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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Can a steady flow have stagnation points?

I am confused by this idea. If a flow is steady, its streamlines are unchanging. Taking the typical example of an airfoil, there is (at least) one streamline which will hit the leading edge of the ...
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How does inlet spillage drag produce a lip suction effect?

From this page: Spillage drag, as the name implies, occurs when an inlet "spills" air around the outside instead of conducting the air to the compressor face. The amount of air that goes through ...
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How does the angle of attack vary in turns?

I read somewhere that when the aircraft banks to turn, its angle of attack increases.Since angle of attack is the angle between the relative wind and chord line, how does turning increase it? Is it ...
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Can airliners benefit from vertical take-off and landing?

A vertical take-off and landing (VTOL) aircraft is one that can hover, take off, and land vertically. We have several military fighter jets, which can takeoff and land vertically (like the Harrier ...
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How do propeller-driven, fixed-wing UAVs counter negative torque from engine rotation?

What cancels the rolling moment produced from the rotation of the engine?
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Why is a rectangular wing planform less efficient than others?

I read somewhere that a rectangular wing is inefficient compared to other wing planforms. Can someone clarify why this kind of wing planform is inefficient compared to other planforms and what causes ...
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Why do slats deploy first?

I know on the 737, the leading edge slats deploy at the first flap setting, and the trailing edge flaps deploy after that at higher flaps settings. Why do the slats deploy before the trailing edge ...
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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 there a maximum lift to drag ratio?

If I recall correctly, the best competition gliders have a L/D ratio as high as 60:1. What imposes this limit? Is there a maximum theoretical L/D ratio, or could sufficiently advanced materials allow ...
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What's the advantage of the F4U Corsair's gull wing design?

What is the advantage of the F4U Corsair's gull wing design? Is there also a disadvantage to this? The wing design just seems odd, and as far as I know it is one of the only planes to use this design....
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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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Why did the Junkers Ju-52 have corrugated external surfaces?

Every time I pass by Munich I have to pay a visit to the Deutsches museum, in particular to the aviation wing. Among the other aircraft on display, there is a Junkers Ju-52. A different photo taken ...
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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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Where is the 'zone of reversed commands...'?

There seems to be some confusion about where the 'zone of reversed commands' really is, i.e. where a decrease of airspeed results in an increase of drag. Some references place that zone to the left ...
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Why does the spiraling slipstream from a propeller hit the left side of the fin?

In the picture below, if the fuselage was shorter/longer, would the spiraling slipstream from a propeller hit the fin on the right side as opposed to the left? Is it a deliberate positioning if yes, ...
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Is the low air pressure on top of the wing the major contributor to lift?

I am kind of old time flyer. Started to fly with those primitive hang-glides with titanium frame and the yoke control, around 1966 and then after a few close calls and getting older I switched to ...
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How much lift comes from the fuselage on modern jets?

I understand this question is broad, but specifically referencing modern jets where composites are used a lot to get complex surfaces (such as in the Beechcraft Premier 1), how much of the total lift ...
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Why is a reduction in lift called 'drag'?

Induced drag is high pressure air 'leaking' to the upper part of the wing (low pressure zone) creating a vortex which means the area of the wing tip with the vortex can't create lift. Drag on the ...
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If a helicopter's tail rotor fails, is it possible to perform an emergency landing?

In the event of a total failure of the tail rotor, is it possible to maneuver a helicopter to an emergency landing spot that is within, say, 30 minutes flying time? What are the maneuvers required ...
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Why does the DC-10's horizontal stabilizer have such a pronounced dihedral?

If you look at this picture, you'll see that the horizontal stabilizer has a very pronounced dihedral in comparison to the wings. Could somebody explain in a simple way why? I understand that a ...
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Why do Boeing and Airbus have distinctively different nose designs?

Boeing aircraft generally have a pointy nose, which seems to me to imply better aerodynamic qualities, less drag etc. Airbus aircraft on the other hand have rather bulbous noses. Is this difference ...
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In a slip or skid, how does one wing have a higher angle of attack and more lift?

I've discussed this with my instructor numerous times, and I have the concept memorized, but from an aerodynamic point of view, I can't see how the angle of relative wind to chord line is different ...
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What is the physical meaning of circulation found in Kutta condition?

The Kutta–Joukowski theorem is applicable for 2D lift calculation as soon as the Kutta condition is verified. When this is the case, there is a circulation $\small \Gamma$ around the airfoil. My ...
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Which aircraft endure the highest Max Q's (aerodynamic pressure)?

What are the highest aerodynamic pressures encountered in any aircraft? And does this limit the maximum speed of any aircraft at certain altitudes? Broadly, 'how fast can you go [at a given altitude]?'...
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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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What is the relation between drag and weight?

Given an aircraft type and fixing its wing configuration (flaps, slats) and fixing its speed and altitude and assuming it flies horizontally, what is the relationship between the aerodynamic drag and ...
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How to find the location of the Aerodynamic centre?

Everywhere I look I'm only able to find information about airfoils. How do I find out the location of the Aerodynamic centre of an arbitrary aircraft irrespective of its type or shape?
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Why is the critical AoA of most flaps 40° when most airfoils stall at 15°?

A plain flap deflected 40 degrees is largely stalled (...) Flaps stall at 40° according to an answer on Quora, why is this so when typical airfoils stall at 15°?
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What is the pressure distribution around a supersonic wing?

In subsonic flight the lift manifests itself at 25% of chord, but shifts to 50% of chord when the airplane goes supersonic. Wondering about that made me think that the reason might be that there is ...
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How do paraglider controls work?

I recently got into paragliding, but I am quite confused on how their controls work. I am quite aware of how the control surfaces work on fixed-wing aircraft. Let's use for example an aileron. ...
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What determines the best glide speed?

I found the best glide speed of cessna 152 is 60 kts. My question is why it is not more or less than 60 kts? What are the factors upon which the best gliding speed is determined?
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How are wind tunnels used with scale models?

This answer introduced me to the problem of using scaled models in a wind tunnel. How are wind-tunnels used in practice (for modelling the performance of subsonic airplanes)? In particular: Do they ...
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Why is stall speed listed in a POH?

In this comment on this question about stall warning systems, it was stated that: You can stall at any airspeed (see this question and this one) and in any attitude, only the AoA is important ...
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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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What are the disadvantages (if any) of using a supercritical airfoil?

The title sums up my question pretty well. I've searched all over this site, having read many of the questions and answers to various supercritical wing topics, but I haven't found any mention of ...
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What is the peak of coffin corner called?

The converging point of Vx and Vy is the absolute ceiling. Can I call the peak of the coffin corner an absolute ceiling as well?
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Does anyone know an equation relating wingspan to gliding distance for a glider?

I found this equation online but it is not from a reputable source and has no derivation. Could anyone help me by deriving this equation or even verifying its accuracy? I would love to cite and use ...
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How can we determine the maximum camber and thickness for airplane wings?

I want to know if there are any standard factors for determining maximum wing camber and thickness for heavy and light airplanes? I'm using an optimization process to find the best wing shape to ...
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Why don't helicopter blades look like other propellers?

While doing an image search, I found many different shaped propellers and asked about them in this question. In it, Peter Kampf answered my question with his usual thoroughness. However, as I looked ...
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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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An airplane has an engine that pushes its flight. What force pushes a glider to fly? [duplicate]

An airplane has an engine that pushes its flight. What force pushes a glider to fly? Is it gravity? I think the flight of a glider is driven by gravity, but some people disagree with me. They say ...
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Why does a helicopter need cyclic control rather than just tilting the whole main rotor?

Helicopters use a cyclic control to tilt each blade differently through the rotor's revolution. This is quite a complex mechanism. What is the advantage of this vs tilting the whole rotor plane? This ...
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What is "settling with power" and how does it differ from vortex ring state?

I've always heard these terms used interchangeably. I figured that "settling with power" was what the pilot did to cause the vortex ring state (VRS). But comments on another question indicate that ...
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What are the advantages and disadvantages of having landing gear doors?

To make comparison easy, let us take the example of B737 and A320, both similar aircrafts with retractable landing gear. As seen on the photo below, the B737 doesn't have gear doors for the wheels, ...
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What is the lift force per unit span?

I got Aircraft Design: A conceptual approach for Christmas, and I'm having a hard time with lift coefficients because I honestly have no idea what "lift force per unit span" means, so can someone ...
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Is this paragraph about the dihedral effect in the FAA's Glider Flying Handbook correct?

I've been reading the FAA's Glider Flying Handbook, 2013 (FAA-H-8083-13A). In chapter 3 ("Aerodynamics of Flight"), the book is discussing stability. On page 3-12, it states: Dihedral is the upward ...
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Why do we use dimensionless expressions in flight mechanics and aerodynamics?

Why do we use non-dimensional expressions in flight mechanics and aerodynamics? We could as well directly calculate forces and moments; would that not be more relevant to the specific problem?
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Why don't helicopters prefer shorter rotors with more blades? [duplicate]

My understanding of helicopters is that, despite theoretically increasing efficiency, longer blades are worse in practice than short ones in every respect (except, perhaps, cost): Longer blades are ...
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How does turning a small plane by opening the doors work?

I've just watched a video of a small Cessna turning not with ailerons or rudder but by opening its doors. They said that the door acts like a rudder, but in the video one of the guys opens the left ...
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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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