Types of R/C helicopters
Common power sources of remote control helicopters are glow fuel (also called nitro fuel, nitromethane-methanol), electric batteries, gasoline (petrol) and turbine engines. For the first 40 years, glow fuel helicopters were the most common type produced. However, in the last 10 years, electric powered helicopters have matured to a point where power and flight times are better, but typically not as long as glow fuel helicopters.
There have been two main types of systems to control the main rotors, mechanical mixing and cyclic/collective pitch mixing (CCPM). Most earlier helicopters used mechanical mixing. Today, nearly all R/C helicopter use CCPM.
Practical electric helicopters are a recent development but have rapidly developed and become more common, overtaking glow fuel helicopters in common use. Turbine helicopters are also increasing in popularity, although the high cost puts them out of reach of most people.
Internal Combustion (Nitro, Gas)
The first RC helicopters have been powered by combustion engines (Glow fuel, or nitro, as well as gas, or gasoline as the fuel source). Original helicopter "classes" were based on the engine size. For example, a helicopter with a 0.30 cu in (4.9 cm3) engine was a 30 class and a helicopter with a 0.90 cu in (14.7 cm3) engine was referred to as a 90 class helicopter. The bigger and more powerful the engine, the larger the main rotor blade that it can turn and hence the bigger the aircraft overall. Typical flight time for nitro helicopters is 7–15 minutes depending on the engine size and tuning.
Electric
Two small electric helicopters emerged in the mid-1990s. These were the Kalt Whisper and the Kyosho EP Concept, flying on 7–8 × 1.2 Ah NiCad batteries with brushed motors. However, the 540-sized brushed-motors were on the limit of current draw, often 20–25 amps on the more powerful motors, hence brush and commutator problems were common.
Recent advancements in battery technology are making electric flying more feasible in terms of flying time. Lithium polymer (LiPo) batteries are able to provide the high current required for high performance aerobatics while still remaining very light. Typical flight times are 4–12 minutes depending on the flying style and battery capacity.
In the past electric helicopters were used mainly indoors due to the small size and lack of fumes. Larger electric helicopters suitable for outdoor flight and advanced aerobatics have become a reality over the last few years and have become very popular. Their quietness has made them very popular for flying sites close to residential areas and in places such as Germany where there are strict noise restrictions. Nitro helicopters have also been converted to electric power by commercial and homemade kits.
The smallest remote-controlled production model helicopter made (Guinness World Records 2006) is the Picooz Extreme MX-1 sold at many toy stores (although this is infrared controlled, not radio), electronics stores and internet stores, costing about $30 (£28). The next smallest is the standard Picooz helicopter.
Multirotor model helicopters
More recently, multirotor designs have become popular in both the RC hobby and unmanned aerial vehicle (UAV) research. These vehicles use an electronic control system and electronic sensors to stabilize the aircraft. Multirotors are generally more affordable, easier to construct, and simpler to operate than RC helicopters. This made multirotor aircraft an appealing platform for amateur model aircraft projects and aerial photography.
Size classes
Nitro RC helicopters are categorised under the following classes:
- 30 size : Engine 0.3 cubic inch, Main Blades 550-600mm
- 50 size : Engine 0.5 cubic inch, Main Blades 600-620mm
- 60 size : Engine 0.6 cubic inch
- 90 size : Engine 0.9 cubic inch, Main Blades 690-710mm
Modern RC helicopters are generally classed by the length of the main blades (with few exceptions). Common classes are:
- Micro (under 200mm main blades)
- Mini (240-420mm blades) - classically called 300-450.
- 500 (425-500mm)
- 600 (600mm)
- 700 (standard competition size)
- 800
