The Engine
The Way Forward
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The engine size for almost all trainers is a 6.5cc. (0.40cu" or "forty") size although many fit a larger engine around 0.46 size.
Electric power has become much more practical and popular in recent years, click here for more information about electric power systems, but remember, although electric models are often smaller and lighter, something too small and light may not let you get much flying done in our typical weather conditions.
Aim for a model of similar size to a 'forty' powered model (about 1500-1700mm wingspan) and you should be fine.
When it comes to an engine you are spoiled for choice.
You want something reliable, not necessarily the most powerful.
Too powerful an engine can be a liability in a trainer, making it too skittish and harder to land.
If it only has to run a little above tickover to fly the plane, it may cool down in flight and not pick up well when asked, or even stop.
If your plane specifies a 40-46, then don't be tempted to fit anything bigger, it won't help.
"Reliable" means it starts, ticks over, runs and stops when it's meant to. Luckily these days the vast majority of engines fall into this category.
For a budget engine SC and ASP engines from China do the job very well, but if you'd rather go for the top end of the market, OS engines from Japan are excellent, and will last for a long, long time.
A good 'in between' choice would an Irvine 46. Sensibly priced and built by OS, it may be the best of both worlds. Possibly one of the best engines for a trainer is the OS 40LA (or 46LA). This is a light, low power engine which is very easy to set up and operate and is cheaper than most OS engines.
But you you should be aware that the LA engines are not very powerful compared to other engines of the same capacity and might not be a good choice for your next model.
What you're looking for in an engine for a trainer is one which starts easily, is easy to set up and runs consistently.
When you're learning, you are unlikely to have the engine running at much more than half throttle. Ask around at the club and watch anyone else learning to fly.
Watch for the amount of time taken to get the engine started. Did the engine run consistently over the flight - full throttle on take off then back to about half throttle? Did it falter just after take-off or die in the air unexpectedly?
As a fairly rough guide, a trainer should be flying about five minutes after the decision to have a flight and should fly around for about ten minutes before landing. There should not be loads of head-scratching, re-starting and bad language!
Some other items are also needed. You should have a couple of propellors, one on the model and a spare, which for a 7.5cc. (0.46cu") engine will probably be 11x6 nylon ones (around £3.00 each).
You also need a couple of glow plugs - again around £3.00 each and a spinner at under £1.00.
You might also consider a silicon exhaust deflector at around £2.50 which will help to keep your model clean by deflecting the exhaust away from the fuselage.