Introduction

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.

Fuelling Safety

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

Starting Safety

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

1. Set the high speed needle as recommended by the manufacturer for the first time starting
2. Start the engine and allow it to warm up for a little while
3. With the model restrained, move the throttle slowly to full power.  Listen to the engine sound:
   1. Lots of smoke and a ‘burbling’ motor – too rich – wind the needle in slowly
   2. Engine ‘screaming’ and no smoke at all – too lean – wind the needle out slowly
4. The ideal mixture is just before the engine starts to ‘scream’ 100% of the time.  It should be hovering just between the two tones
5. Now get a helper to hold the aircraft with the nose pointing vertically upwards at full power
6. 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
7. 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

1. Start the engine and run at full throttle for a few seconds
2. Cut the throttle quickly  and listen to the engine sound:
   1. If the engine speed drops or cuts the mixture is too rich – close the screw a little
   2. If the engine speeds up the mixture is too lean – open the screw a little
3. When set correctly the engine should idle nice a slowly with no change in speed
4. 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.

Electric Engines

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

Introduction

Radio Safety is the most important part of flying a radio control model aircraft.  If a student pilot cannot demonstrate an understanding of safe radio operating procedures then they would never be allowed to switch their aircraft on, let alone fly it!

The Frequency Key System

Most model clubs adopt some sort of frequency peg, or key, system to identify which transmitter frequencies are in use and which pilot’s are using them.  LMMAC is no different operating a ‘keyboard’ style system to indicate which frequencies are in use.
Your transmitter will be set to, or contain a crystal that allows it transmit on a certain frequency within the 36 megahertz band.  A sticker on the back of your transmitter will show the frequency displayed as something like 36.470.  This number tells us the transmitting channel, in this case channel 647.
When you want to switch on your transmitter you must place your frequency key into the relevant slot in the keyboard before switching on your transmitter.  Your key then stays in the board until after your transmitter is switched off and placed back into the compound.
When not using your transmitter, make sure you return it to the shelves below the keyboard and hang your key over your aerial.

NB:

It is important to get transmitters certified to ensure their safety.  The club should already have provided instructions on how to do this.  Certified transmitters use a narrow yellow key, uncertified a wider blue key to ensure a wider safety margin.  These keys will be provided by the club.

Radio Installation

As you are building your first trainer aircraft, your instructor will be able to help you with installing the radio gear correctly to ensure trouble free operation.

Servos

Use all four screws provided with standard servos and attach the rubber anti-vibration grommets correctly.  Usually this involves placing a rubber grommet over each servo mounting hole and pushing in the small metal sleeve from the underside.  Your instructor will help to explain this to you.

Linkages

Check all linkages from servo to pushrod and pushrod to control horn are secure.  Short lengths of silicone tubing should be used to ensure clevises do not vibrate loose in flight.

Receiver & Battery

Plenty of foam should be used to ensure the receiver and flight battery are safe from vibration.  Make sure they are fixed down and cannot move around in flight.

Aerial Routing

Receiver aerials should be routed outside or inside the fuselage and stretched out to their full length.  They should not be in contact with servo leads or pushrods as this can cause interference.  Aerials should be taped or fixed in place so that they cannot swing forward and foul the propeller.

Switch Mounting

If mounting your receiver switch outside the aircraft, ensure to locate it on the opposite side to the engine exhaust.

The Range Check

Once your engine is started and before the first flight of the day it is important to do a range check.
With the aerial on your transmitter down, walk backwards from the pits to the edge of the runway all the time watching the control surfaces on the aircraft.  You are looking for any unexplained movement not originating from a control input.  Any movement might be a sign of a ‘glitch’, or interference in your receiver.  Once at full distance, check full throttle response and movement of your controls before coming back.  It sometimes helps to have a helper stand next to your model to give you the ‘thumbs up’ if everything is okay.

S.M.A.R.T

S.M.A.R.T is a useful acronym to remember.  It stands for:

• SWITCH – Is everything switched on?
• METER – Are your batteries fully charged?
• AERIAL – Is your transmitter aerial fully extended?
• RATES – Do you need high or low rates selected (if applicable) for this model?
• TRIMS – Is the model trimmed?  Are all the controls moving freely and in the correct direction?

2.4GHz Radio

The new 2.4GHz radio technology allows a greater safety margin than 36MHz as it seeks and locks onto a free channel before it will work.  LMMAC still requires pilots using 2.4GHz sets to place a key in a different board so that other pilots are aware a 2.4GHz set is in use.

Always switch on your transmitter BEFORE you switch on your receiver!