Building RC electric helicopters used to be a challenging process. Now we can buy components “off the shelf” (or purloin them from other people’s crashed RC helicopters) the process is a good deal easier. You will be continually tweaking and adjusting all the way through, so make sure you have a fully charged battery pack.

As this article is also designed to help people who are upgrading their RC helicopters, we’ll first take a look at servos – a popular component for replacement, as they wear out so quickly. Instructions for installation are available from the manufacturers, or on line, if those provided aren’t clear enough.

The output arms should be kept at 90o to the pushrods. Similarly, pushrods are placed at 90o to the bellcranks. This will make it easy when it comes to the final trimming. People “cobbling together” two RC helicopters into one often have to make compromises in areas like this, to make the whole thing fit together, but try to keep this to a minimum.

On RTF electric helicopters, the pushrods are set to an optimum length. When building your own, you have the opportunity to change this to suit your own needs, but initially set them to the recommended length. This is measured from the centre of the ball links. Position the linkage balls so they are relative to the centre of the servo arm, again as per the manufacturer’s instructions.

If you have upgraded your servos you must remember to buy compatible linkages and bearings, and to use the recommended settings provided with these, rather than those for the original. Whenever RC helicopters are upgraded, it is vital the components you have chosen are compatible with those you are exchanging them for.

With the competition season now well ahead (and the world F3C Championships in Muncie, Indiana just a few short weeks away) it’s worth taking a look at the high profile world of professional RC Helicopters.

FAI competitions are the next stage on from BMFA flying. Strictly speaking, there is no such thing as a professional RC competition. We tend to think of “professional” pilots as those who, along with their RC helicopters, are sponsored to fly at events. In other words, they are the Olympic hopefuls of electric helicopters.

Pro 3D competitions are marked the same way as local BMFA ones – only more stringently. Because RC helicopters have improved so much, it follows that today’s competitions are far more complex than those of a few years back, and the pilots are allowed far fewer errors.

The word here is “precision”. As you might expect from sponsored championships, both the pilots and their radio control helicopters are at the top of their game. FAI competitions involve precision manoeuvres over and between set points, within a 3D “box” area (hence, 3D flying). The judges are looking for speed, accuracy and smooth transitions – just as in local shows. However, pilots in the know have christened 3D flying as “Dressage for Electric Helicopters” and F3C competitions as the difference between a local gymkhana and the Hickstead 3 Day event.

F3C competitions are flown to the same schedules across the world, and are changed every season. This means that someone flying RC helicopters at F3C competitions in Calcutta can travel halfway across the world (to Chobham, say) and follow exactly the same schedules there.

The manoeuvres have some weird names, but anyone can download the FAI schedules, which include clearly laid-out diagrams. For the 2006 F3C schedule, manoeuvres included: Flipping Pullback, Vertical Spike, Cobra Roll with Half Rolls, Cuban Eights and Push Over with 360 Pirouette.

Not surprisingly the RC electric helicopters competing at international level are often worth thousands.

What do the ESky Belt, the Walkera Dragonfly, the ESky King and the E-Flite blade electric helicopters have in common? Well, among other things they all have belt-driven variable pitch tail rotors. They are also superb to fly; the two are very much connected.

RC helicopters with variable pitch rotors are powered from the main motor (i.e. the one that also drives the main blades). The main rotor and tail rotors are so connected that changes in the main rotor pitch effect a change in the rotational speed of the tail rotor.

VP tail rotors are more complicated than fixed pitch designs (which have their own motor, and are run independently of the main blades). However, they are much better in terms of manoeuvrability and control; they also last longer.

A variable pitch rotor has several components. These are:

1) Two blade grips. These connect the rotor blades to:
2) The tail rotor hub. This is the part of the tail that the tail shaft passes through.
3) A tail pitch slider. This moves back and forth along the tail shaft, and is connected to the tail rotor blade grips. Its movement changes the pitch angle of the tail blades, and therefore the thrust of the tail rotor, via a servo. The electric helicopters with the greatest pitch range are those where the slider connects to the leading edge of the blade grips.

The tail servo is controlled via a gyro, which fine-tunes the yaw commands the pilot sends via his transmitter, constantly cancelling out unwanted yaw and pitch changes due to alterations in wind speed and direction.

RC helicopters with pitch sliders quite often have a heading hold gyro as standard. The two work together to maintain the helicopter’s heading, or left/right yaw direction as input by the pilot. These are far smoother in flight – but take a lot of skill to master.

Most collective pitch RC helicopters are equipped with autorotation, which is an essential skill for any pilot to learn. It is another way that electric helicopters are similar to the real thing – autorotation is part of every commercial and military pilot’s training.

For this reason, many Fun Fly events have an autorotation contest, to test the mettle of their pilots. But what is it, and how is it applicable to RC helicopters under normal flying conditions?

Anyone, at any time, can have need to call on their autorotation skills. It’s a method for safely landing radio control helicopters that have suffered a loss of power. If the engine cuts out, or the battery dies, the rotor drive systems will fail. When this happens, the helicopter will fall from the sky like a stone unless it is equipped with autorotation.

The most likely RC helicopters to lack AR are fixed pitch design – collective pitch electric helicopters usually have an autorotation clutch fitted as standard. The clutch allows the rotor to spin freely in mid-air, when the power is cut. Imagine “free-wheeling” a car downhill by disengaging the clutch and putting the gears in neutral, it’s a similar concept.

However, having the device is one thing. Knowing how to use it is another.

When power is lost, the clutch engages. Now, the pilot must bring the throttle/collective all the way back. This causes the main rotor to have negative collective pitch, and begins the descent. The air moving through the blades keeps them spinning, whilst at the same time slowing the helicopter down.

As the helicopter gets nearer the ground, the pilot puts the pitch back in positive position by increasing the throttle/collective. This causes the helicopter to lift momentarily, further slowing its descent and allowing a soft landing.

RC helicopters don’t have to stall to make a perfect landing. Many of the factors used in the autorotation procedure can be adapted for normal flight. For example, if your descent is too fast, you can “jiggle” the collective control to avoid a heavy and potentially disastrous arrival at the helipad.

The simplest way of explaining how co-axial electric helicopters work, is the torque versus yaw option. When radio control helicopters fly, the main rotor creates torque, which makes the body rotate in the opposite direction.

To counteract this, an opposing force is applied via a tail rotor – this is called yaw. Co-axial RC Helicopters involve two contra-rotating head rotors, rather than a single head rotor and tail rotor, to achieve the same effect. These are easier to control.

However, there’s a bit more to it than that. There are, in fact, several designs of co-axial electric helicopters.

The very simplest co-axial choppers are little more than toys. However, at hobby level the duel rotors can be individually controlled to spin at different rates. This causes the nose to turn, creating a similar effect to yaw in tail rotor RC helicopters. Yaw can be adjusted to cause a deliberate, but controlled “pirouette,” or torque effect.

Co-axial RC helicopters are called this not because both rotors occupy the same axis, or axial, but because each rotates on its own axial. The central mast has two separate axials, one inside the other. Each is connected to its own gear, and each of these gears is connected separately to a motor.

In electric helicopters with independent co-axial control, the gears are connected to two independently controlled motors (single main blade RC helicopters have just the one motor, with sometimes a separate smaller one for the tail). Generally, the top rotor does the job of yaw control, and spins counter clockwise.
Since the two rotors spin in opposite directions, the blades are curved so that each can get maximum effect from the airflow.

Many co-axial RC helicopters also have a tail rotor. This allows great manoeuvrability, as the tail rotor takes over the job of pitch while the central rotors control yaw. Thus the helicopter can fly forwards, backwards, hover and turn at variable speeds (a simple co-axial lacking a tail rotor can only do a few of these things)
Co-axial RC helicopters are normally fixed pitch, 3 or 4 channel designs. However, some of the larger models, such as the Esky Lama V4, have collective-pitch. These 4 channel machines have no tail rotor. The central rotors control pitch, bank and yaw. They also fly backwards, forwards and hover although they cannot do the advanced 3-D movements that conventional CP electric helicopters can.

Electric helicopters are becoming ever more popular with photographers. From being a fun hobby, manufacturers have now developed a whole range of RC helicopters specifically for aerial photography.
These have taken off in two directions. For the professional photographer, with little interest in the sport of flying, electric helicopters have morphed into specialised UAV “drones”. These are totally unrecognisable as RC helicopters, rotors notwithstanding.

“Spy” RC helicopters are aimed at hobby photographers, and much more familiar. These are micro electric helicopters with built-in cameras. Normally 2 or 3 channel co-axial in design, they are more of a novelty than anything, and can’t be flown outdoors (where the action is).

For the professional spy wanting to commit aerial subterfuge, neither of these RC helicopters really fit the bill. Now, Prox Dynamics have crossed that divide, with the world’s first professional Micro Spy Helicopter.
At first glance, the PD-100 looks just like all the other FP micro RC helicopters out there. But these are targeted specifically at police, military and intelligence forces. The Prox might be one of the smallest electric helicopters ever built, but it’s a mini-beast with a powerful punch.

In flight, it is totally silent – but incredibly powerful. Just a few grams in weight, it nonetheless carries a powerful motor, CP digital stabilisation, rear rotor and heading hold gyro. Despite its size, the PD-100 can fly outside in powerful wind and will hold its “head” with sudden updrafts. With a pro digital camera payload, it can still reach speeds of over 20 mph.

These RC helicopters have one other amazing feature: an integrated transmitter and display screen. You don’t have to download images to the PC – they appear on the tx as you’re operating it, along with full flight data.

Presently, things are still at the experimental stage, but Prox Dynamics expect to announce a release date early in 2010.

There is a new generation of RC helicopters today that were never designed for the average flying field. They were created specifically for aerial photography, which some call covert spying.

Covert means concealed, but it’s hard to see how anyone could conceal the Draganflyer X6 – or any of the other Draganfly products, for that matter. This latest, 6 rotor addition to their range of electric helicopters is just as outlandish as their earlier 4 rotor and Mark1 6 rotor versions. These are more akin to Torchwood aliens, than Walkera RC helicopters. Maybe this is why the manufacturers call them UAVs, or Unmanned Aerial Vehicles, instead – a shorter word is drones.

Unsurprisingly, both police and military forces have been clambering over each other to get their mitts on these – and not just because they’re fun to play with, either. They can go in all the places a conventional chopper can – and many places they can’t. They can venture into dangerous, unsafe areas such as minefields and teenage bedrooms, and are undetectable by radar.

The Dragan X6 has just been sanctioned for police use in the US and Canada, and has already collected evidence for a homicide investigation.

All the same, you could do all this with an ESky, so why else are these drones so sought after? Well, they’re a lot more manoeuvrable for a start. Just like conventional RC electric helicopters they have pitch, yaw, roll and collective control. But putting the rotors around a central disc, with all the weight in the centre, means total balance and 360o accuracy – without needing a PhD in flying 3D electric helicopters first.

Despite the 9 channel inputs, Dragans are deceptively easy to use – meaning the pilot can apply all the attention to the job in hand, i.e. collecting video or photographic evidence. There is even the option of wearing video specs – real James Bond stuff. The bad news is, that unlike the RC electric helicopters on this site, these guys are expensive: expect a starting price of around $3000 – without the camera.

Draganflyers hover superbly in all weathers – although whether they dodge flying bullets is another matter. A promotional video of the improved Dragan X6 can be found on the Draganly home page.

The hero is, of course, the Airwolf Helicopter, star of the supersonic armour-plated action series of the same name, back in the mid 1980s. The series has just been released on DVD, attracting a whole new generation of electric helicopters which replicate the Airwolf’s looks – if not her speed.

Now, with a big action movie about to hit the big screen (with the inevitable spin-off RC helicopters sure to follow), there has never been a better time to take a look at one of the TV originals - the Walkera 5G4Q3 Airwolf 2.4Ghz.

Walkera’s Airwolf is, like many scale model electric helicopters, a 4 channel contra-rotating design. Co-axial RC helicopters are an excellent choice for the beginner pilot, in terms of both price and ease of use. The Walkera scores highly on both counts. It’s one of the most stable 4 channel co-axial electric helicopters on the market and, at less than £100, one of the most affordable.

The TV Airwolf was a full-size modified Bell 222 with added props and sound effects (which we were supposed to think were top-secret military gadgetry. If anyone knows why a self-camouflaging spy chopper needs to howl like a wolf in idle mode, please let us know).

However, while the wolf howl and high pitched supersonic scream are effects you might have to add yourself, Walkera have faithfully reproduced many of the exterior props. Thus, you’ve got side-mounted and front facing weaponry, rear tail fins, a (fake) tail rotor, and 3-wheel undercarriage – plus the “Orca” livery unique to the original.

As with all things iconic the image is paramount and so chances are you’ll want to show this baby off in public. Amazingly, the two figure asking price includes a 2.4GHz transmitter, allowing you to share the field with plenty of other RC helicopters with no worry about interfering frequencies.

The Walkera Airwolf is almost identical to the Century RC Helicopters model of the same name. It will be interesting to see who releases the movie model first.