Air Force One is the official air traffic control call sign of a United States Air Force aircraft carrying the President of the United States. In common parlance the term refers to those Air Force aircraft specifically designed, built, and used for the purpose of transporting the president. The Presidential aircraft is a prominent symbol of the American presidency and its power. The idea of designating specific military aircraft to transport the President arose in 1943, when officials of the United States Army Air Forces – the predecessor to the U.S. Air Force – became concerned with relying on commercial airlines to transport the President. A C-87 Liberator Express was reconfigured for use as a presidential transport; however, it was rejected by the Secret Service amid concerns over the aircraft's safety record. A C-54 Skymaster was then converted for presidential use; this aircraft, dubbed theSacred Cow, transported President Franklin D. Roosevelt to the Yalta Conference in February 1945, and was subsequently used for another two years by President Harry S. Truman. The "Air Force One" call sign was created after a 1953 incident during which a flight carrying President Dwight D. Eisenhowerentered the same airspace as a commercial
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Air Force One is the official air traffic control call sign of a United States Air
Force aircraft carrying the President of the United States. In common
parlance the term refers to those Air Force aircraft specifically designed,
built, and used for the purpose of transporting the president. The Presidential
aircraft is a prominent symbol of the American presidency and its power.
The idea of designating specific military aircraft to transport the President
arose in 1943, when officials of the United States Army Air Forces – the
predecessor to the U.S. Air Force – became concerned with relying on
commercial airlines to transport the President. A C-87 Liberator Express was
reconfigured for use as a presidential transport; however, it was rejected by
the Secret Service amid concerns over the aircraft's safety record. A C-54
Skymaster was then converted for presidential use; this aircraft, dubbed
theSacred Cow, transported President Franklin D. Roosevelt to the Yalta
Conference in February 1945, and was subsequently used for another two
years by President Harry S. Truman.
The "Air Force One" call sign was
created after a 1953 incident
during which a flight carrying
President Dwight D.
Eisenhowerentered the same
airspace as a commercial airline
flight using the same call sign.
Several aircraft have been used
as Air Force One since the
creation of the presidential fleet, including two Boeing 707s introduced in the
1960s and 1970s, respectively; since 1990, the presidential fleet has
consisted of two Boeing VC-25As – specifically configured, highly
customized Boeing 747-200B series aircraft. The Air Force is looking into
replacing the two VC-25 aircraft with three replacement aircraft beginning in
The airline check-in's main function, however, is to accept luggage that is to
go in the aircraft's cargo hold and issue boarding passes.
Check-in options and procedures vary per airline with some airlines allowing
certain restrictions other airlines have in place, and occasionally the same
airline at two separate airports may have different check-in procedures. Such
differences are usually not noted by the average passenger and occasionally
lead to service interruptions when one carrier refuses to abide by the
procedure that another carrier normally would be willing to do.
In-town check-in service is a service offered by some cities such as Abu
Dhabi, Seoul, Hong Kong, Delhi, Kuala Lumpur, Stockholm,Vienna and Taipei,
where passengers may check in luggage in designated places within the city
but outside the airport. This reduces check-in time and queuing at the
airport.
A propeller is a type of fan that transmits power by
converting rotational motion into thrust. A pressure difference is produced
between the forward and rear surfaces of the airfoil-shaped blade, and a fluid
(such as air or water) is accelerated behind the blade. Propeller dynamics
can be modelled by both Bernoulli's principle and Newton's third law. A
marine propeller is sometimes colloquially known as a screw
propeller or screw.
Aircraft propellers
The twisted airfoil (aerofoil) shape of modern aircraft propellers was pioneered by the Wright brothers. While some earlier engineers had attempted to model air propellers on marine propellers, they realized that a propeller is essentially the same as a wing, and were able to use data from their earlier wind tunnel experiments on wings. They also introduced a twist along the length of the blades. This was necessary to ensure the angle of attack of the blades was kept relatively constant along their length.[13] Their
original propeller blades were only about 5% less efficient than the modern equivalent, some 100 years later. The understanding of low speed propeller aerodynamics was fairly complete by the 1920s, but later requirements to
handle more power in smaller
diameter have made the problem more complex.
Alberto Santos Dumont, another early pioneer, applied the knowledge he gained from experiences with airships to make a propeller with a steel shaft and aluminium blades for his 14 bis biplane. Some of his designs used a bent aluminium sheet for blades, thus creating an airfoil shape. They were heavily undercambered, and this plus the absence of lengthwise twist made them less efficient than the Wright propellers. Even so, this was perhaps the first use of aluminium in the construction of an airscrew.
History
In the second half of the nineteenth century, several theories were developed.
The momentum theory or disk actuator theory—a theory describing a mathematical
model of an ideal propeller—was developed by W.J.M. Rankine (1865), Alfred
George Greenhill (1888) and R.E. Froude (1889). The propeller is modelled as an
infinitely thin disc, inducing a constant velocity along the axis of rotation. This disc
creates a flow around the propeller. Under certain mathematical premises of the
fluid, there can be extracted a mathematical connection between power, radius of
the propeller,torque and induced velocity. Friction is not included.
The blade element theory (BET) is a mathematical process originally designed
by William Froude (1878), David W. Taylor (1893) and Stefan Drzewiecki to
determine the behaviour of propellers. It involves breaking an airfoil down into
several small parts then determining the forces on them. These forces are then
converted into accelerations, which can be integrated into velocities and positions.
velocities imparted to the fluid by the forward propeller (known as "propeller swirl").
The flow field behind the aft propeller of a contra-rotating set has very little "swirl",
and this reduction in energy loss is seen as an increased efficiency of the aft
propeller.
An azimuthing propeller is a propeller that turns around the vertical axis. The
individual airfoil-shaped blades turn as the propeller moves so that they are always
generating lift in the vessel's direction of movement. This type of propeller can
reverse or change its direction of thrust very quickly,
Type of propellers
In designing propellers, the maximum performance of the airplane for all condition of operation from takeoff, climb, cruising, and high speed. The propellers may be classified under eight general types as follows:
1. Fixed pitch: The propeller is made in one piece. Only one pitch setting is possible and is usually two blades propeller and is often made of wood or metal. Wooden Propellers: Wooden propellers were used almost exclusively on personal and business aircraft prior to World War II .A wood propeller is not cut from a solid block but is built up of a number of separate layers of carefully selected .any types of wood have been used in making propellers, but the most satisfactory are yellow birch, sugar marble, black cherry, and black walnut. The use of lamination of wood will reduce the tendency for propeller to warp. For standard one-piece wood propellers, from five to nine separate wood laminations about 3/4 in. thick is used.
Metal Propellers: During 1940, solid steel propellers were made for military use. Modern propellers are fabricated from high-strength, heat-treated, aluminum alloy by forging a single bar of aluminum alloy to the required shape. Metal propellers are now extensively used in the construction of propellers for all type of aircraft. The general appearance of the metal propeller is similar to the wood propeller, except that the sections
2. Ground adjustable pitch: The pitch setting can be adjusted only with tools on the ground before the engine is running. This type of propellers usually has a split hub. The blade angle is specified by the aircraft specifications. The adjustable - pitch feature permits compensation for the location of the flying field at various altitudes and also for variations in the characteristics of airplanes using the same engine. Setting the blade angles by loosened the clamps and the blades are rotated to the desired angle and then tighten the clamps.
3. Two-position: A propeller which can have its pitch changed from one position to one other angle by the pilot while in flight.
4. Controllable pitch: The pilot can change the pitch of the propeller in flight or while operating the engine by mean of a pitch changing mechanism that may be operated by hydraulically.
5. Constant speed: The constant speed propeller utilizes a hydraulically or electrically operated pitch changing mechanism which is controlled by governor. The setting of the governor is adjusted by the pilot with the rpm lever in the cockpit. During operation, the constant speed propellers will automatically changes its blade angle to maintain a constant engine speed. If engine power is increase, the blade angle is increased to make the propeller absorb the additional power while the rpm remain constant. At the other position, if the engine power is decreased, the blade angle will decrease to make the blades take less bite of air to keep engine rpm remain constant. The pilot selects the engine speed required for any particular type of operation.
6. Full Feathering: A constant speed propeller which has the ability to turn edge to the wind and thereby eliminate drag and wind milling in the event of engine failure. The term Feathering refers to the operation of rotating the blades of the propeller to the wind position for the purpose of stopping the rotation of the propeller to reduce drag. Therefore, a Feathered blade is in an approximate in-line-of-flight position , streamlined with the line of flight (turned the blades to a very high pitch). Feathering is necessary when the engine fails or when it is desirable to shutoff an engine in flight.
7. Reversing: A constant speed propeller which has the ability to assume a negative blade angle and produce a reversing thrust. When propellers are reversed, their blades are rotated below their positive angle , that is, through flat pitch, until a negative blade angle is obtained in order to produce a thrust acting in the opposite direction to the forward thrust . Reverse propeller thrust is used where a large aircraft is landed, in reducing the length of landing run.
8. Beta Control: A propeller which allows the manual repositioning of the propeller blade angle beyond the normal low pitch stop. Used most often in taxiing, where thrust is manually controlled by adjusting blade angle with the power lever.
List of large aircraft
Fixed-wing
Civilian
AircraftFirst flight
Note
Antonov An-225 Mriya
21 December 1988
Generally acknowledged as the largest airplane in the world, the Antonov An-225 is the world's heaviest aircraft ever (max. takeoff weight greater than 640 tons) and the largest aerodyne (in length and wingspan) ever entering operational service.
Airbus A340-600
23 April 2001
World's second longest passenger aircraft at 75.36m.
Airbus A38027 April 2005
Largest mass-produced aircraft in the world and the highest-capacity passenger aircraft
Antonov An-124 1982The second largest mass-produced aircraft in the world until the Airbus A380 was produced. Remains the World's largest military aircraft.
Antonov An-2227 February 1965
World's largest turboprop-powered airplane
Boeing 7479 February 1969
Highest-capacity passenger aircraft until surpassed by Airbus A380
747 with enlarged fuselage for 787 parts transport (65,000 cubic feet)
TupolevMaxsim Gorki
19 May 1934
Physically the largest aircraft, and heaviest land-based aircraft of the 1930s era (63 meter/206.7 ft wingspan, 53 tonne MTOW), required eight 900 hp Mikulin V12 engines for flight
Dornier Do X12 July 1929
Largest successful flying boat and heaviest aircraft in the world from 1929 until 1942 when the even heavier Boeing B-29 Superfortress first flew.
Military
AircraftFirst flight
Note
Blohm + Voss BV 238
11 March 1944
Largest aircraft in the world 1944 to 1946 when the even heavier Convair B-36 first flew. Very large flying boat.
Boeing B-29 Superfortress
21 September 1942
Largest aircraft in the world from 1942 to 1943 when the even heavier Junkers Ju-390 first flew. It was one of the largest bombers used
Largest aircraft in the world 1946 to 1947 when the even heavier Hughes H-4 Hercules first flew. First intercontinental strategic bomber, longest wingspan for a combat aircraft
Convair XC-9923 November 1947
Developed from B-36, largest piston-engined land-based transport aircraft ever built
Kawanishi H8KJanuary 1941
Largest WWII aircraft produced by Japan in any quantity
Linke-Hofmann R.II
1919Largest aircraft ever to fly with only one propeller, used largest airplane propellor ever used.
Lockheed C-5 Galaxy
30 June 1968
Largest USAF strategic airlifter and one of the largest military aircraft in the world
Martin JRM Mars
1941 Largest flying boat to enter production (7 built)
Messerschmitt Me 323 "Gigant"
1941Biggest land-based cargo airplane during World War II
1981 Derivative of the M-4 as outsized cargo aircraft
Tupolev Tu-16018 December 1981
Heaviest combat aircraft ever built
Zeppelin Staaken R.VI
Circa 1917Largest aircraft to see regular squadron service in World War I
Experimental/proposed
AircraftFirst
flight[Note 1] Note
Airbus A380-900
2006 development
Announced in 2006 as a derivative of the Airbus A380-800. World's highest-capacity passenger aircraft in history
Beriev Be-2500 1980s proposalWould be the largest aircraft ever, if built; development started in the 1980s
Boeing Pelican 1990s proposal Concept only
Ekranoplan KM October 16, 1966
The ekranoplan had wingspan of 37.6 m, length - 92 m, maximum take-off weight - 544 tons. Until An-225 it was the largest aircraft in the world.KM was tested at the
Caspian Sea for 15 years until 1980. In 1980, pilot error caused a crash without human casualties. The vehicle was too heavy to be recovered from its watery wrecksite.
Boeing 2707SST
1960s design. A mockup was built but no prototype.
Planned as an answer to the European Concorde Supersonic Transport. At 306 feet (93 m) long it would have been one of the longest airframes ever flown. Problems with the weight of the swing-wing mechanism and air friction heating in Mach 3 flight provoked a drastic redesign, by which time airline interest in SSTs was dropping because of environmental concerns. The U.S. Congress cut government funding and airlines began canceling orders.
McDonnell Douglas MD-12
1990 proposalProposed passenger aircraft, Designed to compete with the A380 and the 747, canceled project
Hughes H-4 Hercules"Spruce Goose"
1947, 2 November
Largest aircraft in the world 1947 to 1952 when the even heavier Boeing B-52 Stratofortress first flew. World's largest flying boat, and largest wingspan of any aircraft. Only one was ever built and it performed only one short flight.
Junkers Ju 390 1943, 20 Largest aircraft in the world 1943 to 1944 when the even heavier Blohm & Voss BV
October238 first flew. Selected and further developed as the Junkers firm's entry for the Amerika Bomber design contract.
Sukhoi KR-860 1990s proposal
KR-860 (Kryl'ya Rossii or Wings of Russia) early named as SKD-717 is super large transport aircraft with weights about 650 tonnes (Antonov An-225 weight is 600 tonnes), payload about 300 tonnes (An-225 payload is 250 tonnes) and 860 to 1000 passengers, a proposed Double decker wide-body Superjumbo jet by Russian aerospace company Sukhoi.
Stratolaunch Carrier Aircraft
2011, 13 December Announcement
a proposed aircraft being developed by Scaled Composites to provide air-launch capability for Stratolaunch Systems
1. Jump up ^ For designs that never flew the year of design or
conception is used instead.
Helicopters and rotary wing aircraft[edit]
Aeroflot Mil V-12 at Groningen Airport in May 1971.