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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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Is there a practical way to demonstrate sustained flight on the back side of the lift curve without an AoA meter?

Here is a $C_L$ / $AoA$ curve that I took from Wikipedia. The better textbooks say that a stall is that condition in which a further increase in angle of attack will result in a reduction of lift. ...
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2answers
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What is the definition of “best L/D”?

What does "best L/D" mean? Is it meaningless without context? Do you need to know "best for what?" Or, is it synonymous with max L/D?
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2answers
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How are the glide polar and L/D ratio charts related?

We know from other questions and answers that airplanes and gliders in particular can have their performance described in terms of glide polar and Lift-to-Drag ratio. As it appears from the images in ...
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3answers
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How is a wing designed to be stall or spin proof?

Yeah, it sounds like two questions, but I suspect the answers are very closely linked (or maybe even have the same answer.) I was told in this question that trainer planes are often designed to be ...
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2answers
735 views

What are the properties of a good general aviation training aircraft?

I've been told that the best kinds of planes to train in are very small ones, like Cessna 150s and 152s. But I've never been clear as to why. I know they are cheaper to operate, so is operation cost ...
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6answers
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Do box-wings suffer from induced drag the same way as normal wings?

Most wings suffer from induced drag due to a pressure difference above and below the wing causing air to sneak around the tip, forming a vortex. There are various methods to minimize these effects, ...
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7answers
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Can aircraft other than rockets go to space?

I always wondered if it was possible for planes and other aircraft to leave the Earth's atmosphere. Normal commercial transport airplanes can fly pretty high, but then they need air to get the speed ...
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8answers
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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’...
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5answers
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Why can't an airplane stall at zero G?

You may be surprised to find out that an airplane can stall at any attitude if the critical angle of attack is exceeded, but it cannot stall at 0 G. This quote found in the April 2014 issue of Flying ...
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4answers
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How to calculate angular velocity and radius of a turn?

How can I calculate with known tangents of different angles and by rules of thumb? Which formulae should I use for fps and NM?
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3answers
2k views

Does an aircraft's nose landing gear extend on take off?

Something I noticed while flying - while on takeoff it feels as if the plane is tilting upwards even though the plane is clearly still on the ground with all sets of landing gear. Does the nose gear ...
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0answers
108 views

How can an airplane fly upside down? [duplicate]

I thought the shape of the wing gave an airplane upward lift. How can it fly if it's upside down?
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1answer
746 views

Do the effects of turbulence change when banking/turning compared to level flight?

Are the effects created by turbulence on the aircraft different when the aircraft is banking or in level flight? By logic I'd say yes but I would like some technical and practical explanation. When ...
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2answers
372 views

Why is the altimeter unwinding unevenely during a spin?

Spencer Suderman recently did a world record 81-turn inverted flat spin, and dropped over 21 thousand feet while doing so. The entire thing is documented on youtube. The spin starts at 3 minutes into ...
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4answers
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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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1answer
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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 when the ...
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5answers
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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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3answers
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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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5answers
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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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2answers
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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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3answers
6k views

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 ...
13
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2answers
2k views

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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5answers
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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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10answers
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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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3answers
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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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4answers
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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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2answers
3k views

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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5answers
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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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2answers
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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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1answer
3k views

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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2answers
4k views

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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2answers
1k views

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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3answers
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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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1answer
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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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5answers
6k views

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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9answers
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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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7answers
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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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2answers
7k views

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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4answers
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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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4answers
3k views

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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5answers
7k views

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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3answers
1k views

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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3answers
16k views

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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2answers
3k views

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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2answers
1k views

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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1answer
2k views

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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2answers
10k views

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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9answers
6k views

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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1answer
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What's the difference between a two-blade prop and three-blade?

I read that a three blade can improve climb performance and decrease noise. How does that work?