Thanks for all the interesting ideas, opjose. I will try that "one channel at a time" test sequence.
I noted in my first post that the motors do respond to throttle stick position. The problem is that they also respond to the position of other sticks[
].
I'm working in my little shop out behind the house. 50 feet or so from the kitchen and its microwave oven. I don't have any WiFi operating but I can't be sure about my neighbors. No wireless phone but I do have my cell phone nearby but I think thats at 2.4 GHz.
The receiver antenna is pretty well extended except for the last 3 or 4 inches which hang down around the vertical fin.
A friend stopped by and we tried it with the TX antenna fully extended and fully retracted. Same behavior. Unfortunately, we didn't try it with the TX further removed from the plane. I'll have to try that but it's more difficult when I'm working alone.
Given this simple "SkySport 4" radio (non-computer??) I doubt that it's probrammed for some other type model.
Hopefully I'll hear back from NitroPlanes with some help. In any case I'll continue to post progress until it's resolved.
Thanks
Frank