Questions tagged [lift]

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

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2answers
215 views

Will air accelerate over a wing and generate lift, if the air has zero viscosity? [duplicate]

Will air accelerate over a wing, if the air has zero viscosity? Will the wing produce any lift under these conditions?
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Streamline Curvature Theorem applied to Airfoils?

I am new to studying aerodynamics and taking up aeromodelling and am currently learning how lift is obtained in-depth. When studying the two common explanations as to how lift is generated by an ...
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How does a forward lifting surface affect ideal lift distribution of a main wing?

In Peter K's answer to this elliptical wing with lowest drag question the minimum induced drag lift distribution for a wing is described as one with a constant downwash angle across its span. When a ...
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1answer
85 views

How do thick and thin airfoils compare in lift generation?

I find myself confused when comparing the lift generation amongst Thick and Thin Airfoils. A paper to which I have added reference below claims that thin airfoils are better in generating lift because ...
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4answers
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Why does NASA say $v^2$ is velocity squared rather than speed squared?

Lift and drag forces scale as the square of the relative flow speed, $v$. But speed is the magnitude of the velocity vector; that is, speed is the square root of the sum of the squared velocity ...
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1answer
43 views

How do I calculate induced drag? [closed]

How would I go about solving this problem? An aircraft has 6000lbs of total lift and a downwash angle of 6 degrees. Remember that the total lift vector is tilted aft by HALF the downwash angle. What ...
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1answer
789 views

Are the lift / drag coefficients considered dimensionless?

Since the lift coefficient, $C_L$, and the drag coefficient, $C_D$, are obtained by rescaling the full lift and drag by $$\frac12 \rho A v^2$$ does that mean they're dimensionless numbers? It's ...
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How much could you increase lift using ailerons alone?

If a plane had ailerons that could be moved in the same direction, could the lift be increased by a non-negligible amount?
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1answer
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What is the relationship between aspect ratio and lift-dependent drag? [duplicate]

It has been a long held view that aspect ratio of the wing has a significant role to play in the lift-dependent drag. However, mixed opinions have been expressed on the importance of aspect ratio in ...
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Getting the cl vs aoa plot from Cp distribution

I am making a CFD simulation where my goal is to calculate the section lift coefficient vs angle of attack plot of an airfoil. From Fundamentals of Aerodynamics (Anderson, 2018), I get the following ...
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1answer
148 views

Is there a limit to how large an airplane wing can be? [duplicate]

There are some agreeably large planes out there, like the C-5 Super Galaxy. But how big can these planes' wings really get? The heavier the plane, it is usually larger, and with size of the fuselage ...
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2answers
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Center of Gravity and Center of Lift stability

I have recently been reading about the center of gravity and center of lift. On the German Wikipedia there are many different graphics about the relation between the center of gravity and the center ...
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Reducing camber for DrelaGW19 for L/D ratio

Okay , Thankyou for letting me know But these airfoils (DrelaGW19 and GW27) have extreme camber on upper surface. Now why is that so? (The first reason could be good lift at high Reynolds number(~ 1.5 ...
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3answers
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Would a flying-wing drone fly farther if filled with helium?

I'm wanting to build a flying wing designed drone and I'm wondering if I were to fill the fuselage with helium if it would improve it's range.
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3answers
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In which part of the flight does a plane reach maximum lift?

In which part of the flight does a plane reach maximum lift? My logic: I think a plane reach maximum lift in a horizontal flight, when a plane start rolling on a runway, landing gear produce more ...
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1answer
138 views

Is it better to reduce drag or increase lift?

Essentially my question is, in general is it better to have a lower drag or a larger lift. I know lift to drag ratios are used as an indicator but I think these don't give the best picture. For ...
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1answer
51 views

What are the best methods for calculating lift during different stages of flight?

Supposing I have the all dimensions of an RC airplane: wingspan, NACA airfoil, aspect ratio, fuselage length, etc., what would be the best methods of calculating the expected lift the aircraft should ...
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1answer
77 views

Center of Pressure(CP) [duplicate]

The center of pressure is: A)The point at which the Total Aerodynamic Force acts B)The point where the lift force acts C)The point where the resistance force acts Only one answer is correct,i think ...
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1answer
94 views

Difference in lift generation for a swept wing and straight wing in subsonic condition

Would there be any differences in lift for a straight wing and swept wing (front or back) with the same airfoil cross section, same chord length, same wing span, and same area when flying in subsonic ...
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4answers
393 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 ...
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If an elliptically-shaped aerofoil gives the optimum lift distribution, why aren't propeller blades designed around this ideal?

So given an elliptical lift distribution is the most efficient, why are propellers not designed around this? Props aren't affected by the adverse stall characteristics that concern a "main", ...
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4answers
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Can lift occur if air is flowing over an object, but not under it?

Can lift occur if air is flowing over a fixed-shape object, but no air is flowing under any part of the object? Maybe the object is the top half of a wing that's glued to the ground, or the object is ...
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1answer
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How does the airflow above an airfoil account for the downward turning-action of the airflow below the airfoil?

Wikipedia provides an explanation of the lift force in terms of flow deflection and Newton's laws, emphasis mine: An airfoil generates lift by exerting a downward force on the air as it flows past. ...
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2answers
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Lift Pressure Distribution [closed]

If the pressure goes always from high to low, we should have a compression, due the lower pressure of the air stream over the upper surface, and an expansion in the airstream in the lower surface. So ...
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1answer
188 views

Is it possible to stall a stationary helicopter through excessive collective input?

I understand that helicopters can suffer from "retreating blade stall" where the retreating side of the rotor has low airspeed and stalls in a typical way that airplane wings stall. This ...
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Why does the tapered part of the wing has high coefficient of lift? Like a Delta wing design

If we take a Trapezoid wing shape as an example and see that it has low 𝑐𝑎 near the root of the wing and very high 𝑐𝑎 at the tip. The Lift generated, however, is reversed to the that of the 𝑐𝑎. ...
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How dangerous are tailwind gusts for STOL aircraft?

If I fly close to stall speed with a STOL plane and gust of 20kts tailwind comes at me,it will cause sudden reduction in lift ,becuase plane has inertia so it can not accelerate instantly. How ...
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increasing lift in a plane by placing engine in such a way that the air coming out of it washes over the wings to create more lift [duplicate]

I was wondering if the engines of a plane can be placed in such a way so that the air coming out of the engines goes from over the wings so that the velocity of air over the wing is higher and more ...
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1answer
257 views

Why aren't grid fins used as wings for low speed aircraft?

Grid fins are used "commonly" in aerospace - usually for things like control of guided bombs or spacecraft. The most obvious example is SpaceX's use on the Falcon 9, but the US and Russian ...
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1answer
118 views

How can the lift induced drag for a wing be calculated?

I have found a lot of information to calculate drag coefficients and I know that total drag can be calculated by $$ D = \frac{1}{2} \rho u^2 S C_d $$ However I was wondering, if I substitute the zero ...
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1answer
63 views

Why generation of lift is more at mid span of the wing?

For the same condition like same density, wing area, free-stream velocity, From the above figure one can see more pressure differential and hence more lift at mid span of the wing? What causes this ...
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1answer
108 views

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 ...
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1answer
106 views

What was the lift-to-drag ratio for WWI biplanes?

I will be interested to know what was the lift-to-drag ration for a few more known WWI biplanes at take-off, cruise and landing speed; with the propeller running, stopped or non existent (tests in ...
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1answer
56 views

Is lift/drag the same as coefficient of lift/coefficient of drag?

I see it being used interchangeably (for example by Airfoil Tools Fusion360 AddIn), so can I just pick an airfoil from the airfoiltools database with a certain CL/CD for my aircraft and assume L/D is ...
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2answers
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I calculated that Flyer I and II (1903-04) of the Wright brothers were underpowered. Are there better (drag, lift) coefficients than those of Culick?

Based on what the Wright brothers said in a few letters and two article (all relevant excerpts have been attached to this post), and also using the experimental data in the study "AERODYNAMICS, ...
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3answers
338 views

Do turbofan nacelles generate lift?

Since they are essentially an annular wing, how much do they contribute if at all to an aircraft's total lift? Would the effect of this lift be noticeable enough to help cancel out the drag they ...
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2answers
336 views

Why is the aerodynamic center for most airfoils located at the quarter chord location?

I've been reading several sources on the location of the aerodynamic center https://web.mit.edu/16.unified/www/FALL/fluids/Lectures/f03.pdf https://en.wikipedia.org/wiki/Aerodynamic_center John ...
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Whats the effect of aerofoil camber and thickness on Clmax and Cdmin?

Does anyone have any experimental references/wind tunnel testing testing data for various thickness and/or camber?
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2answers
631 views

Does the center of lift have to be in line with the center of mass?

Imagine 2 theoretical planes, A and B, shown in the image below. The center of mass is yellow, and the center of lift is blue. Would plane A and plane B work as well as an airplane with the center of ...
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1answer
278 views

Is there any plane that has wing of both aerodynamic and geometric twist?

For the proper lift distribution, afaik either of the twist are used? Is there any significant difference having one over another and both? Thank you. The above question has one line answer and both ...
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Would this quadrilateral-shaped airfoil produce lift with a zero angle of attack?

I have been recently studying the shapes and characteristics of different high-lift airfoils that have been used for VTOL aircrafts. While studying these different designs today, a particular ...
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2answers
224 views

How to distinguish the induced drag of a lift-producing wing from its pressure drag?

Quote John Anderson Fundamentals of Aerodynamics: "The three-dimensional flow simply alters the pressure distribution on the finite wingin such a fashion that a net pressure imbalance exists in the ...
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Could propeller wash provide sufficient lift to take off - even in theory?

I know this seems a crazy thing to ask but it is not the same as lifting oneself by the bootstraps. If you try to lift yourself that way, there are two equal and opposite forces, yet there are ...
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2answers
283 views

What is the reason why dihedrals are used when building a plane? [duplicate]

How does dihedral affect flight characteristics of a plane? I know it increases stability, however is it the only reason why it is implemented? If so, aren’t there more effective methods to stabilize ...
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2answers
227 views

Will this specially shaped can produce any lift?

I am wondering if a specially shaped can will produce any lift as it moves through the air. Please reference the drawing below: This drawing is showing a hollow can that has been cut so that it will ...
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1answer
212 views

When using the Source Panel method and dealing only with sources and sinks, why do lift and drag equal zero?

I am trying to deal with the airfoil with the "Source Panel method", and when I try to calculate the lift and drag, they always equal to zero. And I have found an explanation in some ...
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2k views

How calculated the drag coefficient lift coefficient with pressure coefficient?

I have got the Cp Plot on a wing, now I am trying to calculate Cl and Cd. And the angle of attack is 0 degrees, the wing has been split into N Panels, and the normal vector ni for every Panel is ...
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1answer
139 views

At any given weight or altitude, an aircraft will always lift-off at the same? [closed]

A: Calibrated Air Speed (CAS) B: True Air Speed (TAS) C: Ground Speed D: Equivalent Air Speed (EAS) I think the answer is CAS, but I also think it could be TAS but, isn't TAS calculated after ...
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3answers
301 views

Why is air accelerating over the wing surface?

I know that there are dozens of questions about lift generation here but after reading them I still don't understand everything. My question is: why does air accelerate over the (upper side) wing? I ...
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1answer
265 views

What happens in an F-16 once the aircraft exeeds its service ceiling?

What exactly is the sequence of events that would unfold as an F-16 attempts to exceed its service ceiling? The scenario is simply full afterburner and attempting to simply climb higher and higher (at ...

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