The RC quadrocopter, also called the quadcopter, quadricopter, quad rotor RC helicopter, and incorrectly Drone; all fall into the category of multi-rotor RC.
They are the 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.
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 absolutely 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 microprocessors to deal with the hundreds (even thousands) of calculations and correction commands every second, can these things fly at all.
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 fast flips and rolls, yet can be put into easy stable flying mode/s as well for beginners.
In these "easy" modes, the electronics on-board simply won't let the aircraft pitch or roll past a certain degree. The electronic stabilization systems also perfectly levels the aircraft out when the control sticks are returned to the neutral "center" position. In that respect, they behave very similar to a super stable micro coaxial RC helicopter, and why they make a good first RC aircraft.
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, obstacle avoidance, "follow me tracking", 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.
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.
Since RC quadcotpers 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, and that was for simple basic units without any sophisticated auto-pilot systems.
With entry level hobby grade quadricopters built for the masses, the costs are always dropping and it just keeps getting better for beginners.
You can be flying and flipping tiny palm sized quads such as the Blade Pico QX , Blade Inductrix , and 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!
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?
As shown here, the vast majority of quadrotors that are sized 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).
With a market place that is saturate with product, where does a newbie even start looking at what might be a good quad to start with?
Well, if it were me, I would start my search with Blade's Quad Rotors. My Blade Helicopter & Quad page goes over all the reasons why I like this brand better than the rest for folks just getting into the hobby. I have links to the many model of beginner friendly low cost hobby grade quads Blade has on that page.
RC Quad/multi rotor safety a big can of worms to open. I've covered it in detail on my "RC Drone Page" so I encourage you to at least glass over that page as this is an important topic many newbies to RC flight are unaware of. Below is a good "basics" primer video as well...
Ah yes, the real driving force behind the multirotor design and the absolute perfect job for them.
Since these things can fly themselves, hover like they are glued in the air, have superior lift efficiency, and don't take 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 quadrocopter 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 solid 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 quadrocopter 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...
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?
There are certainly all kinds out there, but right now, there is one that leads the pack in almost all areas...
The DJI Mavic Pro Quad Copter is without question, the current top rated & best selling aerial imaging quadrotor on the market right now. It includes everything you need such as the 4k camera and stabilization gimbal, as well as various "bundle packages" based on your specific imaging needs.
The DJI Phantom's & Mavic Pro have very good GPS auto pilot & stabilization systems built-in (based on DJI's original Naza system). Over and above hands off hovering with the autopilot turned on, even if you get out of radio range or engage the "return to home" function; the GPS auto pilot systems will bring them right back to your position and auto land.
Flight times are crazy impressive at over 20 minutes not to mention all the other cool technology such as obstacle avoidance and "follow me".
Ready to fly, off the shelf quad-copters like the DJI's with all these
features have essentially narrowed the gap between the low cost hobby
variety of AP capable quads with the higher quality industrial quads.
For the ultimate off the shelf aerial imaging, DJI's Inspire 1 is truly a remarkable machine that caters to true AP professionals.
Last but not least, DJI also offers "Frame Wheel" 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. These Frame Wheel kits are for the true multi-rotor hobbyists who want to build their own machine.
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).
The latest exciting quadrocopter development is the ability for them to hover inverted and perform true 3D flight similar to what conventional collective pitch RC helicopters can do. I have an entire writeup on the topic of 3D Quadrotors - very cool.