Linked Questions

37
votes
4answers
14k views

Do jets breaking the sound barrier leave shredded metal on the ground?

As a kid (1960s and 1970s) we would find shredded metal rolled into a loose ball similar to the shredded paper one might find in an Easter basket, in the hills surrounding our farm. We had the Royal ...
47
votes
8answers
12k views

How complete is our understanding of lift?

I'm currently studying for my PPL and one of the accepted textbooks contains the following disclaimer at the end of the Principles of Flight section on lift: It is important to note that the ...
35
votes
8answers
19k views

How does stall depend on angle of attack but not speed?

Everyone says that the angle of attack is what determines a stall, not the speed. I understand the theory and understand that it is separation of the airflow that matters for stalling. However, I don’...
31
votes
3answers
8k views

What is the immediate cause of stall?

The direct cause of stall is unclear to me. I heard about exceeding maximum angle of attack (around 40°) ; I heard about reaching the stall speed in the current configuration (flaps, etc). I heard ...
26
votes
2answers
10k views

What is the purpose of the small fins on top of the wing surface of Boeing aircraft?

I've noticed on most Boeing aircraft that there are small fins on the upper surface of many of their wings. They are about one inch high and maybe two inches long (it's difficult to judge size from ...
11
votes
4answers
55k views

What happens when an aircraft breaks the sound barrier?

What happens when an aircraft breaks the sound barrier? Why can't it break the sound barrier near the ground?
25
votes
2answers
6k views

How do insects decrease aircraft performance?

Is it true that insects hitting the fuselage could decrease aircraft performance and increase fuel consumption? Insects are small in mass. I think even a large amount of them accumulate on the ...
15
votes
2answers
15k views

What is the reason for the poor low-speed characteristics of sweptback wings?

I know there are advantages of swept-back wings delaying shock-wave allowing a aircraft to fly faster. However, what are the disadvantages. I know one of them is that they have very poor low speed ...
20
votes
5answers
13k views

What are the advantages of a Trimmable Horizontal Stabilizer?

What are the advantages of a Trimmable Horizontal Stabilizer (THS)? For example, a THS is used on some Airbus and Embraer aircraft. What is the most important advantage, and why don't some other ...
18
votes
2answers
7k views

Why do some airplanes have vertical strakes?

A lot of different aircraft have vertical or near-vertical fins below the empennage, or above the empennage and attached to the front of the vertical stabilizer. What purpose do these devices serve?
20
votes
3answers
24k views

What is a high speed stall?

I'm told that planes can actually stall when the airflow over the wing goes past Mach 1? Why does this happen and how do you design an aircraft to avoid it?
18
votes
3answers
31k views

What is a vortex generator?

I saw a vortex generator mentioned in an aircraft listing. What is a vortex generator?
20
votes
2answers
3k views

What are the advantages of the NASA LEAPTech propeller on wing technology?

NASA has detailed experiments with a new type of parallel array of small electric propellers on the leading edge of the wing technology that they are calling LEAPTech. The press release notes that ...
23
votes
2answers
3k views

Is a golf ball surface a good idea for wings or fuselage?

I searched for an infamous golf ball question on this site but did not find any, so I guess it's time for one. Would a dimpled surface like a golf ball somehow improve the aerodynamics of an airplane?...
8
votes
5answers
24k views

What is profile drag?

I know about induced drag, parasite drag, form drag, skin drag, wave drag, and interference drag. But I don't encounter the term profile drag often, and I can't find a good definition of it. Is ...
16
votes
2answers
8k views

What is the significance of the speed of sound to aerodynamics and aircraft design?

Almost every aspect of flight seems to be affected by the speed of sound, somewhat in the same way that nearly everything in physics is determined by the speed of light. Obviously it's not exactly ...
11
votes
4answers
4k views

Why do airfoil's trailing edges point downward?

The trailing edge of and airfoil is mostly pointing downward. Is there any reason for that? Down wash increases drag and down wash is due to the direction of air pointing down. If the trailing edge is ...
21
votes
1answer
21k views

Accelerated Stall, what is it, how do you prevent it?

I've read a lot of NTSB crash reports regarding small, GA aircraft (just trying to figure out what went wrong and what to avoid.) There seem to be a lot of reports that talk about "low altitude high ...
13
votes
3answers
2k views

What is the difference between flow separation and turbulent flow?

For air flowing over a wing, both flow separation and turbulent flow involve disturbed flow next to the surface and smooth flow further away. At what point does one say "oh, this flow has changed ...
16
votes
4answers
4k views

Why are swept wings better for breaking the sound barrier?

I'm told that swept wings perform better when an aircraft is trying to break the sound barrier. I was wondering why that would be?
11
votes
2answers
57k views

What are the advantages and disadvantages of a delta wing compared to a swept wing?

What advantage does a delta wing have over a swept wing with high AR for supersonic flight? And what disadvantage does a delta wing have over a swept wing with high AR for transonic flight? The ...
8
votes
4answers
14k views

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

If you search Google for span wise flow, the first result under the pictures tab is a image of a wing with the span wise flow at the trailing edge: (Source) If you look at some other photos you ...
10
votes
3answers
3k views

How is the area rule applied on airliners like the A380?

Wikipedia says that because of the area rule's impact on wave drag: aircraft have to be carefully arranged so that at the location of the wing, the fuselage is narrowed or "waisted", so that the ...
10
votes
2answers
2k views

How would an airfoil react if it was flown backwards?

Out of curiosity what would happen? Would pressure on both top and bottom flip? or stay the same or act as a normal wing with less lift? I'd assume it would still take longer to travel over the top ...
5
votes
4answers
1k views

What is the fundamental physics behind L/D decreasing as AoA increases beyond the optimal point?

Why does lift over drag decrease with AoA past the optimum AoA? Is it because the backwards vector for a given lift force on the wing is now larger for a given air particle compared to lower AoA? ...
9
votes
2answers
2k views

What causes the reduction in speed across the shockwave?

Wherever I read about shock waves, it is mentioned that there is a reduction in speed across the shock wave. Can someone please explain what happens at the molecular level, i.e. the physics of the ...
6
votes
5answers
3k views

What happens during a powered descent?

I was having a discussion with my friend about equilibrium condition in flight: Scenario: While going in straight and level flight, say I reduced my airspeed by 30 mph. At the same time keeping the ...
4
votes
5answers
3k views

What is the relation between the boundary layer and lift of an aerofoil?

Why do we try to reduce the thickness of the boundary layer over an aerofoil as much as possible if the boundary layer is responsible for creating lift?
10
votes
2answers
3k views

What are the pros/cons of all-moving rudder?

All-moving flight control surface (stabilator instead of a stabilisator+elevator) are common on supersonic aircrafts but this is usually used for pitch control only. For rudder, this design (one all-...
4
votes
1answer
13k views

What is the effect of airfoil thickness on aerodynamic lift?

More than once I`ve read that the airfoil thickness contributes little to the lift compared to the angle of attack and airfoil curvature and has more to do with airfoil stall characteristics. Could ...

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