This one is getting the best of me. Here goes – I recently purchased a U-Can-Do with the engine/radio already installed. The engine is a Saito 100 and it has the following radio components:
Receiver: Hitec (Standard) channel 27
Rudder: Hitec mini hi-torque
Elevator: Hitec hi-torque (x2)
Ailerons: Hitec standard bb
Throttle: Futaba standard bb
I purchased a new crystal (58), and was told that there should be no problems in going from one range of channels to the other. I was told once that you should get the receiver ‘conditioned’ if you do jump ranges – I was also told that this is only for AM radios.
Anyway, I used my new (as of xmas) Futaba 6EXA for the transmitter since this was my second plane on this radio. I had to flip one of the elevator servo arms 180° since I did not have a servo reverser/y-harness available. I set the aileron servos in slot 1 and 6, using the flaperon feature of the radio. I found a 2 into 1 harness for the elevators but this did not correct the alternate direction of the elevator throws (thus the reversed arm), and used one channel each for the rudder, and throttle. The plane flew very well for a couple dozen flights in this configuration. I then got my hands on a servo reverser and corrected the servo arm problem – now all linkages/pushrods are straight.
Here is where the problems begin, after two weeks in the new setup, I noticed the airplane twitching a little in the air. No big deal here in ‘windy’ Wyoming – just thought it was a breeze that was aloft affecting the flight. After a couple more flights and the twitching getting noticeably worse I decided to bring it in and figure this out. Out of nowhere ‘bam’ the rudder kicks hard (I mean all the way to the limits) right and I almost lose the plane on the turn from base to final (talk about pucker factor). A successful landing and I was off to clean out my shorts.
I get the plane home and turn everything on – no buzzing or twitching of any kind (at least for a couple of minutes). Then you hear a slight tick, tick here and there – I move around the transmitter a little and when I hit the ‘sweet spot’ all heck breaks loose. Then I move the transmitter a little more and nothing. I replaced the receiver with another one I had laying around – bought a new crystal and figured that should ‘fix’ the problem (the antenna is routed outside of the fuse just aft of the wing attachment point). Took it to the field for our ‘picnic’ day and when range checking it, the ‘glitch’ was back (I couldn’t duplicate the glitch at home after the receiver replacement – thus thought it was fixed). We tried almost everything – from bypassing the switch, to routing the antenna out to the wingtip. Nothing worked. We also replaced the servo reverser to see if that might be producing feedback – nope. So another day lost (at least the plane wasn’t).
At home I turned the airplane on and also turned on my other plane on the same channel – the U-Can-Do twitched like mad and the Four Star was as solid as a rock. So I pulled the Futaba receiver (that came with the 6EXA) and placed it and the battery in the U-Can-Do. Maybe the problem was with the Hitec system, or battery. Put a full charge on it and took it to our fun-fly this weekend. Guess what – same thing! I forgot to mention that we are range checking the plane with the antenna down on the transmitter at about 40 paces – the glitch begins sometimes in the teens (paces) or sometimes to 30 – but never consistent. So a buddy of mine on the same channel turned on his transmitter to see if that is the problem – nope the plane still twitches even with his transmitter on and mine off. I pulled all of the radio equipment out of the plane – checked all of the leads and servos – the rudder servo had a bare spot on the red wire – when I plugged it into a receiver with other servos they all bounced around when I plugged it in. Thinking I had this problem licked – I installed a spare Hitec standard bb servo in the place of the rudder servo, installed the high-torque Hitec elevator servos, and replaced the throttle servo with a new bb Futaba standard. To my disappointment it still twitches. I checked the throttle linkage – it has a metal clevis – but goes to a plastic servo arm, the other end has a metal ball/plastic ‘cup’ on the other end to a plastic throttle arm. I’m not sure if this is the culprit – but I am almost at my wits end on this. Sometimes when it is glitching, I can move the transmitter just a little bit to one direction or another and it will stop. The receiver antenna is routed in a straight line (no loops or anything), and all the leads look in good shape.
Please help.
bill
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