Editing Aircraft engine (section)

===Reciprocating (piston) engines===
{{main|reciprocating engine}}

====In-line engine====
''For other configurations of aviation inline engine, such as [[X engine|X-engines]], [[U engine|U-engines]], [[H engine|H-engines]], etc., see [[Inline engine (aeronautics)]].''{{main|Straight engine}}{{Empty section|date=March 2025}}[[File:Ranger L-440.jpg|thumb|Ranger L-440 air-cooled, six-cylinder, inverted, in-line engine used in [[Fairchild PT-19]]]]

====V-type engine====
[[File:Rolls-Royce Merlin.jpg|thumb|left|A Rolls-Royce Merlin V-12 Engine]]
{{main|V engine}}{{Empty section|date=March 2025}}

====Horizontally opposed engine====
{{main|Flat engine}}
[[File:UL350iS ULPower aircraft engine.jpg|left|thumb|A [[ULPower Aero Engines|ULPower UL]]350iS horizontally opposed air-cooled aero engine]]{{Empty section|date=March 2025}}

====H configuration engine====
{{main|H engine}}{{Empty section|date=March 2025}}

====Radial engine====
[[File:Pratt & Whitney R-2800 Engine 1.jpg|thumb|right|A [[Pratt & Whitney R-2800]] engine]]
{{main|Radial engine}}{{Empty section|date=March 2025}}

====Rotary engine====
[[File:Le Rhone 9C.jpg|thumb|right|Le Rhone 9C rotary aircraft engine]]
{{main|Rotary engine}}

Rotary engines have the cylinders in a circle around the crankcase, as in a radial engine, (see above), but the crankshaft is fixed to the airframe and the propeller is fixed to the engine case, so that the crankcase and cylinders rotate. The advantage of this arrangement is that a satisfactory flow of cooling air is maintained even at low airspeeds, retaining the weight advantage and simplicity of a conventional air-cooled engine without one of their major drawbacks.
The first practical rotary engine was the [[Gnome Omega]] designed by the Seguin brothers and first flown in 1909. Its relative reliability and good power to weight ratio changed aviation dramatically.<ref>{{cite book|title=Aviation|last=Gibbs-Smith|first= C.H.|publisher=NMSO|location=London|year=2003|isbn= 1-9007-4752-9 |page=175}}</ref>

====Wankel engine====
{{main|Wankel engine}}
[[File:WankelPP.jpg|thumb|upright|right|Powerplant from a [[Schleicher ASH 26]]e self-launching [[motor glider]], removed from the glider and mounted on a test stand for maintenance at the [[Alexander Schleicher GmbH & Co]] in [[:de:Poppenhausen (Wasserkuppe)|Poppenhausen]], [[Germany]]. Counter-clockwise from top left: propeller hub, mast with belt guide, radiator, Wankel engine, muffler shroud.]]

The [[Wankel engine|Wankel]] is a type of rotary engine. The [[Wankel engine]] is about one half the weight and size of a traditional [[four-stroke cycle]] [[piston engine]] of equal power output, and much lower in complexity. In an aircraft application, the power-to-weight ratio is very important, making the Wankel engine a good choice. Because the engine is typically constructed with an aluminium housing and a steel rotor, and aluminium expands more than steel when heated, a Wankel engine does not seize when overheated, unlike a piston engine. This is an important safety factor for aeronautical use. Considerable development of these designs started after [[World War II]], but at the time the aircraft industry favored the use of [[turbine]] engines. It was believed that [[turbojet]] or [[turboprop]] engines could power all aircraft, from the largest to smallest designs. The Wankel engine did not find many applications in aircraft, but was used by [[Mazda]] in a popular line of [[sports cars]]. The French company [[Citroën]] had developed Wankel powered {{Interlanguage link|Citroën RE-2|fr|3=Citroën RE-2|lt=RE-2}} [[helicopter]] in 1970's.<ref name="PBoulay">{{Cite book|language=fr|first=Pierre|last=Boulay|title=Les hélicoptères français|editor=Guides Larivière|year=1998|publisher=Larivière (Editions) |isbn=978-2-907051-17-0}}</ref>

In modern times the Wankel engine has been used in [[motor glider]]s where the compactness, light weight, and smoothness are crucially important.<ref>{{cite web
|url = http://www.alexander-schleicher.de/englisch/produkte/ash26/e_ash26_main.htm
| publisher = Alexander Schleicher | title = ASH 26 E Information
|access-date = 2006-11-24 | location = DE
|archive-url = https://web.archive.org/web/20061008125929/http://www.alexander-schleicher.de/englisch/produkte/ash26/e_ash26_main.htm |archive-date = 2006-10-08}}</ref>

====Combustion cycles====
Starting in the 1930s attempts were made to produce a practical [[aircraft diesel engine]]. In general, Diesel engines are more reliable and much better suited to running for long periods of time at medium power settings. The lightweight alloys of the 1930s were not up to the task of handling the much higher [[compression ratio]]s of diesel engines, so they generally had poor power-to-weight ratios and were uncommon for that reason, although the [[Clerget aircraft engines|Clerget 14F Diesel radial engine]] (1939) has the same power to weight ratio as a gasoline radial. Improvements in Diesel technology in automobiles (leading to much better power-weight ratios), the Diesel's much better fuel efficiency and the high relative taxation of AVGAS compared to Jet A1 in Europe have all seen a revival of interest in the use of diesels for aircraft. [[Thielert]] Aircraft Engines converted Mercedes Diesel automotive engines, certified them for aircraft use, and became an OEM provider to Diamond Aviation for their light twin. Financial problems have plagued Thielert, so Diamond's affiliate&nbsp;— Austro Engine&nbsp;— developed the new [[Austro Engine E4|AE300 turbodiesel]], also based on a Mercedes engine.<ref>{{cite web
|url = http://www.flyingmag.com/pilot-reports/pistons/diamond-twins-reborn
|title = Diamond Twins Reborn
|publisher = Flying Mag
|access-date = 2010-06-14
|archive-url = https://web.archive.org/web/20140618032748/http://www.flyingmag.com/pilot-reports/pistons/diamond-twins-reborn
|archive-date = 2014-06-18
|url-status = dead
}}</ref>