Main page | Categories & Main topics | Tasks and Projects |
Aviation is the activities surrounding mechanical flight and the aircraft industry. Aircraft includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air balloons and airships.
Aviation began in the 18th century with the development of the hot air balloon, an apparatus capable of atmospheric displacement through buoyancy. Some of the most significant advancements in aviation technology came with the controlled gliding flying of Otto Lilienthal in 1896; then a large step in significance came with the construction of the first powered airplane by the Wright brothers in the early 1900s. Since that time, aviation has been technologically revolutionized by the introduction of the jet which permitted a major form of transport throughout the world. (Full article...)
External aerodynamics is the study of flow around solid objects of various shapes. Evaluating the lift and drag on an airplane, the shock waves that form in front of the nose of a rocket is an example of external aerodynamics. Internal aerodynamics is the study of flow through passages in solid objects. For instance, internal aerodynamics encompasses the study of the airflow through a jet engine.
The ratio of the problem's characteristic flow speed to the speed of sound comprises a second classification of aerodynamic problems. A problem is called subsonic if all the speeds in the problem are less than the speed of sound, transonic if speeds both below and above the speed of sound are present (normally when the characteristic speed is approximately the speed of sound), supersonic when the characteristic flow speed is greater than the speed of sound, and hypersonic when the flow speed is much greater than the speed of sound. Aerodynamicists disagree over the precise definition of hypersonic flow; minimum Mach numbers for hypersonic flow range from 3 to 12. Most aerodynamicists use numbers between 5 and 8. (Full article...)
...that five USAAF airmen were awarded the Medal of Honor following Operation Tidal Wave, a low-level bombing of Romanian oil refineries on 1 August 1943? ...that the BAE Systems HERTI is the first and only fully autonomous UAV to have been certificated by the United Kingdom? .. that five UH-1 Iroquois helicopters of the Experimental Military Unit were shot down by a single Viet Cong soldier armed with an AK-47 rifle?
The Boeing 777 is a long-range, wide-body twin-engine jet airliner manufactured by Boeing Commercial Airplanes. It is the world's largest twinjet and is commonly referred to as the "Triple Seven". The aircraft has seating for over 300 passengers and has a range from 5,235 to 9,380 nautical miles (9,695 to 17,372 km) depending on model. Its distinguishing features include the largest diameter turbofan engines of any aircraft, six wheels on each main landing gear, a circular fuselage cross-section, and blade-shaped tail cone. Developed in consultation with eight major airlines, the 777 was designed to replace older wide-body airliners and bridge the capacity difference between the 767 and 747. As Boeing's first fly-by-wire airliner, it has computer mediated controls; it is also the first entirely computer-designed commercial aircraft.
The 777 is produced in two fuselage lengths. The original 777-200 model first entered service in 1995, followed by the extended range 777-200ER in 1997; the stretched 777-300, which is 33.3 ft (10.1 m) longer, began service in 1998. The longer-range 777-300ER and 777-200LR variants entered service in 2004 and 2006, respectively, while a freighter version, the 777F, debuted in 2008. Both longer-range versions and the freighter feature General Electric GE90 engines, as well as extended and raked wingtips. Other models are equipped with either the GE90, Pratt & Whitney PW4000, or Rolls-Royce Trent 800 engines. The 777-200LR ranks as the world's longest-range airliner and holds the record for longest distance flown by an unrefuelled commercial aircraft, with the demonstrated capability to fly more than halfway around the world.
United Airlines first placed the 777 into commercial airline service in 1995. As of October 2009, 56 customers have placed orders for 1,116 aircraft of all variants, with 822 delivered. The most common variant used worldwide is the 777-200ER, with 412 aircraft delivered, and Emirates operates the largest 777 fleet, with 78 aircraft. The airliner has had one hull-loss accident, with no passenger fatalities, attributed to a Trent 800 engine fuel component as of October 2009.
Through the 2000s, the 777 has emerged as one of its manufacturer's best-selling models. Because of rising fuel costs, airlines have acquired the type as a comparatively fuel-efficient alternative to other wide-body jets and have increasingly used the aircraft on long-haul, transoceanic routes. Direct market competitors include the Airbus A330-300 and the A340, with the upcoming A350 XWB and Boeing 787 programs currently in development.
During his formative years Trenchard struggled academically, failing many examinations and only just succeeding in meeting the minimum standard for commissioned service in the British Army. As a young infantry officer, Trenchard served in India and in South Africa. During the Boer War, Trenchard was critically wounded and as a result of his injury, he lost a lung, was partially paralysed and returned to Great Britain. While convalescing in Switzerland he took up bobsleighing and after a heavy crash, Trenchard found that his paralysis was gone and that he could walk unaided. Some months later, Trenchard returned to South Africa before volunteering for service in Nigeria. During his time in Nigeria, Trenchard commanded the Southern Nigeria Regiment for several years and was involved in efforts to bring the interior under settled British rule and quell inter-tribal violence.
In 1912, Trenchard learned to fly and was subsequently appointed as second in command of the Central Flying School. He held several senior positions in the Royal Flying Corps during World War I, serving as the commander of Royal Flying Corps in France from 1915 to 1917. In 1918, he briefly served as the first Chief of the Air Staff before taking up command of the Independent Air Force in France. Returning as Chief of the Air Staff under Winston Churchill in 1919, Trenchard spent the following decade securing the future of the Royal Air Force. He was Metropolitan Police Commissioner in the 1930s and a defender of the RAF in his later years.