Aviation, or air transport, refers to the activities surrounding mechanical flight and the aircraft industry. Aircraft includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, parachutes, as well as lighter-than-air craft such as 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; then a largest 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 with the introduction of the jet which permitted a major form of transport throughout the world.
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Understanding the motion of air (often called a flow field) around an object enables the calculation of forces and moments acting on the object. Typical properties calculated for a flow field include velocity, pressure, density and temperature as a function of position and time. By defining a control volume around the flow field, equations for the conservation of mass, momentum, and energy can be defined and used to solve for the properties. The use of aerodynamics through mathematical analysis, empirical approximation and wind tunnel experimentation form the scientific basis for heavier-than-air flight.
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.
U.S. F/A-18 Hornet flying at transonic speeds. In aerodynamics, the sound barrier is a physical boundary that was once thought to be stopping large objects becoming supersonic. When an aircraft is near to the speed of sound, an unusual cloud sometimes forms. A drop in pressure, in this case due to shock wave formation, causes water droplets to condense and form the cloud.
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.
2008 –Two American UH-60 Black Hawk helicopters collide while trying to land in Baghdad. An Iraqi soldier was killed, while two Iraqis and three Americans were injured. Incident was due to mechanical failure.
2007 – Africa One Antonov An-26 crash: An Antonov An-26 (9Q-COS) from Africa One / El Sam Airlift and charted by Malift Air crashes shortly after taking off from the Kinshasa-N’Djili Airport, Congo. The airplane bound for Tshikapam crashed on the outskirt of Kinshasa killing 21 on board (1 crew survived) and at least 28 on the ground. This accident forced the Congolese minister of transportation to resign.
2004 – Gordon Cooper, one of the original astronauts in Project Mercury, dies. (b. 1927).
2001 – Siberia Airlines Flight 1812, a Tupolev Tu-154, is suspected to be shot down by a Ukrainian missile over the Black Sea. All 66 passengers and 12 crew members are killed.
1992 – El Al Flight 1862, a Boeing 747, freighter, crashes into high-rise apartment buildings in Amsterdam after two of its engines detach from the wing. Forty-three people, including the plane's crew of 3, are killed. The incident became known as the Bijlmerramp (Bijlmer disaster).
1984 – 61 year old Elaine Yadwin lands a Piper Cherokee Warrior II safely in Florida after her husband, the plane's pilot, dies during the flight.
1977 – First production prototype FMA IA 58 Pucará, AX-03, of the Fuerza Aérea Argentina, crashes during preparations for the 50th Anniversary of the Fabrica Militar de Aviones at Córdoba, due to pilot error.
1975 – A Cessna 310Q airplane crashes over Wilmington, North Carolina, killing the pilot and severely injuring several pro wrestlers affiliated with the NWA’s Mid-Atlantic promotion. One of the survivors is the legendary Ric Flair.
1946 – The B-29 Pacusan Dreamboat sets a world nonstop, unrefueled distance record of 9,500 miles on a flight from Honolulu to Cairo, Egypt.
1943 – During Operation Leader, aircraft from the American aircraft carrier USS Ranger (CV-4) raid German shipping along the coast of Norway, sinking six steamers and damaging four others, including a transport on which about 200 German troops are killed.
^Ernesto Londoño (2008-08-05). "2 U.S. Copters Crash in Iraq; 1 Iraqi Is Killed". Washington Post. Retrieved 2010-02-17. Seven U.S. soldiers were killed Sept. 18 when a CH-47 Chinook, a transport helicopter, crashed in southern Iraq. Officials have cited mechanical failure in that incident