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101-409: The Sopwith Bee was a small biplane built in 1916 as a personal aircraft for Harry Hawker , Sopwith's chief test pilot. The Bee was a single-bay biplane powered by a 50 hp (37 kW) Gnome Omega rotary engine, intended for use by Hawker as a runabout and for aerobatics . As with contemporary Sopwith fighter aircraft, great effort was made to concentrate the heaviest components as close to

202-411: A monoplane is its ability to combine greater stiffness with lower weight. Stiffness requires structural depth and where early monoplanes had to have this provided with external bracing, the biplane naturally has a deep structure and is therefore easier to make both light and strong. Rigging wires on non-cantilevered monoplanes are at a much sharper angle, thus providing less tension to ensure stiffness of

303-426: A biplane has the wings positioned directly one above the other. Moving the upper wing forward relative to the lower one is called positive stagger or, more often, simply stagger. It can increase lift and reduce drag by reducing the aerodynamic interference effects between the two wings by a small degree, but more often was used to improve access to the cockpit. Many biplanes have staggered wings. Common examples include

404-519: A deep stall. Two Velocity aircraft crashed due to locked-in deep stalls. Testing revealed that the addition of leading-edge cuffs to the outboard wing prevented the aircraft from getting into a deep stall. The Piper Advanced Technologies PAT-1, N15PT, another canard-configured aircraft, also crashed in an accident attributed to a deep stall. Wind-tunnel testing of the design at the NASA Langley Research Center showed that it

505-448: A dive. In these cases, the wings are already operating at a higher angle of attack to create the necessary force (derived from lift) to accelerate in the desired direction. Increasing the g-loading still further, by pulling back on the controls, can cause the stalling angle to be exceeded, even though the aircraft is flying at a high speed. These "high-speed stalls" produce the same buffeting characteristics as 1g stalls and can also initiate

606-624: A documented jet-kill, as one Lockheed F-94 Starfire was lost while slowing down to 161 km/h (100 mph) – below its stall speed – during an intercept in order to engage the low flying Po-2. Later biplane trainers included the de Havilland Tiger Moth in the Royal Air Force (RAF), Royal Canadian Air Force (RCAF) and others and the Stampe SV.4 , which saw service postwar in the French and Belgian Air Forces. The Stearman PT-13

707-513: A faster and more comfortable successor to the Dragon. As the available engine power and speed increased, the drag penalty of external bracing increasingly limited aircraft performance. To fly faster, it would be necessary to reduce external bracing to create an aerodynamically clean design; however, early cantilever designs were either too weak or too heavy. The 1917 Junkers J.I sesquiplane utilized corrugated aluminum for all flying surfaces, with

808-477: A helicopter blade may incur flow that reverses (compared to the direction of blade movement), and thus includes rapidly changing angles of attack. Oscillating (flapping) wings, such as those of insects like the bumblebee —may rely almost entirely on dynamic stall for lift production, provided the oscillations are fast compared to the speed of flight, and the angle of the wing changes rapidly compared to airflow direction. Stall delay can occur on airfoils subject to

909-408: A high angle of attack and a three-dimensional flow. When the angle of attack on an airfoil is increasing rapidly, the flow will remain substantially attached to the airfoil to a significantly higher angle of attack than can be achieved in steady-state conditions. As a result, the stall is delayed momentarily and a lift coefficient significantly higher than the steady-state maximum is achieved. The effect

1010-432: A low wing loading , combining both large wing area with light weight. Obtaining a large enough wing area without the wings being long, and thus dangerously flexible was more readily accomplished with a biplane. The smaller biplane wing allows greater maneuverability . Following World War I, this helped extend the era of the biplane and, despite the performance disadvantages, most fighter aircraft were biplanes as late as

1111-409: A lower speed. A fixed-wing aircraft can be made to stall in any pitch attitude or bank angle or at any airspeed but deliberate stalling is commonly practiced by reducing the speed to the unaccelerated stall speed, at a safe altitude. Unaccelerated (1g) stall speed varies on different fixed-wing aircraft and is represented by colour codes on the airspeed indicator . As the plane flies at this speed,

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1212-507: A minimum of struts; however, it was relatively easy to damage the thin metal skin and required careful handling by ground crews. The 1918 Zeppelin-Lindau D.I fighter was an all-metal stressed-skin monocoque fully cantilevered biplane, but its arrival had come too late to see combat use in the conflict. By the 1930s, biplanes had reached their performance limits, and monoplanes become increasingly predominant, particularly in continental Europe where monoplanes had been increasingly common from

1313-417: A multi-engine non-centreline thrust aircraft), or from less likely sources such as severe turbulence. The net effect is that one wing is stalled before the other and the aircraft descends rapidly while rotating, and some aircraft cannot recover from this condition without correct pilot control inputs (which must stop yaw) and loading. A new solution to the problem of difficult (or impossible) stall-spin recovery

1414-432: 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 constant until the critical angle is reached. The airspeed at which this angle is reached is the (1g, unaccelerated) stalling speed of the aircraft in that particular configuration. Deploying flaps /slats decreases the stall speed to allow the aircraft to take off and land at

1515-482: A risk of accelerated stalls. When an aircraft such as an Mitsubishi MU-2 is flying close to its stall speed, the sudden application of full power may cause it to roll, creating the same aerodynamic conditions that induce an accelerated stall in turning flight even if the pilot did not deliberately initiate a turn. Pilots of such aircraft are trained to avoid sudden and drastic increases in power at low altitude and low airspeed, as an accelerated stall under these conditions

1616-500: A small loss in altitude (20–30 m/66–98 ft). It is taught and practised in order for pilots to recognize, avoid, and recover from stalling the aircraft. A pilot is required to demonstrate competency in controlling an aircraft during and after a stall for certification in the United States, and it is a routine maneuver for pilots when getting to know the handling of an unfamiliar aircraft type. The only dangerous aspect of

1717-473: A somewhat unusual sesquiplane arrangement, possessing a more substantial lower wing with two spars that eliminated the flutter problems encountered by single-spar sesquiplanes. The stacking of wing planes was suggested by Sir George Cayley in 1843. Hiram Maxim adopted the idea for his steam-powered test rig, which lifted off but was held down by safety rails, in 1894. Otto Lilienthal designed and flew two different biplane hang gliders in 1895, though he

1818-473: A spin if there is also any yawing. Different aircraft types have different stalling characteristics but they only have to be good enough to satisfy their particular Airworthiness authority. For example, the Short Belfast heavy freighter had a marginal nose drop which was acceptable to the Royal Air Force . When the aircraft were sold to a civil operator they had to be fitted with a stick pusher to meet

1919-401: A stall is a lack of altitude for recovery. A special form of asymmetric stall in which the aircraft also rotates about its yaw axis is called a spin . A spin can occur if an aircraft is stalled and there is an asymmetric yawing moment applied to it. This yawing moment can be aerodynamic (sideslip angle, rudder, adverse yaw from the ailerons), thrust related (p-factor, one engine inoperative on

2020-418: Is 19% higher than V s . According to Federal Aviation Administration (FAA) terminology, the above example illustrates a so-called turning flight stall , while the term accelerated is used to indicate an accelerated turning stall only, that is, a turning flight stall where the airspeed decreases at a given rate. The tendency of powerful propeller aircraft to roll in reaction to engine torque creates

2121-411: Is a two bay biplane , the extra bay being necessary as overlong bays are prone to flexing and can fail. The SPAD S.XIII fighter, while appearing to be a two bay biplane, has only one bay, but has the midpoints of the rigging braced with additional struts; however, these are not structurally contiguous from top to bottom wing. The Sopwith 1½ Strutter has a W shape cabane, however as it does not connect

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2222-438: Is a condition in aerodynamics and aviation such that if the angle of attack on an aircraft increases beyond a certain point, then lift begins to decrease. The angle at which this occurs is called the critical angle of attack . If the angle of attack increases beyond the critical value, the lift decreases and the aircraft descends, further increasing the angle of attack and causing further loss of lift. The critical angle of attack

2323-497: Is better known for his monoplanes. By 1896 a group of young men in the United States, led by Octave Chanute , were flying hang gliders including biplanes and concluded that the externally braced biplane offered better prospects for powered flight than the monoplane. In 1903, the Wright Flyer biplane became the first successful powered aeroplane. Throughout the pioneer years, both biplanes and monoplanes were common, but by

2424-429: 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,

2525-417: Is dependent upon the airfoil section or profile of the wing, its planform , its aspect ratio , and other factors, but is typically in the range of 8 to 20 degrees relative to the incoming wind ( relative wind ) for most subsonic airfoils. The critical angle of attack is the angle of attack on the lift coefficient versus angle-of-attack (Cl~alpha) curve at which the maximum lift coefficient occurs. Stalling

2626-480: Is increased when the wing surfaces are contaminated with ice or frost creating a rougher surface, and heavier airframe due to ice accumulation. Stalls occur not only at slow airspeed, but at any speed when the wings exceed their critical angle of attack. Attempting to increase the angle of attack at 1g by moving the control column back normally causes the aircraft to climb. However, aircraft often experience higher g-forces, such as when turning steeply or pulling out of

2727-421: Is increased. Early speculation on reasons for the crash of Air France Flight 447 blamed an unrecoverable deep stall, since it descended in an almost flat attitude (15°) at an angle of attack of 35° or more. However, it was held in a stalled glide by the pilots, who held the nose up amid all the confusion of what was actually happening to the aircraft. Canard-configured aircraft are also at risk of getting into

2828-624: Is much more common. The space enclosed by a set of interplane struts is called a bay (much as the architectural form is used), hence a biplane or triplane with one set of such struts connecting the wings on each side of the aircraft is a single-bay biplane . This provided sufficient strength for smaller aircraft such as the First World War -era Fokker D.VII fighter and the Second World War de Havilland Tiger Moth basic trainer. The larger two-seat Curtiss JN-4 Jenny

2929-447: Is provided by the ballistic parachute recovery system. The most common stall-spin scenarios occur on takeoff ( departure stall) and during landing (base to final turn) because of insufficient airspeed during these maneuvers. Stalls also occur during a go-around manoeuvre if the pilot does not properly respond to the out-of-trim situation resulting from the transition from low power setting to high power setting at low speed. Stall speed

3030-433: Is reduced by the wing and nacelle wakes. He also gives a definition that relates deep stall to a locked-in condition where recovery is impossible. This is a single value of α {\textstyle \alpha } , for a given aircraft configuration, where there is no pitching moment, i.e. a trim point. Typical values both for the range of deep stall, as defined above, and the locked-in trim point are given for

3131-423: Is very difficult to safely recover from. A notable example of an air accident involving a low-altitude turning flight stall is the 1994 Fairchild Air Force Base B-52 crash . Dynamic stall is a non-linear unsteady aerodynamic effect that occurs when airfoils rapidly change the angle of attack. The rapid change can cause a strong vortex to be shed from the leading edge of the aerofoil, and travel backwards above

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3232-536: The Bristol M.1 , that caused even those with relatively high performance attributes to be overlooked in favour of 'orthodox' biplanes, and there was an allegedly widespread belief held at that time that monoplane aircraft were inherently unsafe during combat. Between the years of 1914 and 1925, a clear majority of new aircraft introduced were biplanes; however, during the latter years of the First World War,

3333-560: The Douglas DC-9 Series ;10 by Schaufele. These values are from wind-tunnel tests for an early design. The final design had no locked-in trim point, so recovery from the deep stall region was possible, as required to meet certification rules. Normal stall beginning at the "g break" (sudden decrease of the vertical load factor ) was at α = 18 ∘ {\textstyle \alpha =18^{\circ }} , deep stall started at about 30°, and

3434-703: The Grumman Ag Cat are available in upgraded versions with turboprop engines. The two most produced biplane designs were the 1913 British Avro 504 of which 11,303 were built, and the 1928 Soviet Polikarpov Po-2 of which over 20,000 were built, with the Po-2 being the direct replacement for the Soviet copy of the Avro 504. Both were widely used as trainers. The Antonov An-2 was very successful too, with more than 18,000 built. Although most ultralights are monoplanes,

3535-617: The Lite Flyer Biplane, the Sherwood Ranger , and the Murphy Renegade . The feathered dinosaur Microraptor gui glided, and perhaps even flew, on four wings, which may have been configured in a staggered sesquiplane arrangement. This was made possible by the presence of flight feathers on both forelimbs and hindlimbs, with the feathers on the forelimbs opening to a greater span. It has been suggested that

3636-556: The Nieuport-Delage NiD 42 / 52 / 62 series, Fokker C.Vd & e, and Potez 25 , all serving across a large number of air forces. In the general aviation sector, aircraft such as the Waco Custom Cabin series proved to be relatively popular. The Saro Windhover was a sesquiplane with the upper wing smaller than the lower, which was a much rarer configuration than the reverse. The Pfalz D.III also featured

3737-477: The critical (stall) angle of attack . This speed is called the "stall speed". An aircraft flying at its stall speed cannot climb, and an aircraft flying below its stall speed cannot stop descending. Any attempt to do so by increasing angle of attack, without first increasing airspeed, will result in a stall. The actual stall speed will vary depending on the airplane's weight, altitude, configuration, and vertical and lateral acceleration. Propeller slipstream reduces

3838-497: The de Havilland Tiger Moth , Bücker Bü 131 Jungmann and Travel Air 2000 . Alternatively, the lower wing can instead be moved ahead of the upper wing, giving negative stagger, and similar benefits. This is usually done in a given design for structural reasons, or to improve visibility. Examples of negative stagger include the Sopwith Dolphin , Breguet 14 and Beechcraft Staggerwing . However, positive (forward) stagger

3939-408: The fluid , foil – including its shape, size, and finish – and Reynolds number . Stalls in fixed-wing aircraft are often experienced as a sudden reduction in lift. It may be caused either by the pilot increasing the wing's angle of attack or by a decrease in the critical angle of attack. The latter may be due to slowing down (below stall speed ) or the accretion of ice on the wings (especially if

4040-425: The weight of the aircraft plus extra lift to provide the centripetal force necessary to perform the turn: where: To achieve the extra lift, the lift coefficient , and so the angle of attack, will have to be higher than it would be in straight and level flight at the same speed. Therefore, given that the stall always occurs at the same critical angle of attack, by increasing the load factor (e.g. by tightening

4141-514: The CR.42 was able to achieve success in the defensive night fighter role against RAF bombers that were striking industrial targets throughout northern Italy. The British Fleet Air Arm operated the Fairey Swordfish torpedo bomber from its aircraft carriers, and used the type in the anti-submarine warfare role until the end of the conflict, largely due to their ability to operate from

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4242-528: The Caribou , performed the first non-stop flight between the Canadian mainland and Britain in 30 hours 55 minutes, although the intended target for this long distance flight had originally been Baghdad , Iraq . Despite its relative success, British production of the Dragon was quickly ended when in favour of the more powerful and elegant de Havilland Dragon Rapide , which had been specifically designed to be

4343-515: The First World War, the British Royal Aircraft Factory developed airfoil section wire named RAFwire in an effort to both increase the strength and reduce the drag. Four types of wires are used in the biplane wing structure. Drag wires inside the wings prevent the wings from being folded back against the fuselage, running inside a wing bay from the forward inboard corner to the rear outboard corner. Anti-drag wires prevent

4444-577: The French Nieuport 17 and German Albatros D.III , offered lower drag than a conventional biplane while being stronger than a monoplane. During the Interwar period , numerous biplane airliners were introduced. The British de Havilland Dragon was a particularly successful aircraft, using straightforward design to could carry six passengers on busy routes, such as London-Paris services. During early August 1934, one such aircraft, named Trail of

4545-661: The Germans had been experimenting with a new generation of monoplanes, such as the Fokker D.VIII , that might have ended the biplane's advantages earlier had the conflict not ended when it had. The French were also introducing the Morane-Saulnier AI , a strut-braced parasol monoplane , although the type was quickly relegated to the advanced trainer role following the resolution of structural issues. Sesquiplane types, which were biplanes with abbreviated lower wings such as

4646-404: The V S values above, always refers to straight and level flight, where the load factor is equal to 1g. However, if the aircraft is turning or pulling up from a dive, additional lift is required to provide the vertical or lateral acceleration, and so the stall speed is higher. An accelerated stall is a stall that occurs under such conditions. In a banked turn , the lift required is equal to

4747-601: The aircraft from recovering from the stall. Aircraft with rear-mounted nacelles may also exhibit a loss of thrust . T-tail propeller aircraft are generally resistant to deep stalls, because the prop wash increases airflow over the wing root, but may be fitted with a precautionary vertical tail booster during flight testing , as happened with the A400M . Trubshaw gives a broad definition of deep stall as penetrating to such angles of attack α {\textstyle \alpha } that pitch control effectiveness

4848-576: The aircraft's centre of gravity in order to optimise manoeverability: this necessitated a large semi-circular cutout in the trailing edge of the upper wing to accommodate the pilot. Lateral control was achieved by wing warping . The Bee was subsequently fitted with a single synchronised Vickers .303 machine gun, possibly with a view to meeting the Admiralty's requirement for a small scout aircraft capable of operating from torpedo-boat destroyers , but this came to nothing and no further development of

4949-425: 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 normally used, rather than full-size machines, special care is needed to make sure that data is taken in the same Reynolds number regime (or scale speed) as in free flight. The separation of flow from

5050-438: The angle of attack must be increased to prevent any loss of altitude or gain in airspeed (which corresponds to the stall angle described above). The pilot will notice the flight controls have become less responsive and may also notice some buffeting, a result of the turbulent air separated from the wing hitting the tail of the aircraft. In most light aircraft , as the stall is reached, the aircraft will start to descend (because

5151-575: The civil requirements. Some aircraft may naturally have very good behaviour well beyond what is required. For example, first generation jet transports have been described as having an immaculate nose drop at the stall. Loss of lift on one wing is acceptable as long as the roll, including during stall recovery, doesn't exceed about 20 degrees, or in turning flight the roll shall not exceed 90 degrees bank. If pre-stall warning followed by nose drop and limited wing drop are naturally not present or are deemed to be unacceptably marginal by an Airworthiness authority

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5252-608: The competition aerobatics role and format for such a biplane well-defined by the mid-1930s by the Udet U 12 Flamingo and Waco Taperwing . The Pitts Special dominated aerobatics for many years after World War II and is still in production. The vast majority of biplane designs have been fitted with reciprocating engines . Exceptions include the Antonov An-3 and WSK-Mielec M-15 Belphegor , fitted with turboprop and turbofan engines respectively. Some older biplane designs, such as

5353-417: The crash of the prototype BAC 1-11 G-ASHG on 22 October 1963, which killed its crew. This led to changes to the aircraft, including the installation of a stick shaker (see below) to clearly warn the pilot of an impending stall. Stick shakers are now a standard part of commercial airliners. Nevertheless, the problem continues to cause accidents; on 3 June 1966, a Hawker Siddeley Trident (G-ARPY),

5454-479: The critical angle of attack is reached (which in early-20th century aviation was called the "burble point"). This angle is 17.5 degrees in this case, but it varies from airfoil to airfoil. In particular, for aerodynamically thick airfoils (thickness to chord ratios of around 10%), the critical angle is higher than with a thin airfoil of the same camber . Symmetric airfoils have lower critical angles (but also work efficiently in inverted flight). The graph shows that, as

5555-404: The deep stall after deploying the anti-spin parachute but crashed after being unable to jettison the chute or relight the engines. One of the test pilots was unable to escape from the aircraft in time and was killed. On 26 July 1993, a Canadair CRJ-100 was lost in flight testing due to a deep stall. It has been reported that a Boeing 727 entered a deep stall in a flight test, but the pilot

5656-444: The downwash pattern associated with swept/tapered wings. To delay tip stall the outboard wing is given washout to reduce its angle of attack. The root can also be modified with a suitable leading-edge and airfoil section to make sure it stalls before the tip. However, when taken beyond stalling incidence the tips may still become fully stalled before the inner wing despite initial separation occurring inboard. This causes pitch-up after

5757-549: The end of World War I . At the start of World War II , several air forces still had biplane combat aircraft in front line service but they were no longer competitive, and most were used in niche roles, such as training or shipboard operation, until shortly after the end of the war. The British Gloster Gladiator biplane, the Italian Fiat CR.42 Falco and Soviet I-153 sesquiplane fighters were all still operational after 1939. According to aviation author Gianni Cattaneo,

5858-401: The hind limbs could not have opened out sideways but in flight would have hung below and slightly behind the fore limbs. Stall (fluid dynamics) In fluid dynamics , a stall is a reduction in the lift coefficient generated by a foil as angle of attack exceeds its critical value . The critical angle of attack is typically about 15°, but it may vary significantly depending on

5959-669: The ice is rough). A stall does not mean that the engine(s) have stopped working, or that the aircraft has stopped moving—the effect is the same even in an unpowered glider aircraft . Vectored thrust in 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 commonly discussed in connection with aviation , this article discusses stalls as they relate mainly to aircraft, in particular fixed-wing aircraft. The principles of stall discussed here translate to foils in other fluids as well. A stall

6060-520: The less the interference, but the spacing struts must be longer, and the gap must be extremely large to reduce it appreciably. As engine power and speeds rose late in World War I , thick cantilever wings with inherently lower drag and higher wing loading became practical, which in turn made monoplanes more attractive as it helped solve the structural problems associated with monoplanes, but offered little improvement for biplanes. The default design for

6161-432: The lift to fall from its peak value. Piston-engined and early jet transports had very 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

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6262-413: The locked-in unrecoverable trim point was at 47°. The very high α {\textstyle \alpha } for a deep stall locked-in condition occurs well beyond the normal stall but can be attained very rapidly, as the aircraft is unstable beyond the normal stall and requires immediate action to arrest it. The loss of lift causes high sink rates, which, together with the low forward speed at

6363-639: The low speeds and simple construction involved have inspired a small number of biplane ultralights, such as Larry Mauro's Easy Riser (1975–). Mauro also made a version powered with solar cells driving an electric motor called the Solar Riser . Mauro's Easy Riser was used by "Father Goose", Bill Lishman . Other biplane ultralights include the Belgian-designed Aviasud Mistral , the German FK12 Comet (1997–),

6464-412: The main wings can support ailerons , while flaps are more usually positioned on the lower wing. Bracing is nearly always added between the upper and lower wings, in the form of interplane struts positioned symmetrically on either side of the fuselage and bracing wires to keep the structure from flexing, where the wings are not themselves cantilever structures. The primary advantage of the biplane over

6565-409: The mean angle of attack of the wings is beyond the stall a spin , which is an autorotation of a stalled wing, may develop. A spin follows departures in roll, yaw and pitch from balanced flight. For example, a roll is naturally 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

6666-411: The mid-1930s. Specialist sports aerobatic biplanes are still made in small numbers. Biplanes suffer aerodynamic interference between the two planes when the high pressure air under the top wing and the low pressure air above the lower wing cancel each other out. This means that a biplane does not in practice obtain twice the lift of the similarly-sized monoplane. The farther apart the wings are spaced

6767-573: The most famed copies was the Siemens-Schuckert D.I . The Albatros D.III and D.V , which had also copied the general layout from Nieuport, similarly provided the backbone of the German forces during the First World War. The Albatros sesquiplanes were widely acclaimed by their aircrews for their maneuverability and high rate of climb. During interwar period , the sesquiplane configuration continued to be popular, with numerous types such as

6868-434: The next generation of jet transports, also introduced unacceptable stall behaviour. The probability of achieving the stall speed inadvertently, a potentially hazardous event, had been calculated, in 1965, at about once in every 100,000 flights, often enough to justify the cost of development of warning devices, such as stick shakers, and devices to automatically provide an adequate nose-down pitch, such as stick pushers. When

6969-609: The night ground attack role throughout the Second World War. In the case of the Po-2, production of the aircraft continued even after the end of the conflict, not ending until around 1952. A significant number of Po-2s were fielded by the Korean People's Air Force during the Korean War , inflicting serious damage during night raids on United Nations bases. The Po-2 is also the only biplane to be credited with

7070-430: The normal stall, give a high α {\textstyle \alpha } with little or no rotation of the aircraft. BAC 1-11 G-ASHG, during stall flight tests before the type was modified to prevent a locked-in deep-stall condition, descended at over 10,000 feet per minute (50 m/s) and struck the ground in a flat attitude moving only 70 feet (20 m) forward after initial impact. Sketches showing how

7171-486: The outbreak of the First World War biplanes had gained favour after several monoplane structural failures resulted in the RFC's "Monoplane Ban" when all monoplanes in military service were grounded, while the French also withdrew most monoplanes from combat roles and relegated them to training. Figures such as aviation author Bruce observed that there was an apparent prejudice held even against newly-designed monoplanes, such as

7272-406: The outer wing. On a biplane, since the angles are closer to the ideal of being in direct line with the forces being opposed, the overall structure can then be made stiffer. Because of the reduced stiffness, wire braced monoplanes often had multiple sets of flying and landing wires where a biplane could easily be built with one bay, with one set of landing and flying wires. The extra drag from the wires

7373-449: The pilot has actually stalled the aircraft. This graph shows the stall angle, yet in practice most pilot operating handbooks (POH) 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 (and is required for certification by flight testing) for

7474-473: The real life counterparts often tend to overestimate the aerodynamic stall angle of attack. 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

7575-657: The relatively compact decks of escort carriers . Its low stall speed and inherently tough design made it ideal for operations even in the often severe mid-Atlantic weather conditions. By the end of the conflict, the Swordfish held the distinction of having caused the destruction of a greater tonnage of Axis shipping than any other Allied aircraft. Both the German Heinkel He 50 and the Soviet Polikarpov Po-2 were used with relative success in

7676-499: The same overall strength and is therefore lighter. A given area of wing also tends to be shorter, reducing bending moments on the spars, which then allow them to be more lightly built as well. The biplane does however need extra struts to maintain the gap between the wings, which add both weight and drag. The low power supplied by the engines available in the first years of aviation limited aeroplanes to fairly low speeds. This required an even lower stalling speed, which in turn required

7777-502: The same portion of the atmosphere and thus interfere with each other's behaviour. In a biplane configuration with no stagger from the upper wing to the lower wing, the lift coefficient is reduced by 10 to 15 percent compared to that of a monoplane using the same airfoil and aspect ratio . The lower wing is usually attached to the fuselage , while the upper wing is raised above the fuselage with an arrangement of cabane struts , although other arrangements have been used. Either or both of

7878-422: The separated regions on the top of the wing increase in size as the flow separation moves forward, 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 usually causes buffeting. Beyond the critical angle of attack, separated flow is so dominant that additional increases in angle of attack cause

7979-728: The series of Nieuport military aircraft—from the Nieuport 10 through to the Nieuport 27 which formed the backbone of the Allied air forces between 1915 and 1917. The performance of the Nieuport sesquiplanes was so impressive that the Idflieg (the German Inspectorate of flying troops) requested their aircraft manufacturers to produce copies, an effort which was aided by several captured aircraft and detailed drawings; one of

8080-458: The stall and entry to a super-stall on those aircraft with super-stall characteristics. Span-wise flow of the boundary layer is also present on swept wings and causes tip stall. The amount of boundary layer air flowing outboard can be reduced by generating vortices with a leading-edge device such as a fence, notch, saw tooth or a set of vortex generators behind the leading edge. Fixed-wing aircraft can be equipped with devices to prevent or postpone

8181-502: The stall speed by energizing the flow over the wings. Speed definitions vary and include: An airspeed indicator, for the purpose of flight-testing, may have the following markings: the bottom of the white arc indicates V S0 at maximum weight, while the bottom of the green arc indicates V S1 at maximum weight. While an aircraft's V S speed is computed by design, its V S0 and V S1 speeds must be demonstrated empirically by flight testing. The normal stall speed, specified by

8282-437: The stalling behaviour has to be made good enough with airframe modifications or devices such as a stick shaker and pusher. These are described in "Warning and safety devices". Stalls depend only on angle of attack, not airspeed . However, the slower an aircraft flies, the greater the angle of attack it needs to produce lift equal to the aircraft's weight. As the speed decreases further, at some point this angle will be equal to

8383-423: The turn) the critical angle will be reached at a higher airspeed: where: The table that follows gives some examples of the relation between the angle of bank and the square root of the load factor. It derives from the trigonometric relation ( secant ) between L {\displaystyle L} and W {\displaystyle W} . For example, in a turn with bank angle of 45°, V st

8484-636: The type was carried out. The aircraft was sometimes referred to as the Tadpole . Data from Mason General characteristics Armament Biplane Biplanes offer several advantages over conventional cantilever monoplane designs: they permit lighter wing structures, low wing loading and smaller span for a given wing area. However, interference between the airflow over each wing increases drag substantially, and biplanes generally need extensive bracing, which causes additional drag. Biplanes are distinguished from tandem wing arrangements, where

8585-400: The upper and lower wings together. The sesquiplane is a type of biplane where one wing (usually the lower) is significantly smaller than the other. The word, from Latin, means "one-and-a-half wings". The arrangement can reduce drag and weight while retaining the biplane's structural advantages. The lower wing may have a significantly shorter span, or a reduced chord . Examples include

8686-505: 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. In particular at high Reynolds numbers the flow tends to stay attached to the airfoil for longer because the inertial forces are dominant with respect to the viscous forces which are responsible for the flow separation ultimately leading to the aerodynamic stall. For this reason wind tunnel results carried out at lower speeds and on smaller scale models of

8787-412: The wing is no longer producing enough lift to support the aircraft's weight) and the nose will pitch down. Recovery from the stall involves lowering the aircraft nose, to decrease the angle of attack and increase the air speed, until smooth air-flow over the wing is restored. Normal flight can be resumed once recovery is complete. The maneuver is normally quite safe, and, if correctly handled, leads to only

8888-411: The wing tip, well aft of the c.g. If the tip stalls first the balance of the aircraft is upset causing dangerous nose pitch up . Swept wings have to incorporate features which prevent pitch-up caused by premature tip stall. A swept wing has a higher lift coefficient on its outer panels than on the inner wing, causing them to reach their maximum lift capability first and to stall first. This is caused by

8989-434: The wing wake blankets the tail may be misleading if they imply that deep stall requires a high body angle. Taylor and Ray show how the aircraft attitude in the deep stall is relatively flat, even less than during the normal stall, with very high negative flight-path angles. Effects similar to deep stall had been known to occur on some aircraft designs before the term was coined. A prototype Gloster Javelin ( serial WD808 )

9090-415: The wing. The vortex, containing high-velocity airflows, briefly increases the lift produced by the wing. As soon as it passes behind the trailing edge, however, the lift reduces dramatically, and the wing is in normal stall. Dynamic stall is an effect most associated with helicopters and flapping wings, though also occurs in wind turbines, and due to gusting airflow. During forward flight, some regions of

9191-419: The wings are placed forward and aft, instead of above and below. The term is also occasionally used in biology , to describe the wings of some flying animals . In a biplane aircraft, two wings are placed one above the other. Each provides part of the lift, although they are not able to produce twice as much lift as a single wing of similar size and shape because the upper and the lower are working on nearly

9292-434: The wings from folding up, and run from the underside of the outer wing to the lower wing root. Conversely, landing wires prevent the wings from sagging, and resist the forces when an aircraft is landing, and run from the upper wing centre section to outboard on the lower wings. Additional drag and anti-drag wires may be used to brace the cabane struts which connect the fuselage to the wings, and interplane struts, which connect

9393-421: The wings from moving forward when the aircraft stops and run the opposite direction to the drag wires. Both of these are usually hidden within the wings, and if the structure is sufficiently stiff otherwise, may be omitted in some designs. Indeed many early aircraft relied on the fabric covering of the wing to provide this rigidity, until higher speeds and forces made this inadequate. Externally, lift wires prevent

9494-604: The wings to each other, it does not add to the number of bays. Large transport and bombing biplanes often needed still more bays to provide sufficient strength. These are often referred to as multi-bay biplanes . A small number of biplanes, such as the Zeppelin-Lindau D.I have no interplane struts and are referred to as being strutless . Because most biplanes do not have cantilever structures, they require rigging wires to maintain their rigidity. Early aircraft used simple wire (either braided or plain), however during

9595-640: Was lost to deep stall ; deep stall is suspected to be cause of another Trident (the British European Airways Flight 548 G-ARPI ) crash – known as the "Staines Disaster" – on 18 June 1972, when the crew failed to notice the conditions and had disabled the stall-recovery system. On 3 April 1980, a prototype of the Canadair Challenger business jet crashed after initially entering a deep stall from 17,000 ft and having both engines flame-out. It recovered from

9696-404: Was able to rock the airplane to increasingly higher bank angles until the nose finally fell through and normal control response was recovered. The crash of West Caribbean Airways Flight 708 in 2005 was also attributed to a deep stall. Deep stalls can occur at apparently normal pitch attitudes, if the aircraft is descending quickly enough. The airflow is coming from below, so the angle of attack

9797-420: Was first noticed on propellers . A deep stall (or super-stall ) is a dangerous type of stall that affects certain aircraft designs, notably jet aircraft with a T-tail configuration and rear-mounted engines. In these designs, the turbulent wake of a stalled main wing, nacelle-pylon wakes and the wake from the fuselage "blanket" the horizontal stabilizer, rendering the elevators ineffective and preventing

9898-578: Was lost in a crash on 11 June 1953 to a "locked-in" stall. However, Waterton states that the trimming tailplane was found to be the wrong way for recovery. Low-speed handling tests were being done to assess a new wing. Handley Page Victor XL159 was lost to a "stable stall" on 23 March 1962. It had been clearing the fixed droop leading edge with the test being stall approach, landing configuration, C of G aft. The brake parachute had not been streamed, as it may have hindered rear crew escape. The name "deep stall" first came into widespread use after

9999-423: Was not enough to offset the aerodynamic disadvantages from having two airfoils interfering with each other however. Strut braced monoplanes were tried but none of them were successful, not least due to the drag from the number of struts used. The structural forces acting on the spars of a biplane wing tend to be lower as they are divided between four spars rather than two, so the wing can use less material to obtain

10100-402: Was vulnerable to a deep stall. In the early 1980s, a Schweizer SGS 1-36 sailplane was modified for NASA 's controlled deep-stall flight program. Wing sweep and taper cause stalling at the tip of a wing before the root. The position of a swept wing along the fuselage has to be such that the lift from the wing root, well forward of the aircraft center of gravity (c.g.), must be balanced by

10201-777: Was widely used by the United States Army Air Force (USAAF) while the US Navy operated the Naval Aircraft Factory N3N . In later civilian use in the US, the Stearman became particularly associated with stunt flying such as wing-walking , and with crop dusting, where its compactness worked well at low levels, where it had to dodge obstacles. Modern biplane designs still exist in specialist roles such as aerobatics and agricultural aircraft with

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