# Invention of the Swept Wing Term Paper

#### Excerpt from Term Paper :

Aviation

Invention of the Swept Wing

This is a paper about the swept wing. There are five references used for this paper.

There have been a number of innovations in the field of aviation over the years. It is interesting to examine the swept wing and determine why it was developed, and if the wing performs the function it was designed for.

The Swept Wing

The theory behind "sweeping an aircraft's wing is to delay the drag rise caused by the formation of shock waves (www.aviation-history.com/theory/swept-wing.htm)." A planform is "the shape and layout of an airplane's wing. A swept-wing is a wing planform, used on high-speed aircraft that spend a considerable portion of their flight time the transonic, the range of velocities just below and above the speed of sound. The swept-wing is a wing that is bent back as some angle, instead of sticking straight out from the fuselage (www.worldhistory.com/wiki/S/Swept-wing.htm)."

A Swept Wing's Function

An extremely powerful and sudden drag on planes nearing and flying at the speed of sound is known as wave drag. This occurs because "the air which would normally follow a streamline around the aircraft no longer has time to 'know' about the approaching object and simply hits it directly, resulting in greatly increased drag (www.worldhistory.com/wiki/S/Swept-wing.htm)." To improve the performance of an aircraft, it is very important to avoid wave drag. To avoid this, it is necessary to create a wing that is "as thin as possible, with a slowly changing profile over a wide chord. Chord is the distance between the front and back of a wing, measured in the direction of the normal airflow. This is basically the opposite goal to low speed wings, which creates a problem (www.worldhistory.com/wiki/S/Swept-wing.htm)." If a wing is too thin, problems can arise such as decreased "internal room for storage of fuel and landing gear, making the wing considerably less stiff, and increased induced drag when flying slower (www.worldhistory.com/wiki/S/Swept-wing.htm)." The swept-wing is used to "fool the air into thinking it is flowing over a thinner wing with more chord (www.worldhistory.com/wiki/S/Swept-wing.htm)."

Developing the Swept Wing

The swept wing concept was developed 1936 by German aerodynamicists who calculated wing thickness "measured along the direction of the airflow, as opposed to along the line of the chord. A thick wing could be made 'effectively thinner' by rotating it at an angle to the airflow, sweeping it back (www.worldhistory.com/wiki/S/Swept-wing.htm)." At the time of this discovery, planes could only fly 400 km/h, so the concept was mainly considered academic. Despite the slow speeds of planes, a considerable amount of research went into the project, and "due to the early research in this area, Germany was able to successfully introduce the swept wing in the jet fighter Messerschmitt ME-262 in 1941(www.aviation-history.com/theory/swept-wing.htm)." However, in the United States and Great Britain, the concept of the swept wing remained virtually unknown until the end of the war.

During this time, the straight-wing design was still being used on British and American jet aircraft, which limited the plane's high-speed abilities. When the war was over, "German advanced aeronautical research data became available to the United States Army Air Force (USAAF) as well as Great Britain. This technology was then incorporated into aircraft designs such as the North American F-86 Sabre, the Hawker Hunter F.4 and the Supermarine Swift FR.5 (www.aviation-history.com/theory/swept-wing.htm)." In 1947, in an effort to remain competitive with other nations, the Soviet Union "introduced the swept wing in the Mikoyan Mig-15, which was the great rival of the North American F-86 Sabre during the Korean War (www.aviation-history.com/theory/swept-wing.htm)."

Early Problems

When the Germans introduced their jet powered Messerschmitt Me 262 and rocket powered Messerschmitt Me 163, they found the aircraft "suffered from compressibility effects that made them very difficult to control at high speeds. In addition, the speeds put them right in the wave drag regime, so anything that could reduce it would increase the performance of their aircraft, notably the notoriously short flight times measured in minutes (www.worldhistory.com/wiki/S/Swept-wing.htm)." This lead to new swept wings being designed, and the prototype Messerschmitt P.1101 was built "in order to research the tradeoffs of the design and develop general rules about what angle of sweep to use (www.worldhistory.com/wiki/S/Swept-wing.htm)."

In the 1950's, another problem was discovered in design of the swept wing. As the swept-wing "travels at high speed, the airflow has little time to react and simply flows over the wing. However at lower speeds there is more time for motion and a strong streamline, and with the front of the wing angled, some of the air is pushed to the side towards the wing tip. At the wing root, by the fuselage, this has little noticeable effect, but as you move towards the tip the airflow is pushed sidewise not only along the wing, but the sidewise moving air beside it, and by the time the tip is reach, the airflow is moving along the wing instead of over it, a problem known as spanwise flow (www.worldhistory.com/wiki/S/Swept-wing.htm)." It was found that the spanwise flow could cause an aircraft to drop below the stall point when it slowed down for landing, resulting in a crash landing. This problem was corrected in a number of ways. One solution was "the addition of a strip of metal known as a wing fence on the upper surface of the wing to redirect the flow to the rear, another closely related design was to add a dogtooth notch to the leading edge, while other radical designs included a wing that grew thicker towards the tip to provide more lift there (www.worldhistory.com/wiki/S/Swept-wing.htm)." Today, the need for custom designs has been eliminated due to shorter landings and takeoffs, and the "addition of leading edge slats and large compound flaps to the wings. On fighter designs, the addition of leading edge extensions, included for high maneuverability also serve to add lift during landing and reduce the problem (www.worldhistory.com/wiki/S/Swept-wing.htm)."

Other minor problems encountered in the swept-wing include "concern in the torque generated at the fuselage, as much of the wing's lift lies behind where the root connects to the plane, and the fact that while it is fairly easy to run the main spars or rods of the wing right through the fuselage in a straight wing design to use a single continuous piece of metal, this is not possible on the swept wing because the spars will meet at an angle (www.worldhistory.com/wiki/S/Swept-wing.htm)."

A Lasting Design

On November 29, 1951, the "first prototype of the B-52 emerged from Boeing's south Seattle plant, under cover of night and a huge tarp. The tail fin was folded down to help conceal the plane's radical, eight-engine, swept-wing design (Johnson, 2001)."

Although the first test pilots knew the plane was well-designed, they had no concept that the plane would endure for over 50 years, being used in Vietnam and the Gulf Wars. In the decade following its introduction, there were eight models of the B-52 designed and 744 planes built. Of these planes, "about 100 H. models remain in service and the Air Force says it may retain them until 2040 (Johnson, 2001)."

The B-52 has a "185-foot wingspan and can carry a crew of five at speeds up to 650 mph. It can fly as high as 50,000 feet or as low as 200 (Johnson, 2001)." While there have been new aircraft introduced, such as the stealth bomber, the B-52 has "outlasted other bombers, including the North American B-70 Valkyrie. A former Air Force officer stated 'It was a design that had a lot of growth potential' (Johnson, 2001)."

Evolving Use

Although the swept-wing was initially devised for use on fighter aircraft, it has "become almost universal on all jets, including airliners and bizjets (www.worldhistory.com/wiki/S/Swept-wing.htm)."

In 1999, Boeing successfully tested highly back-swept wing tips, which were designed to "improve the overall aerodynamic…

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