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COAXIAL RC HELICOPTERS

Art-Tech Eurocopter EC-135 Coaxial rc helicopter

Electric coaxial rc helicopters, sometimes referred to as dual-rotor or contra-rotating helicopters, have been responsible for bringing thousands of new people into the hobby of radio control flying in the last few years, and it's easy to see why. Coaxial rc helicopters are relatively very easy to fly, and their inherent stability in the air makes them perfect first-time helicopters. Of course, they're not limited to new pilots. Very experienced rc helicopter pilots are having a great deal of fun with coaxial helis too!

Coaxial rc helicopters like the Bell 47 Twister come RTF, or 'Ready To Fly', and can be flown with confidence pretty much straight from the box. They are much much easier to master than a conventional helicopter that has a single main rotor and tail rotor, and are equally capable of holding a steady hover. Flying them indoors is a realistic option too, because their stability makes them easy to control within confined spaces. Coaxial radio control helicopters work, and indeed work very very well. They are the best helicopters to learn to fly with.

A conventional helicopter has a single main rotor, which when turns generates a natural force called torque. The natural reaction to this force is for the fuselage of the helicopter to spin in the opposite direction to the rotor blades. So, a tail rotor is used to generate sideways thrust which prevents the helicopter from spinning wildly out of control. The amount of thrust generated by the tail rotor can be changed by the pilot, either by changing the pitch angle of the tail rotor blades or, on smaller models, by changing the speed of the tail rotor motor. This change in thrust controls the yaw of the helicopter ie which direction the nose is pointing in, by either giving in to the natural reaction against the torque (lessening tail rotor thrust) or by pushing the helicopter round in the same direction as the main blades (increasing the thrust).

The illustration below shows the basic forces at work:

 

However, coaxial rc helicopters don't have a tail rotor, and instead of a single rotor they have two main rotors, one mounted directly above the other. These 2 main rotors spin in opposite directions to each other, as the illustration below shows:

Because the blades are spinning against each other, each one cancels out any torque generated by the other one. As a result, there is no tendency for the fuselage of the helicopter to spin round one way or the other. However, this is only the case so long as both sets of blades are spinning at exactly the same speed. As soon as one set changes speed to the other one, then torque immediately appears. This is exactly how yaw is controlled in coaxial rc helicopters, by making one set of blades spin faster or slower then the other to purposely generate the torque that causes the helicopter to change direction.

In most coaxial helis, the top blades are mounted on the main shaft and the lower blades are mounted on a larger diameter shaft that immediately surrounds the main one. Twin side-by-side electric motors control one shaft each, and hence independent rotor speed control is possible. The picture to the right shows a typical coaxial setup for the main drive gear, with each motor cog driving one of the main vertically mounted sprockets (view is from under the helicopter).

 

Coaxial rc helicopters are, without doubt, the easiest and safest way of getting into the hobby of flying radio control helicopters, and they're suitable for anyone, regardless of helicopter-flying experience. They can easily be flown indoors, but are equally suited to outdoor flying on calmer days.

 

FULL SIZE COAXIAL HELICOPTERS

You could be forgiven for thinking that rc helicopters with dual rotors are completely made-up designs, but there are a number of such full size helicopters. The Russian helicopter manufacturer Kamov have produced several dual rotor helicopters for both civilian and military use, the KA32 shown below is one such example:

RADIO CONTROL HELICOPTER FLYING LESSONS

Email us at: helicopterutes@optusnet.com.au

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All detected copyright breaches will be vigorously prosecuted. The author, publisher, and distributor assume no responsibility for incidents or accidents that may occur amongst readers/users of this book, as they transfer their gained knowledge to actual radio control model helicopters.

Originally distributed worldwide by Helicopter Utilities, PO Box 16 Georges

Hall NSW 2198 - Phone 0403 785 947 - helicopterutes@optusnet.com.au

(The CD book is no longer produced and distributed)                                                             

                  RC HELICOPTER FLYING LESSONS    By Bob Bell

                                          Copyright 2003.

So, you've just bought an r.c. helicopter kit and built it. You have everything installed. Radio, servos, gyro, and it’s been set-up and is ready to fly. But the problem is that you don’t know how to fly it. And to try to get your expensive new toy airborne at this tender stage in your r.c. career would be not be a smart thing to do. You would almost certainly crash. And any crash would most likely be very expensive. Perhaps a new tail boom required. Or a new rotor mast. Almost certainly new main rotor blades. Or maybe, much worse. The answer to overcoming this daunting problem is now easy:  The Real Flight RC helicopter S-I-M-U-L-A-T-O-R!

The Real Flight RC simulator will literally save you many hundreds of dollars repairing crash damage to your r.c. helicopter. The heli simulator teaches you the building-block first steps towards actually flying r.c. helicopters. Yes, Real Flight  is the best possible r.c. helicopter simulator solution. Or fixed wing, for that matter! Everyone should train on it before attempting to fly their expensive real-world radio control model helicopter or aeroplane model. We strongly suggest you combine the exercises here with the powerful simulator experience. You could even clock up some hands-on "stick time" on an electric powered miniature coaxial rotor indoor helicopter, like the Bell 47 Medevac.

This will really build your skill levels and confidence. Then you can transfer your new-found knowledge and skill to your first full collective pitch gas-powered rc helicopter.

Even experienced r.c. fliers practice complicated 3D (aerobatic) flying manoeuvres on a simulator before trying them out on their actual r.c. helicopters! So take a tip, and before you destroy your beloved helicopter, invest in the "Real Flight simulator", and L-E-A-R-N to fly properly first. Meaning you can then get some real hands-on flying training on electric coaxial rotor  "beginner" helicopters. As a result of eliminating crashes, will have money in your pocket, which will enable you to afford to buy more add-ons for your own model aircraft!

Essential radio control helicopter piloting skills.

1. RC Helicopter main rotor blade (MRB) balancing

2. RC Helicopter main rotor blade tracking

3. Hovering technique (every flight starts and ends in a hover!)

4. Flying "Figure Eights"

5. Nose-in flying (chopper headed towards you!)

6. Fly-Arounds, and then later……Flying Circuits

7. Auto-rotations (Emergency Landings with engine "out")

8. Stall turns

 

1. Main Rotor Blade Balancing.

This subject, plus "Main Rotor Blade Tracking", is extremely important. Poorly balanced and tracked blades will cause or induce lots of problems, which normally manifest themselves as vibrations in your r.c. helicopter. Extreme cases can result in loss of control. Most brand new carbon fibre rotor blades come from the factory pre-balanced. But even so, you should run a check on how well the factory has done it’s job in this regard. You require a very fine set of accurate, lightweight digital scales which will measure very small weights. Weights under 100 grams. You also need a Stanley Knife blade, embedded horizontally in a block of wood, with the blade 90 degrees square to the wooden block.

First, weigh both blades individually on the fine electronic scales. If you have no such scales, request your local Post Office staffer to weigh them for you. Mostly they will oblige. It only takes a few seconds. Each 30 size carbon-fibre rotor blade should weigh around 105 to 106 grams. If they both weigh the same amount precisely, you now have to check the Centre Balance Point (CBP) of each blade. First, place one blade on and across the knife edge, and move it left or right resting on the blade, until the Centre Balance Point is identified, and the blade balances on the knife edge perfectly.

Matching the trailing edge of the first blade to the trailing edge of the second, place the second blade on the knife edge, and carry out a similar operation with it. One blade will be slightly different to the other in terms of Central Balance Point. For example, if the second blade happens to be heavier on the right hand end, cut a piece of lead tape (available either at hobby stores or a stationers) from the roll, and place it neatly on the tip of the second blade. While you are performing this operation, the underside of the blade should be facing uppermost, as the underside is where you will eventually apply the tape permanently. Keep adding small bits of lead tape and just resting them there until it equals the balance profile of the first blade.

Once you have equalised the weight, and it balances, permanently attach the lead tape you have added to the blade, and stick it to the tip of the second blade, horizontally, one third back from the leading edge. Due to the fact that when we originally weighed the blades, their weight was the same, now, to keep the weight equal, we need to also place the same amount of lead tape on the first blade, to match the lead tape added to the second. But this time, in the centre portion of the blade. On the Central Balance Point, across the blade, push lightly down on it. That will leave a slight "score" mark or line across the blade. Lightly mark this by drawing along the line with a Texta marker pen.

Add the same amount of lead tape that you placed on Blade 2 to this blade, by folding the lead tape in half, then attaching it to the centre point of the blade, one third of the way back from the leading edge, horizontally. The "half way" point will be accurately marked for you by the fold mark you made when you folded the tape in two. Now take the blades back to the Post Office and have them re-weighed, or weigh them on your own fine scales. They should weigh exactly the same. Around 105 to 106 grams. Remember, when attaching lead tape to the blades, always attach the tape to the underside of the main rotor blades.

 

2. Tracking Main Rotor Blades.

If you observe the main rotor disc edge, or side on, and from the rear, with the blades turning under power, and with the blades approximately at your eye level, you are able to check the "tracking". This can be done by yourself as you fly the machine in a hover, or preferably power it up on the ground just prior to lift-off power. The best way in this instance is to get someone to assist you. And have him squat down well behind the machine (at least 3 metres) so he can see the rotor disc edge clearly from the rear of the helicopter, and how the blades are tracking. If the tracking is perfect, as the blades turn, you will only see what appears to be the edge of one blade revolving. However, if the pitch of one blade is at a slight variance from the other, you will observe what appears to be a low blade as well, or a high blade revolving. Two quite separate "images" to your eye, that look like they are a centimetre or so apart.

(Before you begin this tracking operation, attach a small piece of red electrical tape firm down on the top of either of the blades. Not both, just one blade. The red tape shows out clearly even while the blades are under power, and you can readily identify which blade is the one out of track.) If for example the red taped blade is higher than the second blade without tape on it, the red taped blade has too much pitch. You then have to go to the ball link for that rotor blade, and vary the pitch to match the other non-taped blade. Usually about two turns of the ball link will do the trick.

After adjusting the ball-link, power the machine up again, and re-check your work. Your main rotor blades should be revolving "in track", and your rotor system will be ready to fly. Your helicopter rotor blades are now both "balanced" and "tracked".

 

3. Hovering Technique.

Every helicopter take-off and landing is accomplished from a hover. So you really have to learn to hover before progressing to any other aspects of flying radio control helicopters. Time taken to learn to hover varies. Some people pick it up quickly. Others don’t. To begin hover training, orient the helicopter in front of you, so it’s tail is facing towards you, with the helicopter nose pointing away from you. While flying a radio control helicopter, you always watch the helicopter nose, not the tail portion of the fuselage. If you watch the tail, you will lose the true picture of where the helicopter is about to fly. From the idling throttle position (which should show about 1 degree of positive pitch in the main rotor blades), slowly move the throttle gimbal stick forward. In Mode 1 flight (99% of Australian RC pilots fly Mode 1), the throttle/collective pitch stick is the right gimbal.

You’ll hear the engine revving up. Just prior to the "mid-stick" point, or about 5 to 5 and a half degrees of positive pitch, your helicopter will get "light on the skids", and start to "move around" on the ground. Just get the feel of what the helicopter is doing with very small changes to your throttle control. Once your have stabilised your helicopter, using the tail rotor control (left gimbal stick left or right), very gradually, advance the throttle/collective (right gimbal stick) up away from you until the chopper is just ready to become airborne. Be very careful! Don’t climb it too high, or you may panic and you could instantly lose control. Once you have it just airborne, about half a metre from the ground, use your left stick tail rotor control function (left or right movement) to stop it drifting around. If it starts getting out of control, gently ease the collective (throttle) down and the helicopter will settle back on the ground. When you become airborne each time, you will notice that the helicopter will have a tendency to "wander" away to the left. This is due to your helicopter blades turning towards the right, so the forces of nature are making the fuselage want to travel in the opposite direction to the rotor blades. "Torque" - this is "Newton’s Law" –"Equal and Opposing Force", and it will try to equalise the rotor force by tending to swing the nose of your helicopter in the opposite direction to the rotor blades direction of travel. Try to counteract this with your left gimbal stick tail rotor control when you lift off in the take-off. Try now to take off and enter the hover, just a few metre or so off the ground. Ease off the throttle (right stick) until the forces of weight and lift are exactly balanced, and the helicopter stays in the exact same space in the air, neither climbing or descending. Use the same right control, either by nudging it right or left, to correct small drift tendencies that the wind may now be exerting on the machine.

Remember, as soon as your r.c helicopter is airborne, the wind is immediately affecting it’s flight. If you can, stay in that hover for ten seconds. Then land in the spot on the same area of ground where you took off from. If you can’t do it, keep trying till you can!

Once you have that little exercise pretty much under control, take off and hover a metre or two in the air, and pick a spot a few metres left or right of where you are, and go land there. This will get you used to cyclic control. The best method is to give the right gimbal (a mix of collective and cyclic functions) a slight "nudge" in the direction you want to go, then "back off". It’ll simply "drift" over. Remember, make very small movements with the gimbal controls. It’s the same in a real helicopter. Small control movements are the way to go!

With a radio control helicopter, where you have no anti-torque pedals to control the tail rotor (such as you would find in a real full-size helicopter), this "pedal" function is included in the left hand gimbal stick. Tail rotor control is achieved by moving the gimbal left or right, and fore and aft cyclic functions are on that same stick, except for cyclic, you are pushing the stick either forward or back towards you. Using your "pedal" function, by operating your left stick either left or right, you can turn your helicopter round 360 degrees "on the spot". In a real full size helicopter it’s called a "pedal turn". Swing the tail of the chopper around just after your skids leave the ground, so the helicopter is side on to you. Now practice hovering, with the chopper side on. When you have mastered this, try it on the other side. Make sure you become proficient in hover from both sides. A great test of your increasing hovering skill is to hover in the once place for an entire tank of fuel! If you can accomplish that, you are doing just great!

Higher Altitude Hovering

If you can hover at 1 metre, you can hover 100 metres above ground level. Hovering is a skill you need to practice and become very proficient in. It is the key skill you need to develop to become an accomplished helicopter pilot, whether it be a radio control helicopter, or indeed, a full-size machine. All helicopter flights begin with and end in a hover. You can practise flying in the hover about 4 to 5 metres above the ground. That’s high enough to get the feel for a much higher hover at a later stage in your training. Start off about 1 metre AGL (above ground level) then as you successfully hover there, increase your altitude another metre, and repeat the process, hovering then 2 metres above the ground. When your hover is stable, increase it another metre, to 3 metres, and so on, until you are about five metres above the ground. Enter the hover and hold it for about ten seconds. Use both gimbal sticks to hold your model helicopter as still as possible in the hover, maintaining a constant altitude. It’s not easy, so just practice, practice, practice! But while you are practising, you are having fun. You will eventually succeed and become very accomplished at this manoeuvre.

Remember:

"If you can hover at one metre, you can hover at a hundred metres!"

 

4. Flying "Figure Eight" patterns

This is a great fun way to learn how to properly fly a radio control helicopter. Really, flying "figure eights" is simply great fun! It’s also the key to learning full forward flight, and also nose-in flying. The importance of being able to competently fly your helicopter "nose-in" cannot be under-stated. After all, when you have flown the helicopter away from you, you then have to fly it back. But flying "nose in", many of the control functions are now reversed. This is where it gets interesting, and difficult. "Nose in" flight is perhaps the most challenging and difficult component of your training that you will have to master when learning to fly your r.c. helicopter.

To get you on the right road, we’ll start you off flying "figure eight" patterns by slow hovering between two reference points on the ground. By the time you have finished, you will be flying the "figure eights" in tightly banked turns. What you need to do is look on each side of your radio control helicopter, at two points about 3 metres each side of the aircraft. Lift off into a hover, then drift over to the spot you have picked out 3 metres on the right. Once there, apply opposite cyclic (right gimbal) so it drifts over to the other spot, now 6 metres away to the left. Keep moving from one spot to the other, and practice doing it without losing altitude. Stay on the direct "path" between the two spots.

Now, once you have mastered that exercise, use your tail rotor control stick (left gimbal) to swing the nose of the helicopter around, so you can face the helicopter in the direction of the other point. Start off by pointing the helicopter nose at a 45 degree angle to the point you are going to. As you get more confident, swing the helicopter nose right around to face the point you are tracking to. Okay – once you have all that under control, it’s time to start flying AROUND the two points, in real "figure eight" patterns.

A really important thing for me to bring up at this time is the very important relationship between your cyclic and collective pitch controls. Just like in a real helicopter, you would have noticed by now that the more cyclic pitch you apply, the more the model helicopter starts descending towards the ground. To overcome this, you need to apply additional collective pitch (altitude/throttle control) to keep the helicopter at the same altitude. Too much collective, and the simulator chopper will climb away to the far distant heavens. Too little, and it will rapidly descend and could crash into the ground. As you fly faster, this cyclic/collective relationship becomes more noticeable. You must be aware of this situation, as that knowledge is essential for fast forward flight in the helicopter. Start out flying your "figure eights" slowly, using your tail rotor gimbal stick (left stick) to control your heading. As you get better at flying the "figure eights", you will be able to use less tail rotor control, and more proper cyclic control, banking the helicopter into the turns. You should fly the figure eight patterns so that the helicopter moves around the points on the ground, rather than just over them. And after crossing each point, the chopper will cross over your original take off area/landing pad.

 

Flying your turns

As you enter the turn, move your cyclic control (right gimbal, left or right) in the direction you are travelling. Slowly reduce pitch, and remember, the faster you are going the more pitch will have to be reduced. As the helicopter starts to bank over, apply tail rotor control (left gimbal, left or right) to bring the nose around into the turn. As it does so, the nose will now tend to point down, and head for the ground. You need to pull back on the left gimbal (aft cyclic), as you are adding the tail rotor left or right. This’ll bring the nose up. The faster you are flying, the more you will have to pull back on the cyclic. If you need to tighten up your turn, pull back some more. Start off your figure eight patterns in a hover, and hover" around the course. As you get more clever, and confident, increase your helicopter’s speed. If you don’t get things quite right, just keep practising. You will soon be flying the "figure eights" like a professional! It’s heaps of fun, and "figure eights" are the step to proper fully controlled forward flight.

 

5. Nose-In flying

After you fly your radio control helicopter away, you’re going to have to fly it back to you. Nose-in is the key to confidence with r.c. helicopters. Once r.c. chopper pilots master nose-in flying, they are no longer "afraid" of their machines. Nose-in flying is best learned on a simulator, for everyone’s sake. After all, your real-world r.c. helicopter is a very expensive acquisition, and you need to be able to fly the aircraft towards you safely, and without damage. Nose-in is very different to flying tail-in (that is, with the helicopter facing away from you, and the tail boom towards you).

Main things to remember about nose-in flying are: The cyclic control inputs you need to make are reversed. That is, if the helicopter is facing you, and is banked slightly to your left, with the left side of the rotor disc lower than the right side, you will need to move the cyclic (left/right) control left. As you do this, the rotor disc will return to a level plane, and the helicopter will be "straight and level" in it’s attitude. Totally opposite to tail-in flight! The tail rotor controls are also reversed in nose-in flight. Most r.c. pilots find it easier to steer the tail to bring it back to where you want the helicopter to fly. Say you are flying nose-in, and the tail of the helicopter drifts away a little to the left, apply right tail rotor control, and the tail boom will fall back into place where you want it.

Spin & Hold

Take off, and fly the helicopter about 15 metres in front of you, then enter a stable hover. Stay in the hover for a few seconds, then use the tail rotor control gimbal (left stick) to turn the helicopter "on the pedals" 180 degrees till it faces you. Try to hold the straight and level attitude in the hover. If you are having trouble, use the tail rotor to spin the aircraft back so it is tail-in, applying a little collective. As your ability and confidence builds, start descending lower and lower, towards the ground, as you practice your nose-in-hovering. And gradually bring the helicopter closer in towards you, to about three metres distance. That’s as close as you want it to be.

 

6. Flying Circuits (and "Fly Arounds")

When you start flying your radio control helicopter at the club flying field, you will need to know how to fly a circuit. Basically, in a fixed-wing environment, with a runway, the circuit starts in the direction that the runway faces, the direction aeroplanes will actually land. That leg of the circuit is the UPWIND leg. Then a turn is made to 90 degrees, to fly across the direction of the runway. That is known as the CROSSWIND leg. Then another 90 degree turn is made, so you are flying back in the opposite direction to landing runway traffic, but parallel with the runway. That is the DOWNWIND leg. Then you make another 90 degree turn to fly across the runway direction again. That is the BASE leg. And finally, another 90 degree turn onto FINAL approach for the runway. You should have the runway threshold directly in front of you now. That is the CIRCUIT. The circuit is in the shape of a rectangle. All helicopters pilots fly circuits, except they normally don’t land their helicopters on runways. They are cleared to land on designated helipad landing areas.

When you are learning to fly circuits, it is best to perhaps perform the "fly around" first. Simply fly the helicopter in a circle around your central position. When you can competently do this, move on to proper circuit patterns. It would be good practice to use the G2 Simulator. Take off on the G2 simulator, using the runway as a guide to flying an UPWIND, CROSSWIND, DOWNWIND, BASE and FINAL leg of a circuit. Think of the circuit as the rectangle shape, which in reality it is. All you are doing is flying around the edges of the rectangle.

 

7. Auto-rotations

This skill may in fact save you hundreds (and possibly thousands of dollars) depending on what your radio control helicopter cost you. It is a difficult skill not easily learned, but with practice, it can be a wallet saver. Once mastered, this r.c. skill is also a lot of fun, and personally very satisfying. While heli flying, what happens if you run out of fuel, blow a glow plug, or have an engine flame-out at 30 metres above the ground?

Most likely, you would crash…..that is, if you haven’t learnt to master auto-rotations! An auto-rotation is using the inertia built up within the rotating main rotor blades to allow your helicopter to glide to the ground in a controlled descent. It occurs at higher speed than a normal descent, but your skill allows the helicopter’s descent to be "arrested" short of the landing, and a smooth touchdown made, without engine power, and hopefully, without any structural damage.

Learning to auto-rotate a helicopter is certainly not easy, and is a tad risky. But it is best to learn how to handle this emergency procedure, as more serious damage may occur as a result of a fast, uncontrolled descent at a later time from high altitude flight when you are flying your expensive radio control helicopter. To learn to "auto", initially climb to about 1 metre AGL, enter a hover, then simply turn the collective control off (right gimbal pulled back towards you), and when the the helicopter is just above the ground, add a bit of collective pitch on the right gimbal. The model should just settle back to the ground. It normally lands with a bit of a bounce. If you can do this without damage, climb to 2 metres and try again. Remember to give the helicopter a small bit of collective just prior to ground contact. Any further than 2 metres above ground level (AGL), and you will always need to also "flare" the helicopter with aft cyclic (left gimbal pulled back) to assist in arresting it’s downward speed. If you are successful at 2 metres, try it from 3 metres. Add a bit of forward speed, to simulate what the chopper would be doing if a real emergency occurred.

Done correctly, auto-rotations can save money and also be extremely personally satisfying. However, if carried out incorrectly, particularly from more than a metre in altitude, they can result in heavy tail boom strikes, and expensive damage, possibly to the tail or main rotor. Possibly to all of these components!

Things to remember during auto-rotations:

1. After an engine failure, you have little more than a second to pull the collective pitch/throttle (right gimbal) to allow the helicopter to enter the auto-rotative glide. Too slow and the helicopter will not glide, but will pitch nose down and crash to the ground heavily, and at high speed.

2. If you have a "driven" tail rotor, you will still have tail rotor control during an auto-rotation.

3. If you haven’t got a "driven" tail rotor, you won’t have such control.

4. If you haven’t got a "driven" tail rotor, while learning to auto, have the idle on sufficiently to allow you to have some tail rotor control available.

5. Make sure your rotor blades are securely fastened to the blade grips. Don’t make them TOO tight as that will cause vibrations.

6. If the blades are too loose, and your auto-rotation has gone wrong, you will lose a lot of "head speed" in the rapid descent, and you have a higher chance of a tail boom strike, than if your rotor blades are securely fastened.

7. Another tip is to make sure your idle pitch is about +1 degrees of positive pitch. The blades will still be "flying" in the idle and will be less likely to strike the tail boom.

8. With gas (nitro powered) r.c. helicopters, make sure the engine will fire up again if you want to abort the "practice auto-rotation". It is best to practice autos on a "warm" engine, so that you are fairly confident the engine will light up again if everything is going wrong, and you want to abort the auto-rotation.

9. Some radio control helicopter pilots practice full (to ground) auto-rotations only after doing a couple of warm-up autos which they terminate in what’s termed "power-recoveries". Just to be on the safe side! I personally would recommend that this approach to practice auto-rotations is a wise and careful approach to this difficult and highly skilled emergency procedure.

10. As stated, you definitely need to auto with some positive pitch, and make sure you don’t have aft cyclic on. If you don’t ensure both of these are attended to, the helicopter may come down with too much "head speed", and the blades may strike the tail boom on your helicopter. This would cause the blades to be torn off the hub, as well as your machine’s tail boom being damaged.

11. In a high-altitude auto-rotation, properly manage your cyclic and collective gimbal controls, so the helicopter begins to flare properly about three metres from the ground.

12. Arrest the descent speed using those two controls, in co-ordination.

13. Bring the chopper down maintaining good "head speed" and keeping control of the flight path of the helicopter.

14. If you are using your real r.c. helicopter to practice auto-rotations, not just the simulator, and the "heading hold" switch on your radio control unit is switched "on", turn it to "off" before starting the practice auto. Otherwise the heading hold may start applying tail rotor to compensate for any yaw movement that the helicopter may experience on the way down.

15. Always auto-rotate your real r.c. helicopter INTO the wind if possible.

16. Flare the radio control helicopter and slowly apply pitch to arrest it’s forward speed at about 12 metres from the ground.

17. At 1 metre above ground level, apply forward cyclic (left gimbal stick), which will level the chopper off.

18. Apply collective pitch and hold in forward collective (right gimbal forward) to prevent having a tail boom strike.

19. Don’t panic, especially when the helicopter  is nearing the ground.

20. Be smooth on the controls. Sudden jerky movements take precious energy away from the rotor disc.

21. Land the helicopter as gently as possible. But remember, you may have to allow the chopper to "slide" across the field on landing, on the skids. Not too hard though, or you may still do some damage.

 

8. Stall Turns

A stall turn is perhaps the first aerobatic (3D) trick that any r.c. helicopter pilot can attempt, after learning fast forward flight.

A stall turn involves entering forward flight at speed, then pulling into a vertical climb. When the helicopter stops having forward momentum, and stalls, tail rotor gimbal control is applied to turn the chopper around 180 degrees to face the way it came up. A good stall turn is one where it pulls out of the "dive" at almost the same spot it went into the original high-speed climb. You need to enter stall turns at 30 metres above ground level, so you have the necessary altitude to fix things if you get into trouble.

First up, fly away from yourself about 30 metres in front of your position, then turn the helicopter nose-in and fly back towards you, building forward speed, at about 75 percent power. Let it fly past your point, and when you are looking at the back of the helicopter, enter the vertical climb. Ease back on the aft cyclic (left gimbal) as the r.c. helicopter goes vertical, then release it, and lower your collective (right gimbal) to mid-stick position. The chopper should now be climbing, near vertical. It will soon come to a full stop in the climb, a stall.

You can now do either of the following: 1. Apply forward cyclic (left gimbal) so the nose "goes over" and the chopper levels out.   2. Execute a 180 degree turn, increasing collective (right gimbal), and the helicopter will simply "fly away", and will not lose altitude.

The next step is to execute the full stall turn. With modern r.c. helicopters, don’t give them FULL tail rotor input, as the modern gyros on board will probably start spinning your machine wildly, or "pirouetting". Simply gently "feed in" the tail rotor input, and your helicopter will come around slowly, and will not spin or "pirouette". The chopper will just "hang there" for a second or two, and will then start falling in the direction it came up. You should not be applying cyclic at this point. When the helicopter reaches the "bottom point" where it entered the climb, gently pull back on the cyclic (left control), and add collective (right stick). The nose of the helicopter will come up, so keep adding collective until it has a slight nose-down attitude. It will/should then level out and fly back the same way it entered the stall turn climb.

ENJOY YOUR TRAINING…..AND YOUR FLYING

I trust that this training program will assist you to appreciate what you need to learn to fly radio controlled helicopters safely. I trust you will thoroughly enjoy your training, and also the many years of successful fun-filled r.c. helicopter flight you have before you. It’s a really great hobby and sport. In fact, it’s the best hobby you can get involved in!

R.C. HELICOPTER SAFETY RULES

1. Join a rotary flight club. Doing so will cover you with insurance for public liability. Most clubs are covered for at least $10 million public liability insurance.

2. Fly your r.c. helicopter in a designated "club" flying location, and not in public areas, like parks, where there are onlookers around, in particular, children. Local Government ordinances may also make it illegal in your area.

8. Do not operate in residential areas, near buildings, playgrounds, roads, railways tracks, airports, and anywhere where there are power lines and poles.

9. Do not fly your helicopter indoors unless it is an indoors electric helicopter, like the Blade CX-2, the Bell 47 Twister, and Twister  Hawk coaxial helicopter.

10. Do not fly when strong winds are prevailing, or in rain. Winds of more than 10 knots can constitute a problem for r.c. helicopter pilots. (I have flown in 18 knot winds, but it is most unpleasant, to say the least.)

11. Always check the condition of the r.c. helicopter flight radio battery and the r.c. controller batteries before flight.

12. Keep in mind that people around you that are also flying r.c. models may be using the same radio frequency as yourself. Check what frequencies others are using BEFORE you fly. Non-observance of this rule may lead to disaster for both helicopters, and possible personal injury to people on the ground at the flying field. Personally, I monitor my own frequency on a radio scanner every time I am approaching any area where I am about to fly. I check for possible interference. Remember, you are legally RESPONSIBLE for whatever personal injury or property damage your r.c. helicopter may cause if it gets out of control. If you mess up badly, you could lose your house, car and every other asset you own, if you are sued for damage or injury your helicopter has caused. And you may be criminally charged if you have committed a criminal offence.  Flying r.c. helicopters is great fun, but it also carries great personal responsibility. Always be aware of this responsibility. In addition to this, never fly when you are fatigued, ill, or generally unwell, or not fit.

13. Before flying your r.c. helicopter, check all screws and bolts for looseness.

14. Replace rotor blades that are in ANY way damaged.

15. Replace all parts displaying defects with new parts. This includes any part that has a crack in it. Defective parts can lead to accidents and crashes.

16. Never get close to the rotor of your r.c. helicopter when it is turning. Stand at least 3 metres away when the blades are turning.

17. After you operate your r.c. helicopter, if you own an electric model, the electric motor and the ni-cad battery are extremely hot. Do not touch them until they cool down.

18. Remember, always turn off the engine of your r.c. helicopter or disconnect the flight battery if it is an electric model, before you turn your radio off! Otherwise, there could be a problem, with the possibility that the helicopter will go wildly out of control and may hurt someone - perhaps yourself.

PRE-FLIGHT CHECKS

Prior to the first flight for the day, carry out these checks.

1) Mechanical check – linkages, servos, T/R gears, fuel line

2) Electrical – plugs, batteries, gyro

3) Radio – range check, battery charge level

4) Main rotor blades – tracking, balance, cracks and dents

5) Tail rotor blades – Same as for main rotor

6) Fasteners – Check for looseness

7) Oil – Swash plate, tail rotor gearing

 

During the flying day.

1) Check all of the above items.

 

Before each flight.

1) Check your radio frequency, and indicate with the appropriate marker which frequency you are using.

2) Check your fuel, and make sure your tank is full, and the fuel line is not in any way clogged. Below is my personal checklist, which you are free to use. Plus the competencies in Australia for R.C. Bronze Wing (MAAA) club award.

My personal checklist. (I follow this checklist to the absolute letter!)

1. Check for bystanders and onlookers.

2. Listen to nearest airport ATIS frequency for wind speed/direction on hand held radio scanning receiver. Or watch bushes and trees nearby for an indication of the wind strength. You really don't want winds over 5 to 8 knots to begin with or your flying can get unpleasant.

3. Check fuel quantity – if sufficient for flight.

4. Check rotor head cap is "off".

5. Check glow plug integrity.

6. Check general airframe integrity.

7. Check canopy integrity and if secured.

8. Check radio antenna and gyro.

9. Check both radio transmitter and receiver battery status.

10. Check radio frequency for interference.

11. Walk-around check – all screws and bolts tight.

12. Check all linkages, gears, fuel lines.

13. Check fuel clamp off.

14. Check integrity of all rotor blades (MRB’s and TRB’s)

15. Position tail rotors for better visibility during range check.

16. Turn transmitter and heli receiver on – conduct range checks

with antenna full down, from at least 100 metres distant.

17. Any problem with range check – do not fly!

18. Re-position tail rotors to normal configuration after radio range check.

19. Connect glow-plug connector to 1.5 volt battery.

20. Set transmitter trim to "zero".

21. Set and check throttle to fully "off" position.

22. Engage top start mechanism.

23. Start engine, holding main rotor blades with left hand while using right hand to operate top starter tool.

24. Monitor start and idling performance for rough running.

25. Disconnect glow plug battery from helicopter.

26. Check throttle still set to full off.

27. Pick up transmitter console.

28. Advance throttle to idle only.

29. When warm, advance throttle to take off power.

 

On shutdown……

1. Cut engine using throttle trim control by moving it to 50%.

2. Wait till engine then the rotors stop, or advance throttle gimbal full forward which will act as "rotor brake" after the engine has cut out.

3. Approach helicopter and turn off helicopter radio.

4. Turn off radio transmitter.

5. Engage fuel clamp.

6. Remove canopy and thoroughly wipe down every part of the r.c. helicopter, ensuring all traces of nitro-methane fuel are removed. (This stuff is volatile. Don’t get any on your car duco!)

7. Check integrity of the helicopter before moving blades back into the tail boom blade tidy thong.

Australian MAAA "Bronze Wings" entry level helicopter requirements.

1. Pre-flight training.

2. Dexterity with equipment.

3. Theoretical knowledge.

4. Lift off to eye level, hover for 10 seconds and land.

5. Lift to skid eye-level, hover, and fly out 10 metres into wind, hover briefly, then tail first return and land.

6. Manoeuvre at skid eye level right 10 metres, then go opposite direction 20 metres, then return to the start point and land.

7. Lift off, hover, fly horizontal "Figure 8" into wind throughout, and then land.

8. Lift off, and fly a 360 degree tail in circle.

9. Execute a 45 degree landing pattern, at a height of 10 metres, and 10 metres out.

 

COPYRIGHT 2003 BOB BELL & HELICOPTER UTILITIES

Originally distributed exclusively by Helicopter Utilities, PO Box 16 Georges

Hall NSW 2198. Phone 0403 785 947 helicopterutes@optusnet.com.au

Copyright ownership transferred 2008 Bob Bell & Small Rotors Helicopters

(This CD book is no longer in production or distribution)

Congratulations! You have learned a great deal, and have become expert at manipulating your r.c. helicopter. Now you really know how to fly, and you can be truly proud of your accomplishment . When you have mastered all the flying tasks in this helicopter course, you will be a competent radio control model helicopter pilot! You will amaze your friends with your newly acquired skills. And make sure you continue to have fun with this hobby – perhaps the most satisfying hobby you will perhaps ever take on!