A two-stroke engine is a type of internal combustion engine which completes a power cycle with two strokes of the piston during only one crankshaft revolution. This is in contrast to a "four-stroke engine", which requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen with the intake and exhaust functions occurring at the same time. Two-stroke engines have a high power-to-weight ratio, power being available in a narrow range of rotational speeds called the "power band". Compared to four-stroke engines, two-stroke engines have a reduced number of moving parts, so can be more compact and lighter; the first commercial two-stroke engine involving in-cylinder compression is attributed to Scottish engineer Dugald Clerk, who patented his design in 1881. However, unlike most two-stroke engines, his had a separate charging cylinder; the crankcase-scavenged engine, employing the area below the piston as a charging pump, is credited to Englishman Joseph Day.
On 31 December 1878, German inventor Karl Benz produced a two-stroke gas engine, for which he received a patent in 1879 in Germany. The first practical two-stroke engine is attributed to Yorkshireman Alfred Angas Scott, who started producing twin-cylinder water-cooled motorcycles in 1908. Gasoline versions are useful in lightweight or portable applications such as chainsaws and motorcycles. However, when weight and size are not an issue, the cycle's potential for high thermodynamic efficiency makes it ideal for diesel compression ignition engines operating in large, weight-insensitive applications, such as marine propulsion, railway locomotives and electricity generation. In a two-stroke engine, the heat transfer from the engine to the cooling system is less than in a four-stroke, which means that two-stroke engines can be more efficient. Crankcase-compression two-stroke engines, such as common small gasoline-powered engines, create more exhaust emissions than four-stroke engines of comparable power output because their two-stroke oil lubrication mixture is burned in the engine, due to the engine's total-loss oiling system, because the combined opening time of the intake and exhaust ports in some 2-stroke designs can allow some amount of unburned fuel vapors to exit in the exhaust stream.
Two-stroke petrol engines are preferred when mechanical simplicity, light weight, high power-to-weight ratio are design priorities. With the traditional lubrication technique of mixing oil into the fuel, they have the advantage of working in any orientation, as there is no oil reservoir dependent on gravity. A number of mainstream automobile manufacturers have used two-stroke engines in the past, including the Swedish Saab and German manufacturers DKW, Auto-Union, VEB Sachsenring Automobilwerke Zwickau, VEB Automobilwerk Eisenach; the Japanese manufacturer Suzuki did the same in the 1970s. Production of two-stroke cars ended in the 1980s in the West, due to stringent regulation of air pollution. Eastern Bloc countries continued with the Trabant and Wartburg in East Germany. Two-stroke engines are still found in a variety of small propulsion applications, such as outboard motors, high-performance, small-capacity motorcycles and dirt bikes, scooters, tuk-tuks, karts, ultralight airplanes, model airplanes and other model vehicles.
They are common in power tools used outdoors, such as lawn mowers and weed-wackers. With direct fuel injection and a sump-based lubrication system, a two-stroke engine produces air pollution no worse than a four-stroke, it can achieve higher thermodynamic efficiency. Therefore, the cycle has also been used in large diesel engines large industrial and marine engines, as well as some trucks and heavy machinery. There are several experimental designs intended for automobile use: for instance, Lotus of Norfolk, UK, had in 2008 a prototype direct-injection two-stroke engine intended for alcohol fuels called the Omnivore which it is demonstrating in a version of the Exige. Although the principles remain the same, the mechanical details of various two-stroke engines differ depending on the type; the design types vary according to the method of introducing the charge to the cylinder, the method of scavenging the cylinder and the method of exhausting the cylinder. Piston port is the most common in small two-stroke engines.
All functions are controlled by the piston covering and uncovering the ports as it moves up and down in the cylinder. In the 1970s, Yamaha worked out some basic principles for this system, they found that, in general, widening an exhaust port increases the power by the same amount as raising the port, but the power band does not narrow as it does when the port is raised. However, there is a mechanical limit to the width of a single exhaust port, at about 62% of the bore diameter for reasonable ring life. Beyond this, the rings will wear quickly. A maximum 70 % of bore width is possible in racing engines. Intake duration is between 160 degrees. Transfer port time is set at a minimum of 26 degrees; the strong low pressure pulse of a racing two-stroke expansion chamber can drop the pressure to -7 PSI when the piston is at bottom dead center, the transfer ports nearly wide open. One of the reasons for high fuel consumption in two-strokes is that so
De Havilland Mosquito
The de Havilland DH.98 Mosquito is a British twin-engine shoulder-winged multi-role combat aircraft, introduced during the Second World War, unusual in that its frame is constructed of wood. It was nicknamed The Wooden Wonder, or "Mossie". Lord Beaverbrook, Minister of Aircraft Production, nicknamed it "Freeman's Folly", alluding to Air Chief Marshal Sir Wilfred Freeman, who defended Geoffrey de Havilland and his design concept against orders to scrap the project. In 1941 it was one of the fastest operational aircraft in the world. Conceived as an unarmed fast bomber, the Mosquito's use evolved during the war into many roles, including low to medium-altitude daytime tactical bomber, high-altitude night bomber, day or night fighter, fighter-bomber, maritime strike aircraft, it was used by the British Overseas Airways Corporation as a fast transport to carry small, high-value cargoes to and from neutral countries through enemy-controlled airspace. The crew of two and navigator, sat side by side.
A single passenger could ride in the aircraft's bomb bay. The Mosquito FBVI was flown in special raids, such as Operation Jericho – an attack on Amiens Prison in early 1944, precision attacks against military intelligence and police facilities. On the 10th anniversary of the Nazis' seizure of power in 1943, a morning Mosquito attack knocked out the main Berlin broadcasting station while Hermann Göring was speaking, putting his speech off the air; the Mosquito flew with the Royal Air Force and other air forces in the European and Italian theatres. The Mosquito was operated by the RAF in the South East Asian theatre and by the Royal Australian Air Force based in the Halmaheras and Borneo during the Pacific War. During the 1950s, the RAF replaced the Mosquito with the jet-powered English Electric Canberra. By the early-mid-1930s, de Havilland had a reputation for innovative high-speed aircraft with the DH.88 Comet racer. The DH.91 Albatross airliner pioneered the composite wood construction used for the Mosquito.
The 22-passenger Albatross could cruise at 210 miles per hour at 11,000 feet, 100 mph faster than the Handley Page H. P. 42 and other biplanes. The wooden monocoque construction not only saved weight and compensated for the low power of the de Havilland Gipsy Twelve engines used by this aircraft, but simplified production and reduced construction time. On 8 September 1936, the British Air Ministry issued Specification P.13/36, which called for a twin-engine medium bomber capable of carrying a bomb load of 3,000 lb for 3,000 mi with a maximum speed of 275 mph at 15,000 ft. Aviation firms entered heavy designs with new high-powered engines and multiple defensive turrets, leading to the production of the Avro Manchester and Handley Page Halifax. In May 1937, as a comparison to P.13/36, George Volkert, the chief designer of Handley Page, put forward the concept of a fast unarmed bomber. In 20 pages, Volkert planned an aerodynamically clean medium bomber to carry 3,000 pounds of bombs at a cruising speed of 300 mph.
There was support in the Air Ministry. There were, counter-arguments that, although such a design had merit, it would not be faster than enemy fighters for long; the ministry was considering using non-strategic materials for aircraft production, which, in 1938, had led to specification B.9/38 and the Armstrong Whitworth Albemarle medium bomber constructed from spruce and plywood attached to a steel-tube frame. The idea of a small, fast bomber gained support at a much earlier stage than is sometimes acknowledged though it was that the Air Ministry envisaged it using light alloy components. Based on his experience with the Albatross, Geoffrey de Havilland believed that a bomber with a good aerodynamic design and smooth, minimal skin area, would exceed the P.13/36 specification. Furthermore, adapting the Albatross principles could save time. In April 1938, performance estimates were produced for a twin Rolls-Royce Merlin-powered DH.91, with the Bristol Hercules and Napier Sabre as alternatives.
On 7 July 1938, Geoffrey de Havilland wrote to Air Marshal Wilfrid Freeman, the Air Council's member for Research and Development, discussing the specification and arguing that in war there would be shortages of aluminium and steel but supplies of wood-based products were "adequate." Although inferior in tension, the strength to weight ratio of wood is equal to or better than light alloys or steel, hence this approach was feasible. A follow-up letter to Freeman on 27 July said that the P.13/36 specification could not be met by a twin Merlin-powered aircraft and either the top speed or load capacity would be compromised, depending on, paramount. For example, a larger, turret armed aircraft would have a range of 1,500 miles carrying a 4,000 lb bomb load, with a maximum of 260 mph at 19,000 feet, a cruising speed of 230 miles per hour at 18,000 feet. De Havilland believed that a compromise, including eliminating surplus equipment, would improve matters. On 4 October 1938, de Havilland projected the performance of another design based on the Albatross, powered by two Merlin Xs, with a three-man crew and six or eight forward-firing guns, plus one or two manually operated guns and a tail turret.
Based on a total loaded
North American P-51 Mustang
The North American Aviation P-51 Mustang is an American long-range, single-seat fighter and fighter-bomber used during World War II and the Korean War, among other conflicts. The Mustang was designed in 1940 by North American Aviation in response to a requirement of the British Purchasing Commission; the Purchasing Commission approached North American Aviation to build Curtiss P-40 fighters under license for the Royal Air Force. Rather than build an old design from another company, North American Aviation proposed the design and production of a more modern fighter; the prototype NA-73X airframe was rolled out on 9 September 1940, 102 days after the contract was signed, first flew on 26 October. The Mustang was designed to use the Allison V-1710 engine which, in its earlier variants, had limited high-altitude performance; the aircraft was first flown operationally by the RAF as a tactical-reconnaissance aircraft and fighter-bomber. Replacing the Allison with a Rolls-Royce Merlin resulted in the P-51B/C model and transformed the aircraft's performance at altitudes above 15,000 ft, allowing it to compete with the Luftwaffe's fighters.
The definitive version, the P-51D, was powered by the Packard V-1650-7, a license-built version of the two-speed two-stage-supercharged Merlin 66, was armed with six.50 caliber M2/AN Browning machine guns. From late 1943, P-51Bs and Cs were used by the USAAF's Eighth Air Force to escort bombers in raids over Germany, while the RAF's Second Tactical Air Force and the USAAF's Ninth Air Force used the Merlin-powered Mustangs as fighter-bombers, roles in which the Mustang helped ensure Allied air superiority in 1944; the P-51 was used by Allied air forces in the North African, Mediterranean and Pacific theaters. During World War II, Mustang pilots claimed to have destroyed 4,950 enemy aircraft. At the start of the Korean War, the Mustang, by redesignated F-51, was the main fighter of the United Nations until jet fighters, including North American's F-86, took over this role. Despite the advent of jet fighters, the Mustang remained in service with some air forces until the early 1980s. After the Korean War, Mustangs became air racing aircraft.
In April 1940 the British government established a purchasing commission in the United States, headed by Sir Henry Self. Self was given overall responsibility for Royal Air Force production and research and development, served with Sir Wilfrid Freeman, the Air Member for Development and Production. Self sat on the British Air Council Sub-committee on Supply and one of his tasks was to organize the manufacturing and supply of American fighter aircraft for the RAF. At the time, the choice was limited, as no U. S. aircraft in production or flying met European standards, with only the Curtiss P-40 Tomahawk coming close. The Curtiss-Wright plant was running at capacity, so P-40s were in short supply. North American Aviation was supplying its Harvard trainer to the RAF, but was otherwise underused. NAA President "Dutch" Kindelberger approached Self to sell the B-25 Mitchell. Instead, Self asked. Kindelberger said NAA could have a better aircraft with the same Allison V-1710 engine in the air sooner than establishing a production line for the P-40.
The Commission stipulated armament of four.303 in machine guns, a unit cost of no more than $40,000 and delivery of the first production aircraft by January 1941. In March 1940, 320 aircraft were ordered by Freeman, who had become the executive head of the Ministry of Aircraft Production and the contract was promulgated on 24 April; the NA-73X, designed by a team led by lead engineer Edgar Schmued, followed the best conventional practice of the era, but included several new features. One was a wing designed using laminar flow airfoils, which were developed co-operatively by North American Aviation and the National Advisory Committee for Aeronautics; these airfoils generated low drag at high speeds. During the development of the NA-73X, a wind tunnel test of two wings, one using NACA five-digit airfoils and the other using the new NAA/NACA 45–100 airfoils, was performed in the University of Washington Kirsten Wind Tunnel; the results of this test showed the superiority of the wing designed with the NAA/NACA 45–100 airfoils.
The other feature was a new cooling arrangement. They discovered that, after much development, the cooling assembly could take advantage of the "Meredith effect", in which heated air exited the radiator with a slight amount of jet thrust; because NAA lacked a suitable wind tunnel to test this feature, it used the GALCIT 10 ft wind tunnel at the California Institute of Technology. This led to some controversy over whether the Mustang's cooling system aerodynamics were developed by NAA's engineer Edgar Schmued or by Curtiss, although NAA had purchased the complete set of P-40 and XP-46 wind tunnel data and flight test reports for US$56,000; the NA-73X was one of the first aircraft to have a fuselage lofted mathematically using conic sections. To aid production, the airframe was divided into five main sections—forward, rear fuselage, two wing halves—all of which were fitted with wiring and piping before being joined; the prototype NA-73X was rolled out in September 1940, just 102 days after the order had been placed.
Curtiss P-40 Warhawk
The Curtiss P-40 Warhawk is an American single-engined, single-seat, all-metal fighter and ground-attack aircraft that first flew in 1938. The P-40 design was a modification of the previous Curtiss P-36 Hawk which reduced development time and enabled a rapid entry into production and operational service; the Warhawk was used by most Allied powers during World War II, remained in frontline service until the end of the war. It was the third most-produced American fighter of World War II, after the P-51 and P-47. P-40 Warhawk was the name the United States Army Air Corps and after June 1941, USAAF-adopted name for all models, making it the official name in the U. S. for all P-40s. The British Commonwealth and Soviet air forces used the name Tomahawk for models equivalent to the P-40B and P-40C, the name Kittyhawk for models equivalent to the P-40D and all variants. P-40s first saw combat with the British Commonwealth squadrons of the Desert Air Force in the Middle East and North African campaigns, during June 1941.
No. 112 Squadron Royal Air Force, was among the first to operate Tomahawks in North Africa and the unit was the first Allied military aviation unit to feature the "shark mouth" logo, copying similar markings on some Luftwaffe Messerschmitt Bf 110 twin-engine fighters. The P-40's lack of a two-speed supercharger made it inferior to Luftwaffe fighters such as the Messerschmitt Bf 109 or the Focke-Wulf Fw 190 in high-altitude combat and it was used in operations in Northwest Europe. However, between 1941 and 1944, the P-40 played a critical role with Allied air forces in three major theaters: North Africa, the Southwest Pacific, China, it had a significant role in the Middle East, Southeast Asia, Eastern Europe and Italy. The P-40's performance at high altitudes was not as important in those theaters, where it served as an air superiority fighter, bomber escort and fighter-bomber. Although it gained a postwar reputation as a mediocre design, suitable only for close air support, more recent research including scrutiny of the records of individual Allied squadrons indicates that this was not the case: the P-40 performed well as an air superiority fighter, at times suffering severe losses, but inflicting a heavy toll on enemy aircraft.
Based on war-time victory claims, over 200 Allied fighter pilots from 7 different nations became aces flying the P-40, with at least 20 double aces in the North Africa, China-Burma-India and Russian Front theaters. The P-40 offered the additional advantage of low cost, which kept it in production as a ground-attack aircraft long after it was obsolete as a fighter. On 14 October 1938, Curtiss test pilot Edward Elliott flew the prototype XP-40 on its first flight in Buffalo; the XP-40 was the 10th production Curtiss P-36 Hawk, with its Pratt & Whitney R-1830 Twin Wasp 14-cylinder air-cooled radial engine replaced at the direction of Chief Engineer Don R. Berlin by a liquid-cooled, supercharged Allison V-1710 V-12 engine; the first prototype placed the glycol coolant radiator in an underbelly position on the fighter, just aft of the wing's trailing edge. USAAC Fighter Projects Officer Lieutenant Benjamin S. Kelsey flew this prototype some 300 miles in 57 minutes 315 miles per hour. Hiding his disappointment, he told reporters that future versions would go 100 miles per hour faster.
Kelsey was interested in the Allison engine because it was sturdy and dependable, it had a smooth, predictable power curve. The V-12 engine offered as much power as a radial engine but had a smaller frontal area and allowed a more streamlined cowl than an aircraft with a radial engine, promising a theoretical 5% increase in top speed. Curtiss engineers worked to improve the XP-40's speed by moving the radiator forward in steps. Seeing little gain, Kelsey ordered the aircraft to be evaluated in a NACA wind tunnel to identify solutions for better aerodynamic qualities. From 28 March to 11 April 1939, the prototype was studied by NACA. Based on the data obtained, Curtiss moved the glycol coolant radiator forward to the chin. Other improvements to the landing gear doors and the exhaust manifold combined to give performance, satisfactory to the USAAC. Without beneficial tail winds, Kelsey flew the XP-40 from Wright Field back to Curtiss's plant in Buffalo at an average speed of 354 mph. Further tests in December 1939 proved.
An unusual production feature was a special truck rig to speed delivery at the main Curtiss plant in Buffalo, New York. The rig moved the newly built P-40s in two main components, the main wing and the fuselage, the eight miles from the plant to the airport where the two units were mated for flight and delivery; the P-40 was conceived as a pursuit aircraft and was agile at low and medium altitudes but suffered from a lack of power at higher altitudes. At medium and high speeds it was one of the tightest-turning early monoplane designs of the war, it could out turn most opponents it faced in North Africa and the Russian Front. In the Pacific Theater it was out-turned at lower speeds by the lightweight fighters A6M Zero and Nakajima Ki-43 "Oscar" which lacked the P-40's structural strength for high-speed hard turns; the American Volunteer Group Commander Claire Chennault advised against prolonged dog-fighting with the Japanese fighters due to speed reduction favouring the Japanese. Allison's V-1710 engines produced 1,040 hp at sea level and 14,000 ft
The Rolls-Royce Vulture was a British aero engine developed shortly before World War II, designed and built by Rolls-Royce Limited. The Vulture used the unusual "X-24" configuration, whereby four cylinder blocks derived from the Rolls-Royce Peregrine were joined by a common crankshaft supported by a single crankcase; the engine was designed to produce around 1,750 horsepower, but continuing problems with the Vulture design meant that the engines were derated to around 1,450-1,550 hp in service by limiting the maximum rpm. Although several new aircraft designs had been planned to use the Vulture, work on the engine's design ended in 1941 as Rolls-Royce concentrated on their more successful Merlin design. Another 24-cylinder engine, the Napier Sabre, would prove more successful after a lengthy development period; the supercharged Rolls-Royce Kestrel, its derivative, the Peregrine was a standard design, with two cylinder banks arranged in a V form and with a displacement of 21 litres. The Vulture, in effect, was two Peregrines joined by a new crankcase turning a new crankshaft, producing an X engine configuration with a displacement of 42 litres.
Although the Vulture used cylinders of the same bore and stroke of the Peregrine, the redesigned cylinder blocks had increased cylinder spacing to accommodate a longer crankshaft, necessary for extra main bearings and wider crankpins. The engine suffered from an abbreviated development period due to Rolls-Royce being required to suspend Vulture development in 1940 during the Battle of Britain to concentrate its work on the Merlin, which powered the RAF's two main fighters, the Hawker Hurricane and Supermarine Spitfire, as a consequence the reliability of the Vulture when it entered service was poor. Apart from delivering less than the designed power, the Vulture suffered from frequent failures of the connecting rod big end bearings, found to be caused by a breakdown in lubrication, from heat dissipation problems. Rolls-Royce were confident that they could solve the problems, but in part because of its accelerated development in 1940, the company's much smaller Merlin was nearing the same power level as the Vulture's original specification, so production of the Vulture was discontinued after only 538 had been built.
The Vulture had been intended to power the Hawker Tornado interceptor, but with the cancellation of Vulture development, Hawker abandoned the Tornado and concentrated on the Hawker Typhoon, powered by the Napier Sabre. The same cancellation caused the abandonment of the Vulture-engined version of the Vickers Warwick bomber; the only aircraft type designed for the Vulture to go into production was the twin-engined Avro Manchester. When the engine reliability problems became clear, the Avro team persuaded the Air Ministry that switching to a four-Merlin version of the Manchester, in development as a contingency plan, was preferable to retooling Avro's factories to make the Handley Page Halifax; the resulting aircraft was called the Manchester Mark III and renamed Avro Lancaster, going on to great success as the RAF's leading heavy bomber. Avro Manchester Blackburn B-20 Hawker Henley Hawker Tornado Vickers Warwick Data from Lumsden and Gunston. Type: X-24 supercharged liquid-cooled piston engine Bore: 5 in Stroke: 5.5 in Displacement: 2,592 cu in Dry weight: 2,450 lb Valvetrain: Overhead camshaft Supercharger: Gear-driven centrifugal type supercharger, two-speed, single-stage Fuel system: Downdraught S.
U. carburettor Fuel type: 100/130 Octane petrol Cooling system: Liquid-cooled, 70% water/30% Ethylene glycol Reduction gear: Spur geared via layshaft, 0.35:1 reduction ratio, left-hand tractor Power output: 1,780 hp at 2,850 rpm, +6 psi boost Compression ratio: 6:1 Rolls-Royce aircraft piston engines Comparable engines Rolls-Royce Exe Daimler-Benz DB 604 Napier SabreRelated lists List of aircraft engines Gunston, Bill. Rolls-Royce Aero Engines. Cambridge, England. Patrick Stephens, 1989. ISBN 1-85260-037-3 Gunston, Bill. World Encyclopedia of Aero Engines: From the Pioneers to the Present Day. 5th edition, Stroud, UK: Sutton, 2006. ISBN 0-7509-4479-X Kirby, Robert. Avro Manchester: The Legend Behind the Lancaster. Earl Shilton, Leicester, UK: Midland publishing Limited, 1995. ISBN 1-85780-028-1 Lumsden, Alec. British Piston Aero-Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6. Rubbra, A. A. Rolls-Royce Piston Aero Engines - a Designer Remembers: Historical Series no 16: Rolls Royce Heritage Trust, 1990.
ISBN 1-872922-00-7. White, Graham. Allied Aircraft Piston Engines of World War II: History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States During World War II. Warrendale, Pennsylvania: SAE International, 1995. ISBN 1-56091-655-9
An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from large gasbags filled with a lifting gas, less dense than the surrounding air. In early dirigibles, the lifting gas used was hydrogen, due to its high lifting capacity and ready availability. Helium gas has the same lifting capacity and is not flammable, unlike hydrogen, but is rare and expensive. Significant amounts were first discovered in the United States and for a while helium was only used for airships in that country. Most airships built; the envelope of an airship may form a single gasbag, or may contain a number of internal gas-filled cells. An airship has engines and optionally payload accommodation housed in one or more "gondolas" suspended below the envelope; the main types of airship are non-rigid, semi-rigid, rigid. Non-rigid airships called "blimps", rely on internal pressure to maintain their shape. Semi-rigid airships maintain the envelope shape by internal pressure, but have some form of supporting structure, such as a fixed keel, attached to it.
Rigid airships have an outer structural framework that maintains the shape and carries all structural loads, while the lifting gas is contained in one or more internal gasbags or cells. Rigid airships were first flown by Count Zeppelin and the vast majority of rigid airships built were manufactured by the firm he founded; as a result, rigid airships are called zeppelins. Airships were the first aircraft capable of controlled powered flight, were most used before the 1940s, their decline was accelerated by a series of high-profile accidents, including the 1930 crash and burning of British R101 in France, the 1933 and 1935 storm-related crashes of the twin airborne aircraft carrier U. S. Navy helium-filled rigids, the USS Akron and USS Macon and the 1937 burning of the German hydrogen-filled Hindenburg. From the 1960s, helium airships have been used in applications where the ability to hover in one place for an extended period outweighs the need for speed and manoeuvrability, such as advertising, camera platforms, geological surveys, aerial observation.
During the pioneer years of aeronautics, terms such as "airship", "air-ship", "air ship" and "ship of the air" meant any kind of navigable or dirigible flying machine. In 1919 Frederick Handley Page was reported as referring to "ships of the air," with smaller passenger types as "air yachts." In the 1930s, large intercontinental flying boats were sometimes referred to as "ships of the air" or "flying-ships". Nowadays the term "airship" is used only for powered, dirigible balloons, with sub-types being classified as rigid, semi-rigid or non-rigid. Semi-rigid architecture is the more recent, following advances in deformable structures and the exigency of reducing weight and volume of the airships, they have a minimal structure. An aerostat is an aircraft that remains aloft using buoyancy or static lift, as opposed to the aerodyne, which obtains lift by moving through the air. Airships are a type of aerostat; the term aerostat has been used to indicate a tethered or moored balloon as opposed to a free-floating balloon.
Aerostats today are capable of lifting a payload of 3,000 pounds to an altitude of more than 4.5 kilometers above sea level. They can stay in the air for extended periods of time when powered by an on-board generator or if the tether contains electrical conductors. Due to this capability, aerostats can be used as platforms for telecommunication services. For instance, Platform Wireless International Corporation announced in 2001 that it would use a tethered 1,250-pound airborne payload to deliver cellular phone service to a 140-mile region in Brazil; the European Union's ABSOLUTE project was reportedly exploring the use of tethered aerostat stations to provide telecommunications during disaster response. Airships were called dirigible balloons, from the French ballon dirigeable or shortly dirigeable; this was the name that inventor Henri Giffard gave to his machine that made its first flight on 24 September 1852. A blimp is a non-rigid aerostat. In American usage it refers to a non-rigid type of dirigible balloon or airship.
In British usage it refers to any non-rigid aerostat, including barrage balloons and other kite balloons, having a streamlined shape and stabilising tail fins. The term zeppelin is a genericized trademark that referred to airships manufactured by the German Zeppelin Company, which built and operated the first rigid airships in the early years of the twentieth century; the initials LZ, for Luftschiff Zeppelin prefixed their craft's serial identifiers. Streamlined rigid airships are referred to as "Zeppelin", because of the fame that this company has acquired due to the number of airships it produced. Hybrid airships fly with a positive aerostatic contribution equal to the empty weight of the system, the variable payload is sustained by propulsion or aerodynamic contribution. Airships are classified according to their method of construction into rigid, semi-rigid and non-rigid types. A rigid airship has a rigid framework covered by envelope; the interior contains one or more gasbags, balloons to provide lift.
Rigid airships are unpressurised and can be made to any size. Most, but not all, of the Ge
Lone Star Flight Museum
The Lone Star Flight Museum, located in Houston, Texas, is an aerospace museum that displays more than 24 significant aircraft, many artifacts related to the history of flight. The museum's collection is rare. Located at Ellington Airport, the museum is housed on about 100,000 ft2 of property, including its own airport ramp; the museum located in Galveston, moved to Houston to avoid a repeat of the devastation suffered during Hurricane Ike. The museum began as a private collection of historic aircraft in 1985. By 1990, that collection had grown enough; the Lone Star Flight Museum, a non-profit organization funded through private donations, was formed for that purpose. The museum reported heavy damage from Hurricane Ike, stating on September 16, 2008, that the hangars and Hall of Fame had received seven to eight feet of water and the lobby three to four. Damaged aircraft include a B-58A and F-100 on loan from the US Air Force Museum, Consolidated PBY-5A, Dehavilland DH-82A, Grumman F3F-2, Lockheed PV-2D, Stinson L-5.
Aircraft flown out of harm's way in advance include their B-17, B-25, DC-3, P-47, F6F, F4U, SBD, PT-17, T-6 and the F8F. Most of the airworthy planes were flown out of the museum prior to the hurricane; those remaining as well as the static displays were destroyed or damaged. The B-58 went to Little Rock Air Force Base; the PBY-5A went to the Pima Space Museum. Following the destruction of Hurricane Ike, the museum made the decision to move to Ellington International Airport in Houston, it is working with the Collings Foundation and Texas Flying Legends to create a combined aviation museum complex. In March 2014, the museum received $7.6 million from FEMA. The museum broke ground at its new location on November 9, 2015. Scheduled to be dedicated on September 1, 2017, the opening was postponed to September 16th due to Hurricane Harvey. On October 23, 2013 a P-51 Mustang owned by the museum crashed in Halls Lake, just south west of the museum. Both the pilot and a paying passenger from the UK were killed in the crash.
The museum's collection participates in airshows across the country. As of 2005, the museum's aircraft annually log more than 40,000 miles of cross-country flying to various air demonstrations; the museum's P-47 Thunderbolt participates in USAF Heritage Flights throughout the year. The USAF Heritage Flight program was established in 1997 to commemorate the Air Force's 50th anniversary, it involves today's state-of-the-art fighters flying in close formation with World War II, Korean and Vietnam era fighters such as the P-51 Mustang and the F-86 Sabre. The flight's mission is to safely and proudly display the evolution of US Air Force airpower and to support the Air Force's recruiting and retention efforts; the museum's North American B-25 Mitchell serves with the Disabled American Veterans program. The DAV Airshow Outreach Program was developed to increase public awareness of disabled veterans and to serve veterans in communities across the nation. Using two B-25 medium bombers, the program reminds.
In 2007, the museum launched its newest program by offering rides in some of its warbirds. The LSFM now operates flights for passengers in the B-17 Flying Fortress, North American B-25 Mitchell, T-6 Texan and the PT-17 Stearman; the Texas Aviation Hall of Fame, located within the museum, honors the contributions of residents or natives of Texas to aviation and spaceflight. Inductees include Howard Hughes, Alan Bean, Senator Lloyd Bentsen, President George H. W. Bush. Bell TAH-1P Cobra 76-22599 – It is on loan from the Vietnam War Flight Museum. Boeing B-17G Flying Fortress 44-85718 Thunderbird Boeing N2S-3 Kaydet 7718 Boeing N2S-5 Kaydet 38490 Cessna 172E Skyhawk – It has been converted to T-41 configuration. Douglas A-1D Skyraider 126882 – It is on loan from the Vietnam War Flight Museum. Douglas TB-26C Invader 44-35371 Douglas DC-3 2213 Douglas A-24B Dauntless 42-54682 – It is painted as an SBD. Fairchild PT-19 Cornell Grumman F6F-5 Hellcat 94204 Grumman TBM Avenger – It was damaged by Hurricane Ike on September 13, 2008.
Lockheed PV-2 Harpoon 37634 – It was damaged by Hurricane Ike on September 13, 2008. North American B-25J Mitchell 44-86734 North American SNJ-5 Texan 85053 Republic P-47D Thunderbolt 44-90368 Tarheel Hal Stinson L-5 Sentinel 42-98798 – It was damaged by Hurricane Ike on September 13, 2008. Supermarine Spitfire TE392 – It was damaged by Hurricane Ike on September 13, 2008. Vought F4U-5N Corsair 121881 Grumman S-2 Tracker – It was damaged by Hurricane Ike on September 13, 2008. Lockheed P2V Neptune Mikoyan-Gurevich MiG-21 North American F-100D Super Sabre – It was damaged by Hurricane Ike on September 13, 2008 and is on loan from the National Museum of the United States Air Force. Scholes International Airport at Galveston Kellar, William H.. "Warbirds Rising: An Update on the Lone Star Flight Museum". Houston History. Retrieved 2 July 2018. Lone Star Flight Museum