FP vs. CP electric RC helicopters
The terms 'FP' and 'CP' stand for Fixed Pitch and Collective Pitch respectively, and the word 'pitch' refers to the angle of the main rotor blades (and rotor disc) in relation to the horizontal airflow over them. But, when comparing FP and CP electric rc helicopters this pitch name only refers to altitude control - cyclic control has the same method on each type of model.
Whether the model is FP, like the Walkera Dragonfly 4, or CP, such as the Blade 400, is an important factor to consider when choosing an electric rc helicopter, and the choice largely depends on what sort of flying you want to do, as well as your budget.
FP is self-explanatory in that the blade pitch is, well, fixed. The main blades do not pivot about their longitudinal axis to change pitch angle, (ie change the amounts of lift) and so the altitude (climb/descent) of the helicopter must be controlled by the motor speed - faster turning blades generate more lift, and vice versa.
Generally speaking, FP helicopters are not particularly responsive in the air and can be a bit more unstable, at least until the pilot gets used to the feel of it. They are, however, cheaper to buy, easier to master and have less components and complexity to worry about.
CP means that the pitch angle of each main rotor blade can be moved to change the amount of lift generated, by tilting each blade about its longitudinal axis. The motor is kept at a more constant speed throughout the flight, and so the altitude is controlled by changing this pitch angle of the blades.
This makes the helicopter much more agile, responsive and smoother in the air, but gives a steeper learning curve for the pilot - and they cost more to buy, and more can go wrong!
Above, left, an FP rotor head compared to a CP one, right
Fixed Pitch electric rc helicopters aren't generally seen as serious models, and certainly not by CP flyers! It's important to understand though, that FP helicopters are not toys, and even though they are more simple than CP ones, they should always be treated with respect!
The bottom line? If you just want an 'entry-level' taste of flying an electric rc helicopter with circuits and hovering, then an FP (or coaxial) helicopter will suit your needs very well. You will be limited in how you can fly it, but you'll get to learn all about cyclic and yaw control, and how to fly a radio control helicopter safely.
But if you see yourself wanting to fly in a more demanding way, and getting in to the hobby seriously, then a CP helicopter is much more appropriate for your needs. It'll cost you more, and take longer to learn, but will reward you with a better flying experience.
Certainly if you want to fly 3D (acrobatically), then a CP helicopter is your only option.
The important thing to remember is that both FP and CP electric rc helicopters have a steep learning curve. Single rotor (ie not coaxial) helicopters are inherently unstable and first flights usually end in disaster! An rc flight simulator such as the RealFlight G4.5 is an excellent idea if you're serious about flying radio control helicopters. You can learn in complete safety, without the worry of crashing your actual model.
See some FP and CP electric rc helicopters in more detail.
Related pages
Electric rc helicopters - an overview of FP, CP and coaxial rc helis.
Coaxial rc helicopters - more info on how coaxial helicopters work.
RC helicopter controls - get a basic understanding of the main helicopter controls.
