# Questions tagged [airfoil]

The 2D shape of a section of aircraft wing.

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7 votes
2 answers
3k views

### What is the difference between static and dynamic stall?

What are the static and dynamic stalls on the aircrafts wing? When would we encounter static and when dynamic one? What is the difference between them?
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3 votes
2 answers
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### How can I tell from the location of flow separation if an airfoil is stalled?

I am in the process of completing a carbon airfoil for my track car (sedan) and I am looking to determine stall angle visually. AKA, wool tufts and highway runs with my GoPro pointed upward from the ...
2 votes
1 answer
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### Why are hexa airfoils used on rockets despite having more drag that diamond airfoils? [closed]

I was doing a study on airfoils shape for a rocket. I tested the diamond and the hexagonal airfoil with Missile DatCom, RasAero and the Shock Expansion theory and from my results it seems like the ...
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5 votes
1 answer
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### What's the theoretical background of the critical angle of attack?

The critical angle of attack seems to be at all (most?) airfoils around 15-20°. Why is that? Why is it in this range and not lower or higher? Is it just the result of optimizing airfoils? Or is it ...
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1 vote
0 answers
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### What is the relationship between the Center of Pressure and flap deployment?

I have been reading regarding the Center of Pressure of an airfoil (Cp) and the relationship with angle of attack. What is a good way to explain in layman's terms why the pressure changes in such a ...
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1 answer
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### Anyone able to help identify what aerofoil this is?

Firstly, apologies for the potato quality of the image below. I am attempting to determine the qualities of a VTOL and cannot find any data online. If anyone knows what aerofoil this could be that ...
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0 answers
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### What is subcritical and supercritical boundary layer?

What is subcritical and supercritical boundary layer? What is the difference between them?
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5 votes
2 answers
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### What is a rudder or fin stall?

What is a rudder or fin stall, how will the aircraft behave in that situation, and how should the pilot recognise it? What is the recovery procedure? And what is rudder reversal?
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1 vote
1 answer
318 views

### What airfoil type is used on the B727-200F?

What airfoil type is used on the Boeing 727-200F? Is it a NACA profile or something else?
0 votes
1 answer
440 views

### What to be considered in designing airplane tail (vertical and horizontal stabilizer, elevators and rudder)? [closed]

I would like to make a small amateur triplane with it maximum weight approximately 400 kgs with maximum speed 100 knots (180 kph). I have read many discussions about how to calculate the wing ...
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2 votes
0 answers
189 views

### Where can I find airfoil data for the Beechcraft 1900D tail?

I am creating a CAD model of Beechcraft 1900D from images for a project. So far most info is available in http://www.users.on.net/~grypen/b1900d.html except the airfoil used by the tails. I have ...
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2 votes
3 answers
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### Fabric-covered Clark Y Max Coefficient of Lift

I'm looking at the Aeronca C-3 Collegian, which had a Clark Y airfoil, and I'm finding the following: Wing area: 142 ft² Empty weight: 466 lbs Payload: 470 lbs Stall speed: 38 mph When I do the math ...
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1 vote
1 answer
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### What was the Airfoil of Handley Page P.115?

This extreme sweptback delta was built to test the Concorde wing at low speeds, sources say it had a biconv 6% airfoil, but I failed in finding data about it.
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12 votes
4 answers
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### Why isn't there a single best airfoil for subsonic flight?

Why does airfoil used by modern subsonic aircraft (this is true for transonic airliners too) vary from plane to plane? Haven't we figured out a single best airfoil shape, with the highest lift to ...
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4 votes
2 answers
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### Why does a sharp leading edge result in a larger pressure peak?

I know in the real world the sharp leading edge (LE) will results in a larger pressure peak compared to a large radius LE. And that there are three types of stall. But I want the explanation in ...
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1 vote
1 answer
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### Is high speed buffet possible at supersonic speed?

Since high speed buffet is caused by boundary layer separation due to shock wave and at supersonic flight there is no shock wave directly onto the airfoil (it is attached to the trailing edge), is ...
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15 votes
4 answers
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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 ...
7 votes
1 answer
626 views

### 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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2 votes
1 answer
505 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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-2 votes
1 answer
665 views

### the usage of thin airfoils for high-speed flight [closed]

what is The usage of thin aerofoils for high-speed flight I tried those answers:  They are perfect for controlling the local angle of attack, for instance in turbomachinery and flaps.  At ...
-1 votes
1 answer
584 views

### How do I choose the correct airfoil for my fast cargo UAV project?

I am not able to decide which airfoil to choose for my UAV project as I am confused. I need to lift a maximum of 100kg of extra payload excluding the aircraft's fuel and empty weight. Cruise velocity ...
2 votes
1 answer
174 views

### What is the function of a sweep cable?

This is Goat3 ultralight with sweep cables,what is the fuction of these sweep cables?
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1 vote
1 answer
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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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1 answer
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### What is the purpose of this span wise "false spar" on Affordaplane wings?

This is the wing of an Affordaplane Ultralight,what is the use of those spanwise foam boards between the foam ribs,I know it's not for aesthetics.
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2 votes
1 answer
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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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4 votes
3 answers
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### What are the rules of airfoil thickness from root to tip on tapered wings?

I'm doing some research on wings and airfoils used in the 30s and 40s, and I'm trying to understand the rules about airfoil proportional thickness changes across the wing (root to tip) on tapered ...
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8 votes
2 answers
820 views

### Transonic buffet - reason for a rapid movements of the shockwave along the wing chord line?

I know that transonic aerodynamic buffet is caused by the separated turbulent boundary layer striking the airframe (horizontal stabilizer, wings, fuselage) with considerable force causing a high ...
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8 votes
3 answers
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### Why does a turbulent boundary layer cause more friction drag than a laminar boundary layer?

From what I understand, friction is caused by viscosity and a bigger Reynolds number signifies lower viscosity. Thus, a higher Reynolds number(i.e. turbulent flow) results in lower friction. But, ...
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1 answer
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### Airfoils designed for reverse flow [duplicate]

This question might seem strange as almost all aircraft have the air flowing over the wing in only one direction. However if you wanted to design an airfoil would have a good L/D in the forward flow ...
1 vote
1 answer
255 views

### How do wing ribs withstand lateral lift force?

During roll,there is a vertical component of lift that keeps the plane in the air and an horizontal component that actually rolls the plane,how are wing ribs designed to help withstand this vertical(...
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2 votes
1 answer
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### How (or where) do I find an airfoil optimized for low reynolds numbers (100,000~150,000)?

Looking to build a RC plane. Because the span is going to be small and the speed relatively low, I estimate the R-number to be around 100,000. Is there an airfoil optimized for that range of Reynold's ...
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2 votes
2 answers
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### Why are cambered airfoils used for horizontal stabilizers in some designs?

From what I know, usually NACA9/12 or similar symmetrical airfoils are used for the tail. Still some aircrafts use highly cambered airfoils for elevators. What are some advantages and disadvantages ...
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5 votes
1 answer
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### What is wing trammelling?

What is wing trammelling and how does it affect wing stability and performance?
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4 votes
2 answers
1k views

### What is the purpose of thinner airfoils used near wing tips?

I know that a thicker airfoil at root will strengthen the root spar but what is the reason behind using thinner airfoils at the tip? Is it because thinner airfoils have higher stalling angles of ...
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3 votes
3 answers
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### Why does the stagnation point on airfoil move with the angle of attack?

What is the physical explanation for the reason the stagnation point is where it is? And, why does it move further down the lower side of the airfoil with an increase in angle of attack?
1 vote
1 answer
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### Are there multiple reasons for the decrease in pressure over a wing?

I'm aware that the decrease in pressure over the wing is due to the curvature of the airfoil which causes a pressure loss due to the spreading of the air as it is redirected. But is it also due to ...
4 votes
1 answer
2k views

### How does the position of the center of pressure change with the use of different high lift devices?

How is the position of the center of pressure affected by different high lift device deployments? My guesses are: When I use a high lift device that just increases the chord length, it moves ...
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3 votes
2 answers
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### What airfoil is used on the Lazair ultralight?

This is the airfoil of the famous Lazair ultralight. What is the name of this airfoil?
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4 votes
1 answer
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### Is it best to use a thick airfoil or an undercambered airfoil for slow speed flight?

The more the thickness,the more the frontal resistance,hence the more the drag a thick airfoil will produce. Under cambered can help increase lift without increasing the airfoil thickness , therefore ...
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1 vote
2 answers
250 views

### Why flaps can deflect up to 25°+ without stalling the wings? [duplicate]

According to this graph,plain flaps have their highest Cl at about 2 and stalls at about 15°,my question is how then do airplane flaps reach 25°+ of delflection when this gragh clearly states that ...
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3 votes
2 answers
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### Would the Wright Flyer have flown better with thicker airfoils?

The Wright Flyer(s) flew with very little wing thickness,would they have flown higher, faster and longer if the wings had greater thickness? Secondly, how do thickness and camber affect a wing's ...
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2 votes
2 answers
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### Is airfoil thickness proportional to drag coefficient?

Does increase in the thickness of a camber airfoil mean more drag will be produced? Why do slow flying planes have thick airfoils when it will just slow them down even more?
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3 votes
2 answers
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### Is the lift produced by a wing with a 10° flap equal to the lift created by a wing with 10° AOA but with no flap?

After reading this article I would like to know if the lift produced by a wing with a 10° flap is equal to the lift created by a wing with 10° AOA but with no flap?
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0 answers
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### What does "lower flatness" mean in airfoil terminology?

What does lower flatness mean in these parameters of a Glenn Martin airfoil?
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2 answers
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### Aerodynamics of double winglets

I've read here on Aviation SE that the aerodynamics of winglets on an aircraft are easily described as "extending the airfoil". Thus, as I understand it, a winglet is like stretching the airfoil a ...
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1 answer
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### What does leading edge radius mean?

What does leading edge radius mean amongst these parameters of a st cyr 24 airfoil?
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1 answer
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### How to calculate Reynolds number?

How do I calculate the Reynolds number of a wing with wing chord,1.2m and speed of 60km/h
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1 vote
1 answer
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### Will I not be able to descend with an airfoil that stalls at -0.5°?

This stats says this airfoil stalls at -0.5°,does this means if I have this airfoil as a wing ,I won't even be able to have a descent aoa? !
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0 votes
2 answers
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### Winglet design and airfoil selection

I'm currently in the process of designing a winglet for my low speed aircraft in xflr. While researching about winglets I read in a Boeing article that if the baseline outboard wing is relatively ...
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3 votes
2 answers
974 views

### 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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