Questions tagged [lift]

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

Filter by
Sorted by
Tagged with
2 votes
3 answers
3k views

What is the "Centre of Pressure"?

This question may sound naive but surprisingly it puzzles me. A wing has a centre of pressure, does it mean that lift acts on point and not on the whole chord of an airfoil?
12 votes
5 answers
7k views

Why are wings load tested upside down?

Why are wings load tested by putting weights on the underside of the wing (placed upside down)? A wing is being pulled into the air from its upper surface in flight, so shouldn't it be load tested in ...
0 votes
2 answers
775 views

How to adjoin wing skin to wing ribs?

I saw a youtube video (from a channel called Real life guys) where gum was used to join the ribs of their homemade plane to the skin and I saw another video where the wing skin(tedlar) was literally ...
0 votes
3 answers
644 views

If we use upper surface blowing and externally blown flap on the same wing will lift correspondingly be very high?

With two engines, one above and one below the wing, will the lift be the sum of two lift increments (produced by upper surface blowing and external blowing)? I am trying to make a jet suit and I am ...
0 votes
1 answer
1k views

why lift is greater at wing root [duplicate]

Is lift greater at the wing root of an horizontal wing,just like it's greater on a tapered wing?
5 votes
1 answer
5k views

How do you calculate total drag on a wing?

I'm not an aeronautical engineer, but I am making a brave attempt to perform a preliminary design for an 4-metre wingspan radio controlled glider. With special thanks to @mns I have now learned a ...
0 votes
1 answer
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 ...
3 votes
3 answers
179 views

How is the centre of lift estimated for airplane models before they are being mounted in a wind tunnel?

They mount the airplane models or parts of an airplane like just a wing, or a rudder in wind tunnels to test their drag and lift, stability, etc. How do they know where to hang it from or mount it on....
9 votes
5 answers
14k views

Where can I find data tables for lift and drag coefficients of airliners?

I'm teaching an introductory course in fluid dynamics and I'd like to show some "real" data regarding drag and lift forces on an airfoil. It is easy to find data on the geometry of typical airfoils, ...
6 votes
2 answers
5k views

How to calculate the Glide Ratio from Drag & Lift?

I know that $c_{d}=0.03 + 0.095c_{l}^2$. What is the glide ratio?
11 votes
1 answer
22k views

How to calculate the Lift Coefficient for the A320?

I'm trying to figure out the lift coefficient of an A320. What I'm doing is the following: during cruise, the lift is equal to the weight of the aircraft ($mg$) so that I used the cruise table taken ...
4 votes
2 answers
421 views

Does wing sweep affect the direction of lift?

Given both a straight and swept wing (identical otherwise), exposed to the same airflow, would the direction of lift be the same? Please see below a crudely drawn example of my thinking. Additionally,...
27 votes
2 answers
4k views

How exactly can an airship lose lift?

On this wiki page (under 'Comparison with heavier-than-air aircraft'), the altitude record of the L-55 Airship states: The ultimate altitude record for a rigid airship was set in 1917 by the L-55 ...
2 votes
1 answer
2k views

What is the mathematical relation between CLmax and Reynolds number?

I know that Reynolds number influences CLmax, but I am not able to find any formula with which I could plot a graph!
7 votes
2 answers
7k views

What are the conditions for an airfoil to be a "thin airfoil?"

I know about the theory differences between regular airfoils and thin airfoils, but is there any condition for saying a given airfoil can be analyzed as if it is thin? The extreme case of infinitely ...
8 votes
1 answer
3k views

How much lift comes from the fuselage on modern jets?

I understand this question is broad, but specifically referencing modern jets where composites are used a lot to get complex surfaces (such as in the Beechcraft Premier 1), how much of the total lift ...
4 votes
3 answers
24k views

How does the aspect ratio of a wing impact its lift?

The wing lift formula shows that lift of a wing is proportional to its area. $ L = {\dfrac 1 2 \times \rho V^2 \color{magenta}S C_L} {\small \begin{align} &{} &&\text{where:} &&L =...
13 votes
2 answers
3k views

Why do the outer parts of wings generate less lift?

In this Wikipedia page it says: Constant chord: parallel leading & trailing edges. Simplest to make, and common where low cost is important, e.g. in the Piper J-3 Cub but inefficient as the ...
1 vote
1 answer
4k views

How can I calculate the thrust of a fan given the diameter of the blade?

How do I calculate the thrust of a multicopter fan blade from its diameter? I am searching for a multicopter blade that can provide a thrust of 15 - 20N. Being someone who doesn't have any ...
7 votes
4 answers
1k views

Is an aircraft's maximum landing weight really weight, or is it mass?

I'm calculating the lift of a Cessna 172 and I don't understand the numbers given for weight. The maximum landing weight is 2550 pounds which is nearly 1134kg. But does that mean 1134 Newtons (weight) ...
3 votes
2 answers
748 views

Does wind provide lift for hang gliders in the air?

Basically, if there are no thermals, but a strong wind, is there a way to use that wind to gain altitude?
5 votes
1 answer
604 views

Is it possible to maintain horizontal flight with the angle of attack above critical value by increasing speed?

In this video a stall happens at 1:40 upon reaching the critical angle of attack. The air flow is now detached from the upper part of the wing, resulting in higher pressure above the upper part of the ...
6 votes
1 answer
2k views

How does rudder size influence its ability to produce lateral lift?

Does anyone know how the area, height and width of a rudder affect how well it provides lateral lift? I've heard that the most effective rudders are around 35% of the vertical stabiliser MAC but is ...
4 votes
1 answer
24k views

How are Cd and Cl calculated from Cp data?

Given pressure coefficient data for corresponding x/c (position along chord) values on a wing, I am looking to calculate coefficients of drag and lift. Here's what I have: b, MAC, S, sweep angles at ...
35 votes
2 answers
5k views

Why do helicopters not roll over when flying forwards?

Related to this answer: with velocities so different at forward going and rearward going blade, why does the helicopter not roll over? The higher airspeed at the forward going blade should cause more ...
15 votes
1 answer
1k views

What amount of lift would be created in the fallacious "lift from equal transit time" theory?

Context A wrong --but simple to understand-- theory for lift states: Air molecules that were close before being separated at the leading edge must be close again after they join back at the trailing ...
1 vote
2 answers
910 views

When the angle of attack is increased does the air flowing below it slow down [duplicate]

So the air above the wing flows faster. So it creates low pressure above the wing. The air flow below the wing, is it slowed down by the increased angle of attack or does it stay the same? So is the ...
7 votes
3 answers
1k views

Would it take 7 to 10 times more energy to lift a turbofan-helicopter?

I want to figure out how much energy it would take to lift a turbofan-helicopter. For reference I started with a rotor helicopter and assumed $T=100\ \mathrm{kN}$ gross weight and $d = 16\ \mathrm m$ ...
5 votes
1 answer
202 views

Would it be a viable option to make the engine generate lift?

I was thinking that if you made the engines generate lift it might help a tiny bit with the amount of time to takeoff, and thus lowering runway lengths.
-1 votes
1 answer
2k views

What is the lift to empty weight ratio of some popular modern helicopters?

What is the lift to empty weight ratio of some popular modern helicopters?
0 votes
1 answer
359 views

Drag coefficient and lift coefficient [closed]

What happens if drag coefficient increases but the lift coefficient remain the same?
1 vote
3 answers
1k views

How does 220 kN of engine thrust create the 700 kN required to maintain the altitude of an A320? [duplicate]

On the Airbus A320, the two engines produce about 220 kN in cruise, whose weight is about 700 kN (about 70 tons). The lift / drag ratio in cruise is about 15 (likely higher), meaning in cruise lift = ...
2 votes
2 answers
3k views

What are typical airspeeds and lift coefficients for UAVs at different flight stages?

I've been trying (unsuccessfully) to figure out the relationship between airspeed of a fixed wing UAV at different flight stages. What I mean is, I would like to know the order of airspeeds from ...
0 votes
0 answers
89 views

In air return flight? [duplicate]

Ok, we had a few beer. Imaging a plane with two cockpits back to back. One Pilot flies to the destination and the other returns without turning the plane. The question is, whether there is a ...
1 vote
2 answers
738 views

Is it possible to obtain the lift and drag coefficients of a 3D body in ANSYS Fluent?

Is it possible to obtain the lift and drag coefficients of a three dimensional body in ANSYS Fluent? Or, would it be acceptable to take the coefficients of several cross-sections along the wings and ...
6 votes
2 answers
684 views

Can wing clouds caused by a high angle of attack be recreated in a lab? Also, why doesn't this work for smaller wings (e.g. r/c planes)

Can this be recreated in a lab? Any equations would be helpful if so. Also, why doesn't this happen during high angles of attack on a smaller wing, such as that of an R/C plane?
8 votes
2 answers
3k views

Will a stalled aircraft fall down like a brick? Or how steep does the Lift-AoA curve fall off after stall?

When an aircraft stalls, do all or most lift forces abruptly disappear or is this transition continuous? Will the aircraft drop from the sky like a brick or can this (losing lift and altitude) happen ...
4 votes
2 answers
699 views

Can a lifting body work at supersonic speeds?

Can lifting bodies be made for supersonic flight, say up to Mach 3? What would they look like? How would they differ from lifting bodies for normal subsonic flight?
6 votes
1 answer
3k views

What is the pressure on the pressure side in relation to the freestream?

The following [edited] images are from a network post: The top image states on the pressure side, the pressure is greater than the freestream. On the bottom image, the $C_p$ varies. According to ...
4 votes
1 answer
950 views

Where does upward momentum come from in leading edge vortex?

I believe I am beginning to understand how a leading edge vortex creates lift. Faster air creates a lower pressure above the wing making lift. But I am hoping to get another view of this in terms of ...
3 votes
2 answers
3k views

Do coaxial rotors provide twice the amount of lift?

Do coaxial rotors provide twice the amount of lift given same diameter and RPM?
2 votes
1 answer
4k views

What is the relation between the Lift Coefficient and the Angle of Attack?

I'm trying to understand the relation between the Lift Coefficient and the Angle of Attack using PEP software for the A320 IAE. However, I notice that often for a given Angle of Attack, there could be ...
5 votes
3 answers
1k views

How to find polar curves of airliners?

The pilots operating manual of our Cessna 182 contains the lift-versus-alpha and lift-versus-drag data of the airplane, so I assume this is data that should be publicly available. Is there a ...
7 votes
3 answers
3k views

Is induced drag caused because of the tilt of the wing backwards?

In this question: Why is induced drag less on a high span wing? In the answer it was stated that wing tip vortices do not cause induced drag. If this is the case then what causes the induced drag. ...
3 votes
1 answer
13k views

How do symmetrical airfoils generate lift? [duplicate]

It is widely understood that the curved shape of a typical airfoil (such as a Clark Y) causes a pressure difference that creates lift. How do symmetrical airfoils do this when the top and lower ...
11 votes
3 answers
4k views

How is lift provided by a wing affected by propeller wake?

Does the lift of that section of the wing which is in the wake of the propeller increase (because the airspeed in that section is higher)? If yes, is this fact used actively to improve the lift ...
3 votes
1 answer
2k views

How to calculate the lift coefficient of a multi element airfoil?

How to calculate the lift coefficient of an airfoil section with flaps and slats if we know the Cl for the individual elements, like Cl of wing, Cl of slat and Cl of flap?
0 votes
3 answers
784 views

How much lift is created by a half-sized rotor?

I wonder if lift is directly proportional to the diameter of the rotor disc. For example, if an engine spinning a 26 ft diameter rotor can lift 635 kg, will a 13 ft diameter rotor using the same ...
3 votes
2 answers
679 views

Would it be beneficial for the Boeing 777x to have a biplane wing design?

The Boeing 777x has huge wings to generate lift even to the point of having to have a hinge and being able to bend them. Would it not be advantageous to have 2 wings like a biplane or one behind ...
13 votes
2 answers
43k 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-...

1
3 4 5
6
7