LARGE RC HELICOPTERS
How Are RC Helicopters Sized & What Is The Best Size To Start With?

by John Salt - Updated March 2021

Large 800 down to tiny 100 size RC helicopters.

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?

Sizing RC Helicopters By Engine/Motor Size

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.

30 size nitro RC helicopter engine

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.

Sizing for 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.

Sizing RC Helis By Blade Size

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.

1: Micro/Nano RC Helicopters

•  Main rotor blade length: 70mm - 130mm (3" - 5")
•  Main rotor diameter: 150mm – 300mm (6" – 12")
•  Electric motor size: 100 - 200 class
•  Combustion engine size: Too small for nitro, gas, or turbine
•  Example helicopters:
  

XK K110 main rotor dia. = 245mm

Align T-Rex 150X main rotor dia. = 271mm

OMP Hobby M1 main rotor dia. = 290mm 

Micro Size Blade mCP RC Helicopter

Pros:

• Inexpensive (helicopter, batteries, parts).
• Very crash resistant due to very low mass & low energy release.
• Can fly "tamely" indoors in average sized rooms.
• Can fly "aggressively" outdoors in smaller yards calm conditions. 
• Generally don't fall under new RC flying regulations & restrictions.
• Low parts count.
• Very safe and non intimidating to self learn on.
• Already built.
  

Cons:

• Hardest to see.
• Can be quite "squirrely" due to low mass & fast reaction.
• Very short flight times.
• Parts tend to wear out quickly.
• Low quality & fragile making them fairly disposable.
• Hard to work on due to small size.
• Can't auto-rotate.
  
• Most have fairly short product runs - long term ownership outlook is poor (a year or two).
  

2: Mini RC Helicopters

• Main rotor blade length: 130mm - 250mm (5" - 10")
  
• Main rotor diameter: 300mm – 600mm (12" –  24")
• Electric Motor Size: 200 – 300 class
• Combustion engine size: 0.049 nitro (too small for gas or turbine)
  
• Example helicopters:

OMP Hobby M2 main rotor dia. = 400mm

Trex 250 main rotor dia. = 460mm

Blade 230 S main rotor  dia. = 536mm               

Mini Size OMP Hobby M2 RC Helicopter

 Pros:

• Somewhat inexpensive (helicopter, batteries, parts).
• Crash resistant to a point, damage is likely under higher speed/energy crashes.
• Can fly indoors in large rooms. Perfect size for gymnasiums.
  
• Can fly outdoors, even able to handle a little wind.
• Perfect size to fly in average to large size yards.
  
• Generally don't fall under new RC flying regulations & restrictions.
• Low parts count.
• Fairly safe & non intimidating to self learn on.
• Already built.
  

Cons:

• Hard to see at moderate distances.
  
• Can be quite "squirrely" due to low mass, fast reaction, and generally higher power than their micro/nano counterparts.
  
• Short flight times.
• Some parts tend to wear out quickly.
• Due to very high head and tail rotor speeds, some bearings wear out quickly.
  
• Somewhat fragile.
  
• Can be hard to work on due to small size.
• Hard or impossible to auto-rotate.
  
• Most have fairly short product runs - long term ownership outlook is fair (a couple years).

3: Small RC Helicopters

• Main rotor blade length: 250mm - 500mm (10" - 20")
  
• Main rotor diameter: 600mm – 1100mm (24" – 44")
• Electric Motor Size: 400 – 500 class
• Combustion engine size: 0.10 – 0.20 (10-20 nitro) / too small for gas or turbine
  
• Example helicopters:

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

Small Size Blade 330X RC Helicopter

Pros:

• Best overall value in the sense of most rotor size per dollar ratio of all sizes.
• Parts don't cost much more than many mini size heli parts, again good overall value.
  
• Quite stable and predictable.
• Longer flight times.
  
• Easy to see at moderate distances.
  
• Best size for acreages & park sized flying areas.
  
• Can handle a fair amount of wind.
• Fairly easy to work on.
• Very educational. People learn a lot with this size of helicopter from both a mechanical and electronic standpoint that will help them with larger helicopters. It has been my experience for example, that most people who can confidently work on, fly, and maintain a heli of this size; are then well prepared and can successfully progress to any of the larger sizes armed with a solid skill base and understanding.
  
• Fairly easy and non intimidating to self learn on.
  
• Higher quality parts last longer as do the helicopters.
• Bearing life is average.
  
• Most use very common and easy to find size and voltage LiPo batteries (largely because these are such common size helis).
• Very broad envelope of flying performance right from beginner skill sets up to hard core 3D smacking.
  
• Scale fuselages available if scale is your goal.
• A really nice size almost all people enjoy flying.
• Can come in both built/RTF & kit versions.
  

Cons:

• A crash will almost always result in broken parts due to higher mass and energy.
  
• Pretty safe but can cause damage to both body and property if you hit someone/something.
  
• Generally fall under new RC flying regulations & restrictions.
  
• Cost is more than micros or minis, but still much less than regular & larger sizes.
• Can be a difficult to auto-rotate.
  
• Most have moderate product runs - long term ownership outlook is fair to okay (several years).
  

4: Regular Size RC Helicopters

• Main rotor blade length: 500mm - 650mm (20" - 26")
  
• Main rotor diameter: 1100mm – 1500mm (44" – 60")
• Electric Motor Size: 550 & 600 class
• Combustion engine size: 0.3 – 0.6 (30-60 nitro) / 20cc gas / too small for turbine
  
• Example helicopters:

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

600 Size 600 ESP RC Helicopter

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.

Pros:

• Lowest cost of the "big" size helicopters.
• One of the nicest sizes to fly & own (my personal opinion).
  
• One of the nicest sizes to instruct on (again, my personal opinion).
• Very stable and predictable.
• Long flight times.
  
• Easy to see.
• Easy to work on.
• Big outdoor environment flying - need lots of room to appreciate full flight potential & stay safe.
• The noise! Once up to this size and larger, you really start hearing the rotor blades interacting with the air and "barking". For many (myself included), this is one the best "sense stimulating" aspects of flying RC helicopters.
  
• Can handle wind no problem.
• Pretty easy to auto-rotate.
  
• Higher quality parts last longer as do the helicopters.
• Overall bearing life is usually pretty decent because they are larger and parts are not rotating as fast.
  
• Huge amount of component options allowing people to customize their builds based on budget & upgrade/update if/when they choose.
  
• All come in kit form and you have to build them. I do consider this a pro because it teaches you so much about the hobby and how collective pitch RC helicopters work.
  
• Very broad envelope of flying performance right from beginner skill sets up to high energy/power hard core 3D.
• Capable of flying very fast.
  
• Lots of scale fuselages available if scale is your goal.
• Long product runs due to moderate development costs - long term ownership outlook is good (many years).

Cons:

• Price jumps substantially over the smaller sizes. Costs are generally at least double for the helicopter, components, parts, engine/motor/ESC, fuel, batteries, etc.
• High parts count.
• Not good for self learning on; instructor or experienced pilot help recommended.
  
• A crash will result in broken parts due to higher mass and energy - repairs can get expensive.
• Dangerous. Heli's of this size & power are capable of causing property damage, injury, and even death.
  
• Increased flying stress/worry over lower cost smaller RC helicopters.
  
• Fall under new RC flying regulations & restrictions.
• Requires access to large, legal open areas to fly (RC flying clubs, big open fields/farms, etc.).

5: Large RC Helicopters

• Main rotor blade length: 650mm and up (26" +)
  
• Main rotor diameter: 1500mm and up (60" +)
• Electric Motor Size: 700 class and up
• Combustion engine size: 0.70 and up (70 nitro) / 20cc and up (gas) / 6 hp and up (turbine)
• Example helicopters:

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

810 Size Bergen Intrepid Turbine RC Helicopter

Pros:

• Best visual experience of all sizes - very easy to see. Usually puts on the best air show for spectators.
  
• Best rotor blade noise produced - period! "Blade barking" getting similar to some smaller performance full size helicopters.
• Immensely rewarding to build, fly, & maintain. Massive grin factor :-)
  
• Most power options available (electric, nitro, gas, turbine).
• They "fly big" with lots of mass and inertia. Very predictable, stable, and smooth (fluid like).
  
• Long flight times.
  
• Big outdoor environment flying - need lots of room to appreciate full flight potential & stay safe.
• Can handle wind no problem.
• Easy to auto-rotate.
  
• Much higher quality parts last longer as do the helicopters.
• Usually very good bearing life.
  
• Huge amount of component options allowing people to customize their builds based on budget & upgrade/update if/when they choose.
• All come in kit form and you have to build them.
  
• Very broad envelope of flying performance right from beginner skill sets up to 3D. Due to high weight/mass however, not as responsive for extreme 3D flying. Perfect for normal 3D, F3C precision pattern flying, and naturally for scale.
  
• Capable of flying very fast.
  
• Many scale fuselages available if scale is your goal.
• Long product runs due to highest development costs - long term ownership outlook is very good (decade +).

Cons:

• Costs jump substantially once again over the previous regular size even though the rotor length isn't necessarily all that much more. Rotor area is however increased substantially and that results in needing much higher power motors/engines, servos, powering systems, higher component quality, etc. It all ads up very fast when getting into large RC helicopters.
  
• High parts count. 
• Not at all good for self learning on; instructor or experienced pilot help highly recommended.
  
• A crash will always result in broken parts due to higher mass and energy - repairs can get very expensive.
• Very dangerous. Heli's of this size are capable of causing massive damage to property, and even death. Envision a 10hp, flying lawnmower, with an exposed 6 foot blade flying at 150+ MPH and you'll get the idea. 
• Increased flying stress/worry over lower cost smaller RC helicopters. Feel sick to your stomach when things go wrong.
  
• Fall under new RC flying regulations & restrictions.
• Require access to large, legal open areas to fly (RC flying clubs, big open fields/farms, etc.).

Best RC Helicopter Size To Learn On?

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.

• Large RC helicopters are more stable and easier to control.
• Wind won't affect large RC helicopters as much - again more stability.
• Large RC helicopters are easier to see while flying.
• Large RC helicopters are easier to work on.

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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