Radio-controlled helicopter
From Wikipedia, the free encyclopedia
Radio controlled (RC) helicopters are model aircraft which are unique from RC airplanes because of the differences in construction, aerodynamics, and flight training. Several basic designs of RC helicopters exist, some more maneuverable than others (such as helicopters with collective pitch). The more maneuverable designs are often harder to fly, but benefit from greater aerobatic capabilities.
Flight controls allow pilots to control the collective and throttle (usually linked together), the cyclic controls (pitch and roll), and the tail rotor (yaw). Controlling these in unison enables the helicopter to perform most of the maneuvers an aeroplane can do, and many that aeroplanes cannot do; in this manner, they are quite similar in operation to full-sized helicopters.
The various helicopter controls are effected by means of small servo motors. A piezoelectric gyroscope is typically used on the tail rotor (yaw) control to counter wind and torque reaction induced tail movement. This "gyro" does not apply a mechanical force, but rather, electronically adjusts the control signal to the tail rotor servo.
The engines used are typically methanol powered two stroke motors, however gasoline, jet turbine and increasingly electric motors are also used.
RC helicopters can range in price from as little as $30 to several thousands of dollars or more.
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[edit] Types of R/C Helicopter
Electric, Glow, Gas, Turbine.
[edit] Electric
Electric helicopters come in many different sizes, sometimes referred to as 300, 400 and 600 etc. This nomenclature originate from the practice applied to brushed motors of giving sizes based roughly on the length of the motor's can in millimetres divided by ten.[1]
One of the smallest commercial electric helicopters made is the Picco Z sold at Radio Shack and on Ebay as well, costing about $50. The next smallest might be the Micron FP helicopter, another battery operated R/C helicopter.
[edit] Glow
Glow-plug engine powered helicopters come in different sizes, typically 30,50,60 and 90 size. These numbers originated from the size of glow-plug engine used in the different models (0.30 cu in, 0.50 cu in etc). The bigger and more powerful the engine, the larger the main rotor blade that it can turn and hence the bigger the aircraft overall.
[edit] Turbine
Turbine power plants are of 3 basic configurations as of 10/2006. These configurations each utilize a single stage compressor wheel, combustion chamber, exhaust turbine wheel. The differences between the three are drive systems; belt, second turbine wheel (2 stage), or gear reduction. From that point on most helicopters are quite similar to 'regular' RC helicopters. They run on JetA, or K1 (Kerosene) and have a little oil mixed in the fuel. Turbines are rated in Kilowatts (KW) of power. Currently marketed turbine powerplants average 3-7 KW.
[edit] Radio Mfgs
Leading radio manufacturers are Spektrum, Futaba, JR,Hitec, Multiplex, Airtronics, Sanwa and Graupner in no particular order.
Small fixed-pitch helicopters need a 4 channel radio (throttle, elevator, aileron, rudder) while collective-pitch models need a minimum of 5 channels with 6 being most common (throttle, collective pitch, elevator, aileron, rudder and gyro gain).
Radio prices vary from $199-$3,000 USD.
[edit] PCM
Pulse Code Modulation. A scheme in which the commanded position for each servo is transmitted as an encoded number.
[edit] PPM
Pulse Position Modulation. A scheme in which the commanded position for each servo is transmitted as the position of a pulse edge with respect to a reference edge.
[edit] Construction
Construction is typically of plastic, glass reinforced plastic, aluminium or carbon fibre. Rotor blades are typically made of wood, fibreglass or carbon fibre. Models are typically purchased in kit form from one of about a dozen popular manufacturers and take 5 to 20 hours to completely assemble.
Construction of a scale helicopter will use all of the above materials, plus others, may take as many at 2500 hours to complete to the builders satisfaction. Many are scratch built from 3D mechanics. Scale (body) kits may be purchased to use with the mechanical portions to create a minature replica.
[edit] Competition
Aerobatic helicopter flying has historically been flown according to the Fédération Aéronautique Internationale rules, which for helicopters are labelled F3C. These include a predetermined routine of hovering and aerobatics.
An advanced form of RC helicopter flying is called 3D. During 3D flying, helicopters perform advanced aerobatics in a freestyle form. There are a number of 3D competitions around the world, two of the best known are the 3D Masters in the UK and the eXtreme Flight Championship (XFC) in the USA.
Scale competition is the competing with a minature replica of a real flying helicopter. In the USA there are local competitions, AMA Scale Helicopter Championships, and IRCHA scale competitions. Some of these models are so detailed as to be indiscernable from the real aircraft. Competition requires documentation of the full sized helicopter being modeled. It is not at all uncommon for a helicopter of this quality to have a value near $20,000 USD. Flying in a scale competition is centered around actual helicopter maneuvers, performed with proper speed, orientation, and consistency.
[edit] Commercial applications
Although RC helicopters are generally used by hobbyists for recreational purposes, they are sometimes used in applications such as aerial photography, filming, and remote observation or inspection. Some companies make RC helicopters specifically for these uses.
