Learn To Fly Model Helicopters

Part 6- Engine Set Up
By Jeff Barrington - Newton Abbot Heli Club

Getting the mixture right on a helicopter is far more important than on a fixed wing model, mainly because the throttle is operating at mid range for a lot of the time and a clean response is required throughout the rev range. This can only be achieved by getting the correct balance between the bottom end (idle) needle and the main needle, most OS motors come out of the box fairly close to the correct setting, but I have found some other makes to be a long way out.

Assuming you have a new engine in your heli I would proceed as follows:

With the glow supply not connected set the throttle at high tick over, put your finger over the exhaust outlet and turn the engine over until you have fuel coming out of the exhaust. If no fuel comes out of the exhaust then either the throttle is not open enough or the idle needle is set to lean, if you have to adjust the idle needle only turn it a maximum of a quarter turn at a time. As soon as you have fuel coming out of the exhaust stop turning the engine, connect the glow supply and attempt to start it, making sure you have a firm hold of the rotor head and are ready to adjust the transmitter should the engine over rev.

If when you disconnect the glow supply, the engine slows down or stops, the idle mixture is probably to rich or the glow plug is duff or not the correct type (to cold). I wont get into the technicalities of glow plugs (cus its boring) but suffice to say that I have used Enya no.3 or OS no.8 in all my engines with no problems.

Setting the main needle can only be done by flying the model but an initial setting of 1.5 to 2.5 turns out is about right for most engines. Plenty of smoke with plenty of power is the ideal situation but some running in will be required before the ideal mixture can be achieved gradually leaning out after a few gallons of fuel.

Try to avoid using tuned pipes as these complicate the mixture set up and are generally noisier than standard mufflers. I have personally never found the need for the extra power these pipes produce, but it depends what you are trying to achieve I suppose.

On the subject of fuel, I use Model Technics Bekra 10 which is a fully synthetic mix with 10% nitro. Fuel with castor oil in the mix is okay but I find it's a bit messy. Raising the nitro content does not in itself give more power, but allows the engine to run on a richer mixture and more fuel going through gives it more power and cooler running.

Hope this has helped a little but don't forget to read the instructions with your engine and again, someone with experience in your club will be a great help.

This page has been contributed by Jeff Barrington
Web Site: Newton Abbot Heli Club