1.
Boeing B-29 Superfortress
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The Boeing B-29 Superfortress is a four-engine propeller-driven heavy bomber designed by Boeing which was flown primarily by the United States during World War II and the Korean War. It was one of the largest aircraft operational during World War II and it was the single most expensive weapons project undertaken by the United States in World War II, exceeding the cost of the Manhattan Project by between 1 and 1.7 billion dollars. A manned tail gun installation was semi-remote, the name Superfortress continued the pattern Boeing started with its well-known predecessor, the B-17 Flying Fortress. Designed for the strategic bomber role, the B-29 also excelled in low-altitude nighttime incendiary bombing missions. One of the B-29s final roles during World War II was carrying out the bomb attacks on Hiroshima. The B-29 served in roles throughout the 1950s. The Royal Air Force flew the B-29 as the Washington until phasing out the type in 1954, the Soviet Union produced an unlicensed reverse-engineered copy as the Tupolev Tu-4. The B-29 was the progenitor of a series of Boeing-built bombers, transports, tankers, reconnaissance aircraft, the type was retired in the early 1960s. The B-29 production total was 3,970 aircraft, dozens of B-29s remain as static displays but only two examples, Fifi and Doc, have been restored to flying status, with Doc flying again for the first time from McConnell AFB on July 17,2016. A transport developed from the B-29 was the Boeing C-97 Stratofreighter, first flown in 1944, followed by its commercial airliner variant and this bomber-to-airliner derivation was similar to the B-17/Model 307 evolution. In 1948 Boeing introduced a variant of the B-29 as the KB-29. A heavily modified line of outsized-cargo variants of the Stratocruiser is the Guppy / Mini Guppy / Super Guppy which remain in service today with operators including NASA, Boeing began work on pressurized long-range bombers in 1938, in response to a United States Army Air Corps request. Boeings design study for the Model 334 was a derivative of the Boeing B-17 Flying Fortress with nosewheel undercarriage. Although the Air Corps did not have money to pursue the design, in April 1939, Charles Lindbergh convinced general Henry H. Arnold to produce a new bomber in large numbers to counter the Nazi production, Boeings previous private venture studies formed the starting point for its response to this specification. Boeing submitted its Model 345 on 11 May 1940, in competition with designs from Consolidated Aircraft, Lockheed, Consolidated continued to work on its Model 33 as it was seen by the Air Corps as a backup in case of problems with Boeings design. Boeing received a production order for 14 service test aircraft and 250 production bombers in May 1941. The B-29 featured a design with circular cross-section for strength
2.
Boeing B-52 Stratofortress
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The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and it has been operated by the United States Air Force since the 1950s. The bomber is capable of carrying up to 70,000 pounds of weapons, the B-52 took its maiden flight in April 1952. Built to carry weapons for Cold War-era deterrence missions, the B-52 Stratofortress replaced the Convair B-36. A veteran of wars, the B-52 has dropped only conventional munitions in combat. The B-52s official name Stratofortress is rarely used, informally, the aircraft has become referred to as the BUFF. The B-52 has been in service with the USAF since 1955. As of December 2015,58 were in service with 18 in reserve. The B-52 completed sixty years of service with its original operator in 2015. After being upgraded between 2013 and 2015, it is expected to serve into the 2040s, the aircraft was to have a crew of five or more turret gunners, and a six-man relief crew. It was required to cruise at 300 mph at 34,000 feet with a radius of 5,000 miles. The armament was to consist of a number of 20 mm cannon and 10,000 pounds of bombs. On 13 February 1946, the Air Force issued bid invitations for these specifications, with Boeing, Consolidated Aircraft, and Glenn L. Martin Company submitting proposals. On 5 June 1946, Boeings Model 462, an aircraft powered by six Wright T35 turboprops with a gross weight of 360,000 pounds. On 28 June 1946, Boeing was issued a letter of contract for US$1.7 million to build a full-scale mock-up of the new XB-52 and do preliminary engineering and testing. However, by October 1946, the air began to express concern about the sheer size of the new aircraft. In response, Boeing produced Model 464, a smaller version with a 230,000 pound gross weight. Boeing responded with two powered by the T-35 turboprops
3.
Aircraft
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An aircraft is a machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the lift of an airfoil. The human activity that surrounds aircraft is called aviation, crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as type, aircraft propulsion, usage. Each of the two World Wars led to technical advances. Consequently, the history of aircraft can be divided into five eras, Pioneers of flight, first World War,1914 to 1918. Aviation between the World Wars,1918 to 1939, Second World War,1939 to 1945. Postwar era, also called the jet age,1945 to the present day, aerostats use buoyancy to float in the air in much the same way that ships float on the water. They are characterized by one or more large gasbags or canopies, filled with a relatively low-density gas such as helium, hydrogen, or hot air, which is less dense than the surrounding air. When the weight of this is added to the weight of the aircraft structure, a balloon was originally any aerostat, while the term airship was used for large, powered aircraft designs – usually fixed-wing. In 1919 Frederick Handley Page was reported as referring to ships of the air, in the 1930s, large intercontinental flying boats were also sometimes referred to as ships of the air or flying-ships. – though none had yet been built, the advent of powered balloons, called dirigible balloons, and later of rigid hulls allowing a great increase in size, began to change the way these words were used. Huge powered aerostats, characterized by an outer framework and separate aerodynamic skin surrounding the gas bags, were produced. There were still no fixed-wing aircraft or non-rigid balloons large enough to be called airships, then several accidents, such as the Hindenburg disaster in 1937, led to the demise of these airships. Nowadays a balloon is an aerostat and an airship is a powered one. A powered, steerable aerostat is called a dirigible, sometimes this term is applied only to non-rigid balloons, and sometimes dirigible balloon is regarded as the definition of an airship. Non-rigid dirigibles are characterized by a moderately aerodynamic gasbag with stabilizing fins at the back and these soon became known as blimps. During the Second World War, this shape was adopted for tethered balloons, in windy weather
4.
Missile
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In modern language, a missile is a self-propelled precision-guided munition system, as opposed to an unguided self-propelled munition, referred to as a rocket. Missiles have four components, targeting and/or missile guidance, flight system, engine. Missiles come in types adapted for different purposes, surface-to-surface and air-to-surface missiles, surface-to-air missiles, air-to-air missiles, all known existing missiles are designed to be propelled during powered flight by chemical reactions inside a rocket engine, jet engine, or other type of engine. Non-self-propelled airborne explosive devices are referred to as shells and usually have a shorter range than missiles. In ordinary British-English usage predating guided weapons, a missile is any thrown object, the word missile comes from the Latin verb mittere, meaning to send. In military usage, munitions projected towards a target are broadly categorised as follows, a powered, unguided munition is known as a rocket. Unpowered munitions not fired from a gun are called bombs whether guided or not, munitions that are fired from a gun are known as projectiles whether guided or not. If explosive, they are more specifically as shells or mortar bombs. Powered munitions that travel through water are called torpedoes, hand grenades are not usually classed as missiles. The first missiles to be used operationally were a series of missiles developed by Nazi Germany in World War II, most famous of these are the V-1 flying bomb and V-2 rocket, both of which used a simple mechanical autopilot to keep the missile flying along a pre-chosen route. Less well known were a series of anti-shipping and anti-aircraft missiles, however, these early systems in World War II were only built in small numbers. Guided missiles have a number of different system components, Targeting and/or missile guidance Flight system Engine Warhead Missiles may be targeted in a number of ways. The most common method is to use some form of radiation, such as infrared, lasers or radio waves and this radiation may emanate from the target, it may be provided by the missile itself, or it may be provided by a friendly third party. The first two are known as fire-and-forget as they need no further support or control from the launch vehicle/platform in order to function. Another method is to use a TV guidance—using either visible light or infrared—in order to see the target, the picture may be used either by a human operator who steers the missile onto its target or by a computer doing much the same job. One of the more bizarre guidance methods instead used a pigeon to steer the missile to its target, many missiles use a combination of two or more of the above methods to improve accuracy and the chances of a successful engagement. Another method is to target the missile by knowing the location of the target and using a system such as INS. This guidance system guides the missile by knowing the current position and the position of the target
5.
Bomb
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A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Bombs have been in use since the 11th century in Song Dynasty China, the term bomb is not usually applied to explosive devices used for civilian purposes such as construction or mining, although the people using the devices may sometimes refer to them as a bomb. The military use of the bomb, or more specifically aerial bomb action, typically refers to airdropped, unpowered explosive weapons most commonly used by air forces. Other military explosive weapons not classified as bombs include grenades, shells, depth charges, warheads when in missiles, in unconventional warfare, other names can refer to a range of offensive weaponry. For instance, in recent Middle Eastern conflicts, bombs called improvised explosive devices have been employed by insurgent fighters to great effectiveness, the word comes from the Latin bombus, which in turn comes from the Greek βόμβος, an onomatopoetic term meaning booming, buzzing. Explosive bombs were used in China in 1221, by a Jin dynasty army against a Song Dynasty city, Bombs built using bamboo tubes appear in the 11th century. Bombs made of cast iron shells packed with explosive gunpowder date to 13th century China, the term was coined for this bomb during a Jin dynasty naval battle of 1231 against the Mongols. When hit, even iron armour was pierced through. The Ming Dynasty text Huolongjing describes the use of gunpowder bombs. During the Mongol invasions of Japan, the Mongols used the explosive thunder-crash bombs against the Japanese, archaeological evidence of the thunder-crash bombs has been discovered in an underwater shipwreck off the shore of Japan by the Kyushu Okinawa Society for Underwater Archaeology. X-rays by Japanese scientists of the excavated shells confirmed that they contained gunpowder, explosive shock waves can cause situations such as body displacement, dismemberment, internal bleeding and ruptured eardrums. Shock waves produced by explosive events have two components, the positive and negative wave. The positive wave shoves outward from the point of detonation, followed by the vacuum space sucking back towards the point of origin as the shock bubble collapses. The greatest defense against shock injuries is distance from the source of shock, as a point of reference, the overpressure at the Oklahoma City bombing was estimated in the range of 28 MPa. A thermal wave is created by the release of heat caused by an explosion. Military bomb tests have documented temperatures of up to 2,480 °C, while capable of inflicting severe to catastrophic burns and causing secondary fires, thermal wave effects are considered very limited in range compared to shock and fragmentation. This would be fatal to humans, as tests have proven. Fragmentation is produced by the acceleration of shattered pieces of bomb casing, the use of fragmentation in bombs dates to the 14th century, and appears in the Ming Dynasty text Huolongjing
6.
Fuselage
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The fuselage is an aircrafts main body section. It holds crew, passengers, and cargo, the fuselage also serves to position control and stabilization surfaces in specific relationships to lifting surfaces, which is required for aircraft stability and maneuverability. This type of structure is still in use in lightweight aircraft using welded steel tube trusses. A box truss fuselage structure can also be out of wood—often covered with plywood. Simple box structures may be rounded by the addition of supported lightweight stringers, allowing the fabric covering to form an aerodynamic shape. Geodesic structural elements were used by Barnes Wallis for British Vickers between the wars and into World War II to form the whole of the fuselage, including its aerodynamic shape. In this type of construction multiple flat strip stringers are wound about the formers in opposite spiral directions and this proved to be light, strong, and rigid and had the advantage of being made almost entirely of wood. A similar construction using aluminum alloy was used in the Vickers Warwick with less materials than would be required for other structural types, the geodesic structure is also redundant and so can survive localized damage without catastrophic failure. A fabric covering over the completed the aerodynamic shell. The logical evolution of this is the creation of fuselages using molded plywood, in this method, the exterior surface of the fuselage is also the primary structure. A typical early form of this was built using molded plywood, a later form of this structure uses fiberglass cloth impregnated with polyester or epoxy resin, instead of plywood, as the skin. An example of a larger molded plywood aircraft is the de Havilland Mosquito fighter/light bomber of World War II, no plywood-skin fuselage is truly monocoque, since stiffening elements are incorporated into the structure to carry concentrated loads that would otherwise buckle the thin skin. The use of molded fiberglass using negative molds is prevalent in the production of many modern sailplanes. The use of molded composites for fuselage structures is being extended to large aircraft such as the Boeing 787 Dreamliner. This is the method of constructing an all-aluminum fuselage. First, a series of frames in the shape of the cross sections are held in position on a rigid fixture. These frames are then joined with lightweight longitudinal elements called stringers and these are in turn covered with a skin of sheet aluminum, attached by riveting or by bonding with special adhesives. The fixture is then disassembled and removed from the fuselage shell, which is then fitted out with wiring, controls
7.
Slip (aerodynamics)
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A slip is an aerodynamic state where an aircraft is moving somewhat sideways as well as forward relative to the oncoming airflow or relative wind. In other words, for a aircraft, the nose will be pointing in the opposite direction to the bank of the wing. The aircraft is not in coordinated flight and therefore is flying inefficiently, Flying in a slip is aerodynamically inefficient, since the lift-to-drag ratio is reduced. More drag is at play consuming energy but not producing lift, inexperienced or inattentive pilots will often enter slips unintentionally during turns by failing to coordinate the aircraft with the rudder. Airplanes can readily enter into a slip climbing out from take-off on a windy day, if left unchecked, climb performance will suffer. This is especially dangerous if there are nearby obstructions under the climb path, a slip can also be a piloting maneuver where the pilot deliberately enters one type of slip or another. Slips are particularly useful in performing a short field landing over an obstacle, or to avoid an obstacle and these methods are also commonly employed when flying into farmstead or rough country airstrips where the landing strip is short. Pilots need to touch down with ample runway remaining to slow down, there are common situations where a pilot may deliberately enter a slip by using opposite rudder and aileron inputs, most commonly in a landing approach at low power. Without flaps or spoilers it is difficult to increase the steepness of the glide without adding significant speed and this excess speed can cause the aircraft to fly in ground effect for an extended period, perhaps running out of runway. In a forward slip much more drag is created, allowing the pilot to dissipate altitude without increasing airspeed, forward slips are especially useful when operating pre-1950s training aircraft, aerobatic aircraft such as the Pitts Special or any aircraft with inoperative flaps or spoilers. Often, if an airplane in a slip is made to stall, a stalling airplane in a slip may do little more than tend to roll into a wings-level attitude. In fact, in some airplanes stall characteristics may even be improved, aerodynamically these are identical once established, but they are entered for different reasons and will create different ground tracks and headings relative to those prior to entry. Forward-slip is used to steepen an approach without gaining much airspeed, the sideslip moves the aircraft sideways where executing a turn would be inadvisable, drag is considered a byproduct. Most pilots like to enter sideslip just before flaring or touching down during a crosswind landing, the forward slip changes the heading of the aircraft away from the down wing, while retaining the original track of the aircraft. To execute a forward slip, the banks into the wind. If you were the target you would see the planes nose off to one side, the pilot must make sure that the planes nose is low enough to keep airspeed up. However, airframe speed limits such as VA and VFE must be observed, a forward-slip is useful when a pilot has set up for a landing approach with excessive height or must descend steeply beyond a tree line to touchdown near the runway threshold. Assuming that the plane is properly lined up for the runway, in the United States, student pilots are required to know how to do forward slips before embarking on their first solo flight
8.
Skeg
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A skeg, is a sternward extension of the keel of boats and ships which have a rudder mounted on the centre line. The term also applies to the lowest point on a motor or the outdrive of an inboard/outboard. In more recent years, the name has been used for a fin on a surfboard which improves directional stability, the term is also often used for the fin on water skis in the U. S. and for the tail bumpers of aircraft in the US Navy. The word originates in the Scandinavian word for beard, in Old Norse, in Icelandic the word remains skegg, in modern Norwegian Bokmål and Nynorsk, it appears as skjegg, in Swedish, it is skägg and in Danish, skæg. The Norwegian pronunciation of the letter combination skj is as in the English sh, the word is related to the English shaggy. It also appears in the English place name Skegness - beard point, from the way in which a series of tombolos forms, here, the English pronunciation reflects a probable Danish origin, which pronounces the sk letter combination as an English speaker would expect. Where a vessels rudder is mounted on the centre-line, it is usual to hang it on gudgeons and pintles, the latter being upright pins and the former, rings to fit round them. This naturally leaves a gap between the sternpost and the rudder, into which stray items like kelp and rope can catch, causing drag. In ships such as Mary Rose, the skeg is a small feature. This somewhat beard-like sternward extension of the keel is the basic skeg, subsequently, the lowest pintle was commonly mounted below the rudder on a metal extension of the keel. This helped further stabilize and protect the rudder and the name skeg was transferred to it and it used to be relatively small until screw propellers were introduced, when it had to reach below the screw and became a proportionately larger feature protecting both screw and rudder from damage. On wooden vessels, the skeg may be protected from damage by the addition of a bug shoe. In more modern installations, with more than one screw, a fitting supports each propeller shaft just ahead of its screw. This is usually called a shaft bracket but the part of it extends below the shaft bearing to protect the lower part of the propeller is also a skeg. Similarly, the projection of the drive casing, below the rotational axis of the propeller of an outboard motor is another form of the skeg. Where a yacht is designed with a fin keel, it will normally and this link shows the profile of such a boat. This type of skeg is pictured at the bottom of the linked page. In surfing, windsurfing, and kitesurfing, skegs, usually known as fins, are attached toward the tail of the board to improve directional stability, fins allow the rider to control the boards direction by varying their side-to-side weight distribution
9.
Empennage
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The empennage, also known as the tail or tail assembly, provides stability for aircraft, in a way similar to the feathers on an arrow. The term derives from the French language word empenner which means to feather an arrow, most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the flight dynamics of yaw and pitch, as well as housing control surfaces. In spite of effective control surfaces, many aircraft that lacked a stabilising empennage were virtually unflyable. Even so-called tailless aircraft usually have a tail fin, heavier-than-air aircraft without any kind of empennage are rare. Structurally, the empennage consists of the tail assembly, including the tailfin, the tailplane. On an airliner this would be all the flying and control surfaces behind the pressure bulkhead. The front section of the tailplane is called the tailplane or horizontal stabiliser and is used to pitch stability. The rear section is called the elevator, and is hinged to the horizontal stabiliser. The elevator is a movable aerofoil that controls changes in pitch, some aircraft employ an all-moving stabiliser and elevators in one unit, known as a stabilator or full-flying stabiliser. The vertical tail structure has a front section called the vertical stabiliser. The rear section of the fin is the rudder, a movable aerofoil that is used to turn the aircrafts nose to one side or the other. When used in combination with the ailerons, the result is a banking turn, some aircraft are fitted with a tail assembly that is hinged to pivot in two axes forward of the fin and stabiliser, in an arrangement referred to as a movable tail. The entire empennage is rotated vertically to actuate the horizontal stabiliser, in some aircraft trim devices are provided to eliminate the need for the pilot to maintain constant pressure on the elevator or rudder controls. The trim device may be, a tab on the rear of the elevators or rudder which act to change the aerodynamic load on the surface. Usually controlled by a wheel or crank. an adjustable stabiliser into which the stabiliser may be hinged at its spar. Usually controlled by a cockpit crank, a bungee trim system which uses a spring to provide an adjustable preload in the controls. Usually controlled by a cockpit lever, an anti-servo tab used to trim some elevators and stabilators as well as increased control force feel. Usually controlled by a wheel or crank
10.
Positive feedback
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Positive feedback is a process that occurs in a feedback loop in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation. That is, A produces more of B which in turn more of A. In contrast, a system in which the results of an act to reduce or counteract it has negative feedback. Both concepts play an important role in science and engineering, including biology, chemistry, mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect. That is, positive feedback is in phase with the input, Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there will typically be exponential growth, increasing oscillations, system parameters will typically accelerate towards extreme values, which may damage or destroy the system, or may end with the system latched into a new stable state. Positive feedback may be controlled by signals in the system being filtered, damped, or limited, Positive feedback is used in digital electronics to force voltages away from intermediate voltages into 0 and 1 states. On the other hand, thermal runaway is a positive feedback that can destroy semiconductor junctions, Positive feedback in chemical reactions can increase the rate of reactions, and in some cases can lead to explosions. Positive feedback in mechanical design causes tipping-point, or over-centre, mechanisms to snap into position, for example in switches, out of control, it can cause bridges to collapse. Positive feedback in systems can cause boom-then-bust cycles. Positive feedback enhances or amplifies an effect by it having an influence on the process gave rise to it. For example, when part of an output signal returns to the input, and is in phase with it. The feedback from the outcome to the process can be direct. Such systems can give rich qualitative behaviors, but whether the feedback is positive or negative in sign has an extremely important influence on the results. Positive feedback reinforces and negative feedback moderates the original process, Positive and negative in this sense refer to loop gains greater than or less than zero, and do not imply any value judgements as to the desirability of the outcomes or effects. A key feature of positive feedback is thus that small disturbances get bigger, when a change occurs in a system, positive feedback causes further change, in the same direction. A simple feedback loop is shown in the diagram, if the loop gain AB is positive, then a condition of positive or regenerative feedback exists. If the functions A and B are linear and AB is smaller than unity, then the system gain from the input to output is finite
