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1925-1926   Introduction of lightweight, air-cooled radial engines The introduction of a new generation of lightweight, air-cooled radial engines revolutionizes aeronautics, making bigger, faster planes possible.

  1917   The Junkers J4, an all-metal airplane, introduced Hugo Junkers, a German professor of mechanics introduces the Junkers J4, an all-metal airplane built largely of a relatively lightweight aluminum alloy called duralumin.

1904   Concept of a fixed "boundary layer" described in paper by Ludwig Prandtl German professor Ludwig Prandtl presents one of the most important papers in the history of aerodynamics, an eight-page document describing the concept of a fixed "boundary layer," the molecular layer of air on the surface of an aircraft wing. Over the next 20 years Prandtl and his graduate students pioneer theoretical aerodynamics.

1933   First modern commercial airliner In February, Boeing introduces the 247, a twin-engine 10-passenger monoplane that is the first modern commercial airliner. With variable-pitch propellers, it has an economical cruising speed and excellent takeoff. Retractable landing gear reduces drag during flight.

935   First practical radar British scientist Sir Robert Watson-Watt patents the first practical radar (for radio detection and ranging) system for meteorological applications. During World War II radar is successfully used in Great Britain to detect incoming aircraft and provide information to intercept bombers.

1937   Jet engines designed Jet engines designed independently by Britain’s Frank Whittle and Germany’s Hans von Ohain make their first test runs. (Seven years earlier, Whittle, a young Royal Air Force officer, filed a patent for a gas turbine engine to power an aircraft, but the Royal Air Ministry was not interested in developing the idea at the time. Meanwhile, German doctoral student Von Ohain was developing his own design.) Two years later, on August 27, the first jet aircraft, the Heinkel HE 178, takes off, powered by von Ohain’s HE S-3 engine.

  1939   First practical singlerotor helicopters Russian emigre Igor Sikorsky develops the VS-300 helicopter for the U.S. Army, one of the first practical singlerotor helicopters.

was the preparation of firing and bombing tables for the Army which at that time, of course, included the Army Air Corps.

The analyzer installed at Aberdeen had ten integrating units and provisions for two input and two output tables as well. But, despite its value as an important mechanical aid to computation, it had several severe limitations.

It was, of course, known that the Moore School of Electrical Engineering of the University of Pennsylvania had a Bush differential analyzer of somewhat larger capacity than the one installed at Aberdeen. As a matter of fact, the one at the Moore School had fourteen integrating units. Therefore one of the first steps taken was the award to the University of Pennsylvania of a contract by the Ordnance Department for the utilization of this device.

he original agreement between the United States of America and the trustees of the University of Pennsylvania, dated June 5, 1943, called for six months of "research and development of an electronic numerical integrator and computer and delivery of a report thereon." This initial contract committed $61,700 in U.S. Army Ordnance funds

The ENIAC was placed in operation at the Moore School, component by component, beginning with the cycling unit and an accumulator in June 1944. This was followed in rapid succession by the initiating unit and function tables in September 1945 and the divider and square-root unit in October 1945. Final assembly took place during the fall of 1945. By today's standards for electronic computers the ENIAC was a grotesque monster. Its thirty separate units, plus power supply and forced-air cooling, weighed over thirty tons. Its 19,000 vacuum tubes, 1,500 relays, and hundreds of thousands of resistors, capacitors, and inductors consumed almost 200 kilowatts of electrical power. But ENIAC was the prototype from which most other modern computers evolved. It embodied almost all the components and concepts of today's high- speed, electronic digital computers. Its designers conceived what has now become standard circuitry such as the gate (logical "and" element), buffer (logical "or" element) and used a modified Eccles-Jordan flip-flop as a logical, high-speed storage-and-control device.

The ENIAC was not originally designed as an internally programmed computer. The program was set up manually by varying switches and cable connections. However, means for altering the program and repeating its iterative steps were built into the master programmer

The ENIAC led the computer field during the period 1949 through 1952 when it served as the main computation workhorse for the solution of the scientific problems of the Nation. It surpassed all other existing computers put together whenever it came to problems involving a large number of arithmetic operations. It was the major instrument for the computation of all ballistic tables for the U.S. Army and Air Force.