# Tag Info

## Hot answers tagged wing-sweep

41

The wing was swept to move the center of lift back, closer to the center of gravity. When the design of the DC-1 was advanced to a point where the center of gravity became clear, a redesign of the wing-fuselage intersection would had been more effort, so the outer wing panels were swept back a little. From this website by Jeff Lucker: the unique and ...

29

Sweeping a wing costs weight, for several reasons. Therefore, if the goal is to fly high and achieve long range, an unswept wing is the better choice. Only when transport performance needs to be maximized will a moderately swept wing look better. Why is a swept wing heavier? Sweep reduces aerodynamic efficiency, so a larger wing is needed to create the ...

22

Disadvantages of wing sweep Lift curve slope is reduced by the cosine of the quarter chord sweep angle. This means more angle of attack for takeoff, which requires a longer take-off run and a longer landing gear to avoid a tail strike on rotation. If you rotate the airplane, the tips of backward swept wings come down when the aircraft rotates for take-off. ...

20

The tail sweep helps to extend its range of angles of attack. For both stability and control, it is very important that the tail doesn't stall before the wing in any circumstances (for a classic design; for canards it may be beneficial). Generally, for high positive angles of attack, the horizontal tail already has an edge because it is set at a lower angle ...

17

It was obvious to the design team that conventional aircraft could not satisfy the required specification; knowing little about high-speed flight and unable to glean much from the Royal Aircraft Establishment or the US, the team at Avro investigated German Second World War swept wing research. The team estimated that an otherwise conventional aircraft, with ...

15

Wing sweep improves the performance by delaying the shock waves and accompanying aerodynamic drag rise caused by fluid compressibility at high (near sonic) speeds. However, there are some disadvantages associated with the wing sweep like: Wing sweep reduces the slope of the lift curve and the maximum lift coefficient of the wing. This means that the swept ...

15

MiG-23 For the MiG-23, it was manual. [The] MiG-23 had a completely manual wing sweep control. But there was no gauge to indicate optimum wing position for the surrounding conditions. "You had to manually put the wings into position to safely fly the airplane," (...) "They had a very nice gauge that showed where the wings were commanded to, ...

13

Mark is right when he says that there is no induced drag at supersonic speeds, but it is an invitation for misunderstandings. Induced drag is replaced by lift wave drag, and all what happens is that aerodynamicists choose to use two different names for basically the same effect: Air gets pushed down. As usual when I post a long answer, I was not quite happy ...

12

This was an intentional test run by Grumman in response to US Navy concerns about asymmetric wing sweep. From The story of F-14A, Aircraft No. 3, BuNo. 157982 One of these [flight tests] was in response to concerns raised by the US Navy regarding asymmetrical wing sweep. No. 3 is best remembered for photo shown at right. A series of flight tests were ...

10

The two pictures in the question only show how to decompose the speed vector into the normal and parallel components. They are nowhere near "real" flow vectors. First I recommend to read this answer so you get an idea how air is accelerated and decelerated when flowing around an airfoil. Note that the low pressure area over the wing will suck in ...

10

I finally found several arguments to answer this question from different sources. Sweep and Mach Number from Airbus This argument is developed in an Airbus magazine from 1985. To grasp it it is important to understand the purpose of swept wing. By sweeping the main wings one introduces an angle between the leading edge of the wing and a line perpendicular ...

10

The oblique wing and the swing wing aim to reduce the drag over a wide range of speeds by changing the wing sweep. While the swing wing rotates a part of the wing to achieve this, the oblique wing rotates the whole wing. The first production aircraft with variable sweep wings was the F111 Aardvark, while the most famous one is the F-14 Tomcat. "F-14 Tomcat ...

10

When looking at statements like these, it's important to consider which parameters are varied and which parameters remain fixed. Let's get this out of the way first by correcting your statements: Lift increases with increase in airspeed with constant angle of attack but induced drag reduces with increase in airspeed with lift force remaining constant ...

9

Advantages of an oblique wing over swing wings: Low wave drag due to favorable volume distribution over length. Lower structural mass. The hinge of a swing wing is heavy! No shift in the center of lift (if the sweep angle is higher than the Mach angle). A swing wing experiences a severe shift in the center of lift. Disadvantages of an oblique wing over a ...

8

Basically, because of its mission requirements. It wasn't intended to fly fast, and because it didn't need to go particularly fast, there was no need to sweep the wing. Instead, it was supposed to provide a massive amount of data (by 20th century standards) along its flight path, which necessitated long flight times: thus the long, straight wings providing a ...

8

I would not say that no other bomber ever had delta wings. Convair B-58 Hustler and Mirage IV both have delta wings. They are both supersonic though. The B-52 did not have to worry too much about MTOW and empty weight since SAC already had bases with long runways capable of really heavy aircraft. That's thanks to B-52's predecessor B-36. The B-36 was the ...

7

The vertical tail and the horizontal tail are wings, and follow the same construction rules. The span-wise lift distribution is much better if the wing is tapered: more lift at the root, less at the tip. The wing can be built lighter, root area is larger, torsion stiffness is higher. Vortex induced drag is lower. As a reference, from Torenbeek: pages 232 &...

7

From Wikipedia, the cruise speeds of the both airplanes are fairly similar: A380, nominal wing sweep angle 33.5 degrees, cruise speed Mach 0.85 Boeing 747: nominal wing sweep angle 37.5 degrees, cruise speed Mach 0.84 .. 0.9, depending on the model. So those numbers would contradict the claim in your question, but align with your expectations. There are ...

6

Yes it could, but don't hold your breath. Forward sweep means that the aeroelastic forces will twist the wing at high lift into an increased angle of attack, so such a wing needs to be stiff in order to avoid divergence (PDF!). Also, aileron effectiveness is excellent, so a forward-swept configuration is a good choice for dogfighting. Since backward sweep ...

6

Lift increases with increase in airspeed but induced drag reduces with increase in airspeed. If you keep weight ($W$) constant, the total lift ($L$) does not change with change in airspeed ($V$). $L=W$ for quasi-steady flight, right? What is changed is the lift coefficient, $C_L$. As speed increases, $C_L$ decreases. Induced drag coefficient ($C_{D_i}$) is ...

5

There is no magical switch that gets flipped once you cross a specific sweep angle. Things are gradually changing with the cosine of the local sweep angle. Now let's look at your questions one by one: What happens to the wingtip wake on a forward-swept wing? Nothing special. It is part of the full wake system and behaves like in any other aircraft of ...

5

A swept wing has less torsional strength than a straight wing, ie there's less structure at 90d to the root supporting the tip of a swept wing. Thus a swept wing twists when it's loaded, which unloads the tips and thus generates less lift at higher weights.

5

In supplement to @Dave's answer and as he said depending on the airplane, the complexity of calculating the c.g. can vary greatly. The manufacturer of every large aircraft I've programmed weight & balance for has had tables for each tank. In Boeing's case for the 747-400, each table line is a tank volume in gallons and the tank c.g. at that volume in ...

5

It depends on the rigidity of the upper and lower skins. As far as large jets go, you see different variations; ribs parallel to the airflow, ribs perpendicular to one of the spars, ribs perpendicular to mean chord. In the 737 cutaway below, they appear to be more or less perpendicular to the rear spar. Aerodynamically it's not important on large swept wing ...

4

A swept wing would most likely adversely affect the handling of a U2 during a typical mission profile, and would adversely affect the structure required (weight) of the aircraft. A swept wing adversely impacts the stall characteristics and stability when flying near a stall. It should be noted that while a swept wing helps manage effects due to the ...

4

One aerodynamic behavior appears at high angle of attack : dihedral or anhedral wake, which affects (in some weird mixture) both roll and yaw stability. Forward swept trailing edge is much more stable than backward swept trailing edge. Some jet fighters (let's say F-22) and most aerobatic airplanes (let's say SU-31) adopted forward swept trailing edges in ...

4

The pivot wing, also called oblique wing is a type of wing design that tries to minimize the drag over the entire speed range of the aircraft. At low speeds, the main concern is the induced drag, which can be reduced by increasing the aspect ratio. That is why low speed aircrafts like gliders have very long slender wings. As the speed increases, the ...

4

Yes. Variable sweep airplanes exist and it shouldn't be a problem to design a system able to sweep the wings forward and rearwards. However, the few aerodynamic advantages of the forward swept wing at low speeds doesn't justify the added complexity, weight and loss of space inside the fuselage.

4

Sweep is not strictly required, but helpful to increase supersonic L/D. Just witness the length to which aircraft manufacturers went to sweep wings for Mach 2+ flight. However, sweep comes with its own set of problems.

4

The tail is swept to move the aerodynamic center aft to provide more "leverage" for the tail in generating down force. Same as sweeping the fin, although that is also for looks. If the airplane had a straight fin and straight horizontal tail, the tail surfaces would have to be larger to have the same tail "volume" (area x moment arm) or the fuselage itself ...

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