Editing De Havilland Comet (section)

===Propulsion===

The Comet was powered by two pairs of turbojet engines buried in the wings close to the fuselage. Chief designer Bishop chose the Comet's embedded-engine configuration because it avoided the drag of [[podded engine]]s and allowed for a smaller [[vertical stabilizer|fin and rudder]] since the hazards of asymmetric thrust were reduced.<ref name=francis101-102>Francis 1950, pp. 101–102.</ref> The engines were outfitted with [[sound baffle|baffle]]s to reduce noise emissions, and extensive [[soundproofing]] was also implemented to improve passenger conditions.<ref>Darling 2001, pp. 35, 46.</ref>

[[File:De Havilland Comet pic 1 REJS.jpg|thumb|The Comet 4's enlarged [[Rolls-Royce Avon]] engine intakes]]
Placing the engines within the wings had the advantage of a reduction in the risk of [[foreign object damage]], which could seriously damage jet engines. The low-mounted engines and good placement of service panels also made aircraft maintenance easier to perform.<ref name=Withuhn88/> The Comet's buried-engine configuration increased its structural weight and complexity. Armour had to be placed around the engine cells to contain debris from any serious engine failures; also, placing the engines inside the wing required a more complicated wing structure.<ref name=francis103>Francis 1950, p. 103.</ref>

The Comet 1 featured {{cvt|5050|lbf|kN}} de Havilland Ghost 50 Mk1 turbojet engines.<ref name=francis100-101/><ref>[http://www.rafmuseum.org.uk/online-exhibitions/comet/comet3.cfm "Ghost engine."] {{webarchive|url=https://web.archive.org/web/20100204110840/http://www.rafmuseum.org.uk/online-exhibitions/comet/comet3.cfm |date=4 February 2010}} ''Royal Air Force Museum Cosford''. Retrieved 1 November 2010.</ref> Two [[hydrogen peroxide]]-powered [[de Havilland Sprite]] booster rockets were originally intended to be installed to [[RATO|boost]] [[takeoff]] under [[hot and high]] altitude conditions from airports such as Khartoum and Nairobi.<ref name=popmech149/><ref name=francis98-102>Francis 1950, pp. 98–102.</ref> These were tested on 30 flights, but the Ghosts alone were considered powerful enough and some airlines concluded that rocket motors were impractical.<ref name=Birtles125/> Sprite fittings were retained on production aircraft.<ref>Gunn 1987, p. 269.</ref> Comet 1s subsequently received more powerful {{cvt|5700|lbf|kN}} Ghost DGT3 series engines.<ref name=walker190/>

From the Comet 2 onward, the Ghost engines were replaced by the newer and more powerful {{cvt|7000|lbf|kN}} Rolls-Royce Avon AJ.65 engines. To achieve optimum efficiency with the new powerplants, the air intakes were enlarged to increase mass air flow.<ref name=d33/> Upgraded Avon engines were introduced on the Comet 3,<ref name=d33/> and the Avon-powered Comet 4 was highly praised for its takeoff performance from high-altitude locations such as Mexico City where it was operated by [[Mexicana de Aviación (1921–2010)|Mexicana de Aviacion]], a major scheduled passenger air carrier.<ref>[https://www.timetableimages.com/ttimages/mx/mx60/mx60-5.jpg En route] Time Table Images</ref><ref>[https://books.google.com/books?id=qiEDAAAAMBAJ&pg=RA1-PA52 "Comet Gets Stronger Engines."] ''Popular Science'', 160(6), June 1952, p. 142.</ref>