Editing Autogyro (section)

=== Early development ===
{{more citations needed section|date=January 2011}}

[[File:Ciervas 1st autogiro.jpg|right|thumb|The first successful autogyro, the C.4, first flew in 1923]]

[[File:Pitcairn autogyro NC-12681at St. Hubert, Quebec. Aug. 19, 1932.jpg|right|thumb|A Pitcairn autogyro NC-12681 at St. Hubert, Quebec. 19 August 1932]]

After four years of experimentation, de la Cierva invented the first practical rotorcraft the autogyro (''autogiro'' in Spanish), in 1923. His first three designs ([[Cierva C.1|C.1]], [[Cierva C.2|C.2]], and [[Cierva C.3|C.3]]) were unstable because of aerodynamic and structural deficiencies in their rotors. His fourth design, the [[Cierva C.4|C.4]], made the first documented flight of an autogyro on 17{{nbsp}}January 1923, piloted by Alejandro Gomez Spencer at Cuatro Vientos airfield in Madrid, Spain (9{{nbsp}}January according to de la Cierva).<ref name="charLeg" />

De la Cierva had fitted the rotor of the C.4 with flapping hinges to attach each rotor blade to the hub. The flapping hinges allowed each rotor blade to flap, or move up and down, to compensate for [[dissymmetry of lift]], the difference in lift produced between the right and left sides of the rotor as the autogyro moves forward.<ref name="govCierva"/><ref name="govGyro">{{cite web |url = http://www.centennialofflight.gov/essay/Rotary/autogiro/HE3.htm |title = The Contributions of the Autogyro |year = 2003 |publisher = [[Centennial of Flight Commission]] |access-date = 14 December 2010 |archive-url = https://web.archive.org/web/20101214081414/http://centennialofflight.gov/essay/Rotary/autogiro/HE3.htm |archive-date = 14 December 2010 |url-status = dead }}</ref> Three days later, the engine failed shortly after takeoff and the aircraft descended slowly and steeply to a safe landing, validating de la Cierva's efforts to produce an aircraft that could be flown safely at low airspeeds.

[[File:Cierva C.6, Madrid 2.jpg|thumb|A [[Cierva C.6]] replica in Cuatro Vientos Air Museum, Madrid, Spain]]

De la Cierva developed his [[Cierva C.6|C.6]] model with the assistance of Spain's Military Aviation establishment, having expended all his funds on the development and construction of the first five prototypes. The C.6 first flew in February 1925, piloted by Captain [[Joaquín Loriga]],<ref>[https://historiadeza.wordpress.com/2013/10/21/loriga-el-primer-viaje-del-autogiro/ "EL PRIMER VIAJE DEL AUTOGIRO"] {{Webarchive|url=https://web.archive.org/web/20180710225343/https://historiadeza.wordpress.com/2013/10/21/loriga-el-primer-viaje-del-autogiro/ |date=10 July 2018 }} ''MADRID CIENTIFICO'', 1924. Nº 1128, página 9</ref> including a flight of {{convert|10.5|km|mi|abbr=off}} from Cuatro Vientos airfield to [[Getafe]] airfield in about eight minutes, a significant accomplishment for any rotorcraft of the time. Shortly after de la Cierva's success with the C.6, he accepted an offer from Scottish industrialist James{{nbsp}}G. Weir to establish the [[Cierva Autogiro Company]] in England, following a demonstration of the C.6 before the British [[Air Ministry]] at [[RAE Farnborough]], on 20{{nbsp}}October 1925. Britain had become the world centre of autogyro development.

A crash in February 1926, caused by blade root failure, led to an improvement in rotor hub design. A drag hinge was added in conjunction with the flapping hinge to allow each blade to move fore and aft and relieve in-plane stresses, generated as a byproduct of the flapping motion. This development led to the Cierva C.8, which, on 18{{nbsp}}September 1928, made the first rotorcraft crossing of the [[English Channel]] followed by a tour of Europe.

United States industrialist [[Harold Frederick Pitcairn]], on learning of the successful flights of the autogyro, visited de la Cierva in Spain. In 1928, he visited him again, in England, after taking a [[Cierva C.8|C.8]] L.IV test flight piloted by Arthur H.{{nbsp}}C.{{nbsp}}A. Rawson. Being particularly impressed with the autogyro's safe vertical descent capability, Pitcairn purchased a C.8 L.IV with a Wright Whirlwind engine. Arriving in the United States on 11{{nbsp}}December 1928 accompanied by Rawson, this autogyro was redesignated C.8W.<ref name="charLeg" /> Subsequently, production of autogyros was licensed to several manufacturers, including the [[Pitcairn Autogiro Company]] in the United States and [[Focke-Wulf]] of Germany.

[[File:Bundesarchiv Bild 102-00996A, Hubschrauber Focke-Wulf C 19 "Heuschrecke".jpg|thumb|A [[Focke-Wulf]]-built [[Cierva C.19]] Mk.IV Autogiro]]

In 1927, German engineer [[Engelbert Zaschka]] invented a combined helicopter and autogyro. The principal advantage of the Zaschka machine is its ability to remain motionless in the air for any length of time and to descend in a vertical line so that a landing could be accomplished on the flat roof of a large house. In appearance, the machine does not differ much from the ordinary monoplane, but the carrying wings revolve around the body.

Development of the autogyro continued in the search for a means to accelerate the rotor before takeoff (called prerotating). Rotor drives initially took the form of a rope wrapped around the rotor axle and then pulled by a team of men to accelerate the rotor{{snds}}this was followed by a long taxi to bring the rotor up to speed sufficient for takeoff. The next innovation was flaps on the tail to redirect the propeller slipstream into the rotor while on the ground. This design was first tested on a [[Cierva C.19|C.19]] in 1929. Efforts in 1930 had shown that the development of a light and efficient mechanical transmission was not a trivial undertaking. In 1932 the Pitcairn-Cierva Autogiro Company of [[Willow Grove, Pennsylvania]], [[United States]] solved this problem with a transmission driven by the engine.

[[Buhl Aircraft Company]] produced its [[Buhl A-1 Autogyro|Buhl A-1]], the first autogyro with a propulsive rear motor, designed by [[Etienne Dormoy]] and meant for aerial observation (motor behind pilot and camera). It had its maiden flight on 15{{nbsp}}December 1931.<ref>[[Buhl Aircraft Company]] [http://www.rcgroups.com/forums/showthread.php?t=2150978 site=www.rcgroups.com Buhl A-1 autogyro – 1931] {{Webarchive|url=https://web.archive.org/web/20150128132226/http://www.rcgroups.com/forums/showthread.php?t=2150978 |date=28 January 2015 }} and [http://www.gyroplanepassion.com/BuhlA-1.html The Buhl A-1 Autogiro] {{Webarchive|url=https://web.archive.org/web/20151208065538/http://www.gyroplanepassion.com/BuhlA-1.html |date=8 December 2015 }}</ref>

[[File:Buhl A-1 Autogiro - autogyro with rear push propeller engine - designer Etienne Dormoy and pilot James Johnson - 1931.jpg|thumb|right|[[Buhl A-1 Autogyro]] with rear push propeller (1931)]]

De la Cierva's early autogyros were fitted with fixed rotor hubs, small fixed wings, and control surfaces like those of a fixed-wing aircraft. At low airspeeds, the control surfaces became ineffective and could readily lead to loss of control, particularly during landing. In response, de la Cierva developed a direct control rotor hub, which could be tilted in any direction by the pilot. De la Cierva's direct control was first developed on the Cierva C.19 Mk.{{nbsp}}V and saw the production on the [[Cierva C.30]] series of 1934. In March 1934, this type of autogyro became the first [[rotorcraft]] to take off and land on the deck of a ship, when a C.30 performed trials on board the [[Spanish navy]] [[seaplane tender]] [[Spanish seaplane carrier Dédalo|''Dédalo'']] off Valencia.<ref>"The first ''Dedalo'' was an aircraft transportation ship and the first in the world from which an autogyro took off and landed." Naval Ship Systems Command, US: ''Naval Ship Systems Command technical news.''1966, v. 15–16, page 40</ref>

Later that year, during the leftist [[Asturian miners' strike of 1934|Asturias revolt]] in October, an autogyro made a reconnaissance flight for the loyal troops, marking the first military employment of a rotorcraft.<ref>Payne, Stanley G. (1993). ''Spain's first democracy: the Second Republic, 1931–1936''. Univ of Wisconsin Press, p. 219. {{ISBN|0-299-13674-4}}</ref>

When improvements in helicopters made them practical, autogyros became largely neglected. Also, they were susceptible to [[ground resonance]].<ref name="govGyro" /> They were, however, used in the 1930s by major [[newspaper]]s, and by the [[United States Postal Service]] for the mail service between cities in the northeast.<ref name="BladeRunner">
{{Cite news |last = Pulle |first = Matt |title = Blade Runner |newspaper = Dallas Observer |location = Dallas, Tx |volume = 27 |issue = 27 |date = 5 July 2007 |pages = 19–27 |url = http://www.dallasobserver.com/2007-07-05/news/blade-runner/ |archive-url = https://web.archive.org/web/20121002054326/http://www.dallasobserver.com/2007-07-05/news/blade-runner/3/ |archive-date = 2012-10-02 |url-status = dead }}</ref>