A T-tail is an empennage configuration in which the tailplane is mounted to the top of the fin. The arrangement looks like the capital letter T, hence the name; the T-tail differs from the standard configuration in which the tailplane is mounted to the fuselage at the base of the fin. The tailplane is kept well out of the disturbed airflow behind the wing and fuselage, giving smoother and faster airflow over the elevators; this configuration may give more predictable design better pitch control. Responsive pitch control is crucial for aircraft flying at low speed, to allow effective rotation on landing; this configuration allows high performance aerodynamics and an excellent glide ratio as the empennage is less affected by wing and fuselage slipstream. A T-tail has a better effective aspect ratio, less interaction drag than a cruciform tail, a more efficient vertical tail, the horizontal tail plate increasing the aspect ratio of the fin by virtue of the'end plate' effect, reducing turbulence and hence the induced drag of the fin.
The rudder will be more effective due to decreased induced drag. Therefore, the T-tail configuration is popular on gliders, where high performance is essential. A T tailed aircraft is easier to recover from a spin than aircraft with other types of empennage, as the elevator is located above the rudder, thus creating no dead air zone above the elevator where the rudder would be ineffective in spin conditions; the aircraft may be prone to suffering a dangerous deep stall condition, where a stalled wing at high angles of attack may blank the airflow over the tailplane and elevators, thereby leading to loss of pitch control. The American McDonnell F-101 Voodoo jet fighter suffered from this throughout its service life; the vertical stabilizer must be made stronger and stiffer to support the forces generated by the tailplane. The T-tail configuration can cause maintenance concerns; the control runs to the elevators are more complex, elevator surfaces are much more difficult to casually inspect from the ground.
The loss of Alaska Airlines Flight 261 was directly attributed to lax maintenance of the T-tail. In order to mitigate some of these drawbacks, a compromise is possible; the tailplane can be mounted part way up the fin rather than right at the top, known as a cruciform tail. The Sud Aviation Caravelle is an example of an aircraft with this configuration; the T-tail is common on aircraft with engines mounted in nacelles on a high-winged aircraft or on aircraft with the engines mounted on the rear of the fuselage, as it keeps the tail clear of the jet exhaust. These layouts are found in military transport aircraft - such as the Ilyushin Il-76, Airbus A400M and the Boeing C-17 Globemaster III - and regional airliners and business jets such as the Pilatus PC-12, Beechcraft Super King Air, Embraer ERJ, British Aerospace 146, Learjet and Gulfstream families, it is seen in combat aircraft, although the Gloster Javelin, McDonnell F-101 Voodoo, Lockheed F-104 Starfighter interceptors all sported T-tails.
Pelikan tail Twin tail V-tail "T-tails and top technology". Flight International. 13 Oct 1979
Schleicher Ka-4 Rhönlerche II
The Schleicher Ka-4 Rhönlerche II, sometimes called the KA-4 or K 4, is a West German high-wing, strut-braced, two-seat glider, designed by Rudolf Kaiser and produced by Alexander Schleicher GmbH & Co. The Rhönlerche II was first flown 7 December 1953, its design goals were to produce a simple and robust two-seat trainer for school and club use. The design was a success and several hundred were constructed; the Rhönlerche II is constructed with a welded steel tube fuselage and a wooden wing and tail surfaces, all finished in doped aircraft fabric covering. The 13.0 m span wing employs a Goettingen 533 airfoil. The aircraft's landing gear is a fixed monowheel, with a nose skid; the aircraft was issued a US type certificate on 28 September 1960. The Ka-4 was used by clubs and schools in West Germany and by Canadian military gliding clubs stationed in West Germany, including the Lahr Gliding Club at CFB Lahr. One of these aircraft was shipped to Canada and operated by the Cold Lake Gliding Club at CFB Cold Lake and in July 2011 was owned by the Gravelbourg Gliding And Soaring Club, Saskatchewan.
In July 2011 there were still five Ka-4s on the United States Federal Aviation Administration aircraft registry. Aviodrome - 3 Technikmuseum Speyer US Southwest Soaring Museum - 2 Austrian Aviation Museum Data from Sailplane Directory and Type Certificate 7G6, The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du Monde, manufacturerGeneral characteristics Crew: one Capacity: one passenger Length: 7.3 m Wingspan: 13 m Wing area: 16.34 m2 Aspect ratio: 10.3:1 Airfoil: root: Göttingen 533 15.7%, mid: Göttingen 533 15.7%, tip: Göttingen 533 12.5% Empty weight: 220 kg Max takeoff weight: 400 kg Performance Stall speed: 56 km/h Never exceed speed: 170 km/h Rough air speed max: 120 km/h Aerotow speed: 120 km/h Winch launch speed: 90 km/h g limits: +4.7 -2.3 at 170 km/h Maximum glide ratio: 17.5:1 at 78 km/h Rate of sink: 1.1 m/s at 62 km/h Wing loading: 24.5 kg/m2 Aircraft of comparable role and era Scheibe Specht Schweizer SGU 2-22 SZD-10 Czapla Related lists List of gliders Media related to Schleicher Ka 4 at Wikimedia Commons
Stall (fluid dynamics)
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs; the critical angle of attack is about 15 degrees, but it may vary depending on the fluid and Reynolds number. Stalls in fixed-wing flight are experienced as a sudden reduction in lift as the pilot increases the wing's angle of attack and exceeds its critical angle of attack. A stall does not mean that the engine have stopped working, or that the aircraft has stopped moving—the effect is the same in an unpowered glider aircraft. Vectored thrust in manned and unmanned aircraft is used to maintain altitude or controlled flight with wings stalled by replacing lost wing lift with engine or propeller thrust, thereby giving rise to post-stall technology; because stalls are most discussed in connection with aviation, this article discusses stalls as they relate to aircraft, in particular fixed-wing aircraft. The principles of stall discussed here translate to foils in other fluids as well.
A stall is a condition in aerodynamics and aviation such that if the angle of attack increases beyond a certain point lift begins to decrease. The angle at which this occurs is called the critical angle of attack; this critical angle is dependent upon the airfoil section or profile of the wing, its planform, its aspect ratio, other factors, but is in the range of 8 to 20 degrees relative to the incoming wind for most subsonic airfoils. The critical angle of attack is the angle of attack on the lift coefficient versus angle-of-attack curve at which the maximum lift coefficient occurs. Stalling is caused by flow separation which, in turn, is caused by the air flowing against a rising pressure. Whitford describes three types of stall, trailing-edge, leading-edge and thin-aerofoil, each with distinctive Cl~alpha features. For the trailing-edge stall separation begins at small angles of attack near the trailing edge of the wing while the rest of the flow over the wing remains attached; as angle of attack increases, the separated regions on the top of the wing increase in size as the flow separation moves forwards and this hinders the ability of the wing to create lift.
This is shown by the reduction in lift-slope on a Cl~alpha curve as the lift nears its maximum value. The separated flow causes buffeting. Beyond the critical angle of attack, separated flow is so dominant that additional increases in angle of attack cause the lift to fall from its peak value. Piston-engined and early jet transports had good stall behaviour with pre-stall buffet warning and, if ignored, a straight nose-drop for a natural recovery. Wing developments that came with the introduction of turbo-prop engines introduced unacceptable stall behaviour. Leading-edge developments on high-lift wings and the introduction of rear-mounted engines and high-set tailplanes on the next generation of jet transports introduced unacceptable stall behaviour; the probability of achieving the stall speed inadvertently, a hazardous event, had been calculated, in 1965, at about once in every 100,000 flights enough to justify the cost of development and incorporation of warning devices, such as stick shakers, devices to automatically provide an adequate nose-down pitch, such as stick pushers.
When the mean angle of attack of the wings is beyond the stall a spin, an autorotation of a stalled wing, may develop. A spin follows departures in roll and pitch from balanced flight. For example, a roll is damped with an unstalled wing but with wings stalled the damping moment is replaced with a propelling moment; the graph shows that the greatest amount of lift is produced as the critical angle of attack is reached. This angle is 17.5 degrees in this case. In particular, for aerodynamically thick airfoils, the critical angle is higher than with a thin airfoil of the same camber. Symmetric airfoils have lower critical angles; the graph shows that, as the angle of attack exceeds the critical angle, the lift produced by the airfoil decreases. The information in a graph of this kind is gathered using a model of the airfoil in a wind tunnel; because aircraft models are used, rather than full-size machines, special care is needed to make sure that data is taken in the same Reynolds number regime as in free flight.
The separation of flow from the upper wing surface at high angles of attack is quite different at low Reynolds number from that at the high Reynolds numbers of real aircraft. High-pressure wind tunnels are one solution to this problem. In general, steady operation of an aircraft at an angle of attack above the critical angle is not possible because, after exceeding the critical angle, the loss of lift from the wing causes the nose of the aircraft to fall, reducing the angle of attack again; this nose drop, independent of control inputs, indicates the pilot has stalled the aircraft. This graph shows the stall angle, yet in practice most pilot operating handbooks or generic flight manuals describe stalling in terms of airspeed; this is because all aircraft are equipped with an airspeed indicator, but fewer aircraft have an angle of attack indicator. An aircraft's stalling speed is published by the manufacturer for a range of weights and flap positions, but the stalling angle of attack is not published.
As speed reduces, angle of attack has to increase to keep lift
Schleicher Ka 6
The Schleicher Ka 6 is a single-seat glider designed by Rudolf Kaiser, built by Alexander Schleicher GmbH & Co, Germany and is constructed of Spruce and plywood with fabric covering. The design featured a conventional tailplane and elevator, replaced by an all-moving tailplane in the -Pe and Ka 6E variants. Variants built before the -CR and -BR used a main skid as the principal undercarriage, with variants including the Ka 6E using a wheel as the main undercarriage with no nose skid. Other modifications for the Ka 6E include a more aerodynamic fuselage with glassfibre nose and wingroot fairings, longer canopy, modified aluminium airbrakes. Dates of initial airworthiness approval in brackets: Ka 6 - Initial version. Ka 6B Ka 6B-Pe - The Ka 6B with all-flying tailplane. Ka 6BR - The Ka 6B with the main skid removed and a relocated mainwheel. Ka 6CR - The Ka 6C with the main skid removed and a relocated mainwheel. Ka 6CR-Pe - The Ka 6CR with all-flying tailplane. Ka 6E The ultimate Ka-6, with all-flying tailplane, US Southwest Soaring Museum - Ka 6B-Pe and Ka 6e Data from General characteristics Crew: 1 Length: 6.66 m Wingspan: 15 m Height: 1.6 m Wing area: 12.4 m2 Aspect ratio: 18.1 Empty weight: 190 kg Gross weight: 300 kg Performance Maximum speed: 200 km/h Maximum glide ratio: 32:1 at 80 km/h Rate of sink: 0.65 m/s Armament Related lists List of gliders Macfadyen, Tim.
BGA Data sheet for Schleicher Ka-6, BR and CR. Leicester. British Gliding Association. 1 July 2003. British Gliding Association, Ka 6 datasheet British Gliding Association, Ka 6E datasheet Ka6 Sailplane history and information website
Alexander Schleicher GmbH & Co
Alexander Schleicher GmbH & Co is a major manufacturer of sailplanes located in Poppenhausen, near Fulda in Germany. It is the oldest sailplane manufacturer in the world; the company was founded in 1927 by Alexander Schleicher using money that he had won as a pilot in a gliding competition. It grew in size and fame, producing many notable designs including the Anfänger, Zögling, Professor and the Stadt Frankfurt. Meanwhile, the aircraft produced under contract by the company continued to grow in size and complexity, reaching their pinnacle with the DFS Rhönadler and DFS Rhönbussard designed by Hans Jacobs, a huge, three-seat experimental glider built from a design by Alexander Lippisch for the Deutsche Forschungsanstalt für Segelflug. By the time war broke out in Europe in 1939, Schleicher was employing hundreds of workers in what was a major enterprise. During World War II, the factory was used to maintain and repair training gliders for the Hitler Youth, who received flight training at the Wasserkuppe.
At the end of the war in 1945, aviation activities were suspended in allied-occupied Germany, Alexander Schleicher returned to his roots, using his factory to build furniture until the restrictions were lifted in 1951, the company could build sailplanes once more. The company is managed by Alexander's grandsons, Peter Kremer, Ulrich Kremer; the first notable post-war designs were made by Rudolf Kaiser and include: Ka 4 Ka 6 Ka 7 Ka 8 ASK 13 ASK 14 ASK 16 ASK 18 ASK 21 ASK 23 The modern era of using composite materials such as fiberglass and carbon fiber began with single-seat gliders designed by Gerhard Waibel. His designs are: ASW 12 ASW 15 ASW 17 ASW 19 ASW 20 ASW 22 ASW 24 ASW 27 ASW 28 Designers Martin Heide and Michael Greiner have produced: ASH 25 ASH 26 ASG 29 ASH 30 Mi ASH 31 ASG 32 Schleicher company website
The Schleicher K7 Rhönadler, aka Ka-7 or K-7, is a West German high-wing, two-seat, glider, designed by Rudolf Kaiser and produced by Alexander Schleicher GmbH & Co. Referred to as the Ka-7 or K-7, the US Federal Aviation Administration type certificate designates it as the K7; the K7 was intended as a two-place trainer with good performance, a rare combination in trainers of its time. The K7 is constructed with a welded steel tube fuselage, covered in doped aircraft fabric covering; the wing is a wooden structure with a doped fabric covering and employs a Goettingen 533 airfoil at the wing root, transitioning to a Goettingen 533 section at the wing tip. The wing features powerful dive brakes; the landing gear is a fixed monowheel. The earlier Ka-2 variant has a plywood monocoque fuselage. After 550 had been built, the K7 was superseded in production by the Schleicher ASK 13; the K7 can be converted into a K7/13 with a conversion kit to lower the wing to the mid-wing position and installation of a one-piece canopy, rendering the aircraft similar to the ASK-13.
A K7 was flown to a new world multi-place glider speed record for flight around a 500 km triangle of 84 km/h in 1964 in South Africa. Ka-2 Early version with a plywood monocoque fuselage K7 Main production version with a steel tube fuselage. K7/13 K7 converted to a mid-wing arrangement, plus a single piece canopy, to resemble an AS-K 13 Data from Sailplane Directory, Soaring and FAA Type Certificate 7g3, The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du MondeGeneral characteristics Crew: one Capacity: one passenger Length: 8.15 m Wingspan: 16.0 m Wing area: 17.56 m2 Aspect ratio: 14.6:1 Airfoil: root: Goettingen 533, mid: Goettingen 533, tip: Goettingen 533 Empty weight: 282 kg Max takeoff weight: 484.5 kg Performance Stall speed: 59.3 km/h Never exceed speed: 200 km/h Rough air speed max: 130 km/h Aerotow speed: 130 km/h Winch launch speed: 100 km/h g limits: +4 -2 Maximum glide ratio: 26:1 at ~83 km/h Rate of sink: 0.70 m/s at 67 km/h Wing loading: 27.34 kg/m2 Aircraft of comparable role and era Scheibe Bergfalke SZD-9 Bocian Related lists List of gliders Media related to Schleicher K 7 at Wikimedia Commons
Australia the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the world's sixth-largest country by total area; the neighbouring countries are Papua New Guinea and East Timor to the north. The population of 25 million is urbanised and concentrated on the eastern seaboard. Australia's capital is Canberra, its largest city is Sydney; the country's other major metropolitan areas are Melbourne, Brisbane and Adelaide. Australia was inhabited by indigenous Australians for about 60,000 years before the first British settlement in the late 18th century, it is documented. After the European exploration of the continent by Dutch explorers in 1606, who named it New Holland, Australia's eastern half was claimed by Great Britain in 1770 and settled through penal transportation to the colony of New South Wales from 26 January 1788, a date which became Australia's national day; the population grew in subsequent decades, by the 1850s most of the continent had been explored and an additional five self-governing crown colonies established.
On 1 January 1901, the six colonies federated. Australia has since maintained a stable liberal democratic political system that functions as a federal parliamentary constitutional monarchy, comprising six states and ten territories. Being the oldest and driest inhabited continent, with the least fertile soils, Australia has a landmass of 7,617,930 square kilometres. A megadiverse country, its size gives it a wide variety of landscapes, with deserts in the centre, tropical rainforests in the north-east and mountain ranges in the south-east. A gold rush began in Australia in the early 1850s, its population density, 2.8 inhabitants per square kilometre, remains among the lowest in the world. Australia generates its income from various sources including mining-related exports, telecommunications and manufacturing. Indigenous Australian rock art is the oldest and richest in the world, dating as far back as 60,000 years and spread across hundreds of thousands of sites. Australia is a developed country, with the world's 14th-largest economy.
It has a high-income economy, with the world's tenth-highest per capita income. It is a regional power, has the world's 13th-highest military expenditure. Australia has the world's ninth-largest immigrant population, with immigrants accounting for 26% of the population. Having the third-highest human development index and the eighth-highest ranked democracy globally, the country ranks in quality of life, education, economic freedom, civil liberties and political rights, with all its major cities faring well in global comparative livability surveys. Australia is a member of the United Nations, G20, Commonwealth of Nations, ANZUS, Organisation for Economic Co-operation and Development, World Trade Organization, Asia-Pacific Economic Cooperation, Pacific Islands Forum and the ASEAN Plus Six mechanism; the name Australia is derived from the Latin Terra Australis, a name used for a hypothetical continent in the Southern Hemisphere since ancient times. When Europeans first began visiting and mapping Australia in the 17th century, the name Terra Australis was applied to the new territories.
Until the early 19th century, Australia was best known as "New Holland", a name first applied by the Dutch explorer Abel Tasman in 1644 and subsequently anglicised. Terra Australis still saw occasional usage, such as in scientific texts; the name Australia was popularised by the explorer Matthew Flinders, who said it was "more agreeable to the ear, an assimilation to the names of the other great portions of the earth". The first time that Australia appears to have been used was in April 1817, when Governor Lachlan Macquarie acknowledged the receipt of Flinders' charts of Australia from Lord Bathurst. In December 1817, Macquarie recommended to the Colonial Office. In 1824, the Admiralty agreed that the continent should be known by that name; the first official published use of the new name came with the publication in 1830 of The Australia Directory by the Hydrographic Office. Colloquial names for Australia include "Oz" and "the Land Down Under". Other epithets include "the Great Southern Land", "the Lucky Country", "the Sunburnt Country", "the Wide Brown Land".
The latter two both derive from Dorothea Mackellar's 1908 poem "My Country". Human habitation of the Australian continent is estimated to have begun around 65,000 to 70,000 years ago, with the migration of people by land bridges and short sea-crossings from what is now Southeast Asia; these first inhabitants were the ancestors of modern Indigenous Australians. Aboriginal Australian culture is one of the oldest continual civilisations on earth. At the time of first European contact, most Indigenous Australians were hunter-gatherers with complex economies and societies. Recent archaeological finds suggest. Indigenous Australians have an oral culture with spiritual values based on reverence for the land and a belief in the Dreamtime; the Torres Strait Islanders, ethnically Melanesian, obtained their livelihood from seasonal horticulture and the resources of their reefs and seas. The northern coasts and waters of Australia were visited s