# Questions tagged [lift]

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

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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 ...
11answers
36k 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?
2answers
906 views

### How do helicopters handle P-Factor?

Propeller-powered aircraft have a "problem" called P-Factor, where the descending blade of the prop is generating more lift (a.k.a. thrust) then the ascending blade due to a higher angle of attack ...
1answer
2k views

### 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?
8answers
7k views

### Is excess lift or excess power needed for a climb?

As answered in this question, aircraft need excess power - not excess lift - to climb. This is plausible when the aircraft's thrust vector has a vertical component (its nose and engine points upwards),...
2answers
510 views

### How is the lift generated by a number of out-of-plane staggered wings calculated?

I want to calculate the lift generated by a number of out-of-plane staggered wings but I don't think a valid approach is to simply use superposition and add the sum of the lift of all the wing's in ...
1answer
2k views

### Does the airflow from a propeller over a wing contribute to lift? [duplicate]

How I understand it, the perfect propeller would move air rearward at the exact same velocity as the free stream, i.e. the propeller air will merge with the free stream and have no real influence on ...
2answers
4k 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?
1answer
929 views

### How to calculate the lift starting from the vertical speed?

Is it possible to calculate the lift of an aircraft knowing its speed (IAS,TAS and GS), its vertical speed, its altitude and its weight? Because if we look at the force of an aircraft in flight: the ...
1answer
18k 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 ...
2answers
30k 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-...
1answer
2k views

### How comes lift is less than weight on take-off? [duplicate]

If $$lift=weight * cos(angle)$$ this means that lift is less than weight during takeoff. Could someone please explain me why it is so
5answers
12k views

### Is there a maximum lift to drag ratio?

If I recall correctly, the best competition gliders have a L/D ratio as high as 60:1. What imposes this limit? Is there a maximum theoretical L/D ratio, or could sufficiently advanced materials allow ...
2answers
6k views

### What is the actual air speed over and under a wing due to Bernoulli's Principle?

Bernoulli's Principle states that as a fluid speed increases, its pressure decreases, and vice versa. Air flowing over the wing of an aircraft flows faster than its neighboring air flowing under the ...
2answers
1k views

### How much lift do planes produce before rotation?

In the takeoff roll, I'm pretty sure planes produce some lift before rotation, but how much? Is it insignificant compared to post-rotation, or is it large compared to the post-rotation lift?
4answers
2k views

### Why do planes not fly “backwards” (up from the planes POV) when in a vertical climb?

As suggested by a user in this question, I'd like to ask this question: One of the most basic aerobatic maneuvers is a vertical climb. This can be achieved by just pitching up to what appears to be ...
4answers
1k views

### What is the fundamental physics behind L/D decreasing as AoA increases beyond the optimal point?

Why does lift over drag decrease with AoA past the optimum AoA? Is it because the backwards vector for a given lift force on the wing is now larger for a given air particle compared to lower AoA? ...
3answers
15k views

### How much thrust is needed by an aircraft to have vertical takeoff?

In some airshows, I have seen some big aircraft (like 737) takeoff almost vertical. Generally, fully-loaded passenger/cargo planes don't do that, I guess due to safety issues but I think there needs ...
5answers
11k 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, ...
1answer
989 views

### Is there a formula to compute the elevator angle to stabilize takeoff?

I'm building a ground effect vehicle, but I'm failing to stabilize the lift-off. At a certain speed, the lift force is equal to the weight force, so the vehicle lifts off. But this implements a change ...
3answers
3k 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 ...
5answers
5k views

### Why is lift larger than thrust? [duplicate]

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) ...
4answers
6k views

### Principle of aerodynamic lift: are misconceptions also taught in flight schools?

Describing lift as the result of "equal transit time" on both sides of an airfoil is a fallacious theory widely found in technical books and articles for general public (see below for details about ...
3answers
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 ...