By Brian James
 If you fly nitro powered R/C helicopters, you have probably heard about governors. Do you need one? What is it? What does it do? How does it work? These are pretty common questions that we get all the time, and they are good questions. I'll try to shed some light on the governor:
What is a Governor?
On a nitro powered model Helicopter, a governor is a device that holds the head speed at a predetermined rpm, eliminating the need for carefully programming throttle curves, and cyclic to throttle mixes.
How do Governors work?
Typically most governors available today work by reading the magnetic field of a magnet. There is a sensor that is called a "hall effect sensor" that is attached to the helicopter engine or sometimes the helicopter frame. The magnet is usually installed in the cooling fan mounted on the engine, or on the clutch bell. You will have to consult the manual for your helicopter, and the governor you choose for proper installation. The governor then takes this rpm reading and takes control of your throttle servo either opening or closing the carburetor in an effort to control RPM. Today's governor's work pretty good when they are set up correctly, and can prevent overspeeding of the rotor head which can be dangerous, and also help to keep all the power going to the rotor blades where it belongs!
Do I need one?
Well that depends. If you are just starting out it will probably add complexity that
You don’t need. BUT, if you are starting 3d flying it can help. I usually recommend learning how
to make a proper throttle curve first, and learn how cyclic to throttle mixes work.
How do I make it work?
Unfortunately, I can’t really answer that one easily because they all set up slightly different. The manual that comes with the Governor you choose will give the instructions on how your governor works, and how to set it up. One thing they ALL have in common is the throttle linkage set up. It is important to have the throttle set up so that when the throttle (left) stick is open exactly half way (and the throttle curve has 50% as it’s mid point) the carburetor is open exactly half way. Also so that when the throttle stick is fully raised that the carburetor is open all the way, and not trying to push further, the when the throttle stick is lowered all the way in normal mode with the throttle trim all the way down the carburetor is fully closed. This is important because the governor needs to “know” the full range of servo travel to work correctly. Another important thing is that most brands of governors need the end points for your throttle channel to be as close to +/- 100% as possible. It will not work correctly if you have +60 and -127 or anything like that. If you find that +/- 100% is not possible, you have to mechanically adjust the linkage and/or the position of the linkage ball on the servo horn and/or throttle arm.
What is the difference between a Governor and a limiter?
A governor attempts to keep the head speed of the model from underspeeding AND overspeeding. A limiter does simply that, limits head speed, or overspeeding. Typically with a limiter you will use an exaggerated throttle curve (some people use 100% throttle on all points of the idle up throttle curve), then the radio is constantly attempting to open the throttle servo all the way, and the limiter is closing it just enough to prevent overspeeding.
Hope that helps!
Brian James
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