Gyro GAIN on the 401 is determined by the settings of the channel that you have the single-wire gain lead plugged in.
If you're using a channel such as the gear channel, and using the gear switch to control gain, one position of the switch will give you AVCS/HH mode, the other position will give you Normal mode. Gain for each mode in this case is set by the travel limits associate with that channel and both of its switch positions. IN both cases, 0 sets a gain of 0, and 100% sets a gain of 100%. Mode is determined by the position of the switch.
If you're using a channel to control the gain such as Aux 2 (channel 7) and a JR/Spektrum radio's Gyro Sense menu in AUTO mode, then the GAIN is controlled by numbers in the Gyro Sense menu. Numbers between 0 and 50 will put you in Normal mode, a setting of 0 = 100% gain, a setting of 50% = 0 gain. Numbers between 50 and 100 put you in AVCS/Heading Hold mode, where 50 = 0 gain, and 100 = 100% gain.
In ALL cases, the RUDDER channel ENDPOINT settings (travel adjust) ONLY control the maximum allowable yaw rate
at which you will allow the heli to spin when you romp on full rudder. Normal setup procedure is to leave the endpoint settings at 100%. Once you get all the rest of the gyro set up and operating, go to a safe hover altitude and apply full rudder. If the heli spins too fast for you, then DECREASE the rudder endpoint setting for that rudder direction. If the heli spins too slowly to suit your skills, then INCREASE the rudder endpoint setting for that direction.
Ideally you would shoot for equal yaw rates for left and right rudder. With the GY-401, this is usually an unachievable goal, but you can usually get close. This also means that your rudder travel endpoints may be different for left and right rudder.
TRAVEL ADJUST to limit the overall servo travel (and therefore prevent your servo from driving the pitch slider into its left and/or right mechanical limi)t is performed using the TRAVEL LIMIT adjustment on the Gyro body. This is usually set in most heli kits today by setting your RUDDER travel endpoints to 100%, centering the servo at neutral, having the proper pushrod to servo arm geometry, then setting your tail rotor pitch slider in the center of its overall travel range. Next you apply full rudder (works best in Normal mode, as the servo follows the stick) and adjust the TRAVEL LIMIT pot just to the point before the pitch slider bottoms out. Check this for both left and right rudder, and adjust accordingly. Again, with the 401 you may not be able to truly get equal amounts of left and right overall travel and this setting will be a compromise.
Remember that when you are flying in heading hold mode, you are no longer directly connected to the tail servo. The gyro is doing the driving, your stick inputs are only telling it which way to let the nose turn (left/right), and how fast to let it turn (amount of stick movement from center). The Gyro actually provides the endpoint limits to your system, the maximum rate at which the heli will spin is controlled by your rudder channel travel adjust setting.
You may or may not choose to use equal gain in all flight modes. The gains you choose will be determined by your flying style in each flight mode, and will be affected by the head speed you're set to run in each flight mode.
In the GY401, switching between Normal and HH mode while airborne can be disastrous, especially if you decided to move the rudder trim tab while flying in Normal mode.
With your 9503, if you're using the Gear Channel to control the gyro, you're plugged into channel 5 of the RX with the gain lead. The UP position of the Gear switch will select AVCS/HH mode, the down position will put you into Normal mode.
You MUST initialize the GY401 at power up in AVCS/HH mode or all bets are off on how (if) well the gyro works. You will end up with a single gain for all flight modes as you're not likely to switch between AVCS/HH and Normal mode in flight.
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