Have you ever seen a turbine powered RC helicopter? If you have then you understand the attraction. Everyone watches as the whines to life and comes up to speed. Turbine RC helicopters are among the coolest aircraft at any flying field. They are not cheap, but if you bank account will allow you to go in this direction in our hobby, you definitely will not be bored!
Let’s take a look at how these turbine engines work. Most people are surprised when they find out how simple the concept actually is. Even though the process is simple, the engines have to be made with extremely precision, and the parts in the engine need to be able to stand very high heat. Those are the biggest reasons these engines are so expensive.
In any jet engine, air is brought in through an intake. It is mixed with fuel and compressed, then ignited, which produces the thrust. The thrust is from the extremely hot air being blown out the back of the engine at very high speeds. That is why you will never see a member of the ground crew at an airport stand in front of or behind a jet engine that is running. They would either get sucked into the engine or blasted with the hot air coming out the back. Either way, they would be very lucky to live to tell about it.
In our turbine powered RC helicopters, we don’t have to be worried about being sucked into anything or blown away by the exhaust. But the way the engine works is the same, just on a much smaller scale. The only complication is we need to make sure the combustion, and resulting thrust, is heading in the right direction. This is the reason the engine compressor must be spun up to a high enough level before the engine is actually started. This forces the jet thrust in the desired direction.
The fuel situation with turbine RC helicopter engines is a bit more complex. We need the fuel to be in a gaseous state in order for it to combust. But kerosene, which is the most commonly used fuel, is liquid at room temperature. So, the process is started with propane being introduced to start the engine. At room temperature, propane is in a gaseous state so can combust immediately. After the engine is hot enough, kerosene is turned on and the propane is turned off.
The way to control thrust is through the amount of fuel fed to the engine. The engine control unit, or ECU, handles this task for us. Basically the ECU is a little computer that both controls and keeps track of an assortment of engine functions like turbine speed, battery voltage, exhaust temperature, throttle commands, etc.
As you can see, turbine RC helicopter engines are a fairly complicated thing, even if the actual combustion process is pretty simple. These engines normally have safeguards built into them. This area of the RC helicopter hobby is not recommended for beginners for obvious reasons. But once you have gained experience, and want to move up to something that is more of a challenge, perhaps jet powered RC helicopters are something you can try. Remember, you will need to spend some money on this part of the hobby, and it can be addictive. You’ve been warned!