by John Salt - Updated March 2021
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. "Bigger is better" in other words. That used to be true with flybars, but not as much now with the help of flybarless electronic stabilization.
Still, larger RC helis (flybar or flybarless) do have some advantages over smaller ones for learning on, and we will look at these advantages. Problem is, just what is considered "large", and for that matter, how are RC helicopters even sized so you know what to look for?
Back when I got started in the hobby (late 80's), when all we had were nitro RC helicopters, sizing RC planes and helicopters was fairly easy & consistent. Basically whatever size nitro 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 different power options now such as electric, and turbine, how on earth can we compare apples to apples?
For instance, that 30 size nitro heli I just mentioned is about the same size a 550 class electric RC helicopter.
Would someone new to the hobby understand that 30 is the same as 550? I've been at this for over 30 years and it makes little sense to me either.
Moreover, electric motor specifications and numbers are all over the place and arbitrary at best.
electric motors is just to indicate physical size/class of the motor - it
doesn't actually indicate how powerful it is or what physical size of helicopter it is meant to be used in.
Nano, micro, and mini helicopter sizing has also clouded the issue with these terms being thrown around more as trendy niche marketing tools than as accurate ways to determine helicopter size.
For example, my own
"micro & mini" heli classification standard is if I can land it and
take it off in my hand safely, I classify the heli as a nano or micro. Anything slightly larger but still small enough to fly safely in my yard is a mini. Totally meaningless unless you understand my sizing method and narrative.
Confusing – You bet!
Fortunately there is a much better and consistent way to determine sizing from small RC helicopters up to large RC helicopters, and that is by the main rotor length or main rotor diameter.
All good RC helicopter manufacturers should indicate both main rotor diameter & main rotor length on their specifications of each helicopter model.
This way you can compare apples to apples without getting lost in engine or motor numbers, or trendy terms.
The main rotor diameter as shown above is simply the distance measured from rotor tip to rotor tip. 735mm on this particular 450 size RC helicopter.
Main rotor blade length on the other hand is measured from main rotor mounting bolt hole out to the tip of the rotor blade.
This blade length method of sizing is finally starting to become the standard. A 700mm long rotor blade as shown below, is used on a 700 size RC helicopter.
I have broken this mess of sizing down to a simple five size list.
Under each size heading, I have included rotor length & diameter range in millimeters and inches. I have indicated possible engine sizes (remember those are subjective & arbitrary, especially for electrics).
I have also
included several popular helicopters in each size range so you can get a better of idea actual sizes of these models and a few pros and cons of each size.
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.
XK K110 main rotor dia. = 245mm
Align T-Rex 150X main rotor dia. = 271mm
OMP Hobby M1 main rotor dia. = 290mm
OMP Hobby M2 main rotor dia. = 400mm
Trex 250 main rotor dia. = 460mm
Blade 230 S main rotor dia. = 536mm
Sab Goblin 280 & Mini Comet - main rotor dia. = 626mm
Blade 330S - main rotor dia. = 715mm
Align T-Rex 450LP ARTF - main rotor dia. = 734mm
Alzrc Devil 380 Fast - main rotor dia. = 856mm
Alzrc Devil 505 Fast - main rotor dia. = 1150mm
Align Trex 550X - main rotor dia. = 1188mm
SAB Goblin 570 - main rotor dia. = 1278mm
SAB Goblin 630 - main rotor dia. = 1428mm
Align Trex 650X - main rotor dia. = 1455mm
Special Size Notation/Clarification:
Something coincidentally funny happens at this "regular" 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.
Important: More manufacturers (SAB, Mikado & Blade for example) are actually starting to size the smaller stuff now as well going by blade length. The SAB Goblin 280 uses 280mm blades for example; the Blade 330S uses 325mm blades; the Mikado Logo 200 uses 180mm size blades. Hopefully this trend continues and one day "soon", all brands & sizes will go by the standard of blade length - let's hope so.
Align Trex 700X - main rotor dia. = 1562mm
Sab Goblin 770 - main rotor dia. = 1728mm
Align Trex 800 - main rotor dia. = 1780mm
Bergen Intrepid - main rotor dia. = 1800mm
Velos 880 - main rotor dia. = 1900mm
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), and very dependent on how you are learning (more on this shortly).
This might not seem to make sense from a cost standpoint, but from an ease of learning to fly standpoint, large RC helicopters have 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 & dangerous if you are self learning.
You also need a large open flying area to safely fly them in and with many new overreaching RC flying restrictions world wide (thanks largely to RC drones), large legal RC flying areas are getting harder to access in some countries.
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 newbies, that means what I have classified as a “Small”
or "Mini" size electric. More
RC heli pilots have recently & successfully
learned to fly
on these sizes than all others.
450 size electrics (315mm-330mm long main rotor blades) are my personal recommendation to friends due to
cost and growth potential. 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). They are just a really nice size and get decent flight times. There are several
complete ready to fly (RTF) packages (the Align T-Rex 450LP ARTF for example) that will give you the "best bang for the buck" in this size segment.
With that said, the introduction of good performing micro & mini collective pitch helicopters thanks to electronic stabilization can also be very good choices for self learning collective pitch on. They don't cost much, they are fairly crash proof, and not at all intimidating.
The other added bonus with them is they can be small enough to be flown in your own yard, or even indoors with the micro sizes! Most are exempt from RC flying restrictions as they pose little threat to people or property.
Micro & Mini RC helis have certain limitations however.
The obvious ones are fairly short flight times, they get small very fast, are finicky to work on, and are somewhat disposable in nature, plus you can't really "grow" into them. They do make wonderful practice tools however, and I personally find them more useful and a lot more fun then time spent on a simulator.
More and more people are starting to successfully learn to fly collective pitch on micro & mini 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 almost always windy in Reno, and in that case getting a big & stable bird to learn on makes good sense. Flight times are also quite long making each training flight more beneficial to the student while maximizing the instructors training time with the student.
I would never recommend for anyone to "self learn" on such a large RC helicopter due to the dangers and costs involved; but with an instructor's help, those concerns are very much reduced.
This is exactly why I point out on my best RC helicopter page, 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 RC helicopter sizing topic off with a video of one of the largest RC helicopters in the world. A turbine powered scale EC145.
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