Heading Hold Gyro setup:
First, if you are using a heading hold gyro (such as the GY240 or GY401) you must make sure your transmitter REVO MIXING option is disabled, because this option is only for non-heading hold gyros.
If you are using a Piccoboard with a heading hold module, you do not need to trim the helicopter properly without the heading hold module installed (e.g. as a yaw rate gyro). Just install the heading hold module and it should work properly as a heading hold gyro. You may need to adjust the gain however.
There are three controls which require setup on the GY240.
Set to ON. AVCS is Futaba's name for "heading hold" and you want this enabled.
Disconnect the heli motor and position the heli so the nose is pointing towards you and the tail is facing away from you.
Turn on the transmitter.
Plug in the heli battery.
Wait for the gyro to initialize.
Hold the heli firmly with the tail pointed away from you and arm the tail ESC by holding full left rudder on the transmitter.
The tail motor should start. Rotate the heli left and right by about 30 degrees. If the tail motor is pushing against the direction of rotation, then this is correct.
If the tail motor is pushing in the same direction as the rotation, this is incorrect, and you will need to toggle the DIR switch to fix the problem.
Set this to 50% to start. It can be decreased later if the tail wags too much, or increased if the tail wanders too much.
There are five controls on the gyro and one on the transmitter which require setup on the GY401.
This should be OFF. There are no tail ESCs which are compatible with the digital servo mode.
The tail motor will behave like a very very slow tail servo so the delay should be set to a large value. Set this to 100% initially.
This controls the range of throttle for the tail ESC. Set this to 100%. If you set the limit too low (less than about 90%) then you will have problems arming the tail ESC.
This is done at the transmitter on channel 5 for both Futaba and JR radios. If you have a newer Futaba radio (like a 9C) this is already handled in the GYRO SENS menu. In this menu set the mode to AVC and the sensitivity to about 50%.
If you have a Futaba/Hitec (negative shift) radio, channel 5 settings below 50% are non-heading hold mode sensitivity and settings above 50% are heading-hold mode sensitivity. Initially, set your channel 5 to about 75% travel.
If you have a JR (positive shift) radio, the settings are swapped, e.g. below 50% is heading hold sensitivity and above 50% is non-heading hold sensitivity. Try setting your channel 5 to about 25% travel.
You should follow your manufacturer's directions.
In addition, you should set the subtrim step size to the smallest increment possible so you can get very fine control of the rudder neutral point so you can match the transmitter's rudder neutral point to the gyro's neutral point. On the Futaba 9C, go to the TRIM menu and change the rudder step size from 4 to 1.
If using a separate yaw rate gyro (not Piccoboard):
You need need to enable the REVO MIXING feature on the transmitter and adjust the REVO MIX curve to effect revo mix changes.
If using any Piccoboard WITHOUT the heading hold module or a 3-in-1 or 4-in-1 combo board:
You will need to adjust the REVO MIX dial on the board to effect revo mix changes.
The revo mix controls the speed or pitch of the tail rotor relative to the throttle position. This is required to counteract the torque generated by the main rotor blades so the heli does not yaw while in flight.
You will need to adjust the revo mix so the heli does not yaw at all throttle positions.
The best way to do this is to buy a "lazy susan" type turntable that will allow the helicopter to rotate freely while the helicopter is weighed down so it won't take off inadvertently. (Rubbermaid appears to make one which is probably suitable)
Perform preflight checks, then slowly apply throttle. The helicopter will start to yaw as you apply throttle. You will need to adjust the revo mix so the heli has no tendency to yaw as you slowly apply throttle. It is normal for the tail to swing a little when changing the throttle, as long as the heli does not continuously rotate while the throttle is not changing.
If the helicopter is rotating and you need to increase the thrust of the tail rotor to counteract the rotation, then you should increase the revo mix at that throttle position or turn right the revo mix dial on the Piccoboard.
If the heli is rotating and you need to decrease the push of the tail rotor to counteract the rotation, then you should decrease the revo mix at that throttle position or turn left the revo mix dial on the Piccoboard.