Understanding The RC Quadrocopter / Multi Rotor

RC Quadrocopter Also Called The Quad Copter or Quad Rotor Helicopter

The RC quadrocopter, also called the quadcopter, quadricopter, and quad rotor RC helicopter all fall into the category of multi rotor RC which is the latest and fastest growing development in radio controlled vertical lift platforms that are able to take off vertically, hover, and fly in all directions. As the name suggests, there are 4 propellers arranged in a cross type configuration.



There is no single large collective pitch rotor or tail rotor that we are all used to seeing on a conventional RC helicopter. These propellers are fixed pitch, two will spin clockwise and the other two will spin counter clockwise. By precisely and accurately spinning these four propellers at different speeds, all the common directional movements of a standard helicopter are attainable - Hover, forward/backward movement, left/right movement, and yaw (turn rate) movement.

This makes the quad rotor and other multi rotor RC helicopters mechanically very simple with hardly any moving parts compared to conventional mechanically complex collective pitch and even fixed pitch RC helicopters. In most cases there are only 4 moving parts on the majority of quad rotor helis; the 4 spinning motor shafts which are directly connected to the 4 spinning propellers - that's it! This also makes quad and multi rotor RC helicopters very easy for enthusiasts to custom build their own machines. All that is needed is the frame, the motors, the ESC's, propellers, the receiver, and the electronic stabilization system, along with LiPo flight batteries of course...

There are certainly other incarnations of the multi rotor design using as little as 3 propellers arranged in a triangle configuration up to six arranged in a hexagonal configuration and even eight (Octocopters); but for ease of explanation, I will stick with the quadrotor variety as it is the most common and if you do end up getting this type of RC helicopter, most likely what you will be starting out with.

Check out Red Rocket Hobby's Quad Copter Page - Lots of neat stuff in there...


How Do Quads & Multi Rotor Work?

The reason RC quadrocopters and multi rotors are fairly new on the scene is the complex and rather heavy computing/processing power required to accurately control all the propellers to not only move the heli about, but to keep it stable. Multi rotors are inherently unstable. Only when all propellers are spinning at the exact same rate, producing equal amounts of thrust and torque, and experiencing equal amounts of drag is hover equilibrium achieved. Controlling this manually is all but impossible and only because of today’s solid state gyro and accelerometer technology, efficient and fast responding brushless or coreless motors, coupled with small micro processors to deal with the hundreds of calculations and control commands every second, can these things fly at all.

For those looking for the meat & potatoes of how this all works together to accuratly move and predict/calculate a multirotor aircraft's position (commonly using the Kalman Filter algorithm), here's a very is a good article on it

When consumer available RC quadrocopters were first introduced a few years ago, they were not that performance minded as the emphasis was on easy going and super stable flight. Times have changed however and many are capable of performing some fairly aggressive aerobatic flight now. In fact, most decent quality hobby grade quads are aerobatic these days capable of performing heart pounding fast flips and rolls, yet can be put into easy stable flying mode/s as well for beginners.  In these "easy" modes, the electronics onboard simply won't let the aircraft pitch or roll past a certain degree so they behave very similar to a super stable micro coaxial RC helicopter.

The latest and greatest generation of mid priced to high end quad rotors are now sporting GPS positioning and an array of other sensors. This gives them even more fully autonomous hands off flight control, way point assigned flight paths, and "return to home" capabilities if the radio link is lost. The level of electronic sophistication required to keep these things airborne is remarkable. They are in effect "aerial robots" since in actuality you are not flying them like a conventional RC helicopter or airplane. You are basically just telling them what to do and the electronics and programming are 100% responsible for the actual flying. 


Does A Quadrocopter Make A Good First RC Heli?

Absolutely Yes! These make a wonderful first RC helicopter if you want the one of easiest flying experiences available to start with yet at the same time, have some aerobatic performance later on as your skills improve; provided you don’t really care about true single rotor RC helicopter flight or flight characteristics. Quadrocopters for the most part appeal to a larger group of people who just want to fly something by radio control and don’t necessarily care for a "real" conventional aircraft feel or look or perhaps just want one of the coolest and funnest flying gadgets around. Likely why multi rotor is showing the strongest growth and popularity over all other types of RC aircraft right now.

Blade Quad Copter

Since mulit rotor RC helicopters are electronically complex, they were also very costly; but again as mass produced electronics and miniaturization becomes more and more common place, prices are dropping sharply. It wasn’t that long ago if you could find one of these things for a thousand bucks you were doing good. With entry level hobby grade quadricopters built for the masses such as the Blade 350 QX for around $450, the Parrot AR Drone quadricopter for about $300, the Blade 180 QX for about $180, and the Blade mQX for about $120, the costs are always dropping and it just keeps getting better for beginners.

Traxxas QR-1 Quadrocopter

You can be flying and flipping tiny palm sized quads such as the Traxxas QR-1 , UDI Micro Quadcopter , Hubsan X4 and my personal favorite palm sized quad, the Blade Nano QX all for under $100 bucks!

I personally don't think it's possible to cram as much flying fun into something so small, so inexpensively. These little quadrocopters rock!

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The AR Drone was my first introduction to the quadrotor design and for the low cost (back then) – it really is an amazing little heli that even boasts real time first person view (FPV) and RF (WiFi) signal strength and battery condition telemetry. I had huge amounts of fun with the Parrot AR Drone - click here to see my full review on it.


How are Multi/Quadrotors Sized?

When looking at many quad and multi rotors on the market, most have a size number such as 180,350,450,550,800, and so on... What does this size number relate to?

How To Size A Quad or Multi Rotor RC Helicopter

As shown here, the vast majority of quadrotors that are size this way are referring the the diagonal distance in millimeters from each motor's center (motor hub to motor hub).

Hexa and octa rotors on the other hand are measured motor hub to motor hub on adjacent motor arms. With this particular quad rotor heli, the diagonal distance from motor hub to motor hub is about 350mm. Yep, this a 350 size quadrocopter (the Blade 350 QX to be exact).


Aerial Photography (AP) & Video & FPV?

Ah yes, the real driving force behind the multirotor design and the perfect job for them. Since these things almost fly themselves, hover like they are glued in the air, have superior lift efficiency, and don't take that much skill to pilot, they have become one of the most popular vertical lift and flying platforms for hundreds of different aerial photo, video, and FPV applications from real-estate to sporting events to wildlife and nature. If you can dream up a use for an "eye in the sky" - chances are there is an AP specific multi rotor heli that can perform the task. Moreover, with all the electronic sophistication and on-board autopilot systems providing a very stable and pinpoint fixed position hands off hover; they give the operator/pilot the freedom and ability to concentrate fully on camera control if he/she so chooses.

If I was starting an AP business (which I have often thought about) and didn't have the time or desire to learn how to fly a single rotor collective pitch helicopter first (generally a year long process), a multi rotor is definitely what I would be using. Even knowing how to fly collective pitch well, if I ever do start an AP business, you can bet there will be at least one multi rotor in the fleet.

You don't have to spend a fortune either these days to get a quad rotor heli with basic aerial video capabilities. The aforementioned Blade 180 QX for example comes ready to fly with a built in video camera that delivers fairly decent aerial video footage and stills for the low cost of around $180.00 bucks!

Have a peek...


Best Quadrocopter for Your GoPro Camera?

GoPro Camera On Quad Rotor RC Helicopter

One of the most common questions I keep getting asked almost daily right now is "what's the best ready to fly quadrocopter or multi rotor for taking pictures and video with my GoPro camera". There are certainly many quadrocopters and other multi-rotors out there now that have the power to lift a GoPro with room to spare. The Gaui 330X was always one of my top recommendations for it's combination of quality, performance, and good price.

That said, the fully ready to fly Blade 350 QX offers very impressive features and value, that in my opinion, make it a better choice over the 330X quadrocopter for those of you who just want to get a quad, put your GoPro on it, and start filming without worrying about all the other components needed including but not limited to pricy GPS auto pilot systems and specific camera mounts.

Blade 350 QX Quadrocopter

The Blade 350 QX quadrocopter is one of the best ready to fly GoPro capable, fully autonomous quadrotors on the market for the price; beating out even the very popular DJI Phantom in many respects. Click on the link above or the photo to be taken to my full review on it.

As I just mentioned, the very popular DJI Phantom and DJI Phantom 2 Quad Copters are two other top GoPro carrying quad rotor RC helicopters.

DJI Pantom 2 with GoPro Hero 3 on motorized gimbal.

Like the Blade 350 QX, the Phantoms have very good GPS auto pilot & stabilization systems built-in which for the low price of under $500 bucks (the Phantom 1) for everything not all that long ago was unheard of. Over and above hands off hovering with the autopilot turned on, even if you get out of radio range with either of these two fully autonomous quadrocopters or engage the "return to home" function; the GPS auto pilot systems will bring them right back to your position.

Many GPS autopilot systems on the market right now capable of "return to home" cost well over $400 on their own, never mind being paired with a very capable quad rotor heli - simply outstanding! Other features like high intensity LED lighting for improved visual foot print and night flying plus the built-in camera mount so you don't have to spend extra on those items really pushes the DJI Phantoms and Blade 350 QX quads far ahead of the pack in terms of value for all the features you get.

Ready to fly quadrotors like the DJI Phantoms and Blade 350 QX with all these features are starting to narrow the gap between the low cost hobby variety of AP capable quads with the higher quality industrial quads. Sure there is still a big difference between hobby grade and industrial quad quality, durability, flight performance, and overall payload lifting capacity, but the gap is narrowing all the time.

DJI F550 Multi Rotor RC Helicopter

DJI for example also offers what could almost be considered light industrial quad, hex, and octo rotor kits which you have to assemble and can option out with all sorts of plug in components depending on what you want to do with them. DJI also has very capable stabilization & GPS systems such as the WooKong-M and Naza-M series systems. If you are serious about multi rotor, purchasing a kit along with all the support equipment is the next fun and rewarding step. I'm very impressed with DJI's Frame Wheel combo kits and have been flying the F550 myself using FPV (first person view)... Stay tuned for a possible review.


Higher End Industrial Multi/Quad Rotor Helicopters

One of the most common and recognizable high end AP radio controlled quadcopters is the Draganflyer X4 industrial vertical lift platform. This quad is the one that started it all. These have been used in surveillance work, search & rescue operations, and law enforcement for example or in much higher demanding image quality aerial photography/video rolls such as professional photography, video brochures, commercials, and aerial real estate to name just a few of the applications. Take a look:

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Chris Bergen and his dedicated team over at Bergen RC also have a very impressive industrial heavy lift class of multi rotors ranging from quadcopters up to octocopters. Anyone who is interested in starting up an aerial photography/video business, or looking for a specific heavy lift multi rotor design for your particular application/camera equipment, I highly encourage you contact Bergen RC. Chris knows the heavy lift industrial AP business better than most.

Here's Chris demoing one of their hexacopters.


Different RC Quadracopters Currently On The Market

With more and more quad & multi rotor RC helis hitting the marketplace all the time, it's really hard to stay current, but here are a few links to companies that manufacture & carry radio controlled quadrotor helicopters from the inexpensive micro hobby variety up to the much more costly industrial heavy lift applications.







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