IC engine or electric?
Historically, the only real choice for powering a trainer was a small 2-stroke IC (internal combustion) engine, probably of about 0.40 ci (cubic inch) capacity for the size of trainer described above. This size of trainer is often referred to as “40-size” for this reason. (One cubic inch is about 16.4 cc, so 0.40 ci is about 5.5 cc.)
One of the biggest changes in RC aircraft in recent years has been the increasing popularity of electric power, as new technologies have pushed down the weight and cost and increased the power of both motors and batteries. As a result, electric power is now a serious option for almost all model aircraft (and for some, the only option). Most pilots in the club have a mixture of electric and IC models.
Generally, most people (at least in this club) still choose the IC option for a first trainer. If you do this, we’d recommend getting the largest engine recommended for the model – for example, most “40-size” trainers recommend a 0.40 – 0.46 ci engine, and we’d recommend going for the “46”. This will make takeoffs easier while you’re learning (especially in winter when the ground gets quite muddy), and a bigger engine will be more useful when you finally outgrow your trainer and want to move the engine to a higher-performance model.
If you want to use electric power for your trainer, you can do this. Several of the modern trainers (including the two recommended on the What type of plane should I buy? page) have been tweaked to better support electric power (notably, by including the mounting hardware for an electric motor, and by including a hatch so the battery can be changed without having to take the wing off each time). However, there are a few things to be aware of with an electric trainer. Firstly, you’ll probably get less time per flight. A typical IC-powered trainer may safely get 10-12 minutes per flight, which is about as long as a new pilot can concentrate for learning anyway. The same plane under electric power may only get 6-8 minutes (depending on the batteries used, but larger batteries add a lot more weight than more fuel does). This means less time learning before your instructor takes over to land the plane. Secondly, there is the cost of batteries, as you’ll need more than one. Expect a fully-used battery to take around 90 minutes to recharge, so you’ll probably want at least three or four batteries if you want to get in a decent amount of learning and practice.
Both IC and electric need specific gear and tools both in the field and when setting up a plane: IC needs things like glow plug power, starting equipment, and a fuel pump; electric needs things like a balance charger, a wattmeter, and quite likely a big lead-acid battery for charging your batteries in the field without flattening your car battery. If you think that you’ll probably end up with a mixture of both types in future, it’s only really a case of which things you’re buying first.