# Questions tagged [lift]

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

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### How does lift depend on velocity in 3D?

Many resources provide the following type of cross-section view when explaining aerodynamic forces: The textbook says that $V_a$ is the speed of the aircraft through the surrounding air mass. Does ...
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### Why does the Neutral Point not vary with Tail incidence angle?

The neutral point is the position where if the CG were present, the aircraft would be statically neutral, ie., the moment about the CG would be constant with varying AoA. Now, consider an aircraft ...
1 vote
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### Why will the max lift point not be at the center of a swept but constant chord wing?

(In this question when I say "swept wing" it means the blue wing seen at the bottom. So no fuselage or anything) If you look at this graph from this answer, you'll see the max lift point of ...
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### How do planes deal with excess lift at high speeds?

If I understand correctly, wind force increases quadratically as airspeed increases. Therefore, all other things being equal, lift should also increase quadratically. Does that mean, a plane going ...
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### How does the air molecules provide wing lift force when only wing is moving or when only the air is moving?

We use to calculate lift force of a wing as function of air speed squared. We can imagine 2 different situations: 1 - the wind has speed thus kinetic energy and momentum while the wing is stationary 2-...
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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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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. ...
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### 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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### 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 ...
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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 ...
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### 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 ...
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### 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 ...
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### Minimum sink speed and maximum endurance speed

For a given airplane, are the minimum sink speed and maximum endurance speed the same? Thankyou
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### 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
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### 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 ...
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### 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 ...
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### 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.
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### 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, ...
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### 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 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 ...
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### 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 ...
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### 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 ...
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### 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^...
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### 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 ...
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### 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 ...
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### 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, ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 :...
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### 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 ...
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### 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 ...
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### What are the complete assumptions and final conclusions from 'Thin Airfoil Theory' in aerodynamics?

I possess expertise in the field of aerospace structures, however I have recently been assigned an 'Aeroelasticity' analysis job at my workplace. In an effort to imbibe the fundamental knowledge which'...
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### Trying to understand this pressure distribution over an aerofoil?

can someone please help me understand why the pressure is like that over the top and bottom surface of this aerofoil please? Also, what do the arrows point out mean? Why are the front and end ones ...
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### How does increasing camber increase lift coefficient?

How does increasing the camber of an airfoil (like the NACA 0018) increase its coefficient of lift? You're just curving the airfoil; I don't see how that increases lift for a given angle of attack?
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### Why does pressure difference between top and bottom surface of wings increase as speed increases?

We observe that lift force increases as speed increases on aircraft wings. Theoretically, there must be increase in pressure difference between top and bottom surface of wings. What I don't understand ...
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### Can I identify wingtip stall by looking at the lift distribution?

I'm projecting a wing in XFLR5. The lift at the tip of the wing looks like it's dropping very quickly close to the stall angle, so I think there may be wingtip stall, however, is there any way I can ...
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### How to compute the direction of the vector perpendicular to the wing?

I'm trying to compute the direction of the vector that extends perpendicularly up from the top of the aircraft's surface. Is there a way to compute the vector's 3-dimensional parameters in Cartesian ...
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### What flaps are used for, if the aircraft has already landed? [duplicate]

When watching the below clip in the final approach sequence we can clearly hear setting flabs to 1, 2 and then to maximum. At 12:05 into the clip, when fully landed ...
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### Impact to lift curve slope for a tapered wing with only trailing edge sweep?

I'd like to use a tapered wing with 0 deg leading edge sweep and 12 deg trailing edge sweep as shown below for my RC model. I understand that lift curve slope, a, is reduced for wings with leading-...
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### How to determine the required twist in the Bell Shaped Lift Distribution (BSLD)

I'm doing a research about flying wings and BSLD and I'm having trouble to find the required twist. I'm using the equation L = ( 1 – x^2 )^3/2 to find the local load (Bowers, 2016). But how can I ...
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