. In addition, I have a spare 921 receiver from the same aircraft I could try.

Has anyone ever run into this type of servo problem before and if so, what was the cure for the problem?

Thanks
Mike

I'd take the smat fly out and see what happens. My guess is you'd still have the same problem.
Then start eliminating stuff one at a time, start with servo extensions I've seen some go bad with no visible signs. Crystals are the weak link in FM recivers so also replace the crystal and see what happens.

I have tried everything you mentioned and this afternoon I switched out the Smart Fly board to one I had flown previously with no problems. Ran it on the ground for 15 minutes or so and it seems fine. Will fly it this weekend and see what happens.
Mike

I need to add that I am using a JR 921 receiver on 2.4 and 2 remote recievers.
Mike

i just had a post about my da 50 surging and it turned out to be my brand new ignition module. 2 of us from our 50 person club had the same problem and narrowed it down to a bad ignition on 2 new engines. da said it was "unusual" but thats pretty bad odds. i started replacing items one at a time until i found the problem.

Thanks Jeff for the information. I will certainly keep this in mind. I am a big advocate of DA Engines and Smart Fly Boards, so I will certainly be looking for a "real" solution to this problem. I think too many times, we just are looking to place "blame" on something. I really hope to pinpoint this problem.
Mike

my surging came at half throttle, with yours going to full throttle and staying there with no control it might not be interference from the ign.

I had a similar oscillating throttle at one time but solved that by using an RF filter. Wrap the throttle servo extension around this ring and snap it closed.

hello i have a Gp extra 330s with a da 50 both have like 5 months old at 1 month ago i start having problems i use one jr 649 receiver spcm 5 digital hitec servos and one standar servo to the throtle when i be flying some times not constan like 2 or 3 time per flight i get some pcm glitch and the fail safe get on the ignition module is near the engine but far away of the reciver about 40cm between , i plan to use some rf filter like one of the pictures but still dont know where to installed on my plane i be thinking to install on the ignition cables and the receiver antenna its that ok ? please help

NO put nothing on the antenna lead never ever..,the coils like in the picture are to go around the servo leads and extensions

Originally Posted by 3ddd

NO put nothing on the antenna lead never ever..,the coils like in the picture are to go around the servo leads and extensions

thanks for your help but can i put some of this rf filter on the cables of the igniton or not-?

as far as the spark lead i don't think it can hurt but i also don't think that will help but it is worth a try, mostly just on the servo leads is what helps the most with rf coils

thanks i gonna try because its not confortable fly in the way i am doing because for intermittent times come that interference