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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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For an aircraft to get off the ground, lift needs to be higher than the weight of the aircraft.

The equation for calculating the lift is

$L = C_L \frac{\rho v^2}{2}A$

which shows you that lift does not depend on the size of the wing alone (A). Other constituents of lift are:

  • lift coefficient $C_L$ which is a variable depending on the type of the wing
  • density of the air $\rho$
  • speed $v$

To calculate the necessary lift, you basically need to know for example the weight of the aircraft and lift coefficient of the wing, and you can then work out the necessary speed range and the area of the wing.

The basic mechanism by which wings produce lift is the mostly the same: wings deflect airstream downwards, and this downwards acceleration creates a lifting force. You mentioned delta wing in your question, delta wings have a "special trick up their sleeves, since they not only "push" the air downwards along their length, but also achieve the downwards motion of air by causing a vortex along the leading edge:

enter image description here

Further and more accurate description of formation of lift gets quite tricky very fast, so I think it's best to leave that out of this.

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    $\begingroup$ Suggest you edit and change mass to weight. $\endgroup$ Dec 1, 2023 at 15:50
  • $\begingroup$ Good catch @CharlesBretana, in this case weight is proper $\endgroup$
    – Jpe61
    Dec 1, 2023 at 17:39
  • $\begingroup$ For almost every other application, mass (or perhaps g times mass), would be correct $\endgroup$ Dec 1, 2023 at 18:27
  • $\begingroup$ Well, weight is g times mass. $\endgroup$
    – Jpe61
    Dec 3, 2023 at 18:12
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    $\begingroup$ Yes, correct, I added the parenthetical because Lift is a force and mass is not, unless you multiple it by the acceleration of the accelerated (non-inertial) frame of reference you are measuring things in. To compare two things in a meaningful way, they need to be in the same units. $\endgroup$ Dec 4, 2023 at 2:24
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Technically, every surface that moves in a fluid creates lift. Lift is a force, and is just the result of all the aerodynamic forces created by individual fluid molecules hitting and bouncing off of a surface. From a Physics perspective, the aerodynamic force is defined as the rate of change in momentum of those molecules as they bounce off the surface.
$L = \frac{d(mv)}{dt}$
In fluid dynamics (the underlying science of aerodynamics), we call this the Lift Distribution. It represents the distribution, across every point on the aircrafts surface, of the force (change in momentum) generated by the air molecules impacting and rebounding from the surface at that point. The total Aerodynamic force is then the vector sum of all those individual forces acting at each point on the surface.

As pilots, or in aviation in general, we often narrow the definition of the word Lift to suit our purposes, such as defining it as the sum of just those forces that oppose gravity, (that hold us up in the air), or just those that are normal (perpendicular) to our flight path, (changing the direction of our flight path, [turn us], as opposed to those that change the magnitude of our velocity, [that slows us down - we call this drag]), or, just the lift from a specific airfoil, (like the wing). All these distinctions, however, are just arbitrary divisions or classifications defined to suit some specific scenario or purpose, to make an analysis simpler or more useful.

You ask "How large do wings have to be to create lift?", then in the text, you ask "How much lift is needed to get an aircraft in the air?" which is perhaps a better question. (whose answer would be somewhat more significant).

The answer to that question is complex, because it would include analysis of all aerodynamic forces from every part of an airframe, not just the wings, and, for conventional aircraft, would include the negative contribution of the horizontal stabilizer, which pulls the aircraft down.

Remember, Lift, just like all forces, is a vector, and has a direction as well as a magnitude. The aerodynamic forces on each point on an airframe push the airframe in the direction of the force, and may contribute to the overall Lift vector positively or negatively.

The analysis would also need to be done for a specific indicated/calibrated airspeed, as lift is a function of how fast the aircraft is moving, which segways nicely to your last question, about the formula.

Yes, there is a formula for lift, we call, not so coincidentally, the Lift Equation:

$L = \frac{1}{2} C_L \rho v^2S$

Where:
$\rho$ (rho) is the air density
$V$ is the true airspeed Velocity
$S$ is the surface area of the airfoil, and
$C_L$ is the coefficient of lift.

For more information, see Lift equation explained

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