Flying wing
Encyclopedia
A flying wing is a tailless
fixed-wing aircraft
which has no definite fuselage
, with most of the crew, payload and equipment being housed inside the main wing structure.
A flying wing may have various small protuberances such as pods, nacelles, blisters, booms, vertical stabilizer
s (tail fins), or undercarriage. Some aircraft have no fuselage but do have a separate horizontal stabilizer surface mounted on one or more booms; these are also commonly referred to as flying wings, although this is not strictly correct. An example of such a design is the Northrop X216H.
Tailless aircraft
have been experimented with since the earliest attempts to fly. But it was not until the deep-chord monoplane
wing became practicable after World War I that the opportunity to discard any form of fuselage
arose and the true flying wing could be realised.
Hugo Junkers
patented a wing-only air transport concept in 1910. He saw it as a natural solution to the problem of building an airliner
large enough to carry a reasonable passenger load and enough fuel to cross the Atlantic
in regular service. He believed that the flying wing's potentially large internal volume and low drag made it an obvious design for this role. In 1919 he started work on his "Giant" JG1 design, intended to seat passengers within thick wings, but two years later the Allied Aeronautical Commission of Control ordered the incomplete JG1 destroyed for exceeding post-war size limits on German aircraft. Junkers conceived futuristic flying wings for up to 1,000 passengers; the nearest this came to realization was in the 1931 Junkers G-38 34-seater Grossflugzeug airliner which featured a large thick-chord wing providing space for fuel, engines and two passenger cabins. However, it still required a short fuselage to house the crew and additional passengers.
The flying wing configuration was studied extensively in the 1930s and 1940s, notably by Jack Northrop and Cheston L. Eshelman in the United States
, and Alexander Lippisch
and the Horten brothers
in Germany
.
Soviet designers such as Boris Ivanovich Cheranovsky started research independently and in secret under Stalin after the 1920s. With significant breakthrough in materials and construction methods, aircraft such as the BICh-3
, BICh-14, BICh-7A and so on became possible. Men like Chizhevskij and Antonov also came into the spotlight of the communist party by designing aircraft such as the tail-less BOK-5 (Chizhevskij) and OKA-33 (the first ever built by Antonov) which were designated as "motorized gliders" due to their similarity to popular gliders of the time. The BICh-11 by Cheranovsky in 1932 was competing with the Horten brothers H1 (and Adolf Galland) at the Ninth Glider Competitions in 1933, but did not demonstrate in the 1936 summer Olympics in Berlin. The BICh-26
was one of the first attempts at a supersonic jet flying-wing aircraft, ahead of its time in 1948 the airplane was not accepted by the military and the design died with Cheranovsky.
Early examples of true flying wings include:
Several late-war German military designs were based on the flying wing concept (or variations of it) as a proposed solution to extend the range of the otherwise very short-range jet engine
d aircraft. Most famous of these would be the Horten Ho 229
fighter. This aircraft, first flown in 1944, combined a flying wing, or Nurflügel, design with twin jet engines. The surviving prototype remains in storage at the Smithsonian Institution
in an unrestored state.
After the war, a number of experimental designs were based on the flying wing concept, but the known difficulties remained intractable. Some general interest continued until the early 1950s, when the concept was proposed as a design solution for long range bomber
s. Such trends culminated in the Northrop
YB-35
and YB-49
, which did not enter production. Those designs did not necessarily offer a great advantage in range and presented a number of technical problems, leading to the adoption of "conventional" solutions like the Convair B-36
and the B-52 Stratofortress
. Early designs of the Avro Vulcan
by Roy Chadwick
also explored flying wing designs.
Interest in flying wings was renewed in the 1980s due to their potentially low radar
reflection cross-sections. Stealth technology
relies on shapes which only reflect radar waves in certain directions, thus making the aircraft hard to detect unless the radar receiver is at a specific position relative to the aircraft - a position that changes continuously as the aircraft moves. This approach eventually led to the Northrop B-2 Spirit
stealth
bomber. In this case the aerodynamic advantages of the flying wing are not the primary needs. However, modern computer-controlled fly-by-wire
systems allowed for many of the aerodynamic drawbacks of the flying wing to be minimised, making for an efficient and stable long-range bomber.
Due to the practical need for a deep wing, the flying wing concept is most practical for designs in the slow-to-medium speed range, and there has been continual interest in using it as a tactical airlift
er design. Boeing
continues to work on paper projects for a Blended Wing Body
Lockheed C-130 Hercules
-sized transport with better range and about 1/3 more load, while maintaining the same size characteristics. A number of companies, including Boeing
, McDonnell Douglas
and de Havilland
, did considerable design work on flying-wing airliner
s, but to date none have entered production.
A clean flying wing is theoretically the most aerodynamically
efficient (lowest drag) design configuration for a fixed wing aircraft. It also offers high structural efficiency for a given wing depth, leading to light weight and high fuel efficiency.
Because it lacks conventional stabilizing surfaces or the associated control surfaces, in its purest form the flying wing suffers from the inherent disadvantages of being unstable and difficult to control. These compromises are difficult to reconcile, and efforts to do so can reduce or even negate the expected advantages of the flying wing design, such as reductions in weight and drag
. Moreover, solutions may produce a final design that is still too unsafe for certain uses, such as commercial aviation.
Further difficulties arise from the problem of fitting the pilot, engines, flight equipment and payload all within the depth of the wing section. A wing that is made deep enough to contain all these elements will have an increased frontal area, when compared to a conventional wing and fuselage, which in turn results in higher drag and thus slower speed than a conventional design. Typically the solution adopted in this case is to keep the wing reasonably thin, and the aircraft is then fitted with an assortment of blisters, pods, nacelles, fins and so forth to accommodate all the needs of a practical aircraft.
Other known problems with the flying wing design relate to pitch
and yaw
. Pitch issues are discussed in the article on tailless aircraft
. The problems of yaw are discussed below.
in yaw.
Flying wings lack the long fuselage which provides a convenient attachment point for an efficient vertical stabilizer or fin. The fin must attach directly on to the rear part of the wing, giving a small moment arm from the aerodynamic center, which in turn means that to be effective the fin area must be large. This large fin has weight and drag penalties, and can negate the advantages of the flying wing. The problem can be minimized by increasing the leading edge sweepback, as for example in a low-aspect-ratio delta wing, but most flying wings have gentler sweepback and consequently have, at best, marginal stability. In the so called ruptured duck configuration, the wing tip sections are angled sharply downwards (anhedral), increasing the area at the rear of the aircraft when viewed from the side.
A consequence of the differential drag method is that if the aircraft manoeuvers frequently then it will frequently create drag. So flying wings are at their best when cruising in still air: in turbulent air or when changing course, the aircraft may be less efficient than a conventional design.
Many hang gliders and microlight aircraft are tailless. Although often referred to as flying wings, these types carry the pilot (and engine where fitted) below the wing structure rather than inside it, and so are not true flying wings.
An aircraft of sharply-swept delta planform and deep center section represents a borderline case between flying wing, blended wing body
and/or lifting body
configurations.
Tailless aircraft
A tailless aircraft traditionally has all its horizontal control surfaces on its main wing surface. It has no horizontal stabilizer - either tailplane or canard foreplane . A 'tailless' type usually still has a vertical stabilising fin and control surface...
fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...
which has no definite fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
, with most of the crew, payload and equipment being housed inside the main wing structure.
A flying wing may have various small protuberances such as pods, nacelles, blisters, booms, vertical stabilizer
Vertical stabilizer
The vertical stabilizers, vertical stabilisers, or fins, of aircraft, missiles or bombs are typically found on the aft end of the fuselage or body, and are intended to reduce aerodynamic side slip. It is analogical to a skeg on boats and ships.On aircraft, vertical stabilizers generally point upwards...
s (tail fins), or undercarriage. Some aircraft have no fuselage but do have a separate horizontal stabilizer surface mounted on one or more booms; these are also commonly referred to as flying wings, although this is not strictly correct. An example of such a design is the Northrop X216H.
History
Tailless aircraft
A tailless aircraft traditionally has all its horizontal control surfaces on its main wing surface. It has no horizontal stabilizer - either tailplane or canard foreplane . A 'tailless' type usually still has a vertical stabilising fin and control surface...
have been experimented with since the earliest attempts to fly. But it was not until the deep-chord monoplane
Monoplane
A monoplane is a fixed-wing aircraft with one main set of wing surfaces, in contrast to a biplane or triplane. Since the late 1930s it has been the most common form for a fixed wing aircraft.-Types of monoplane:...
wing became practicable after World War I that the opportunity to discard any form of fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
arose and the true flying wing could be realised.
Hugo Junkers
Hugo Junkers
Hugo Junkers was an innovative German engineer, as his many patents in varied areas show...
patented a wing-only air transport concept in 1910. He saw it as a natural solution to the problem of building an airliner
Airliner
An airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such aircraft are operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an aircraft intended for carrying multiple passengers in commercial...
large enough to carry a reasonable passenger load and enough fuel to cross the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
in regular service. He believed that the flying wing's potentially large internal volume and low drag made it an obvious design for this role. In 1919 he started work on his "Giant" JG1 design, intended to seat passengers within thick wings, but two years later the Allied Aeronautical Commission of Control ordered the incomplete JG1 destroyed for exceeding post-war size limits on German aircraft. Junkers conceived futuristic flying wings for up to 1,000 passengers; the nearest this came to realization was in the 1931 Junkers G-38 34-seater Grossflugzeug airliner which featured a large thick-chord wing providing space for fuel, engines and two passenger cabins. However, it still required a short fuselage to house the crew and additional passengers.
The flying wing configuration was studied extensively in the 1930s and 1940s, notably by Jack Northrop and Cheston L. Eshelman in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, and Alexander Lippisch
Alexander Lippisch
Alexander Martin Lippisch was a German pioneer of aerodynamics. He made important contributions to the understanding of flying wings, delta wings and the ground effect. His most famous design is the Messerschmitt Me 163 rocket-powered interceptor.Lippisch was born in Munich, Kingdom of Bavaria...
and the Horten brothers
Horten brothers
Walter Horten and Reimar Horten , sometimes credited as the Horten Brothers, were German aircraft pilots and enthusiasts, and members of the Hitler Youth and Nazi party...
in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
Soviet designers such as Boris Ivanovich Cheranovsky started research independently and in secret under Stalin after the 1920s. With significant breakthrough in materials and construction methods, aircraft such as the BICh-3
BICh-3
|-See also:-References:* Gunston, Bill. “The Osprey Encyclopaedia of Russian Aircraft 1875 – 1995”. London, Osprey. 1995. ISBN 1-85532-405-9-External links:* http://www.ctrl-c.liu.se/misc/RAM/bich-3.html...
, BICh-14, BICh-7A and so on became possible. Men like Chizhevskij and Antonov also came into the spotlight of the communist party by designing aircraft such as the tail-less BOK-5 (Chizhevskij) and OKA-33 (the first ever built by Antonov) which were designated as "motorized gliders" due to their similarity to popular gliders of the time. The BICh-11 by Cheranovsky in 1932 was competing with the Horten brothers H1 (and Adolf Galland) at the Ninth Glider Competitions in 1933, but did not demonstrate in the 1936 summer Olympics in Berlin. The BICh-26
BICh-26
|-See also:-References:* Gunston, Bill. “The Osprey Encyclopaedia of Russian Aircraft 1875 – 1995”. London, Osprey. 1995. ISBN 1-85532-405-9-External links:* http://www.ctrl-c.liu.se/misc/ram/bich-26.html* http://www.aviation.ru/BICh/BICh-26.jpg.php...
was one of the first attempts at a supersonic jet flying-wing aircraft, ahead of its time in 1948 the airplane was not accepted by the military and the design died with Cheranovsky.
Early examples of true flying wings include:
- The Soviet Boris Ivanovich CheranovskyBoris Ivanovich CheranovskyBoris Ivanovich Cheranovsky was a Soviet aircraft designer, notable for creating world's first fly-worthy flying wing aircraft - the gliders BICh-1 and BICh-2 from 1924, and powered BICh-3 later. They used tailless parabolic planform....
built and tested tailless flying wings, from 1924 gliders, eventually also powered BICh-3BICh-3|-See also:-References:* Gunston, Bill. “The Osprey Encyclopaedia of Russian Aircraft 1875 – 1995”. London, Osprey. 1995. ISBN 1-85532-405-9-External links:* http://www.ctrl-c.liu.se/misc/RAM/bich-3.html...
. - The French Charles FauvelCharles FauvelCharles Fauvel was a French aircraft designer noted for his flying wing designs, and in particular, his flying wing sailplanes...
designed the AV3 glider, successfully flown in 1933, featuring a self-stabilizing airfoil on a straight wing. - The German Horten H1Horten brothersWalter Horten and Reimar Horten , sometimes credited as the Horten Brothers, were German aircraft pilots and enthusiasts, and members of the Hitler Youth and Nazi party...
glider flown with partial success in 1933, and the subsequent H2 flown successfully in both glider and powered variants. - The American Freel Flying WingFreel Flying WingThe Freel Flying Wing was the creation of Charles Lewis Freel . As a student of San Diego High School, in San Diego, California, Freel learned about aerodynamics under the instruction of LeTain Kittredge, in the aircraft rigging/woodshop class....
glider flown in 1937. - The American Northrop N-1MNorthrop N-1M|-See also:-References:NotesCitationsBibliography* Coleman, Ted. Jack Northrop and the Flying Wing: The Real Story Behind the Stealth Bomber. New York: Paragon House, 1988. ISBN 1-55778-079-X....
of 1940. - The American Northrop N-9MNorthrop N-9MThe Northrop N-9M was a one-third scale aircraft used for the development of the Northrop XB-35 and YB-35 Flying Wing long-range bomber program...
of 1942. - The American Northrop YB-35Northrop YB-35The Northrop XB-35 and YB-35 were experimental heavy bomber aircraft developed for the United States Army Air Forces during and shortly after World War II by the Northrop Corporation. It used the radical and potentially very efficient flying wing design, in which the tail section and fuselage are...
of 1946. - The American Northrop YB-49Northrop YB-49The Northrop YB-49 was a prototype jet-powered heavy bomber aircraft developed by Northrop shortly after World War II. Intended for service with the U.S. Air Force, the YB-49 featured a flying wing design...
of 1947. - The British Armstrong Whitworth A.W.52Armstrong Whitworth A.W.52-See also:- External links :*** at *...
G of 1944, a glider test bed for the later Armstrong Whitworth A.W.52Armstrong Whitworth A.W.52-See also:- External links :*** at *...
jet-powered version. - The German Horten Ho 229Horten Ho 229The Horten H.IX, RLM designation Ho 229 was a late–World War II prototype fighter/bomber designed by Reimar and Walter Horten and built by Gothaer Waggonfabrik...
of 1945 - the world's first twin jet engine pure flying wing
Several late-war German military designs were based on the flying wing concept (or variations of it) as a proposed solution to extend the range of the otherwise very short-range jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
d aircraft. Most famous of these would be the Horten Ho 229
Horten Ho 229
The Horten H.IX, RLM designation Ho 229 was a late–World War II prototype fighter/bomber designed by Reimar and Walter Horten and built by Gothaer Waggonfabrik...
fighter. This aircraft, first flown in 1944, combined a flying wing, or Nurflügel, design with twin jet engines. The surviving prototype remains in storage at the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...
in an unrestored state.
After the war, a number of experimental designs were based on the flying wing concept, but the known difficulties remained intractable. Some general interest continued until the early 1950s, when the concept was proposed as a design solution for long range bomber
Bomber
A bomber is a military aircraft designed to attack ground and sea targets, by dropping bombs on them, or – in recent years – by launching cruise missiles at them.-Classifications of bombers:...
s. Such trends culminated in the Northrop
Northrop Corporation
Northrop Corporation was a leading United States aircraft manufacturer from its formation in 1939 until its merger with Grumman to form Northrop Grumman in 1994. The company is known for its development of the flying wing design, although only a few of these have entered service.-History:Jack...
YB-35
Northrop YB-35
The Northrop XB-35 and YB-35 were experimental heavy bomber aircraft developed for the United States Army Air Forces during and shortly after World War II by the Northrop Corporation. It used the radical and potentially very efficient flying wing design, in which the tail section and fuselage are...
and YB-49
Northrop YB-49
The Northrop YB-49 was a prototype jet-powered heavy bomber aircraft developed by Northrop shortly after World War II. Intended for service with the U.S. Air Force, the YB-49 featured a flying wing design...
, which did not enter production. Those designs did not necessarily offer a great advantage in range and presented a number of technical problems, leading to the adoption of "conventional" solutions like the Convair B-36
Convair B-36
The Convair B-36 "Peacemaker" was a strategic bomber built by Convair and operated solely by the United States Air Force from 1949 to 1959. The B-36 was the largest mass-produced piston engine aircraft ever made. It had the longest wingspan of any combat aircraft ever built , although there have...
and the B-52 Stratofortress
B-52 Stratofortress
The Boeing B-52 Stratofortress is a long-range, subsonic, jet-powered strategic bomber operated by the United States Air Force since the 1950s. The B-52 was designed and built by Boeing, who have continued to provide maintainence and upgrades to the aircraft in service...
. Early designs of the Avro Vulcan
Avro Vulcan
The Avro Vulcan, sometimes referred to as the Hawker Siddeley Vulcan, was a jet-powered delta wing strategic bomber, operated by the Royal Air Force from 1956 until 1984. Aircraft manufacturer A V Roe & Co designed the Vulcan in response to Specification B.35/46. Of the three V bombers produced,...
by Roy Chadwick
Roy Chadwick
Roy Chadwick, CBE, FRAeS was an aircraft designer for Avro. Born at Marsh Hall Farm, Farnworth in Widnes, son of the mechanical engineer Charles Chadwick, he was the Chief Designer for the Avro Company and was responsible for practically all of their aeroplane designs...
also explored flying wing designs.
Interest in flying wings was renewed in the 1980s due to their potentially low radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
reflection cross-sections. Stealth technology
Stealth technology
Stealth technology also termed LO technology is a sub-discipline of military tactics and passive electronic countermeasures, which cover a range of techniques used with personnel, aircraft, ships, submarines, and missiles, to make them less visible to radar, infrared, sonar and other detection...
relies on shapes which only reflect radar waves in certain directions, thus making the aircraft hard to detect unless the radar receiver is at a specific position relative to the aircraft - a position that changes continuously as the aircraft moves. This approach eventually led to the Northrop B-2 Spirit
B-2 Spirit
The Northrop Grumman B-2 Spirit is an American heavy bomber with low observable stealth technology designed to penetrate dense anti-aircraft defenses and deploy both conventional and nuclear weapons. The bomber has a crew of two and can drop up to eighty -class JDAM GPS-guided bombs, or sixteen ...
stealth
Stealth aircraft
Stealth aircraft are aircraft that use stealth technology to avoid detection by employing a combination of features to interfere with radar as well as reduce visibility in the infrared, visual, audio, and radio frequency spectrum. Development of stealth technology likely began in Germany during...
bomber. In this case the aerodynamic advantages of the flying wing are not the primary needs. However, modern computer-controlled fly-by-wire
Fly-by-wire
Fly-by-wire is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires , and flight control computers determine how to move the actuators at each control...
systems allowed for many of the aerodynamic drawbacks of the flying wing to be minimised, making for an efficient and stable long-range bomber.
Due to the practical need for a deep wing, the flying wing concept is most practical for designs in the slow-to-medium speed range, and there has been continual interest in using it as a tactical airlift
Airlift
Airlift is the act of transporting people or cargo from point to point using aircraft.Airlift may also refer to:*Airlift , a suction device for moving sand and silt underwater-See also:...
er design. Boeing
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
continues to work on paper projects for a Blended Wing Body
Blended wing body
Blended Wing Body aircraft have a flattened and airfoil shaped body, which produces most of the lift, the wings contributing the balance. The body form is composed of distinct and separate wing structures, though the wings are smoothly blended into the body...
Lockheed C-130 Hercules
C-130 Hercules
The Lockheed C-130 Hercules is a four-engine turboprop military transport aircraft designed and built originally by Lockheed, now Lockheed Martin. Capable of using unprepared runways for takeoffs and landings, the C-130 was originally designed as a troop, medical evacuation, and cargo transport...
-sized transport with better range and about 1/3 more load, while maintaining the same size characteristics. A number of companies, including Boeing
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
, McDonnell Douglas
McDonnell Douglas
McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It formed from a merger of McDonnell Aircraft and Douglas Aircraft in 1967. McDonnell Douglas was based at Lambert-St. Louis International Airport...
and de Havilland
De Havilland
The de Havilland Aircraft Company was a British aviation manufacturer founded in 1920 when Airco, of which Geoffrey de Havilland had been chief designer, was sold to BSA by the owner George Holt Thomas. De Havilland then set up a company under his name in September of that year at Stag Lane...
, did considerable design work on flying-wing airliner
Airliner
An airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such aircraft are operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an aircraft intended for carrying multiple passengers in commercial...
s, but to date none have entered production.
Design issues
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
efficient (lowest drag) design configuration for a fixed wing aircraft. It also offers high structural efficiency for a given wing depth, leading to light weight and high fuel efficiency.
Because it lacks conventional stabilizing surfaces or the associated control surfaces, in its purest form the flying wing suffers from the inherent disadvantages of being unstable and difficult to control. These compromises are difficult to reconcile, and efforts to do so can reduce or even negate the expected advantages of the flying wing design, such as reductions in weight and drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
. Moreover, solutions may produce a final design that is still too unsafe for certain uses, such as commercial aviation.
Further difficulties arise from the problem of fitting the pilot, engines, flight equipment and payload all within the depth of the wing section. A wing that is made deep enough to contain all these elements will have an increased frontal area, when compared to a conventional wing and fuselage, which in turn results in higher drag and thus slower speed than a conventional design. Typically the solution adopted in this case is to keep the wing reasonably thin, and the aircraft is then fitted with an assortment of blisters, pods, nacelles, fins and so forth to accommodate all the needs of a practical aircraft.
Other known problems with the flying wing design relate to pitch
Flight dynamics
Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...
and yaw
Flight dynamics
Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...
. Pitch issues are discussed in the article on tailless aircraft
Tailless aircraft
A tailless aircraft traditionally has all its horizontal control surfaces on its main wing surface. It has no horizontal stabilizer - either tailplane or canard foreplane . A 'tailless' type usually still has a vertical stabilising fin and control surface...
. The problems of yaw are discussed below.
Directional stability
For any aircraft to fly without constant correction it must have directional stabilityDirectional stability
Directional stability is stability of a moving body or vehicle about an axis which is perpendicular to its direction of motion. Stability of a vehicle concerns itself with the tendency of a vehicle to return to its original direction in relation to the oncoming medium when disturbed away from...
in yaw.
Flying wings lack the long fuselage which provides a convenient attachment point for an efficient vertical stabilizer or fin. The fin must attach directly on to the rear part of the wing, giving a small moment arm from the aerodynamic center, which in turn means that to be effective the fin area must be large. This large fin has weight and drag penalties, and can negate the advantages of the flying wing. The problem can be minimized by increasing the leading edge sweepback, as for example in a low-aspect-ratio delta wing, but most flying wings have gentler sweepback and consequently have, at best, marginal stability. In the so called ruptured duck configuration, the wing tip sections are angled sharply downwards (anhedral), increasing the area at the rear of the aircraft when viewed from the side.
Yaw control
In most flying wing designs, the stabilizing fins are so far forward that any control rudders mounted on them have little effect, thus alternative means for yaw control must be provided. The only practical solution is differential drag: the drag near one wing tip is artificially increased, causing the aircraft to yaw in the direction of that wing. Typical methods include:- Split ailerons. The top surface moves up while the lower surface moves down, to create an air brake effect.
- SpoilersSpoiler (aeronautics)In aeronautics, a spoiler is a device intended to reduce lift in an aircraft. Spoilers are plates on the top surface of a wing which can be extended upward into the airflow and spoil it. By doing so, the spoiler creates a carefully controlled stall over the portion of the wing behind it, greatly...
. A spoiler surface in the upper wing skin is raised, to disrupt the airflow and increase drag. This effect is generally accompanied by a loss of lift, which must be compensated for either by the pilot or by complex design features. - SpoileronSpoileronIn aeronautics spoilerons are flight control surfaces, specifically spoilers that can be used asymmetrically to achieve the effect of ailerons, i.e. to roll an aircraft by reducing the lift of one wing but unlike ailerons not increasing the lift of the other wing...
s. An upper surface spoiler which also acts to reduce lift (equivalent to deflecting an aileron upwards), so causing the aircraft to bank in the direction of the turn - the angle of roll causes the wing lift to act in the direction of turn, reducing the amount of drag required to turn the aircraft's longitudinal axis.
A consequence of the differential drag method is that if the aircraft manoeuvers frequently then it will frequently create drag. So flying wings are at their best when cruising in still air: in turbulent air or when changing course, the aircraft may be less efficient than a conventional design.
Borderline cases
Some aircraft have no fuselage but do have a horizontal stabilizer mounted on one or more booms. Strictly, these are not flying wings although they are usually referred to as such. An example is the Northrop X-216H, which has a tail stabilizer mounted on two tail booms but is regarded as Northrop's first flying wing type.Many hang gliders and microlight aircraft are tailless. Although often referred to as flying wings, these types carry the pilot (and engine where fitted) below the wing structure rather than inside it, and so are not true flying wings.
An aircraft of sharply-swept delta planform and deep center section represents a borderline case between flying wing, blended wing body
Blended wing body
Blended Wing Body aircraft have a flattened and airfoil shaped body, which produces most of the lift, the wings contributing the balance. The body form is composed of distinct and separate wing structures, though the wings are smoothly blended into the body...
and/or lifting body
Lifting body
A lifting body is a fixed-wing aircraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing...
configurations.
See also
- List of flying wing aircraft
- Blended wing bodyBlended wing bodyBlended Wing Body aircraft have a flattened and airfoil shaped body, which produces most of the lift, the wings contributing the balance. The body form is composed of distinct and separate wing structures, though the wings are smoothly blended into the body...
- Delta wingDelta wingThe delta wing is a wing planform in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta .-Delta-shaped stabilizers:...
- Lifting bodyLifting bodyA lifting body is a fixed-wing aircraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing...
- Oblique flying wing
- Vincent BurnelliVincent BurnelliVincent Justus Burnelli was an American aeronautics engineer, instrumental in furthering the lifting body and flying wing concept.-Early life:...
- AlsomitraAlsomitraAlsomitra is a genus of the plant family Cucurbitaceae .The seeds of Alsomitra macrocarpa are among the largest winged seeds in the Plant Kingdom and their shape inspired Igo Etrich to build gliders, later it would inspire the Horten brothers to build the first flying wing aircraft.-Selected...
External links
- History of the Flying Wing at Century of Flight.
- The Nurflügel page
- Flight to the Future by Joe Mizrahi, Wings, April 1999, Vol. 29, No. 2
- Glen Edwards and the Flying Wing
- Flying Wings Are Coming, March 1942