42
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 ...
- 228k
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 ...
- 228k
23
votes
What is the reason for the poor low-speed characteristics of sweptback wings?
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 ...
- 228k
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 ...
- 9,003
18
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 ...
- 228k
15
votes
What is the reason for the poor low-speed characteristics of sweptback wings?
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 ...
- 99.8k
15
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 ...
- 151
14
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 ...
- 829
13
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 ...
- 228k
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 ...
- 22.6k
10
votes
What are the advantages and disadvantages of an oblique wing over a swing wing?
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 ...
- 99.8k
10
votes
Accepted
What are the advantages and disadvantages of an oblique wing over a swing wing?
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 ...
- 228k
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 ...
- 228k
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:
...
- 12.7k
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, ...
- 702
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 ...
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 ...
- 228k
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 ...
- 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 ...
- 61.2k
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=...
- 11k
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:
...
- 228k
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 ...
- 4,588
5
votes
What aerodynamic characteristics arise from trailing edge sweep angle?
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 ...
- 4,368
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 & ...
- 39.1k
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 ...
- 125k
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 ...
- 6,932
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 ...
- 26.7k
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 ...
- 17.7k
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