Interesting problem ...input invited
A control problem recently appeared in my old Sweetstik. I've been flying this for the past several years as my ski plane and never had an issue, old, tough, heavy , reliable plane.
I left it on 72mhz as I have only been flying it in the winter and never had an issue with it. At the field with some other planes on 72 before converting over I would get hit in a certain spot and the hit would be nothing more than a quick wobble and everything would be OK in a split second and it only happened on certain channels. There is a radio tower several miles away and a building about 1500' away with an alam system so I've always contributed one or the other as causing the hits.
Now I've flown it around 5 times this winter on 72 with no issues as normal and one day coming past this area all of a sudden the elevator goes full down and the plane is inverted going away from me at high rate of speed. It took me by surprise and I gave it full down , did an outside loop and got it heading back to me and again it went full down ! I got it back , cut throttle and landed it out in the lower forty...thank goodness there was 8" of snow on the ground!
I took out the 72 reciever and put in a 2.4 reciever on a different radio and checked all of the servos, wiring, etc...and all looked OK. Went out the next time now on 2.4 with a different radio and the same thing happened in the same spot! I got in back and flew in the rest of the way and landed it.
I thought the elevator servo might be failing so I replaced it and took it out yesterday and again it did the same violent maneuver in the same general area and I got it back and landed it.....getting good at this now !
Thinking it might be the battery or a bad servo drawing down the system, I put it on the bench and monitored the voltage on the reciever with all servos being actuated at the same time and the voltage never dropped below 5.8 from a resting voltage of 6.2.
Next I'll monitor the current and see what's happening there.
Interesting problen and if I can't find the issue I'll strip it out and put in different servos and battery.
Here is what's in it:
60 FS nitro, 6volt NiMh pack,Futaba 148 servos in the fuselage, 9201's in the wing , (2) 440 metal rods controlling the rudder and elevator but no metal-to-metal control rod connections between the servo arms and control horns, nyrod on the throttle,only servo extensions are for the wing.