RC Plane Nitro Engines: Glow Engines Explained for Beginners
“Nitro” RC airplane engines are glow engines: small two- or four-stroke engines that run on a methanol fuel with oil and some nitromethane, ignited by a glow plug heated for starting by a glow driver. Sizes are given in cubic inches, from about .15 for small planes up to 1.20 and beyond for large ones. They give realistic sound and long run times with a full tank, but need starting gear, tuning, cleaning and fuel, which is why many pilots have moved to electric or gasoline engines.
By Kyle HilsonUpdated: October 20263 min read
Two-stroke vs four-stroke
| Feature | Two-stroke | Four-stroke |
|---|---|---|
| Power for size | Higher | Lower |
| Sound | High-pitched | Deeper, more scale-like |
| Fuel use | Higher | Lower |
| Props | Smaller, faster | Larger, slower |
| Cost/complexity | Simpler, cheaper | Valves, more parts |
Four-strokes are covered in 4-stroke RC airplane engines.
Common sizes
- .15–.25: small trainers and sport planes.
- .40–.46: the classic trainer and sport size.
- .60–.91: larger sport and scale planes.
- 1.20 and up: big models, where gas engines also compete.
Fuel
Glow fuel is mostly methanol with oil (castor, synthetic or a blend) and typically 5–15% nitromethane for airplanes. Use the oil and nitro content the engine maker recommends, store fuel sealed and away from heat, and use the same blend when tuning.
Starting equipment
- Glow plug driver (igniter).
- Electric starter or chicken stick.
- Fuel pump and fuel.
- Spare glow plugs and plug wrench.
- Field box to carry it all.
Break-in and tuning
- Follow the maker’s break-in method (often a few tanks slightly rich).
- Set the high-speed needle by leaning from rich to peak RPM, then back off slightly rich.
- Adjust the low-speed needle for a reliable idle and clean transition.
- Check with the nose pointed up; it should not lean out and quit.
- Make small adjustments and recheck.
Safety
Spinning props injure people. Stand behind the propeller arc, restrain the plane when starting, never reach over a running prop and keep spectators back. Use a balanced, undamaged prop of the recommended size.
Care after flying
Wipe off oil residue, run the engine dry or use after-run oil, and store it clean. Methanol attracts moisture that can corrode bearings, so after-run oil prevents rust during storage. More on engine choices is in O.S. model airplane engines.
Nitro vs electric vs gas
Electric is cleaner and simpler for most sport flying; gasoline engines are cheaper to run in big planes. Glow remains popular with pilots who enjoy the engine itself, the sound and quick refuelling.
Common problems
Most glow engine trouble comes from a few causes. An engine that won’t start is often flooded, has a dead glow plug or a flat glow driver, or isn’t getting fuel because of a split fuel line or blocked filter. An engine that dies on landing usually has an idle that’s too low or a low-speed needle set too rich or too lean. Sagging power can mean a worn plug, an air leak around the carburettor or backplate, or old fuel. Check the simple things first: fresh fuel, a bright glowing plug, sound fuel tubing and a correctly sized prop. Make changes one at a time so you know which one fixed the problem.
FAQ
Is nitro fuel the same for cars and planes?
Airplane fuel usually has less nitro and different oil; use what the engine maker recommends.
What size engine for a trainer?
Commonly a .40–.46 two-stroke for a 40-size trainer.
Do I need a glow driver?
Yes, to start the engine.
Why does my engine quit when the nose is up?
Usually it’s set too lean.
More on this topic: the complete RC Airplanes guide covers the basics behind this article.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
