Editing Model aircraft (section)

====Internal combustion====
[[File:c-130j.hercules.model.arp.jpg|thumb|"Giant scale" {{convert|18|ft|6|in|m}} wingspan [[Lockheed C-130 Hercules]] radio control flying model powered with four internal combustion engines. A crew of five fly and maintain it.]]
{{Main|Model engine}}
For larger and heavier models, the most popular powerplant is the [[Glow plug (model engine)|glow plug engine]]. Glow engines are fueled by a mixture of slow burning [[methanol]], [[nitromethane]], and lubricant ([[castor oil]] or [[synthetic oil]]), which is sold pre-mixed as glow-fuel. Glow-engines require an external starting mechanism; the glow plug must be heated until it is hot enough to ignite fuel to start. [[Reciprocating engine|Reciprocating]] cylinders apply torque to a rotating [[crankshaft]], which is the engine's primary power-output. Some power is lost from converting linear motion to rotary and in lost heat and unburned fuel, so efficiency is low.
[[File:Model Aircraft Engines.JPG|thumb|Model Aircraft Engines]]
These are rated by [[engine displacement]] and range from {{cvt|0.01|cuin|cc}} to over {{cvt|1.0|cuin|cc}}. The smallest engines can spin a {{convert|3.5|in|cm}} propeller to over 30,000 rpm, while the larger engines turn at 10–14,000 rpm.

The simplest glow-engines use the [[two-stroke cycle]]. These engines are inexpensive, and offer the highest [[power-to-weight ratio]] of all glow-engines, but are noisy and require substantial [[expansion chamber]] mufflers, which may be [[tuned exhaust|tuned]]. [[four-stroke cycle]] glow engines, whether using [[poppet valve]]s or more rarely [[rotary valve#Use in engine design|rotary valves]] are more fuel-efficient, but deliver less power than similar two-stroke engines. The power they deliver is more suited to turning larger diameter propellers for lighter weight, higher drag airframes such as with in [[biplane]]s. Four-stroke engines are now popular as they are quieter than two-stroke engines, and are available in [[flat-twin engine|horizontally opposed twins]] and [[radial engine]] configurations. Variations include engines with multiple-cylinders, spark-ignition gasoline operation, carbureted diesel operation and variable compression-ratio engines. Diesels are preferred for endurance and have higher torque, and for a given capacity, can "swing" a larger propeller than a glow engine. Home manufacture of model aircraft engines is a hobby in its own right.