My APM 2.5 running ardupilot 2.68 with an A/S indicator, seems to bump and bounce around while the plane is on the ground and not moving. It's not a lot, just a little movement, shouldn't it be completely still? Can anyone suggest what setting I should adjust to get the attitude more stable?
That is completely normal and becomes more accurate and precise when your aircraft is in motion.
Mine is bumping around too.
Just a little bit, between 10 cms and half a meter at most
Don't worry about it, thats just the way the barometric altitude sensor is reacting to changes in air pressure and temperature.
Haven't had a single problem while flying.