Last Updated 12/14/98
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With the advancements in piezo gyro design technology, various manufacturers have been working overtime to out do each other with that extra feature which makes their product more preferable. The "Heading Hold" technique implemented first on CSM gyro was probably the best thing that has happened since the introduction of digital proportional radios to the R/C industry. And it sets off other manufacturers scrambling to come up with units with similar capabilities. |
 The old meets the new. Note the difference in size. |
The latest gyro from Futaba, GY-501, is their attempt to regain the gyro market with their version of heading hold called Active Velocity Control System (AVCS). This little gem has enough bells and whistles to make it one of the most flexible gyro on the market. Since it is not intended for beginners, setting it up may be a bit tricky. But before we go into that, let's check out some of its features. |
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Physical Appearance:The gyro is housed in metallic anodized plastic casing, a bit heavier than its G501
predecessor. There are 4 screws holding the gyro casing together, one of them covered with
silicon for possible anti-tempering purpose. The wire that comes out of the gyro is the
standard Futaba black/red/white wire with normal servo lead, not the black insulated wires
in their previous gyros. |
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To an untrained eye, the gyro amplifier looks exactly like the
Futaba GV1 governor. Similar to GV1, there are 4 push buttons, two of which for function
select, and two for data settings in each function. The menu accessing logic is similar to
that of Futaba 7/8UHP radios. The input/output jack layout is identical to previous Futaba
gyros, two leads goes into rudder and gyro gain channel on receiver, two jacks to accept a
servo and the gyro itself. The most noticeable feature on the amplifier is the 8 character
dot-matrix alphanumeric display which provides a good feedback of adjustments being done.
There is also a small dial for adjusting the contrast of the LCD display. There is no
power switch on this gyro. Upon powering up the gyro, the screen displays some funny characters and the RX's voltage. It was not until today that I was pointed out about the "funny characters" was in fact picture of a helicopter spinning its blades. Cute! |
| Included with the gyro is Futaba’s new 9205 servo
specifically designed for GY501. The spec lists its speed at 0.11sec/60 degrees with 4.8
volts, but it seems to be faster than other servos I had. I can’t tell much physical
difference between it and 9203 though. This servo operates at the standard frequency similar to all other Futaba servos. Therefore the "framing rate" setting on the gyro should be set to normal. Setting to "half framing" rate would fry the 9205, as it is reserved for servo specifically designed to operate in faster framing rates (such as JR's 2700G or Futaba's brand new S9250 digital servo). I also noticed my 9205 was buzzing constantly. This was confirmed to be normal. |
Functions:User are able to access 9 function layers from the push buttons, each of which contains adjustment to certain feature of the gyro. I have not had the chance to experiment with all these features, but here are brief explanations of what each one does: |
**IDLE** This is displayed when RX is switched on with the TX being off. |
Setups
 gy501 amp on Reza Fatemi's XL-Pro
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The instruction booklet I received
wasn’t very helpful since it was in Japanese. The English manual is now available
on top of this page. It does show some diagram of example setups for both 9Z and 8UHP
TX. I opt to set mine similar to CSM to avoid complications. Basically the gain channel is
used to adjust gyro gain and switch between AVCS and normal gyro modes. The gyro is in
normal mode when the gain channel output is between 0% and 50%. 50% to 100% will switch
the gyro into AVCS mode. The amount of output in each mode’s range is interpreted as
the amount of gain on the gyro. No suprise here. What is very interesting is the way it centers
the rudder trim. The way to trim this gyro is this: First the mounting point on the
servo horn needs to be 13.5mm from the center, with the horn EXACTLY 90 degrees
perpendicular to the sides of servo case. Up on powering up in the CMT mode, switch to
normal mode and trim the rudder with rudder trim tabs. When satisfied, land the helicopter
and then switch the gyro mode 3 times in one second between AVCS/Normal mode. This will
force the gyro to memorize the center point for AVCS mode. There is no need to trim
anything electronically or mechanically in AVCS mode. The LCD display will indicate the
updating process through different codes. Should the gyro become off center for whatever
reason (hasn't happen to me yet), repeat the above procedure will cause the gyro to
re-memorize the centering point. Another feature worth mentioning is that the actual gain as result of gain adjustment on TX and on gyro is displayed on the gyro’s LCD screen. In another words, the gain percentage display on the LCD is the actual gain calculated from the TX setting and the gyro setting. Latest Update (12/14)It has been a couple of months, and I have been trying to learn all the features on the gyro to fine tune its parameters and to explore its capabilities. Between busy work schedule and other commitments, I didn't have enough time to experiment much. I have since fitted my Baron30 with a carbon/titanium pushrod from Central Hobbies and a K&S tailboom servo mount. This combination was able to remove 90% of the slop in the system, which allowed the gyro gain to be increased a bit. The engine in the Baron seems to have broken in which is indicated by smoother transitions between needles. My current gain in AVCS mode is at 47% in normal, and 30% in idle-ups, still well below the 70+% indicated in the manual. I thought it was due to the belt driven tail, but the tail still locks in perfectly. I had to play around with the channel delay and tracking to remove the bouncing effect after pirouette. Absolutely no drifting was observed, and the tail just stay pointed at where you left it! I have never tried my CSM in this Baron, but compared it to my Concept where the CSM used to reside, the GY501 is more precise with a crispier feeling to it. When I get the chance to move the CSM into the Baron, I will be able to make comparison and report any differences then. The overall quality of the unit is superb, as expected from Futaba. With all these features incorporate in such a small unit, it should be a serious contender to the gyro market. Update! Here are my final settings on a Futaba 9ZHP radio:
On the gyro itself:
Questions and Answers > What I am trying to think out now, if I use a low throttle point to trigger > the governor, I'll be ^^%$ when I try to go inverted, right? You'll be fine if you keep your idle-up throttle curves as they were before the GV-1 was installed. Just don't try to flip it in normal mode. :-) > I am going to try to use the idle up as the on/off. What I hope to accomplish > is for the governer to function only in idle up 1 and 2 and for normal to be > just as it was before the governor. This is new territory for me...any > further or continued advice would be appreciated. Basically, you need a channel that changes positions when you toggle your idle-up switch. What kind of radio do you have? With the Futaba 8U, channel 8 will do what you're looking for. With other radios, I dunno. If you've got a channel set up to switch gyro gains when you go into idle-up, you might be able to get what you want by connecting the same output (via a y-harness) to the GV-1 on/off input.
> We tried having the GV-1 kick on and off at a low throttle stick > position and had your fears come to light - forgetting to switch to > idle up and having the throttle go to idle. You can guess the rest of > the story. Sure, but just don't go inverted unless you're in idle-up and everything is OK. Unless you expected the GV-1 to allow you to fly 3D in normal mode, I don't understand why this is a concern. It seems to me that having the GV-1 disengage at low throttle is a great feature - that way it will automatically turn itself off after you land in normal mode and bring hte stick down, or after you hit throttle hold from any mode, and this is without any special Tx programming or extra switches to toggle. > We use normal for starting and shutting down. We have the govenors > kick in at 1000. So, the procedure is: start engine in normal and move > heli into position, advance throttle to about half stick, as rotor > gets close to speed switch to idle up 1, reduce pitch to preclude an > inadvertent lift off at low head speed, when the govenor has > stabilized take off. All of our flying is done in idle up 1 & 2. Land > in idle up 1 and switch to normal to throttle down. With this routine, there's no reason NOT to set the GV-1 up so it disengages at low throttle. If you find that it turns off when you're in idle-up, you can either raise the lowest throttle point in your curve, or lower the percentage at which the GV-1 disengages. I just leave the GV-1 in the 'on' position all the time. At some point during the first spool-up (or after an auto) you'll hear the GV-1 start to take over the throttle. After that, everything is no different than without the GV-1. At the end of the flight, you can land in normal mode, bring the throttle stick down, the GV-1 will disengage and the engine will return to an idle. No new habits to learn or switches to mess with. > It takes a little practice to getused to landing in idle up. I've gotten into the habit lately of spending all of my time in idle-up-2, and yeah, landing this way is a little twitchy with a 30. Now I hover down to 1-2 feet and hit throttle hold. My idle-up-2 and throttle hold pitch curves are the same, so the heli just settles down gently. As a bonus, the rotor speed decays quickly, so you can carry the heli back to the bench a little quicker. :-)
> For a JR 8103 transmitter I like the idea of tying the the gov on/off > to the throttle channel (not the stick position!). I have plugged the > gov on/off lead into channel three as slave to throttle. Actually, the GV-1 has a built-in feature that watches the throttle and turns on and off accordingly, WITHOUT using the on/off lead. So disconnect the on/off lead for now... Just plug the GV-1's throttle input to your Rx throttle output, and set up the StSw (stick switch) function in the GV-1. The GV-1 instructions will probably explain this better than me. Leave your throttle curves where they are, don't change them.
> If the govenor is set to turn off at a throttle position what happens > when you unload the rotor (i.e descend) and the governor in an attempt > to prevent the blades overspeeding fully closes the throttle. The GV-1 will never reduce the throttle beyond a pre-set amount. I think that amount is about 25% but I'm not sure. This was done, I'm told, to keep the GV-1 from killing your engine during extreme descents. As a side-effect, some of us have noticed that you still get a little bit of overspeeding during descents. From the reports here, I think this is mostly only an issue with glow engines on tuned pipes, and with gassers. In any case, it's a very minor issue in my opinion. My Concept showed a little bit of overspeeding during descents, but my Futura never did. > Does the governor then turn off ? The governor watches the throttle INPUT to decide when to turn on and off, so changes to the throttle OUTPUT shouldn't have any effect. > I previously had my GV1's set up via the throttle and am sure that I > had this occur which scared me away from this setup method. What makes you think that the GV-1 was closing your throttle all the way? Did your engine sputter out during a descent? The GV-1 is designed not to do this, so I suspect there's something else going wrong. |
 YS's new 61ST2 engine  The other side  Close up of the 3-needle carb |
YS 61ST-2 EngineAs my luck would have it, Reza fatemi was running the new YS 61ST-2 engine on the XL-Pro where the pictures of GY501 were taken. The heli was screaming doing fast forward flight using Hatori muffler and 30% PowerMaster synthetic. According to Reza, this engine puts out noticably higher power than the previous 61ST. The new 3 needle carb allows fine tuning of the throttle curve. Expect this engine to be available in the near future. |
Specifications
| GY501 Operating voltage Range: 3.8-6.0V DC |
S9205 Speed: 0.11sec / 60 degrees |
S9250 [Image 1] [Image2] Speed: 0.11 sec/60
degrees (4.8v) |
![[Image2]](http://stephen.eni.net/heli/gyro/psn00002.jpg){kind=link}
This from stephen's web page ->http://stephen.eni.net/heli/gyro/
I promised to put in some disclaimers on this page, so here it goes:
All above content are the opinion of the author. Futaba does not guarantee any comments or claims made on this page. Any comments or feedback are greatly appreciated.
Futaba, AVCS, and all pictures are copyright by Futaba Corporation of America.
Thanks to Reza Fatemi for helping me set up the AVCS mode and patiently answer all my questions.
Thanks to DA and Ranger for their help and translation of user’s guide.