# Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

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### How does aileron reversal work?

I want to know how aileron reversal takes place when control reversal velocity is higher than divergence speed and operating speed is in between them (for conventional wing)
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### Why do hydraulic jack stalls result in pitch up and right roll?

Quoting from page 162 of the book "Fatal traps for helicopter pilots" by Greg Whyte: Hydraulic jack stall (servo transparency) in (AS-350) helicopter is an aerodynamic phenomenon can occur ...
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### Can the pitch be very different from the angle of attack?

How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to ...
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### How does a flying wing keep from going into a flat spin when maneuvering?

How do flying wings, like the B-2 Stealth bomber, actually keep themselves from yawing out of control without a vertical stabilizer? For the record, I assume this has to be a simple mechanics process....
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### What does the zig-zag pattern on Hawker Hunter's leading edge represent?

On some Hawker Hunters, there is a zig-zag on the leading edge of the wing, as shown below. Why do only some Hawker Hunters have this feature, and what is it for?
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### What is the difference between flaps and slats?

I have heard pilots talk about flaps and slats, seemingly interchangeably. Is there a difference between a flap and a slat or they are the same thing?
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### Why do some military aircraft use variable-sweep wings?

There are a couple of American military aircraft (the retired F-14 and the B-1 come to mind immediately), that have variable swept wings. I know that they keep the wings full out (roughly ...
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### How significant is antenna drag on light GA aircraft?

Antennas sticking out of an aircraft obviously increase profile drag, but the folks who design antennas have done a lot to improve aerodynamics: High performance aircraft can have antennas mounted ...
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### Should full flaps be deployed on takeoff?

Are full flaps ever used on takeoff? One flying book I read strongly discouraged anything more than quarter flaps on most planes due to the amount of drag produced. I was just wondering if there are ...
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### What happens when an airplane stalls and why do pilots practice it?

When a non-pilot hears the word stall, it brings to mind what happens when a car stalls - the engine quits. It seems like that would be a dangerous scenario in an airplane. From a non-pilot ...
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### Why do commercial flights turn / bank so sharply?

When I take commercial flights, or you see turns in the vapour trails, they turn very sharply. What's the reason for this - wouldn't it be more efficient to turn gradually?
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### How do conventional and T-tails differ?

What design considerations go into the decision between conventional tails and T-tails? Functionally the horizontal stabilizer/stabilator are the same in both cases, providing negative lift, the ...
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### What is the benefit of spoilerons compared to ailerons?

Some airplanes like the B-52 or the MU-2 use spoilerons instead of ailerons to control roll. What is the benefit of ailerons vs spoilerons and vice versa?
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### Why is the wrong explanation of "air travels a longer distance and creates a lift" so popular?

When I was learning for my license, one of the first diagrams I remember was about the wing profile. The air going around the wing and on the upper side it has to travel a longer way, thus generating ...
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### If the profile of a wing pulls a plane up, why can planes fly inverted?

I'm simplifying here, but every introduction to flying shows us that the profile of a wing leads to lower pressure on the upper side of the wing, hence the wing and the plane attached to it will be ...
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### Is it possible to fly a large aircraft inverted?

I am curious if the inverted plane in the movie Flight 2012 has anything to do with reality / emergency practices. And if it does, can you please explain the concept/ aerodynamics behind of it , or ...
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### When Boeing designed the 737NG, what factors influenced the change in the flap system?

The early Boeing 737 models had wings with triple-slotted flaps that appeared to be derived from the 727. When the 737 was redesigned as the Next Generation series (dash 600 through 900), these flaps ...
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### What happens in a stall during a slip?

In flight training we're warned against skidding turns since they have a higher potential for a stall/spin (the classic example being the stall/spin on the base to final turn). However, how does the ...
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### Where are the first structural damages after maximum speed is passed? [closed]

What 2 parts of the airframe are the first to have structural failure after exceeding maximum speed? Sorry. I just thought there might be a part that usually failed first.
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### What are the effects of the Boeing 787's very flexible wings?

I recently came across this picture of the Boeing 787 series aircraft's incredible wingflex: I suppose this is a consequence of using very light CFRP wings, but how does the wingflex itself improve ...
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### Is flutter speed always smaller than divergence speed for aircraft?

In aeroelasticity, there are three main phenomena that one should take care of: divergence, aileron reversal and flutter. Each of them has an associated speed at which the phenomenon might start to ...
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### Would connecting propeller blades with a continuous ring reduce induced drag?

Turbine engines are covered, which of course is to contain the process (just like a super/turbocharged engine is as soon as the air enters the intake). But it got me thinking, doesn't this also reduce ...
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### What are the pros and cons of high-wing compared to low-wing design?

What are the advantages and disadvantages of a high-wing vs. low-wing aircraft design? When might one prefer one to the other? Is the answer the same for large and small aircraft?
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### Why would a glider have water ballast? If it is trying to stay aloft without an engine, wouldn't it be better to be as light as possible?

So I was looking at the description of a ASW 27 B glider and ran across this statement: Two water tanks in the wing plus a further 35 liter tank in the fuselage enable the ASW 27 B to carry more ...
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### What are the differences in aircraft performance between tractor and pusher propeller designs?

Some aircraft have pusher type propellers. In what ways is it different from a tractor type propeller? What's are the advantages and disadvantages over a tractor type.
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### Why would an airplane pilot choose to intentionally use more runway than required for a takeoff?

An assumed temperature takeoff intentionally requires a pilot to use more runway than would be normally required. Why would someone want to do that instead of getting off the runway in the minimum ...
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### How do I explain what makes an airplane fly to a non-technical person?

As an engineer I can explain in very technical terms exactly what makes an airplane fly, however, it isn't easily understood by non-technical people. How can I explain it to a non-technical person, ...
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### How does an aircraft tailplane work?

How does an aircraft tailplane keep the aircraft stable, and prevent it from tipping over? Also, how does the lift generated by a tailplane compare to that generated by the wing?
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### Is a slip an intentional consequence of a cross-control?

In flight training, you're always told not to cross-control, (for example, rolling right aileron, and stepping on the left rudder), but it seems to me that is exactly what a slip is doing. Is it that ...
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### How can I calculate maximum rate of climb?

By what way and with which variables could you determine a plane's maximum rate of climb per time? If I'm not mistaken, I'm looking for VY.
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### Why do only some aircraft require tail anti-icing?

Why do some aircraft require anti-icing on the tail while others (Dassault Falcon Jets, Boeing 737, 747, etc.) don't?
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### Why should isobars be aligned with the leading edge of the main wing for a transonic cruiser?

When designing an airplane meant to cruise at transonic speeds (or supersonic speeds), I heard that one should look at the isobars on the main wing in order to assess if the shape, sweep angle and ...
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### Why the different wing and tail designs in similar sized jets vs turbo prop?

I was flying on Porter Airlines and they had an info card about how similar the Bombardier (I still say DeHavilland) Dash 8 Q400s are to the Bombardier CSeries they have ordered. There was a cool ...
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### What's P-Factor and why does it occur?

Whenever I hear anyone talking about P-Factor, (whether it be single-engine left turning tendencies or multi-engine loss of directional control scenarios), someone always brings up the fact that the ...
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### What is ground effect?

We've all heard the "acts like a cushion of air" explanation tossed casually around by CFIs. There's also plenty of books and reference materials that give a detailed, accurate, and complete ...
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I read that a three blade can improve climb performance and decrease noise. How does that work?
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### What causes aileron and elevator flutter?

This video shows a Hawker jet with the wing fluttering up and down like it's about to break. What can cause flutter like that? Can it actually cause a wing or stabilizer failure? How can flutter be ...
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### What are the operational differences between an airplane equipped with a constant speed propeller and one with a fixed pitch propeller?

What makes a constant speed prop different from a fixed pitch prop, and what are the operational differences between airplanes with the two?
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### Is a rotary wing craft capable of supersonic flight?

Just what the title states. Since the Wright brothers, aviation technology for fixed-wing craft has advanced by an order or more. Rotary wing craft on the other hand (I know little about aviation; ...
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