The operation and tuning of radio control model engines is a huge topic and we will not go into all the details here. This lesson presumes you will have a 2-stroke internal combustion glow engine of around .40 to .60 cubic inch capacity (which is what you should be running in a first aircraft anyway). This lesson covers engine safety and basic tuning, it does not tell you how to start or run a model engine. Please refer to the instructions that came with your engine for more details.
The most important things to remember when fuelling your model are:
- Always refuel away from sources of ignition (cigarettes, hot engines, mobile phones etc.)
- Always refuel through the correct tube. This is usually the engine fuel pickup tube or a dedicated third tube from the tank
- Always use the correct fuel for your engine
- Never leave fuel sitting in the tank at the end of a day’s flying
Once an engine is running the only things that will stop it is a fuel flow interruption (caused by incorrect flow or a tuning problem), or something hard – i.e. your fingers – getting in the way of the propeller!
When starting your engine always follow the same safety procedures:
- Complete all pre-flight checks to ensure engine is mounted correctly and propeller is not damaged
- Make sure the model is adequately restrained from moving forwards once the engine is running
- No observers should be near the engine or standing in line with the propeller
- Always restrain the model with one hand before trying to start the engine
- Always use an electric starter or ‘chicken stick’ to start the engine
- Once the engine is running always keep clear of the propeller
- Always approach a running engine from behind
- Never reach over a running engine to tune it or remove the glow clip
- Always stop your engine by closing the throttle completely or disconnecting/pinching the fuel line
- Never throw anything into the propeller to stop the engine
Basic Engine Tuning
This guide is only intended as a very basic guide. Refer to the instructions supplied with your engine for more detailed and engine specific guidelines.
Your instructor and other club members are a wealth of information on R/C engines. Ask for help when starting your engine for the first time.
High Speed Needle Tuning
- Set the high speed needle as recommended by the manufacturer for the first time starting
- Start the engine and allow it to warm up for a little while
- With the model restrained, move the throttle slowly to full power. Listen to the engine sound:
- Lots of smoke and a ‘burbling’ motor – too rich – wind the needle in slowly
- Engine ‘screaming’ and no smoke at all – too lean – wind the needle out slowly
- The ideal mixture is just before the engine starts to ‘scream’ 100% of the time. It should be hovering just between the two tones
- Now get a helper to hold the aircraft with the nose pointing vertically upwards at full power
- The engine should speed up a little and will probably be ‘screaming’ all the time – this indicates how the engine will perform in the air
- If the engine stops when vertical the mixture is too lean – open the needle a little
Always make needle movements slowly or a little at a time to get the fine tuning just right.
Low Speed Needle Tuning
- Start the engine and run at full throttle for a few seconds
- Cut the throttle quickly and listen to the engine sound:
- If the engine speed drops or cuts the mixture is too rich – close the screw a little
- If the engine speeds up the mixture is too lean – open the screw a little
- When set correctly the engine should idle nice a slowly with no change in speed
- Go back and check the high speed needle setting as this can be affected by the low speed setting
Always make tiny adjustments to the low speed needle. This is often best done with the engine stopped.
It is possible to learn to fly and take your Bronze Wings with a suitable electric aircraft. If you intend to do this you should make the club aware so that you can learn to fly with an instructor skilled in electric flight.
The parts of the Bronze Wings tests that focus on glow-engine safety will be replaced with items specific to electric models such as battery safety, ESC arming procedures and propeller safety.
The most important things to remember with electric engines are:
- Always switch your transmitter and receiver (if RX battery used) on before connecting the flight battery
- Always use the correct motor, battery, ESC, propeller combination to reduce the risk of overload and fire
- Once the battery is connected and armed the engine should be considered live and dangerous, even if the propeller is not spinning