# Questions tagged [aerodynamics]

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

1,117 questions
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### What should be the relative positions of a wing's aerodynamic center and center of gravity?

A positively cambered wing with finite length L has its aerodynamic center AC located 25% from the wing's leading edge. What about the CG of the wing itself (not the CG of the whole plane)? Is there ...
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### What is the first cause of induced drag changes?

What causes induced drag to change with speed: speed itself or angle of attack? I have found in different sources 2 versions: 1). Most cited version according to which, with ↑ speed in straight and ...
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### What is the cooling air exhaust velocity for the piston engine of a propeller driven aircraft?

Piston engines of propeller driven aircrafts need to be cooled. There are engine cowlings which accomodate the inflow of air to "wash" over the engines within them and which is then exhausted out into ...
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### What would be a simple aerodynamics simulation software for a student? [closed]

I have a project due 2 weeks from now that demands we make a glider using Styrofoam. I'd like to simulate the results as I plan my glider before I build it. Which simple software, which allows ...
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### Does a rotating control surface change the wing area?

It might seem like a silly question, but bear with me. I am using the standard formula to calculate the lift force of a wing. L = (1/2) d v2 s CL My question related to the s part of the formula. ...
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### Model for flutter analysis of Aerofoil

Why is a aerofoil modeled by attached torsional and linear spring in a wing flutter analysis.The model does not even satisfy the boundary condition of zero displacement of wing at point of attachment ...
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### How does angle of attack vary during climbing flight?

I'm a little confused by the angle of attack of an aircraft during climbing flight. Suppose you have an aircraft in level flight which then rotates to some angle x. Just after rotation, I would assume ...
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### How widely accepted and used is the International Standard Atmosphere?

Is it used in the US as well for an example, where there is the US Standard Atmosphere. With different standard models, how widely is the International Standard Atmosphere applicable? Or is it only ...
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### What prevents BFS from becoming unstable when pitching from horizontal to vertical?

In this video from (SpaceX's BFS landing) there is a point where the ship tilts from horizontal « belly first » terminal velocity freefall, to vertical « engine first » landing position. The graph ...
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### What was the first Russian jet designed with the use of area rule?

What was the first Russian jet designed with the use of area rule? Also, how did the Russians acquire the knowledge of this design method? Was Whitcomb's discovery public?
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### How does maximum speed vary with altitude?

Question: How does a commercial jetliner's highest possible groundspeed vary with altitude (assuming wind=0) ? My understanding is that drag decreases with altitude, therefore maxspeed increases with ...
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### How is the inflow velocity distributed of a tilted and trimmed rotor in hover?

I'm wondering of how the inflow velocities per blade look during one revolution of a real-life helicopter in hover (no inflow velocity into the rotor plane) with a tilted rotor plane about 20 deg. Is ...
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### Why does the aerodynamic center exist?

I am a glider pilot and instructor with a master’s degree in actuarial mathematics. I teach aerodynamics every winter for upcoming glider pilots. As you surely know, the aerodynamic center is the ...
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### What is the Relation between Critical AoA with Chordline? [duplicate]

I read here an explanation about angle of attack (AoA) as below: Overly long (forward-back wise) wings will generally have a smaller critical Angle of Attack while smaller ones will have more ...
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### Are there any aircraft designs that are (relatively) insensitive to the effects of airframe icing?

Snow and ice buildup on aircraft (especially the wings) is a well-known and feared hazard of cold-weather operations; it roughens the surface of the wings and changes their profile, which combine to ...
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### Caravan 208B EX Glide ratio

What is the glide ratio for the new EX Cessna 208B with 8750 amphibian floats?
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### Does Lift generation create a vacuum over an aerofoil? [duplicate]

According to Bernoulli’s principle, Airflow speeds up over an aerofoil which decreases the pressure. and I read somewhere that when airflow speeds up over an aerofoil, this creates a vacuum. how true/...
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### Control free and fixed static margin

For many aircraft root and tip chord is given but the exact location of aerodynamic center and center of gravity is not given. Considering this information; How can I calculate control free and fixed ...
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### Does the Lilium VTOL wings produces lift during takeoff?

I just had a look on some of the recent development in the personal VTOL electrical aircrafts. I am wondering if the Lilium VTOL wings produces lift during takeoff? I would expect a quit high wind ...
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### What is the aerodynamic purpose of an Acorn?

This is an IL-62. On the tail of the aircraft, there is a large cone, protruding out of the vertical and horizontal stabilizer which is called acorn. I am trying to figure out what is the aerodynamic ...
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### Why does strong shock wave-boundary-layer interaction produce a bubble reattachment?

The picture represents a lambda type shock wave, separating the boundary layer at its foot. Separation causes a recirculation bubble to appear. I understand why separation has happened, but what is ...
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### What is the purpose of the serrated trailing edge spoilers on the B52?

At around 50 seconds on the linked video you can see the serrations on the trailing edge of the B52's spoiler. What purpose does it have, and what gives it advantage/disadvantage over the standard ...
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### Circular arc airfoil wing: why does the wing nose down twist due to camber?

I am reading this paper: "Computational Investigation of Microscale Shrouded Rotor Aerodynamics in Hover" Vinod K. Lakshminarayan, James D. Baeder ; JOURNAL OF THE AMERICAN HELICOPTER SOCIETY56, ...
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### How to calculate the amount of weight my plane can takeoff with?

This is how I approached this problem- My takeoff run is limited. So, depending on my configuration I calculated the maximum possible velocity I can attain in my groundroll. I assumed that at the end ...
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### How to calculate the forces and moments required to aerodynamically actuate slats?

I am trying to make a wing where slats automatically deploy once it hits a higher angle of attack, let's say right before stall. I need to roughly estimate the forces and moments acting on the ...
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### How would a sudden change in weight affect a plane? [duplicate]

If I have a plane trimmed for perfect straight and level flight and then suddenly I removed some mass from the airplane (let’s ignore any momentums introduced by mass release) – how would the aircraft ...
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### Does the pressure at the static ports drop as the aircraft's speed increases?

This answer by Tyler Durden explains what static ports are and how they work: The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. ...
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### How to calculate the induced drag coefficient?

In an exercice of Flight mechanic, I have to compute the drag coefficient at zero lift: $C_{D0}$.We saw in class two ways to find it : $$C_{D0} = \frac{\pi AR e}{4E_{max}^2}$$ With $AR$ the aspect ...
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### How to calculate the shear centre of a wing?

How is shear centre of a wings calculated? i.e. how can I calculate the wing shear centre of a two spar wing with main spar at 0% of wing chord and rear spar at 75% of wing chord? (Assuming the two ...
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### Why then don't aircraft fly even higher, for even greater efficiency? [duplicate]

After reading various superb QA on here I now see that (basically) aircraft are more efficient per passenger-mile, at higher altitudes. Why don't we go even higher, than current typical airliner ...
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### Is there any effect that contributes to roll stability even in the absence of sideslip?

Is there any physical dynamic-- involving high wing placement, "pendulum" effect of CG far below wing, or anything else-- that contributes to roll stability in a way that is NOT dependent upon the ...
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### Why commercial planes fly at high altitudes? [duplicate]

L= Clq(TAS)^2*S/2 D= Dlq(TAS)^2*S/2 Some say it is due to lower friction drag due to lower density. However if our weight does not change, that means lift does not change as well. So when air density ...
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### Does Wing Area vary with angle ot attack?

For a very basic airplane, say like Cessna 150 is built with Wing Area (S)=15 meter squared (say it 15m*1m). In another part said that the Lift (L)=0.5*rho*(V)^2*Cl*S. Mean, Lift is affected by the ...
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### Lift to drag ratio of airliners

I don't know if this is the right place to ask, but I am looking for lift-to-drag ratios (L/D) of different airliners. I have found a paper [1] which has some estimates of L/D for some jetliners, but ...
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### Why do stealth aircraft generally lose in maneuverability?

Whilst stealthy built aircraft have (or claim to have) many anti-detection systems, they seem to have to compromise on less maneuverability features, and even have to keep their missiles inside, not ...
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### Why do we see a reduction in temperature in a wind tunnel by increasing the velocity, but in a real flight it's the opposite?

In a real flight, when the speed of an aircraft increases, we see an increase in temperature too. So that at high Mach numbers the surfaces of the aircraft will be very hot. Now I have encountered ...
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### What is compressibility drag?

I don't mean wave drag here. What is compressibility drag, which is understood to be a form of miscellaneous drag?
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### Does shrouding a propeller minimize induced drag by equalizing the downwash velocity along its blades?

EDIT: It's not a duplicate of Are ducted fans more efficient? That question and the answers doesn't address the reason for the higher theoretical efficiency, it is more about efficiency in practice (...
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### Which airfoil would be optimum for a glider?

The glider I am designing has a mission requirement to fly for as much time as possible. It will fly in the low Re range of about 150,000 to 250,000. While comparing different airfoils I am looking ...
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### Is winglet height equivalent to duct height?

Winglets increase effective wingspan by causing vorticies to be generated further away from the wing root in proportion to the height of the winglet (if vertical), likewise with winglets on propellers....
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### 'Gravitational' power vs. engine power

A glider gets the power it needs to fly from the decrease of gravitational potential energy associated to the descent. My question is: for the same weight $W$, airspeed $V$, and a prop efficiency of ...
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### Why do I see moisture coming from the middle of the wing as well as wingtip vortices? [duplicate]

A lot of times I see small tube like streams of visible moisture training from the middle of an airliners wing. I assume this is induced drag created by wingtip vortices, when the aircraft is heavy, ...
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### How does the line of thrust affect longitudinal stability?

I’ve been studying Pilots Handbook of Aeronautical Knowledge FAA-H-8083-25B and on p 5-17 they talk about thrust line and stability. Can someone explain why the moment changes when thrust is applied? ...
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### What are these lumps on the top side of the wings of military aircraft? [closed]

There is an online video game called War Thunder that lets you fly various planes from roughly the 30s to the late 50s. It has some pretty detailed models, and I've noticed these lumps on the wings of ...
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### What are stick position stability and stick force stability?

What are stick position stability and stick force stability? What are the difference between them? How will changing trim of an aircraft affect them?
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### Could reduced-lift wingtips allow an airplane to generate less wake turbulence?

Would it be possible to weaken the wake vortices generated by a large aircraft (which can be dangerous to smaller aircraft behind the large aircraft, and are the limiting factor determining how ...
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### In general, how do aircraft handle differently in inverted flight versus in upright flight?

Inverted flight is flight with a roll angle between 90° and 270° (although it classically referred specifically to flight with a roll angle of 180° - i.e., upside-down). In what ways, in general, ...
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### Is the aircraft neutral point a function of the tail incidence angle?

While using XFLR v5 for a basic analysis I am facing this issue. For a fixed configuration I varied the tail incidence angle and XFLR is displaying a change in the Neutral point location. But as per ...