GY 401 With 9253 Digital Servo

What else can I say about this gyro, but EXCELLENT!

This is Futaba's new Gy401 heading hold (avcs) Piezo gyro with a digital 9253 servo. It has to be one of the easiest gyro's I have ever set up and flown with. It has easy to use features in a small size package. Its about 1" x 1" x 3/4" in size (27m x 27m x 20m). Very light weight and compact. I'm sure it would even do well in a small electric helicopter. The 9253 digital servo is FAST. 0.08secs. While the torque isn't that strong, only 2kg, it seems to hold very well during mile high tail slides.

The package contains the gyro, 9253 digital servo, 3 small double sided foam mounting pads, miniature adjusting tool, and instructions.

These are the gyro's features:

Dir - (direction) This allows you to set the direction of the tail rotor servo.

DS - (digital servo) This option is to set it for either a digital servo or a non-digital servo.

LIMIT - This option is to set the amount of travel for the tail rotor servo. It will allow up to 140% travel on the tail rotor servo. Ideally you want to stay at least 100%.

DELAY - This trimmer will allow you to set the amount of "delay" after you do pirouettes. If you get any "hunting" after you stop the pirouette, use this feature to eliminate this.


This is my setup for my X-cell SE. I also use the futaba 9zw2 for control, but its a basic set up that practically any transmitter can take advantage of. You should have at one extra channel for control between heading hold and normal settings, and for gain control. A switch channel is recommended.

First I mounted the gyro using the included foam mounting pads. Then mount the tail rotor servo and route the lead accordingly. I connected the "sensitivity switching connector" to channel 5. The other lead goes into your rudder channel. By the way they did a nice job to give you long enough leads to the receiver, but as usual the lead to the tail rotor servo is "just" long enough. They ran a "4" lead wire to the receiver and split it at the last few inches. This was nice because now you only have the "one" lead to route to the receiver.

Set Your transmitter ATV's to 100% for both travel. If your using the 9z, make sure the ATV's are all set for each flight mode. MAKE SURE YOU TURN OFF ALL TAIL ROTOR MIXES, AND REVOLUTION MIXES. I mounted a large wheel the tail rotor servo. My length out ended up being 15mm out from the servo center. This gave me just over 100% on the "limit" function, bind to bind. I did however back it off a little more so I could make sure I didn't bind the servo. During flying this proved not to be a big issue. I still had plenty of gain combined with pirouette rate.

You should be able to get pretty close to "equal" throw on both sides. If your off move your drilled servo arm hole in either direction. Get as close as you can.


When you turn on your transmitter then receiver, wait till the tail rotor servo centers. MAKE SURE YOUR IN HEADING HOLD (avcs) before you turn on your receiver. Unlike other gyro's this one will "neutralize" pretty fast, about 3 seconds.

Before lift off turn the gyro into the "normal" mode. Lift off the helicopter and adjust the t/r trim to keep the helicopter straight. Then you can adjust the amount of gain. Adjust this till the helicopter starts to "hunt" then back it off from there. Right now I'm using 45% gain. My helicopter will not "hunt" till about 85% gain. So you can see the amount of lee-way you have. I figure that the farther away from "max" gain you are the better. This will keep the servo from "over working" and hopefully last longer. This 45% gain will allow me to have enough gain to do tail slides and backwards flight. But the end result of course is up to you.

You don't want a lot of rudder trim in normal mode. If you do need allot you should "retrim" the tail rotor pushrod. Make sure you don't bind the servo again.

After you have the helicopter trimmed for "normal" you can set the "heading hold" or avcs as futaba calls it. Land the helicopter and switch between "normal" and avcs mode 3 times real fast. This will tell the avcs side of the gyro what "neutral" is. Hover the helicopter again and set the gain for the avcs side. Like stated above, I use about 45% gain here also.

I didn't need any of the "delay" function. If you do some pirouettes and when you release the stick the helicopter stops but does a little "wag" or hunting, then adjust it out with this "delay" function.

Remember though, Don't adjust the "limit" function again. Its there to keep the servo from binding. You can adjust the pirouette rate using the rudder ATV function in the transmitter. Between this and the gain settings you will end up with a great flying / working gyro.

These are my settings.


ATV rudder = 120% left

ATV rudder = 130% right

ATV channel 5 (gyro gain) 45% for both sides. (normal and heading hold)

Servo distance out from center to pushrod = 15mm

As you can see, I ended up with different ATV's for rudder gain. This is because I used the travel adjustment to make the helicopter pirouette at the same rate in both directions. This travel gave me a super fast pirouette rate.

That's about it. Very easy to set up. It took me about 5 minutes to do the complete flying setup. In a "nut shell"... hover in normal, trim rudder, set gain, land, flip between avcs and normal 3 times fast, hover, set gain, set rudder atv for pirouette rate, have fun!

Be safe, have fun!


Copyright © 1999 by [Helibuf's World]. All rights reserved.
Revised: 27 Aug 2003 20:33:32 -0700 .