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The Junkers G 31 was an advanced tri-motor airliner produced in small numbers in Germany in the 1920s. Like other Junkers types, it was an all-metal, low-wing cantilever monoplane. Compared to modern aircraft, only the corrugated duralumin metal skin, so typical for Junkers aircraft, seems unusual. However in the mid-1920s all-metal construction and an aerodynamically 'clean' configuration were remarkable. ==Development== Professor Junkers wanted to follow up on the commercial success of the tri-motor G 24 with a new design that would be larger, more comfortable for passengers, and simpler to operate and maintain.〔Wolfgang Wagner "''Hugo Junkers'' Pionier der Luftfahrt - Seine Flugzeuge" Bernard & Graefe Verlag, Bonn 1996 ISBN 3-7637-6112-8 (in German)〕 The G 31 was the first Luft Hansa airliner to feature a flight attendant (Wagner p. 264〔), who served food and drinks (which were not complimentary). This earned the G 31 the nickname 'flying dining car' ('fliegender Speisewagen' in German). Because of its large fuselage it was also called the flying moving van ('fliegender Möbelwagen' in German). Behind the cockpit were compartments for a radio operator, baggage and an APU that provided compressed air for main engine starting and drove a generator for electric power.〔Karl-Dieter Seifert"''Der Deutsche Luftverkehr 1926 - 1945'' auf dem Weg zum Weltverkehr" Bernard & Graefe Verlag, Bonn 1999 ISBN 3-7637-6118-7 (in German)〕 The cabin was divided into three compartments that held eleven regular passenger seats, four jump seats for passengers, a jump seat for the steward, and an enclosed lavatory. Instead of the passenger seats, ten beds could be made up for night flying. There was a baggage and freight hold under the cabin. The wings had trailing edge flaps that reduced the landing speed by ten percent (Wagner p. 267〔). Professor Junkers originally requested the G 31 have landing gear that would retract into the wings. After extensive wind tunnel experiments Ernst Zindel, the leader of the design team, persuaded Professor Junkers that the gain in speed provided by reduced air resistance, would not outweigh the increased weight, cost and complexity of either retractable landing gear or simple wheel fairings. The tail skid incorporated a roller, to avoid damage to grass airfields(Wagner p. 262-263〔). The intended power plant was three Junkers L5 engines. When these proved too weak, it was suggested to use the Napier Lion, considered to be the best aero engine at the time ("the best engine for the best plane"). This however was too expensive. Especially since it would have had to be paid for in convertible currency, not German Reichsmark. Most G 31s flew with foreign air-cooled radial engines in the 500 hp range, which were licence-built in Germany (see list of variants below)(Wagner p. 265-267〔). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Junkers G 31」の詳細全文を読む スポンサード リンク
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