Fixed Pitch is exactly that. The pitch of the main rotor blade is held at a fixed or constant angle of attack.

You control the amount of lift to your helicopter by simply varying the speed of the engine/motor. If you increase the speed of the engine, the rotor blades turn faster and produce more lift. The reverse happens if you lower the speed of the engine.

This is a very simple means of controlling the amount of lift to your RC helicopter and if you just want a very simple and inexpensive model heli, this method of controlling lift does work.

There are several major draw backs to this type of control however. Engines, whether they are electric motors, nitro or gas engines, or turbines don’t speed up or slow down instantaneously when you give them a command to do so.

The mass of the rotor blades and rotor mechanism compound this problem as the engine or electric motor has to overcome the inertia to get the rotor spinning faster or the kinetic energy stored in the rotor assembly to slow it down.

So what does this all mean? Lots of lag time from the time you make your control input to the time your helicopter reacts.

For example, let’s say you are in a hover and want to increase your height. You increase the throttle control, the engine speeds up, the rotor starts speeding up and spins faster producing more lift, and the heil starts gaining altitude.

Now you are getting too high, you decrease the throttle a bit, but your heli is still climbing because the rotor takes a while to slow down. You decrease the throttle even more to try and get your bird back down.

Now it starts descending, but you have to increase throttle again to keep it from descending too fast and hitting the ground. In effect, you are always one step behind what is going on, it is very difficult to fly a RC helicopter this way, never mind learning how to fly one.

This is a very simple hovering example. There are other forces acting on your heli during all types of flight that make this method of lift control even worse. These are discussed in the Helicopter Theory section of this web site.

The only helicopters that fly not too bad with a fixed pitch set up are very small mini or micro electric helicopters. This is because the electric motor reacts much quicker than an engine, and the mass of the rotors and rotor mechanism is very small. This means the the rotor will speed up and slow down much quicker resulting in faster response times, with less lag.

So unless you are getting a very small and light electric helicopter, and have absolutely no interest in even the most basic aerobatic maneuvers, I wouldn’t even consider getting a fixed pitch RC helicopter, especially for your first RC helicopter – they are just too darn frustrating to fly or learn on.

With this system of control, you change the pitch or angle of attack of the rotor blades while the engine speed stays more or less constant. Let’s go back to our hover example.

This time when you want to gain altitude, you increase the pitch of the rotor blades, and your helicopter starts lifting almost instantaneously with no lag time.

Now you want to stop the rate of climb - you decrease the pitch of the rotor blades and again, the response of the helicopter is almost immediate.

It takes only very small movements of the rotor blade pitch angle to achieve these instantaneous corrections and gives you very precise immediate control of your RC helicopter.

Again, this hover example is very simple and there are many more advantages to Collective pitch control that are discussed in the Helicopter Theory section as well as constantly changing translational lift that makes a fixed pitch heli very hard to learn on. The main thing is you understand why you should only consider getting a hobby grade RC helicopter with collective pitch. Yes – it makes flying a RC helicopter much more enjoyable and FUN!