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44 votes
Accepted

Why did the DC-3 have wing sweep?

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 ...
Peter Kämpf's user avatar
29 votes

Why does the U-2 Dragon Lady not have swept wings?

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 ...
Peter Kämpf's user avatar
20 votes
Accepted

Why do some airplanes have simultaneously a straight wing and a swept horizontal stabilizer?

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 ...
Zeus's user avatar
  • 9,083
19 votes

Why is the coefficient of drag for straight wings at supersonic speeds lower than for swept wings?

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 ...
Peter Kämpf's user avatar
16 votes

For aircraft with variable-sweep wings, how unstable is it to have each wing in a different position?

I was the lead flight test engineer for Grumman on this project. The Navy had experienced a few mechanical failures that resulted in asymmetric wing sweep and this prompted a flight test program to ...
Paul Conigliaro's user avatar
15 votes
Accepted

For aircraft with variable-sweep wings, how unstable is it to have each wing in a different position?

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 ...
Erin Anne's user avatar
  • 838
14 votes
Accepted

Jettisonable wingspan for early long-range airplanes

US supersonic bomber concepts were studied in the Fifties where the outer wing could be jettisoned. The WS-110 concept by North American shown below (source) sported wing extensions with fuel tanks ...
Peter Kämpf's user avatar
11 votes

Is it feasible for an individual with limited current knowledge to undertake the development of an aircraft from scratch?

It's not possible to solo-develop a 9-12 seat airplane to a legally flyable condition. The authorities want passenger aircraft built by people who know what they're doing, then checked again by ...
Therac's user avatar
  • 27.4k
10 votes

Where is the spanwise flow? How does the span wise flow point the air towards the wingtip?

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 ...
Peter Kämpf's user avatar
10 votes
Accepted

Does an increase in lift always cause an increase in lift-induced drag?

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: ...
Sanchises's user avatar
  • 13.4k
10 votes
Accepted

If sweep delays compressibility, why does 747 cruise slower than A380?

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, ...
Apfelsaft's user avatar
  • 702
8 votes
Accepted

Could a variable sweep aircraft also use negative angle?

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 ...
Peter Kämpf's user avatar
8 votes
Accepted

Why did the Avro Vulcan use a delta wing?

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 ...
Johan Fredriksson's user avatar
8 votes

Why does the U-2 Dragon Lady not have swept wings?

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 ...
JBeck's user avatar
  • 335
7 votes

Why are Vertical tails generally tapered?

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 ...
Koyovis's user avatar
  • 61.8k
6 votes

Does an increase in lift always cause an increase in lift-induced drag?

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=...
JZYL's user avatar
  • 11.1k
6 votes

Swept outer section of the wing on turboprops

Don't think of those wings as swept. As far as aerodynamics are concerned, they are straight wings. Think of them as tapered -- The taper is there to improve the lift distribution. The line about ...
Rob McDonald's user avatar
  • 12.6k
5 votes
Accepted

Spanwise flow and wingtip vortices in forward-swept wings

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: ...
Peter Kämpf's user avatar
5 votes
Accepted

Why would lift coefficent change with weight on swept-wing aircraft?

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 ...
RAC's user avatar
  • 4,616
5 votes

How is the change of moment handled in a Weight and Balance calculation with a swept wing aircraft?

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 & ...
Terry's user avatar
  • 39.2k
5 votes

How ribs angle change wing overall shape?

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 ...
John K's user avatar
  • 132k
5 votes

How does a variable-sweep-wing aircraft keep wing-mounted payloads straight?

Mechanically this can be done using the simplest form of pantograph, as a hinged parallelogram with one end fixed to the fuselage and the other to the ordnance pylon. Or, I suppose you could implement ...
Guy Inchbald's user avatar
  • 7,062
5 votes

How does a variable-sweep-wing aircraft keep wing-mounted payloads straight?

I was able to find this Panavia Tornado cutaway picture (took about 5 seconds): (Air International 1984-09 / P.Jackson - Tornado) Inside the left hand wing you can see a part labelled 197, with ...
Jpe61's user avatar
  • 28.9k
4 votes

Why does the U-2 Dragon Lady not have swept wings?

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 ...
mongo's user avatar
  • 17.8k
4 votes

Could a variable sweep aircraft also use negative angle?

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 ...
Gypaets's user avatar
  • 4,385
4 votes

Is wing sweep needed on supersonic aircraft?

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 ...
Peter Kämpf's user avatar
4 votes

Why do some airplanes have simultaneously a straight wing and a swept horizontal stabilizer?

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 ...
John K's user avatar
  • 132k

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