Which engine?

Like many other things, a good engine is worth it's weight in gold. A sub-standard engine that won't run will send you to the crazy house and maybe (God forbid) make you give up this hobby altogether.

Most helicopters will have a recommended engine. The most popular type of engine in R/C helicopters is the glow engine which takes a fuel mixture of nitromethane, synthetic (or castor - but you shouldn't use that these days) oil and methanol. There are other alternatives though, including electric powered helicopters and petrol engined helicopters.

You can get either two-stroke or four stroke engines (but you wouldn't go four stroke by choice).

There are a number of different engine manufacturers around, OS, YS, Thunder Tiger, Novarossi, Rossi, etc. In general, the most popular make of engine is the OS two stroke engine line.

Again, engines come in all different sizes. In the two stroke line for helicopters there are the 30 size engines followed by the 50, 60, 70 and lately the 80 and 90 sizes for larger helicopters.

You want to match the engine capacity to the size recommended by your helicopter kit manufacturer.

When you're looking to buy an engine, you've got to take into account a number of things. Some of these are:

• How much it costs.
  Obviously important in any purchasing decision.
• Fuel requirements.
  Some engines take a different fuel mixture than others. For example, some manufacturers recommend a higher nitromethane requirement than others. Nitromethane isn't cheap, so you might want to take that into account.
• Engine reputation.
  Some engines are absolute dogs to get running correctly. Make sure you ask around and get some experienced opinion before purchasing.
• Local knowledge.
  If you're getting into your first engine, you'll probably need all the help you can get to get optimum performance from your power plant. Try and get one of the more popular engines at your field.
• Exhaust Options
  Some engines have very limited options for suitable exhaust systems. OS have a lot of options, as do YS and Thunder Tiger.

Two Stroke Two strokes are by far the most popular helicopter engine. Most aren't too hard to set up and produce good, reliable power.	One of the OS line of engines. Very popular modelling engines.

Four Stroke Four strokes aren't very popular just yet. They often require a lot of tuning and can be somewhat underpowered.

OS's 52 four stroke engine.

Petrol Petrol engines are based upon chainsaw or weedeater engines. They take a mixture of petrol and two stroke oil as used by chainsaws. Petrol's have tonnes of torque at low speeds which means they can often hover at around 30% power (depending on your setup). They're very economical to run both because the cost of fuel is low and their fuel consumption is also very low. For example, most petrol helicopters will fly for about 30-40 minutes on a tank of gas.

Hanson modified Zenoah G23 petrol engine.

My own personal experience
Get an engine that is popular at your field, be it an OS, YS or even a Thunder Tiger. After all, it's gonna be the people at your field that will be helping you to get it set up, you may as well get an engine they're familiar with.