airplane heading gyro question
the following components/settings were used to install a heading gyro in a quarter-scale tailwheel aircraft: Futaba 6EX 2.4 GHz transmitter. Futaba R606FS receiver. Detrum GY48V gyro. Futaba analog servo. 4.8V nicad. JR JRPA004 on-off switch. Unused gear channel 5 used for gyro gain control. gear switch on transmitter used to select between heading hold and rate modes. heading hold will not be utilized, so its gain set to 3% to simulate the off position for the gyro. Rate mode will be used, and its gain set to 80%. The following problem exists: when system is powered up and heading hold is selected, system works as intended (no rudder movement when yaw introduced and servo remains quiet). Now when rate mode is selected and yaw is simulated, servo acts to counteract yaw as intended; however, the rudder servo has a constant low level chatter/jitter in idle mode (no yaw introduced). This chatter can be eliminated by taking the 80% gain down to about 30%, but this severely limits the rate mode function. Any ideas out there about what's causing this chatter at the 80% gain setting? Different quality servos have been tried, but all so far have just about the same chatter. Any wisdom greatly appreciated.