Futaba's Gv-1 is a model helicopter throttle governor to help maintain the helicopters rotor head speed. As you can see it's a nice and compact unit. While designed to work with all the nice features of the 9zhp and 8uh helicopter radios, it will work with others. However, you might not get to take full advantage of its exceptional feature packed options. While it can be purchased for about $180 street price, it is well worth it will all its options. Its performance will out do any of the other electronic throttle controllers on the marked. Futaba really has did a nice job with this unit. I have flown mine now for a couple of months now and have configured it in many different ways since I used there 9zhp radio.
First I would like to list the features of this unit.
1- It comes with a 52 page manual.
2- comes with the needed hardware to mount
The onboard electronic features
3- RPM - speed display
4- MAX - max speed display
5- RSX - speed setting
6- Disp - speed display mode
7- GRT - rotor gear ratio
8- SWPT - governor on/off switch position setting
9- STSW - governor on/off stick operation setting
10- SWCD - governor on/off condition
11- GVOF - governor off high point stick operation setting
12- VOLT - battery voltage display
13- MXMD - mixture servo operation mode
14- MD - mixture rate setting
15- ATV - mixture atv
16- MSX - mixture servo reverse
17- MTRM - mixture trim
18- B/FS - battery fail safe
19- B/FD - battery fail safe position
20- LMT - limit setting
21- TST - throttle servo operation test
22- SEN - rotation sensor monitor
As you can see the GV-1 is packed with options. All of these features are displayed on a LCD screen. The unit is designed to keep the rpm of the main blades at a constant rpm. While nothing is perfect it, and depending upon your set up it should be able to keep the rpm within 50 rpm. So far I have been able to do so and the only time I really notice any over speeding is when I give a full negative pitch, right side up and "push" the helicopter into the ground, or at least towards the grown. Then I notice the rpm's picking up but still its well within a controlled and non threatening speed.
Now I will go through the features listed above and explain some of there functions. All are fully displayed on the LCD display that you can scroll through to find the function your after.
RPM - This will display the current engine or rotor RPM. You have the option of displaying either and controlling either.
MAX - This feature will display the max RPM above 95% throttle. This will help you find the max engine power. The unit will remember this rpm will the unit is powered on.
RSX - This is where you set the desired RPM of the rotor. You can have a 3 - position switch assigned to it so you can have 3 different rpm's. Its like having 3 idle ups. If you set any one of the rpm's to 1000 it will turn off the unit. This will and can come in handy. By default it is set to 1300 rpm's, 1500 rpm's, and 1700 rpm's.
Disp - This is where you set either to display the engine speed or rotor speed. By default it is set to rotor speed.
GRT - This is where you will set your main gear ratio. Then the unit can calculate your rotor speed based upon engine speed divided by gear ratio.
SWPT - This screen will set the direction of a on/off switch if you use it.
STSW - this screen is where you set the governor to be turned on by the throttle stick position.
SWCD - This displays the present governor on/off status.
GVOF - You can set the governor to turn off at the high side of the throttle setting. The rpm's must be over 1600 to do so though.
VOLT - The unit has a built in battery voltage meter. When the voltage drops below 3.8 volts the battery alarm will flash a "low batt" to let you know.
MXMD, MD, ATV, MSX, MTRM - are all part of a built in 9 point mixture control. The unit it self has a out put for a separate mixture control servo. These functions will allow you to set up and control the mixture servo from with in the unit. You can reverse the servo, trim the servo, set the atv of the servo.
B/FS - During set up if your radio has a throttle battery fail safe then you turn this off. Then you can use the built in battery fail safe of the unit. If you don't' have that feature in your transmitter, well you have one now. This will monitor the battery voltage of the rx and take the throttle to a preset (that you set) to let you know you receiver batteries are low and its time to land.
B/FD - This is where you set the where the throttle will go to when the battery voltage is low (3.8 v). Once your battery gets that low the throttle will drop to this preset position. All you have to do is take the throttle to max low position to reset the throttle so you can land. However you have only 30 seconds before this low throttle starts again.
LMT - Limit set. This is where you set the range of your throttle stick movement. This is to let the unit know what range you have for stick movement and can figure out where idle and high throttle is.
TST - This allows you to test your throttle travel.
SEN - After you install the magnet you need to make sure that the GV-1 is getting a good magnetic field to the sensor. This will give you a read out between 0% and 100% and to make sure the unit is going to work correctly, you are trying to get a 60% or better reading. So with this function it will take any guess work out of setting up the unit.
What a do all unit! Any ways. The first thing you do is mount the magnet into the engine fan. Now you can do this some times with out removing the engine but its better if you just break down and remove it. This is much better then messing up your equipment. The unit is supplied with 2 very little magnets. For the most part, the amount of material that you remove from the fan is replaced with the magnet so its an option to you if you want to rebalance the fan / magnet unit. I went ahead and did this and found that the unit still for the most part rebalance I have a metal fan so what I did was used the same drill to drill the hole for the magnet to just lightly "Kiss" the heavy side of the fan to remove just a little weight. What I did when I drilled the unit was to use a slightly larger drill bit then was recommended in the instructions. This gave me a "V" wedge shape. I slightly drilled a little at a time and trial fitted the magnet into the fan till it was just on the verge of being level with the bottom of the fan. Then all you have to do is glue the magnet in. However before you do this you need to use the unit to make sure you have the correct side of the magnet for the sensor. If you put it in upside down, the unit will sense nothing and will not work. All you need to do is turn on the sensor and go to the "SEN" function and find which side will give you a reading. Mark this side will something. Then you install the magnet with 30 minute or longer epoxy…DO NOT use JB weld glue or any other glues that might have any metal particles in it. Since I drilled the fan and it gave me the "V" shape I could then put the epoxy in the hole and lightly press in the magnet. This gave me a extra bond from a press fit. I also encapsulated the magnet with some epoxy. To this day I have not thrown a magnet. (Grin)
The unit comes with some 30 and 60 size sensor mounting plates that will attach to the engine mounting bolts. These should align to most fans.
Now the set up.
It is recommend that you use a fast servo for the throttle. This gives a faster throttle response do to the faster sampling rate of the unit. I personally did not want to by a fast $100 dollar servo for the throttle, so I installed a Futaba 132h servo. This servo has a .12 transit time and its ball bearinged also. This to me made it a very good choice and so far it has worked great.
At first I was a little leery not knowing how fast the unit would take over the throttle. Turns out it operates at a very moderate speed. This will keep you from tearing up any main gears. At first I set up the unit so it would turn on above a 20% throttle stick position. I also set up a 3 position switch for my desired head speed. Position 1 was set up to 1000 rpm's. This keeps the unit in the off position. Position 2 was set for 1550 and position 3 was set for 1700. While this was a good place to start it has changed. The nice thing about this unit is that it will tell you what your max rpm is. So I flew into a hover, turned on the unit. It worked as expected and elevated and hesitation about how fast it would take over the task of controlling the throttle. What I found was that the engine was at a different speed then what I originally set up. Since my engine was happy before I put in the governor, I reset the position 2 to 1510 rpm's to match my original throttle curves. In the manual it says to reset you throttle curves to a linear setting. However based upon talking to others I just left mine alone. The unit will totally take over your curves but in a event of failure of the unit it defaults back to your curves, so…. I left mine. Then I went to a full throttle climb. This then would keep in the "MAX" setting what my top end pitch rpm was. I landed and checked the unit and it told my I was running a 1680 rpm at top pitch. Since I set the unit up for 1700 originally I reset it to a 1630 rpm. I did this because I like to have the engine slightly increase in power do to the loading of the climb, also since the unit might vary within 50 rpm's this was a good / happy place for me to set it.
One word of caution here. If you set the rpm's for, lets say, 1700 rpm's and your original set up gave you 1800 rpm's the unit will restrict the throttle from achieving a full 100% setting. To avoid this I set my original curve at a slightly higher pitch setting. What this did was at a climb my original 1520 head speed would drop off to lets say 1480 rpm's. This way I knew that the throttle was achieving 100% when I turned on the governor. By setting it high and working back down to what was needed I could make sure it was giving me that 100% throttle.
One of the problems I faced with the setup using the throttle stick position was that, if I flew around in normal and came in for a approach was that the governor turned off. Well this isn't so bad but during a bail out, I came back up with the throttle and the governor took control again, it had that moderate turn on speed and I hit more pitch then throttle. This really bogged down the engine. Not good! Now with the idle ups on you don't face this any more because my throttle would be always above that initial 20% turn on setting I set.
Next I set the unit up to give me a on/off switch instead of a stick position on/off. This would always leave the unit on and in normal I don't have to worry about the unit turning off. However with the position 1 set to 1000 rpm's the unit now has 2 off switches. So I can either set up another head speed or just turn inhibit the on/off switch all together. This is the great thing about the 9zhp. You get many choices to do things with.
So as you can see this unit has large possibilities. Your particular radio will dictate how you set yours up and which switch settings you can and will use. With this unit you can really improve your flying because now your head speed will stay much more constant, this in turn will make your tail rotor set up much more predictable and this will make your flying look and sound much more controlled. Its a real eye opener to find out how far your original setup is off when things become much more constant!
One last note here. If your engine does not run right or has a slow reaction time the GV-1 might not work for you. If your engine is running ruff and "hunts" then the GV-1 will also see this as it samples the engine rpm's and is going to try to compensate for it. This in turn is going to make the "hunting" effect more pronounced. When I first put the unit in, I had a rich engine and it was pulsating. While flying and I turned on the unit, you could defiantly hear the engine pulsate, and this made the helicopter fly worse then it did with out the unit on.
Enjoy - now go fly.