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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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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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7answers
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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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4answers
377 views

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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1answer
62 views

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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0answers
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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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1answer
73 views

Caravan 208B EX Glide ratio

What is the glide ratio for the new EX Cessna 208B with 8750 amphibian floats?
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2answers
180 views

Does lift generation create a vacuum over an airfoil? [duplicate]

According to Bernoulli’s principle, airflow speeds up over an airfoil which decreases the pressure, and I read somewhere that when airflow speeds up over an airfoil, this creates a vacuum. Is this ...
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2answers
170 views

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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0answers
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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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2answers
329 views

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 ...
7
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1answer
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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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1answer
359 views

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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1answer
164 views

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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2answers
151 views

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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2answers
110 views

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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0answers
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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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3answers
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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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1answer
168 views

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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0answers
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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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6answers
8k views

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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5answers
103 views

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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1answer
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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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4answers
319 views

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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1answer
241 views

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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3answers
458 views

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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1answer
161 views

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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3answers
296 views

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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3answers
267 views

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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1answer
448 views

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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0answers
53 views

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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2answers
362 views

'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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1answer
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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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2answers
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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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1answer
216 views

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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0answers
125 views

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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2answers
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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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4answers
217 views

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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5answers
461 views

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 ...
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1answer
198 views

Why does the Aurora D8 have vents on the bottom of its fuselage?

The Aurora D8 is a concept of an experimental aircraft (not an actual aircraft for now), described in this site. It's discussed in this question here on Aviation.SX. I was watching the embedded video ...
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0answers
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How to transform a NACA airfoil into a near-circle using the inverse Karman-Trefftz?

Is there anyway to find the leading-edge's center of curvature of a NACA Airfoil? I'm trying to transform a NACA airfoil into a near-circle using the inverse Karman-Trefftz transformation. the ...
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2answers
198 views

How is a propeller diameter for given application determined?

let's say I need 1000 N of thrust for a given aircraft and flight velocity. I have available a fixed pitch propeller with a given shape, and thus given performance to advance ratio curves. Let's say ...
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0answers
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How much lift can be generated by the intake lip of a duct?

How to calculate the extra lift gained by the intake lip of a duct? Aside from improving efficiency by preventing tip vortices, if a duct has a bell-shaped intake, this lip around the edge creates ...
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1answer
103 views

What is the relation between hinge moment at the control surface and servo torque? [closed]

I am trying to estimate the required servo torque for my design using hinge moment at the elevator. XFOIL results were as follows- I am getting a Hinge moment of about 0.06-0.08 Nm. for the given ...
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1answer
230 views

Difference between Mach buffet and shock stall

What is the difference between Mach buffet and shock stall?
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3answers
339 views

What has happened to make me experience negative G with the control stick FULL AFT near the top of a loop?

I experienced negative G with the control stick FULL AFT near the top of a loop. My questions: Aerodynamically, what happened? Was the wing meeting the air at a negative-lift angle-of-attack (...
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0answers
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Is this the right way to calculate the roll damping moment coefficient of a projectile in free-flight?

Let's say that I already have data for the spin rate $p\:\frac{rad}{s}$ and velocity of a projectile $V\:\frac {ft}{s}$ in free-flight at multiple points along its trajectory. Presently, I calculate ...
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0answers
53 views

Induced drag - inverse proportion between induced drag and parasitic drag [duplicate]

I recently learned that the slower an aircraft is traveling, the higher the induced drag and the lower the parasitic drag. The parasitic drag is lower because the particles have less force against the ...
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2answers
261 views

Propeller Characteristics at Different Altitudes

Assuming I have a propeller with a given diameter (D), pitch, blade twist, and number of blades, I can theoretically analyze discrete airfoil sections in XFOIL and come up with lift and drag polars ...
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1answer
90 views

Accounting for torsional forces during wing load tests

According to this aviation.se question, wing load tests are done by placing weights on the wings (upside down). This unfortunately only tests the wings bending loads (for cantilever wings) and the ...