Editing Model aircraft (section)

===Power sources===
[[File:James Pelly-Fry flying models.jpg|thumb|Typical rubber powered model having the rubber band (hidden in the fuselage) tightened by turning the propeller backward, here being done with a handcrank]]
Powered models contain an onboard ''powerplant'', a mechanism powering propulsion of the aircraft through the air. [[Electric motor]]s and [[internal combustion engine]]s are the most common propulsion systems, but other types include [[rocket engine|rocket]], small [[Gas turbine|turbine]], [[pulsejet]], compressed gas, and tension-loaded (twisted) rubber band devices.

====Rubber====
The oldest method of powering free flight models is [[Alphonse Pénaud]]'s elastic motor (or extensible motor) of 1871, essentially a long [[rubber band]] that is twisted to add tension, prior to flight. It is the most widely used powerplant, found on everything from children's toys to competition models. The elastic offers simplicity and durability, but has a short running time, and the initial high torque of a fully wound motor drops sharply before plateauing to a steady output, until the final turns unwind and power drops off completely. Using it efficiently is one of the challenges of competitive free-flight rubber flying, and variable-pitch propellers, differential wing and tailplane incidence and rudder settings, controlled by timers, can help to manage the torque. There are also usually motor weight restrictions in contest classes. Even so, models have achieved flights of nearly 1 hour.<ref>Testing Commercial Rubber – R.J. North, Model Aircraft magazine, Feb 1961</ref><ref>{{cite web |url=http://www.indoornews.com/indoorrecords/record_list.php |title=Archived copy |access-date=2007-10-23 |url-status=dead |archive-url=https://web.archive.org/web/20080629140125/http://www.indoornews.com/indoorrecords/record_list.php |archive-date=29 June 2008  }}</ref>

====Compressed gases====
Stored compressed gas, typically [[carbon dioxide]] (CO<sub>2</sub>), can power simple models in a manner similar to filling a balloon and then releasing it. Compressed CO<sub>2</sub> may also be used to power an expansion engine to turn a [[propeller (aircraft)|propeller]]. These engines can incorporate speed controls and multiple cylinders, and are capable of powering lightweight scale [[radio-controlled aircraft]]. Gasparin and Modela are two recent makers of CO<sub>2</sub> engines. CO<sub>2</sub>, like rubber, is known as "cold" power because it generates no heat.

Steam is even older than rubber power, and like rubber, contributed much to [[history of aviation|aviation history]], but is now rarely used. In 1848, [[John Stringfellow]] flew a steam-powered model, in [[Chard, Somerset]], [[England]]. [[Samuel Pierpont Langley]] built both steam- and internal-combustion-powered models that made long{{quantify|date=December 2022}} flights.

Baronet Sir [[George Cayley]] built, and flew, internal and external combustion [[gunpowder]]-fueled model aircraft engines in 1807, 1819, and 1850. These had no crank, working [[ornithopter]]-like flappers instead of a propeller. He speculated that the fuel might be too dangerous for manned aircraft.

====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.

====Jets and rockets====
[[File:PST Model Airplane Jet Trainer.png|thumb|Miniature jet turbine]]
Early "jet" style model aircraft used a multi-blade propeller [[ducted fan]], inside ductwork, usually in the fuselage. The fans were generally powered by 2 stroke engines at high RPM. They generally had {{cvt|0.40|to|0.90|cuin|cc}} displacements, but some were as small as {{cvt|0.049|cuin|cc}}. This fan-in-tube design has been adopted successfully for electric-powered jets while glow engine powered ducted-fan aircraft are now rare. Small [[jet turbine]] engines are now used in hobbyist models that resemble simplified versions of the turbojet engines found on commercial aircraft, but are not scaled-down as Reynolds numbers come into play. The first hobbyist-developed turbine was developed and flown in the 1980s but recently have commercial examples become readily available. Turbines require specialized design and precision-manufacturing, and some have been built from car engine [[turbocharger]] units. Owning or operating a turbine-powered aircraft is prohibitively expensive and many national clubs (as with the USA's [[Academy of Model Aeronautics]]) require members to be certified to safely use them.<ref>{{cite web |url=http://www.modelaircraft.org/documents.aspx#Turbines |title=AMA Documents – Turbines |author=AMA |publisher=AMA |access-date=5 October 2012}}</ref> 
[[V-1 flying bomb]] type [[Pulsejet]] engines have also been used as they offer more thrust in a smaller package than a traditional glow-engine, but are not widely used due to the extremely high noise levels they produce, and are illegal in some countries.
[[File:Mohinhmaybayphanluc.jpg|thumb|A Vietnamese pilot prepares his model jet (Bien Hoa Air Base, Vietnam)]]
[[Rocket engine]]s are sometimes used to boost gliders and sailplanes. The earliest purpose-built rocket motor dates back to the 1950s, with the introduction of the [[Jetex]] motor, which used solid fuel pellets, ignited by a wick fuse, in a reusable casing. Flyers can now also use single-use [[model rocket]] engines to provide a short, under 10 second burst of power. Government restrictions in some countries made rocket-propulsion rare but these were being eased in many places and their use was expanding, however a reclassification from "smoke producing devices" to "fireworks" has made them difficult to obtain again.

====Electric power====
[[File:Bleriot type traversée de la Manche.jpg|thumb|Small electric powered model of a pre-WW1 era [[Bleriot XI]]]]
Electric-powered models use an [[electric motor]] powered by a source of electricity - usually a [[battery (electricity)|battery]]. Electrical power began being used on models in the 1970s, but the cost delayed widespread use until the early 1990s, when more efficient battery technologies, and [[brushless DC electric motor|brushless motors]] became available, while the costs of motors, batteries and control systems dropped dramatically. Electric power now predominated with ''park-flyer'' and ''[[3D-flyer]]'' models, both of which are small and light, where electric-power offers greater efficiency and reliability, less maintenance and mess, quieter flight and near-instantaneous throttle response compared to internal combustion engines.

The first electric models used [[brushed DC electric motor|brushed DC motors]] and [[nickel cadmium]] (NiCad) rechargeable cells that gave flight times of 5 to 10 minutes, while a comparable glow-engine provided double the flight-time. Later electric systems used more-efficient [[brushless DC electric motor|brushless DC motor]]s and higher-capacity [[nickel metal hydride]] (NiMh) batteries, yielding considerably improved flight times. [[Cobalt]] and [[lithium polymer batteries]] (LiPoly or LiPo) permit electric flight-times to surpass those of glow-engines, while the more rugged and durable, cobalt-free [[lithium iron phosphate]] batteries are also becoming popular. [[Solar power]] has also become practical for R/C hobbyists, and in June 2005 a record flight of 48 hours and 16 minutes was set in California. It is now possible to power most models under {{cvt|20|lb}} with electric power for a cost equivalent to or lower than traditional power sources.

Recent developments have resulted in the use of brushless three-phase motors in model aviation. Brushless motors are more powerful and offer greater torque and efficiency. The design of brushless motors also means less internal friction, as there is no requirement for brushes to be in contact with any rotating parts. This increase in efficiency results in longer flight times.<ref>{{Cite web|title=MAS.865 2018 How to Make Something that Makes (almost) Anything|url=https://fab.cba.mit.edu/classes/865.18/motion/brushless/index.html|access-date=2022-01-21|website=fab.cba.mit.edu}}</ref>