When the United States declared war on Germany on 6 April 1917, thereby reversing its previous declaration of neutrality, the country had neither the manpower nor materiel to fight a war. Thus began a rushed attempt to enlarge and equip all military branches. Among the many things desperately needed were aircraft engines. European engine designs were not readily convertible to U.S. production techniques, not to mention that all European engine candidates came with very dear license fees. No high-power (400 hp) U.S. aircraft engine was in production or contemplated. An Aircraft Production Board was organized on 16 May 1916 to advise the U.S. Army and Navy on aeronautical matters. At the same time, two U.S. engine manufacturers, the Hall-Scott Motor Car Company of Berkley, California and the Packard Motor Car Company of Detroit, Michigan were selling a few engines to the U.S. military.
Starting off life as the Austro Daimler 6, the basis for this engine design began in 1910. The six-cylinder design was always going to be an aero engine from the start, not always a given in this era of development. The engine proved to be very popular and was copied by many companies across Europe.
Long before BMW became the car building multi-national we all know today they built aero engines. The first product to ever come out of the BMW works was the IIIa. It proved to be a very popular design with great performance.
The J-7 series was the first group of the J-7 produced. These were reverse-engineered from the MiG-21F-13 kits supplied by the USSR. However, due to the inability of the Chinese aerospace industry to produce some of the components, the design went through four major changes. The initial production of J-7 was seriously affected by the political turmoil at the time, namely the Cultural Revolution, which delayed the planned production run. Due to the urgent need of the fighter, planned improvements for the early models were scaled back to allow production to begin sooner, allowing improvements to be made later when the technologies matured.
The J-7I was the improvement of earlier J-7, with production starting in March 1969 after the order was formally placed on August 25, 1968. However, the original goal proved to be too ambitious for the Chinese aerospace industry at the time, especially during the political turmoil of Cultural Revolution. The program only succeeded after general designer Tu Jida obtained the permission to drastically reduce the originally planned six major upgrades to merely three. 781b155fdc