Questions tagged [lift]

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

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52 views

Why does the Center of Pressure move forward on high-wing airplanes and aft on low-wing airplanes?

I've been trying to figure this out using variety of manuals but still not found a satisfactory answer. Can somebody explain in detail?
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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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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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1answer
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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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How did the F28 have such a good L/D ratio?

The second link given on a Google search for "Breguet Equation" is to a PDF document from MIT. On page 7 of this document is a chart showing L/D ratios for various commercial aircraft (turboprop, ...
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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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How complete is our understanding of lift?

I'm currently studying for my PPL and one of the accepted textbooks contains the following disclaimer at the end of the Principles of Flight section on lift: It is important to note that the ...
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122 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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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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Why is ground effect greater over smooth hard surfaces?

Helicopter Flying Handbook: Ground effect is the increased efficiency of the rotor system caused by interference of the airflow when near the ground. The air pressure or density is increased, ...
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1answer
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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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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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What is the highest possible thrust generated by 15cm ducted fan?

I recently developed a sudden interest in flying. I'm wondering whether a pair of small ducted fans could lift a person off the ground. Lets say the ducted fan is 15cm in diameter. What would be the ...
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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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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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How does an aircraft maintain an orientation that was actually caused by a external disturbance?

What is the difference between centre of pressure, aerodynamic centre and neutral point? At this link, there is an image used to explain the answer, but not much has been spoken about it. I ...
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Descending on a given glide slope (e.g. ILS) at a given airspeed— is the size of the lift vector different in headwind versus tailwind?

We had a discussion with friend and we were talking about if the airplane is on approach and the one is landing with tailwind and the other one is landing with headwind, so both have the same value of ...
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Do software simulations and wind-tunnel tests accurately predict Cd and Cl in real-world conditions?

Will the lift coefficient (Cl) and drag coefficient (Cd) I obtain by using software simulations or subsonic wind-tunnel tests be the same as on an actual aircraft while cruising? Or will there be some ...
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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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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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167 views

How to find the static stall angle of attack for a given airfoil at given Re?

For vertical axis wind turbines applications I'm wondering how one would find the static stall angle of an airfoil at a given Reynold number? Is it just the critical angle of attach (AoA) where ...
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Are high lift wings bad for faster speeds

I notice a trend in many aircraft designs. If the aircraft was designed to go slowly but have shorter takeoffs/landings they use airfoils with a high lift. However for long endurance flights they use ...
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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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How do wings generate lift?

Just the basic question that every aviation enthusiast must be curious about: exactly how does a wing generate lift?
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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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How does vorticity change the lift coefficient of an airfoil?

For airfoils in unsteady motion, the lift coefficient oscillates and the wake is characterized by vortex shedding. How does vortex shedding affect the lift coefficient for an airfoil?
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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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The lift and moment of the tail equations

We have The lift of the tail, $$ L_t = C_L.q.S_t $$ The moment of the tail around c.g. $$ M_(cg,t) = C_M.q.S.c $$ look at the S in the two equations. Why the lift of the tail is proportional to the ...
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How can we find maximum lift coefficient of Airfoil?

I am trying to find the maximum Lift coefficient for airfoil NACA 64A-404. I chose this airfoil for wing. I am stuck at finding the Clmax. I tried to use javafoil but javafoil is showing Cl less than ...
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Does thin airfoil theory work at very high angles of attack?

Thin airfoil theory says that lift coefficient is directly proportional to the angle of attack in radians. I haven't been able to find any limit, short of stall, for applying this theory. It would ...
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Why should the centre of mass be ahead of the centre of pressure?

Why is the centre of mass located ahead of the centre of pressure? And what would happen if centre of mass would be too close or too far away from the centre of pressure?
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Does an increase in lift always cause an increase in lift-induced drag?

An increase in lift causes an increase in drag. Is it always true? I am confused with two points. Lift increases with an increase in airspeed but induced drag reduces with an increase in airspeed. ...
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What is area in equation of lift?Does it remain constant during flight? [duplicate]

I am beginner & learning aerodynamics concept. What is area in equation of lift(L) =Coffecient of lift x area x density x square of velocity/2. Does increase in angle of attack increases the area &...
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107 views

Is the total lift of a quadcopter the sum of the lift from each propeller?

In this diagram each rotor R1,R2,R3,R4 has an individual lift force of 490 N. All combined, does the total force on this aircraft equal to 1960 N? The aircraft in question is similar to a quadcopter.
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Does bi-wings create essentially double the uplift as single wings?

This puzzles me a bit, and I cannot find the answer anywhere. Does bi-wings create essentially double the uplift as single wings?
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How to calculate CL with the use of MTOW?

I have a problem that it gives us the MTOW of a UAV (200 kg), the speed and the reference area. So its probably easy to find the CL knowing that it flights at steady level flight (L = W). I'm confused ...
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What is the effect of flow separation on lift, pressure distribution and drag?

Consider an airfoil (a wing) in an airflow. When angle of attack increases, at some point the flow start to separate from trailing edge. By increasing the angle of attack more, this separation area ...
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Is drag the only aerodynamic force that acts upon an asymmetric body (a glider in particular) travelling through the air?

It is known that for a symmetric body, like a sphere falling through the air, the only aerodynamic force that acts upon it is the drag that points always in the opposite direction relative to its ...
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What is the amount of lift produced by friction?

As Mr. John D. Anderson states, the aerodynamic forces on a body are due to only two sources: pressure distribution over the body and shear stress distribution. Shear stress is acting tangential to ...
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Why the gradient of $C_L$-$\alpha$ graph increases with the Mach number?

From the JAA ATPL Book 13 (Principles of flight) the gradient $\frac{dC_L}{d\alpha}$ of the $C_L$-$\alpha$ graph increases for higher Mach numbers. Can someone explain why this is the case?
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What is boundary layer tripping?

I came across the term "Boundary layer tripping" but I can't really underastand it. After searching on internet I cannot find any video or an image explaining that concept. Could you please explain ...
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How do conventional missiles fly?

With the exception of cruise missiles, most missiles don't have any obvious lifting device. If you watch a missile being fired, prior to its rocket firing it does exactly what you'd expect: ...
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Tapered Wing Providing low Coefficient of Lift

Hi I am currently analyzing different wing designs using ANSYS Fluent. One of my designs has a straight leading edge but a swept trailing edge thus it is tapered with wing root chord at 50mm and wing ...
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Why do autogyros exist? [duplicate]

This question has been intriguing me for some time. In Autogyro the rotary blades merely acts as what fixed wings act in normal aircrafts to generate lift. So why not simply have a fixed wing instead ...
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Can lift be increased by increasing the angle of incidence of the wing? [closed]

Can the lift of a plane be increased by increasing the Angle of Incidence (angle between the chord line of the main wing and the axis of the fuselage)? Meaning, can more lift be generated while the ...
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Why is lift larger than thrust?

It's been a while since I tried to read a little about flight mechanics and aerodynamics, but I remember one question I had back then: Is the thrust of a common passenger aircraft (A320, B737) ...
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How do droops help to avoid stalls?

Droops are deployed on the leading edge of a wing of an aircraft, and they work by changing the camber of the wing. How do they help in delaying stall?

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