# Questions tagged [lift]

The force acting on an aircraft in opposition to gravity which keeps the aircraft in the air.

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### wave drag: Lift coefficient in Korn's Equation

I have been using the Korn equation: $$M_c = \frac{0.95}{cos(\lambda)}-\frac{t/c}{cos(\lambda)^2}-\frac{C_L}{10cos(\lambda)^3}-\sqrt[3]{\frac{0.1}{80}}$$ to estimate the critical mach number of a ...
80 views

### Lift without aerofoil? [duplicate]

I have seen some RC planes flying without any form of airfoil, the wing is literally a flat board. What I want to understand is how lift is generated under these conditions. I understand kinetic ...
44k views

### What is the method to calculate a finite wing's lift from its sectional airfoil shape?

I am struggling to get my head around a concept that I believe should be fairly simple to understand. Lift versus drag and AoA data of many airfoils are freely available, for instance the NACA 4-...
272 views

### In a hot air balloon what proportion of the lift comes from the heated air compared to that from the combustion products?

A hot air balloon is heated with propane or similar hydrocarbon. One of the products of combustion is H2O with molar mass 18 so it is substantially less dense than air (78% nitrogen, molar mass 28 and ...
1k views

### How can the wing generate more lift than the thrust? [duplicate]

I recently checked about the max takeoff weight of an A380 and the thrust it can provide at TO/GA power and I was quite shocked by the results. The total thrust by the engines was only about 127000 ...
9k views

### 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 ...
2k views

### Does more lift cause a plane to stall at a lower airspeed?

Does more lift cause a wing to stall later? (By more lift I mean a bigger wing) I was looking and saw this question, but the answers didn’t really address why more lift will help a plane not stall. ...
91 views

### How does the lift-to-drag ratio depend on absolute sizes?

A dependency is provided here $$(L/D)_{\max} = \frac{1}{2} \sqrt{\frac{\pi \varepsilon ~ \mathrm{AR}}{C_{D,0}}}$$ AR significantly affects the outcome in this dependency. AR varies significantly among ...
1k views

### How beneficial are flaps when landing with a tailwind?

I understand that flaps are devices used to increase the amount of lift and drag. When landing with a tailwind your groundspeed will be higher. Therefore, flaps would help reduce this groundspeed, ...
28k views

### Does lift equal weight in a climb?

This subject keeps coming up in the discussions and questions such as this one, which asks if lift equals weight in level flight. Good answers there, pointing out that upwards force has many sources. ...
140 views

### Conundrum about designing a glider relating to coefficient of lift

I'm designing a high-altitude glider. Just to clarify a few points before my question: The glider will weigh close to 200 grams. It will be using the A18 airfoil. The glider is dropped from 80,000 ...
148 views

### Which is more efficient, thickening an airfoil or adding a bottom-surface curve?

So if you were to take a standard airfoil and increase the thickness, you’d increase the lift (Bernoulli’s principle), but it would also increase the drag. Now imagine you have the same airfoil, but ...
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### Lift distribution of a swept wing with twist, dihedral, taper

I am trying to get the lift distribution of a swept wing with taper (in chord and thickness along the span), twist, and dihedral. I know that Kuchemann Index method is used for swept wings but I am ...
382 views

### In which position does Starship wings produce the most drag?

I was watching the video from a few years ago where SN15 did the flip manoeuvre and landing. The actuated fins (lower flaps) can help Starship to pitch while during its descent. However, I am ...
51k views

### How do wings generate lift?

Just the basic question that every aviation enthusiast must be curious about: exactly how does a wing generate lift?
1 vote
1k views

### Do wingtip vortices cause a decrease in the lift component of aerodynamic force, and do planes need to pull more AoA to compensate?

So, from what I know about wingtip vortices, they shift the angle of the relative airflow to where the effective angle of attack of the airfoil is lowered. Since the aerodynamic force is always ...
143 views

### Does the lift force comes from the bottom or from the top of the wing? [duplicate]

My team and I discussed yesterday how lift is generated based on the pressure analysis. The most popular explanation from books and other sources is that pressure is lower on the top and slightly ...
135 views

### Minimum sink speed and maximum endurance speed

For a given airplane, are the minimum sink speed and maximum endurance speed the same? Thankyou
221 views

### What on Earth is Going on with NASA's PRANDTL-3 Wingtips?

I'm afraid this will require some explanation. I'm sorry, this will be a long read but I hope it's an interesting conundrum. If anyone reading this isn't familiar with NASA's PRANDTL wing research, Al ...
1 vote
91 views

### Spanwise lift distribution units

I was recently reading NASA/Boeing’s report on the Transonic Truss Braced Wing (the SUGAR IV final report), and noticed that when they graph the spanload for the design they graph lift coefficient ...
1k views

### How does the horizontal component of lift when flying at a bank angle cause the aircraft to follow a circular path?

I understand that when the aircraft is put into some bank angle, the lift vector now acts at that angle instead of directly against gravity, so we can pitch the aircraft up to increase AoA to increase ...
2k views

### Is pressure lower than ambient on the pressure (bottom) side of an airfoil? [duplicate]

I've been reading about this for quite some time and thought I understood it. Then somewhere someone mentions that air under the wing has higher velocity than ambient thus a lower pressure than ...
43 views

### Does this comment thread incorrectly conflate glide ratio with lift-to-drag? [duplicate]

In the comments on niels nielsen's answer to "Why are no recent small aircraft designed to be 'characteristically incapable of spinning' as the Ercoupe was?," John K commented, "[The ...
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### How large do wings have to be to create lift?

How much lift is needed to get an aircraft in the air? Is there a specific formula? And also what wing shapes offer different types of lift? I.e a delta wing formation.
2k views

### What causes lift?

Now this seems to be the question of the ages, and various questions on this site regards it. The often told description of lift is that it is due to air traveling faster over the wing than under it, ...
533 views

### Can an airplane propeller become supersonic?

Is it possible for an aircraft propeller to become supersonic? I am not referring as for the aircraft, only the rotating blade. I know it is extremely unlikely for a propeller plane to go supersonic, ...
786 views

### If in a coordinated turn, the horizontal lift vector is equal to the Centrifugal force. Then how is the aircraft still turning?

Image source How does the Aircraft continue to turn when the both the Horizontal component of lift and the centrifugal force are equal?
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### How do coefficient of lift/drag variation with speed differs between swept and unswept wings?

Trying to understand the coefficient of lift/drag of swept and unswept wings as speed increases. Some example questions and statements- A swept wing will have a lower max Cl at subsonic and ...
492 views

### How is the wing area of an airplane determined?

Picture source is from here. Here are wing areas of several airplanes. As we can see the Spitfire, B747-400, and Mirage 2000, their wing area are not rectangular. The line drawn from left side to the ...
1 vote
1k views

### What happens to the pressure differential of airflow under and over the wing as the critical angle of attack is reached?

I've been doing a research project for mathematics which involves calculating the relationship between lift and angle of attack. While this may seem pretty easy, it's not for a 12th-grade student like ...
1 vote
335 views

### How to calculate lift and drag coefficients of an airfoil with slotted flaps?

I am doing a project attempting to determine the increase in lift and drag coefficients of an airfoil as the angle of its flap increases. In my research, I have found the thin airfoil with flap ...
1 vote
1k views

### Is there a formula for calculating lift coefficient based on the NACA airfoil?

Are there any formulas that can be used to calculate this?
828 views

### How does the lift force stop increasing itself after a certain point?

I am currently trying to create a basic flight simulator and am very confused by the concept of lift. This is the equation of lift shown below that I found on the internet.  F_l = \frac{1}{2} \rho v^...
1k views

### How does increasing the angle of attack increase the lift?

When the pitch of a plane increases (facing upwards), it has a positive angle of attack, and when it decreases to face downwards, it has a negative angle of attack. Increasing the angle of attack ...
2k views

### Why does a flat plate create less lift than an airfoil at the same AoA?

This picture of the lift curve slopes for four-digit NACA airfoils and a flat plate is from another question on this topic. It shows that at the same positive AoA, a flat plate generates less lift ...
440 views

### Does the CH-47 Chinook generate differential yaw as a side effect of generating differential lift?

I have been reading up on the controls of the CH-47 Chinook. I understand how yaw movement is created not by counter torque but by opposite cyclic on the front and back rotors. What I'm wondering ...
437 views

### Why are the strings on paramotors so long?

I don't completely understand why the strings on paraglider/paramotors (connecting the vehicle/person to the parafoil) are so long. Couldn't they be made shorter to reduce the amount of space used? It ...
68 views

### How does wing sweep impact lift? [duplicate]

Given that swept wings (according to a google search) decrease lift, how much is lift affected? Why are they so commonly used in aircraft nowadays, like the SU-27, and subsonic aircraft like the ...
73 views

### Sluggish response to transients in very high L/D ratio airfoils

A sailplane has very high aspect-ratio wings and can have a glide ratio up to 70:1 (the wing L/D ratio is even higher since the fuselage adds drag). The flow at such high L/D ratios for such long, ...
1 vote
151 views

### Forces acting on ram air parachute (for pulling ships)

I recently stumpled across this question about the ram-air parachutes for use in pulling ships. In this answer it is stated that the parachute needs to travel perpendicularly to the ship's motion in ...
5k views

### Why a kite flying at 1000 feet in "figure-of-eight loops" serves to "multiply the pulling effect of the airflow" on the ship to which it is attached?

In CNN's June 30, 2023 Giant kites could pull cargo ships across the ocean – and slash their carbon emissions “What differentiates it from other wind solutions,” says Bernatets1, “is that the wing is ...
376 views

### Helicopter blades flapping with the cyclic – can you help with the explanation?

I am now reading books about helicopter aerodynamics. And I have one question about blades flapping. If you push forward on the cyclic, the swashplate will tilt forward and will set the maximum pitch ...
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### If an aerofoil is placed in a narrow wind tunnel, how will that affect the lift it produces?

This is NACA 0000 aerofoil: This is just a straight line - roughly what a paper plane's aerofoil section looks like (I chose this aerofoil for its simplicity). If we put this aerofoil in a wind ...
3k views

### Explained intuitively, why does aspect ratio affect induced drag?

Over the last few hours, I've been trying to intuitively understand induced drag, and how aspect ratio affects it. I already know the equations, but while they explain the relationship, they do not ...
181 views

### glide ratio of an airplane formula

Good morning everyone, I found out that the glide ratio of an airplane can be calculated by this formula : 1/tan(y) considering y the angle formed by its nose and an horizontal line. Check this photo :...
2k views

### How come deflected flaps cause a nose-up pitching moment in high-wing aircrafts and a nose-down pitching moment in low-wing aircraft?

I imagine that the increased downwash due to the new camber of a high-wing aircraft causes a down-force on the horizontal stabilizer which in turn causes a nose-up pitching moment. However, I read ...
427 views

### Am I correct about how airships control their altitude?

I have read about how airships work, especially about how they control their altitude. Because what I understand from readings about the Zeppelin airships is that they were able to perform long range ...
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### Can anyone explain lift before the experiment?

The sensors on the wing tell me lower pressure above the wing, the smoke visualization tells me the air stream is faster when flowing over the curve. But can anyone tell me why they behave like that ...