Turbine RC helicopters are RC helicopters powered by jet engines. Nothing quite compares to seeing one of these monsters power up at the flight field, hearing the jet engine come up to speed and start to spin the rotors. Although they’re not very common, mostly due to the enormous cost of running a model jet engne, RC turbine helicopters are some of the coolest machines around. In part 1 of this article, we’ll look at how model jet engines work in general, and then move on to their application to RC helicopters.

How RC Helicopter Jet Engines Work

So how to jet engines work? They’re not actually that complicated, its the precision machining and temperature tolerances that make them expensive. On the most basic level, RC helicopter jet engines work the same way that full size jet engines do. Air enters the jet through an intake, is compressed and mixed with fuel, and then ignited, producing thrust and spinning a turbine. The turbine is connected to the compressor via a shaft, starting the process over again. Air is compressed in the engine because it increases the thrust obtained by burning the fuel air mixture. The end result of this whole process is a lot of hot air travelling out the back of the jet engine at a great speed, which results in thrust.

How does this process get started? After all, if the fuel / air mixture is burnt in the engine, shouldn’t the resulting air flow be able to go out the front and the back? The answer is simple: the jet engine compressor has to be spinning at a speed high enough to create enough pressure at the front of the engine to force the airflow out the back. In order to do this, the engine has to be spun up before starting. This is done by either blowing hot air into the front of the engine with a leaf blower, or spinning it up with a high speed electric starter. In some cases, jet engines have these electric starters built in. There’s only one more problem: in order to combust, the fuel must be in a gaseous state. Kerosene, the most commonly used jet fuel, is liquid at room temperature. To solve this, propane is used as fuel when starting the engine. Propane is a gas at room temperature, so it can enter the engine and combust right away. Once the engine is hot enough, the propane is turned off and the kerosene introduced.

Once started, we need some way to control the jet engines thrust. This requires precision control of the amount of fuel entering the engine, handled by a device called the ECU – engine control unit. The ECU is just a small computer that controls and monitors various engine functions, including:

• the turbine speed, usually measured in RPM (rotations per minute)
• the throttle command from the transmitter
• the fuel pump’s battery voltage
• the exhaust gas temperature (EGT)
• the total engine run time

Jet ECUs usually have a number of advanced features and fail safes built in for safety.

In  the next article, we’ll look at how RC jet engines are used to power RC helicopters.