I have been trying to isolate an intermittent servo twitch the last couple days. I have the APM 2.5 in an X8 running ArduPlane 2.68.
I have power going to the output rail with a 5V Castle BEC.
The twitch is very random and fairly small deflection. In manual mode if I slowly move the elevator or aileron stick I can get it to do it, just not 100% repeatable.
I have flown the plane a few times. I tested stabilize mode and it worked great, but while flying in either manual or stab mode the plane will twitch randomly as if a side gust hits it.
I started removing components one at a time to see if it would stop. I pulled out the BEC and have been using a JR 4.8v receiver pack for the rest of the testing.
I was down to just the APM (no GPS, telemetry or airspeed connected) and the Futaba receiver. It still did it. Straight out of the receiver it was OK.
I tried a new APM loaded with same firmware and I got the same results.
I have tried both analog and digital servos from Hitec, JR and Futaba.
I had the same APM in my Skywalker and it did not have a twitch. Only change was to add a airspeed sensor and elevon mixing when I installed it into the X8.
Just disabled the elevon mixing in the radio and the APM. Same results
Just tried another Futaba 8FG, calibrated it and same results.
I just remembered that I had a DragonLink through a JR9303 radio on the other Skywalker.
Swapped out to a Spektrum DX7/AR7000, calibrated and twitch went away.
OK, so now I need to find out why the Futaba is causing a twitch. I am using the Futaba R6208SB receiver..
I will try a couple different rx's to see if that changes anything.
Before I swapped receivers I changed the output to MULT vs MLT2.
MLT2 mode enables channels 9-12.
That did not fix it either.
Tried a R617FS receiver and no more twitching!
This requires changing the "frequency" screen from MULT to 7CH
Any ideas what is changing in the Futaba radio to cause a twitch when an 8 channel or higher receiver is used?