Size is a "big" topic. Many people say large RC Helicopters are the best to learn on once you make the fun progression to single rotor collective pitch. This is true in most cases, but what is considered large and how are RC helicopters sized?
With so many sizes available and so many different ways advertisers are promoting RC helicopters, where do you even start?
In the good old days when all we had were nitro engines , sizing planes and helicopters was easy. Basically whatever size engine was used in the helicopter – that’s what size it was referred to.
This is still a convenient way to size nitro models. For example a 30 size nitro helicopter would mean it uses a 0.30 cubic inch nitro engine ... a very popular entry level nitro helicopter size to this day.
With so many different power options now like electric and gas, how on earth can we compare apples to apples? For example a 600 class electric RC helicopter is roughly the same size as a 50 size nitro heli. Of course electric motor specifications and numbers are all over the place. Sizing for electric motors is just to indicate physical size of the motor - it doesn't actually indicate how powerful it is or how fast it turns per volt.
Micro and mini helicopter sizing has also clouded the issue with both terms being thrown around more as trendy niche marketing tools than as ways to determine helicopter size. Micro and mini are therefore completely subjective without any common point of reference. My own "mini & micro" heli classification standard is if I can land it and take it off in my hand safely, I classify the heli as a mini - anything bigger is a micro or larger.
Confusing – You bet! Fortunately there is a better way to determine large RC helicopter size from small, and that is by the main rotor diameter.
All RC helicopter manufactures will indicate main rotor diameter on their specifications of each helicopter model. This way you can compare apples to apples without getting lost in engine or motor numbers.
The rotor diameter is simply the distance measured from rotor tip to rotor tip – just the same as measuring wing span on an airplane. For helicopters, this distance is usually measured in millimeters; however, there are a few manufactures that indicate rotor diameter in inches as well.
I have broken this mess of sizing down to a simple five size list. Under each size heading, I have included rotor diameter range in millimeters and inches. I have indicated possible engine sizes – remember those are subjective especially for electrics. I have also included several popular helicopter sizes with approximate rotor diameters in each size classification so you can get a better of idea of where they fall within the size range.
Hopefully this will help you get your head around all this large RC helicopter vs small RC helicopter, micro vs mini talk by pointing out some relative scale and examples.
Blade Nano CPx main rotor diameter = 197mm
Blade mCPx main rotor diameter = 245mm
Blade 120SR main rotor diameter = 318mm
Blade 130 X main rotor diameter = 325mm
Trex 250 main rotor diameter = 460mm
Blade 300 X main rotor diameter = 550mm
Align Trex 450 Plus DFC main rotor diameter = 715mm
Align Trex 500 main rotor diameter = 978mm
Align Trex 550 main rotor diameter = 1188mm
Align Trex 600 main rotor diameter = 1350mm
Special Size Notation/Clarification:
Something coincidentally funny happens at this size and larger. The length of the main rotor blades often is very close to the size of the electric motor rating. For example a 600 size RC helicopter will generally be spinning rotor blades that are about 600mm in length (rotor blade length, not rotor diameter). Again, this is just an interesting coincidence. I thought I should mention it because it's confusing and some people figure this is how RC heli sizing works across the board; but it doesn't, only with 550's and larger. A 450 for example spins 325mm blades, a 300 spins 250mm blades, and a 250 spins 200mm blades. It's confusing - no question.
Align Trex 700 main rotor diameter = 1562mm
Align Trex 800 main rotor diameter = 1780mm
Bergen Intrepid main rotor diameter = 1800mm
Now that we have our 5 basic sizes identified let's look at which will be your best collective pitch RC helicopter to learn on.
As stated in the opening paragraph:“The Bigger The Better” (up to a point).
This might not seem to make sense from a cost standpoint, but from an ease of learning to fly standpoint, large RC helicopters have many advantages.
The down side to large RC helicopters is they cost more than small ones – sometimes a lot more. They also cost more to repair and operate and can be very intimidating if you are self learning.
Generally, the best way is to start out with the largest RC helicopter you can afford to purchase, operate, and maintain (within reason). For most people that means what I have classified as a “Small” size 400/450 series electric or "Regular" size electric or nitro. More RC heli pilots have successfully learned to fly on these two sizes than any other (talking collective pitch here).
450 electrics are the most popular size due to
cost. The nice thing about this size is the price - you generally get the most rotor diameter to dollar ratio with 450 size helicopters over all other sizes (micro to monster). There are several
complete ready to fly (RTF) packages available such as the
Trex 450 Plus
that will give you the "biggest bang for the buck".
That said, with the introduction of good performing micro collective pitch helicopters; these can be another very good choice for self learning collective pitch on as they are both fairly crash proof and not at all intimidating.
They do have certain limitations however. The obvious ones are fairly short flight times, they get small very fast, and are finicky to work on, plus you can't really "grow" into them - but they do make wonderful practice tools and I personally find them more useful and a lot more fun then time spent on a simulator.
After all, more and more people are starting to successfully learn to fly collective pitch on micro CP these days so they do work for some folks very well.
180 degrees on the other end of the micro size spectrum, I recall getting an email from a fellow a while back who lived in the Reno Nevada area who was just getting into the hobby. He didn't want to self learn but would rather learn from an instructor to speed up the process. So, he joined the local RC helicopter flying club and signed up for lessons. They would not instruct him on anything smaller than a 600 size RC helicopter but were really pushing toward a 700 and that's what he ended getting as his very first RC helicopter and is what he took his his lesson on from day one - very successfully I might add.
Why did they want to start him out on such a large RC helicopter? Well, it's always windy in Reno, and in that case getting a big & stable bird to learn on makes good sense. I would never recommend for anyone to self learn on such a large RC helicopter due to the dangers and costs involved if and when you mess up; but with an instructor's help, those concerns are very much reduced. This is exactly why I point out there is no "best size" to learn on for everybody as it's all dependent on flying location, how you learn to fly, and naturally your budget...
May as well end this large RC helicopter topic off with a video of one of the largest RC helicopters in the world. A turbine powered scale Cobra with main rotor diameter of 3350mm. Now that's a large RC helicopter! Almost twice as big as my Intrepid turbine.