Here are some professional unmanned helicopters:

 

  • Kaman K-max UAV
  • Unmanned Little Bird
  • SW4-‘SOLO‘ RUAV
  • MQ 8C Firescout
  • Yamaha R-MAX
  • Saab Skeldar
  • QH-50C DASH Anti Submarine

 

Unmanned helicopters can be built for a variety of purposes. Unmanned helicopters can be equipped with satellite navigation systems, aerial camera systems, environment recognition systems. UAV helicopters can have various degrees of autonomy: some need constant piloting via RC remote, some can autonomously execute preplanned mission via a tap of a single button without the need for a pilot. Some can even more.

Let’s focus on hobby grade RC helicopters.

 

Basics of control

 

A basic RC 4CH aircraft transmitter has two joysticks. Basically, a flight is controlled by those 2 joysticks. Each of those 2 joysticks can move up/down/right/left quite like a computer mouse. The control is fully proportional so we can make very precise movements. Those two joysticks take the role of the cyclic stick, the collective lever/throttle, and the anti-torque pedals.

There are two popular types of RC transmitter controls, it’s like having a car with a steering wheel on left or right. It’s a personal preference. I’ve learned to fly in MODE2 setup,

 

  • MODE2: throttle/collective/yaw is controlled by left hand and forward/backward/left/right in my right hand.
  • MODE1: forward/backward/sideways is controlled by left hand and throttle/collective/yaw is in right hand.

 

RC transmitters with more channels have also a computer with a display of input parameters and additional switches which can be used for lights, retracts, camera operation, flight modes, autopilot modes etc.

Most modern radios are built in digital 2.4Ghz system which means they don’t need the big antenna like in older analog systems. There are many types of systems and different transmitters. And really, you don’t have to worry about range. You will lose it out of sight before you ran out of range.

 

 

4 Channels

 

The simplest RC model helicopter starts with 4 channel remote control to fly like a helicopter:

  1. forward/backward
  2. left/right sideways
  3. yaw left/yaw right
  4. up/down

Let’s use a term RC model helicopter for at least 4 channel model. Toys with only 2 or 3  channels is a not really worth your time, I’ve described them in the latter part.

 

Fixed Pitch RC Helicopter

 

4Ch Fixed Pitch Helicopter RC Transmitter Mode2
left sideways / right sideways (cyclic) right joystick left/right
forward / backward (cyclic) right joystick fore/aft
left/right yaw (tail) left joystick left/right
throttle (up/down) left, joystick fore/aft

 

In Fixed Pitch RC helicopter we control the rotor thrust by only rpm change because the blades have fixed pitch. Most of the RC fixed pitch helicopter have a 4CH control system. There is a swashplate for directional control but a swashplate in fixed pitch heli can’t move up or down. Fixed Pitch Helis are called four channel ones because it’s a minimum required to control them. You can, of course, buy a transmitter with more channels which can be used for: dual rate switch, lights, retracts, autopilot etc

 

 

Collective Pitch RC Helicopters

 

6Ch Collective Pitch Helicopter 6Ch RC Transmitter Mode2
left sideways / right sideways (cyclic) right joystick left/right
forward / backward (cyclic) right joystick fore/aft
left/right yaw (tail) left joystick left/right
Collective and Throttle Mixed left joystick fore/aft
Throttle Hold* first on/off switch
Flight Mode Switch** second on/off switch

 

In Collective Pitch RC helicopter, the throttle is mixed with the collective so we control both of them for changing the rotor thrust.

We can also create a negative angle of attack. This way we can fly the RC helicopterlike “grass cutter” inverted  (rotor down – skids up)

To set up the angle of attack and throttle mix we can enter our preferred values into a transmitter computer. In modern computer RC transmitter with displays, we can change almost any value.

*by using Throttle Hold we can either turn on or off the motor for autorotation. Autorotation really works well especially with the bigger models with the bigger rotors with higher inertia.

** by using this switch we can change the helicopter flight mode. In normal flight mode, the collective is automatically mixed with throttle like in a real heliscopter with the governor. We can, however, engage the aerobatic mode in which the throttle is always at a preplanned value (for example 90%) and in this mode, we only change the blade pitch so it allows aerobatics and inverted flight.

Collective Pitch Helis are called six channel ones because it’s a minimum required to control them. You can, of course, buy a transmitter with more channels which can be used for: dual rate switch, lights, retracts, autopilot etc

 

Fixed Pitch RC Helis vs Collective Pitch RC Helis

In Fixed Pitch RC helis the altitude is controlled only by motor rpm. In the collective Pitch RC helis, the altitude is controlled by changing blade angle of attack – mixed with motor rpm. You can really feel the difference when flying RC helicopters with fixed pitch vs RC helicopters with collective pitch. The fixed pitch reaction is much slower than the reaction of collective pitch in even very small versions of RC helicopter. The 6ch ones are more precise in control the 4ch ones. Even when you don’t fly 3D, It just takes some time for the fixed pitch rotor system to react due to its inertia. When you can change the pitch, it just flies better than fixed pitch heli, because pitch change reacts instantly.

Collective Pitch Helis can also perform inverted flight thanks to a possibility to create a netagtive angle of attack.

 

Toy Grade vs Hobby Grade

Many toy-grade helicopters are 3channel ones. Example:

There are some cheap coaxial helicopters with a small propeller on the tail pointing upwards. Those cheap 3 channel coaxial helis don’t have a swashplate so you can fly:

 

  1. up/down by adjusting throttle of both coaxial rotors
  2. left/right by adjusting more or less torque on the clocwise or counterclockwise rotor
  3. more or less thrust in the back which gets the tail up/down so the heli moves forward/backward

 

No swashplate, no sideways movement. It’s more like a car than a helicopter. I say it’s not worth buying two or 3 channel RC helis. It can take off above the ground… but just doesn’t fly like a helicopter.

To have a controllable model helicopter It’s necessary to have 4 controls – 4 channels, it’s minimum. Don’t even bother yourself with 2 or 3 channels, that’s my advice.

Keep in mind: You can buy a 4ch Coaxial heli and it’s going to fly quite well but don’t buy 3 channel ones ( or 2 channel ones… )

 

RC Helicopter shapes and sizes

 

RC helicopter may have different rotor configurations such as coaxial, tandem, intermeshing, conventional etc.

There are various RC heli scales, like micro, 450, 500, 600, 700, 800

Generally, most RC helicopters can be divided into 4 tasks:

  • utility helicopters (camera system/spraying/aerial mapping)
  • scale RC helicopters
  • 3D RC helicopters
  • other

 

Tail Rotor

In very small rc helicopters a tail motor without tail rotor pitch change is ok hovhverIn general, the best hobygrade. IT gives the best resposne tail. The tail is powered via a gearbobo from the main motor like in a real conventional helicopter.

 

During 3D flight you can really feel the difference when flyinh rc helicopters with fixed pitch tail rotor controlled by motor vs adjusted pitch tail deisng.

 

Tail rotor gyro

RC helicopters are equipped with a gyro, which controls the tail. Gyro holds the tail so that we’don’t have to be worried about thrust change. Wo don’t have to constantly change the yaw, gyro system do this for us constatly regulating the tail rotor thrust. We can of course adjust the yaw axis but gyro constatly help us with maintaint heading.

 

 

Flybar vs Flybarless

Some time ago rc helicopters were equipped with a special fluybar system which was. Flybar system was similar in look.to those which we can find for example on HUye helicopter. Flybar in rc helicopters helped but it also so the helicopter wasn’t as agile as it could be.

 

Most modern rc helicopters are equipped with an flybarless system. It’s basically an electronic module which took the work of . The’re so no longer a need for a flybar because a computer constatnly adjust the servomotors to adjust the aswahplatn to maintain stable flight. You can really feel the difference when flyinh rc helicopters with flybar vs rc helicopters with flybarless system.  Flybarless systems control both the main rotor and the tail rotor – they have the tail gyro function in themselfves. The helicopters with a stabilisation is going to hover but withouth gps module it’s gonna drift with the wind. Additional stalibisation and level of it can be turned on and off depending on our preferences.

 

Advanced Autopilot

 

Some helicopters are also equipped with a stabilisation feutre. We can add a GPS module so they would stay in place in hover or autnomusly return to home and land after a transmitter failure.

 

Some rc helicopters can be equipped with an additional nawigational autopliopt system which can make the helicopter eecute preplanned missions. Simplifying, we tell the helicopter what is has to do during it’s flighth by uploading a special file with a waypoint map. Then we have just ot click start and the helicopter will autonously takeoff, fly throught those waypoints and then land fully autonously. Some of those systems have additional enviorment sensor such as for example obstacle avoidance.

 

I’ts worth to know more about spare parts availablility

 

Jet turbine powered RC helicopters sounds like real machines. Some scale RC helicopters powered by electric motors are equipped with special sound system with speaker built insdie the fuseluge to sound like a real helicopter.

 

 

Scale model helicopters were used in many films as props and supporting CGI.