The old DX6 was based on the JR 662 radio. Gyro programming is done as follows:
Plug the gyro gain control lead into RX channel 5.
You have four different switch selections to choose from to control the gyro:
The HOLD Switch
The Aileron Dual-Rate Switch
The Elevator Dual-Rate Switch
The Flight Mode Switch
The switch that will be used is set in the system menu window titled "GER":
In the GER window, "H" selects the Hold switch, "A" selects the Aileron D/R switch, "E" selects the Elevator D/R switch, and "F" selects the Flight Mode Switch.
NO matter WHICH switch you choose, the GEAR channel Travel Adjust/End point setting is what controls the gain.
A related system menu in your transmitter is the D/R SW menu, where you again have four choices to select how to control the dual-rate settings:
E.A -- the elevator and aileron dual-rate switches operate independently
.A -- the Aileron D/R switch controls BOTH aileron and elevator dual-rate settings
E. -- the Elevator D/R switch controls BOTH aileron and elevator dual-rate settings
CF -- the flight mode switch controls BOTH aileron and elevator dual-rate settings
Generally, no matter which of the four switches you use to control the gyro gain (Hold, Aileron D/R, Elevator D/R, or Flight Mode Switch), you'll have one switch position that selects NORMAL mode operation (gain adjusted by the 0 to -100 value of the Gear channel endpoints), and the other switch position will select HH mode (gain adjusted by the 0 to + 100 value of the gear channel endpoint setting).
Beware that this presents a problem if you use the Flight Mode switch to control the gyro, as simply changing flight modes will switch you between Normal and HH mode. That's usually not desirable. The second problem this introduces is that the 401 MUST be initialized in HH mode for it to work properly. If your flight mode switch is in the wrong position when you turn things on, the gyro won't work properly.
This is less of a problem if you assign the gyro control to the HOLD or either of the Dual-Rate switches, as you can just leave the switch in the HH select position all the time.
BUT -- there is a nifty workaround for this problem. If you increase the SUB TRIM setting of the GEAR channel (positive sub-trim), you can make it so that EITHER switch position selects HH mode (gain is still controlled by the GEAR endpoint settings, and the gain number will be relative to the sub trim value (the endpoint setting that goes 0 to +100 will make the gyro more sensitive relative to the Sub trim number, the endpoint setting that goes 0 to -100 will make the gyro less sensitive relative to the sub trim number).
If you were to make the SUB TRIM number negative, you could end up with two switch positions to control gain, but neither would put the gyro in HH mode. That would not be desirable, as you MUST initialize the 401 in HH mode.
With this solution, however, you will have two DIFFERENT gains, dependent upon the gain control switch selection. You cannot have the same gain for each flight mode IF you use the flight mode switch to control the gyro.
Your best bet would be to assign the gyro control to one of the Dual Rate switches, leave the sub trim for the GEAR at zero, and that would allow you to have one HH gain setting, and one Normal mode setting. If you added in positive SUB TRIM to the GEAR channel, and used one of the Dual Rate switches to select gain, you could have two different heading hold gains, selected by that switch.
If you do choose to use one of the two dual-rate switches to control the gain, then it would be best to set the Dual-Rate select menu up so that switch does NOT do anything with the dual rates.
For example, if your GER menu is set to GER = "A", you would NOT want the D/R SW menu set to D/R SW = "A". Set it to "E" or "CF".
The last step in setting up the heli, after you have it all trimmed correctly, is to RE-BIND the receiver to set up the fail-safe settings.
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