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THROTTLE CURVES
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THROTTLE CURVES

Throttle curves will vary from one machine to another due to varying setup factors such as engine type, gear ratio, weight, use etc. You will need to develop & tailor a throttle curve that suits your heli. Throttle curves are important in the event that the governor fails during mid flight, it is not only good practice but a failsafe. Set throttle cures for all modes of flight. Some choose to fly without a governor at all & rely entirely on throttle curves.
You can set throttle curves by using the governor, optical tachometer or an on board tachometer.
                                                                 
Start with a linear throttle curve. As a guide generally start with the throttle midpoint position set at approximately 35% & the ¾ position set to 50%. i.e. 0% - 20% - 35% - 50% - 100%.

Start up in Normal mode & throttle up to mid stick position, now measure the head speed with a tachometer. From your measured RPM adjust the mid stick throttle point on the curve up or down until the target head speed is achieved, example   1710 RPM.

Example only Normal: 0%-20% -32.5% -50%- 100%

Repeat the same process at ¾ stick position (hover). The engine will be under more load due to blade angle & mass. Lift off into a hover and tacho the head speed, then adjust the 3/4 stick throttle point for the proper target head speed ( this example Normal 1710 RPM).

Example only Normal: 0%-20% -32.5%-45.5% - 100%

If your on your own & only have a hand held optical tacho, the goal posts at a disused sports field makes a good rig to mount your tacho with some double sided tape & cable ties. Always measure at the same point on the blades, I use the advancing blade tip.

Now adjust from ½ stick down to idle to be a gradual linear throttle back. If at low stick point you find there is too little throttle (governor off), you can increase to maintain RPM in a descent. The GV1 cuts off at around 20% throttle value, check you manual depending which governor you are using. If you have a five point curve I would suggest keeping the first point or low stick position no less than 25%. This force’s the GV1 to stay engaged at low stick position. Allow at least -3 degree pitch for low stick position in normal mode. 

Example only Normal: 0% - 30% - 32.5% - 45.5% - 100% 

For full pitch give full throttle 100% value. We are setting throttle curves in the event that the governor may fail during mid flight. If you are setting & flying without a governor limit the upper throttle limit to say around 65-70% tacho & adjust (or listen for engine speed changes in the air). When in governor mode the governor holds back the throttle to maintain constant head speed.

 
Example only Normal: 0% - 30% - 32.5% - 45.5% - 100% 

 
Example only Normal mode without governor: 0% - 30% - 32.5% - 45.5% - 65%

If you are using the GV1 this is a really good link to setting up the gv1 for gasser use;

http://rc.runryder.com/helicopter/t547042p1/)

Go to idle up 1 position start with a curve of 100-50-40-50-100 as a reference start point & repeat the exercise using the target head speed for idle 1 position say 1800 RPM. Adjust the curve for both mid stick & ¾ stick positions leaving the high point position (H) at 100%. Now mirror ¾ stick & high stick position as shown below so low stick (L) = full power & ¼ stick = ¾ stick power setting.
If you are working on your own you can set the cures in idle 1 & 2 to be linear from 0 then mirror figures to achieve the v curve.

Throttle curve may be something like: 100% - 46.5% - 38% - 46.5% - 100%.
or without a governor                       :   65% - 46.5% - 38% - 46.5% - 65%.
Repeat the process again for idle 2 using the desired Target head speed for idle
2.

Always Tailor your own throttle curves & never rely on someone elses values as every machine, setup & radio is different.

 



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