Question

The upward lift on an aircraft wing is directly proportional to the atmospheric density. All other factors aside, will the upward lift on an aircraft wing increase or decrease as it gains altitude? Explain, using concepts discussed in chapter 1 regarding the vertical structure of our atmosphere.

Answer 1

Answer:

upward lift on an aircraft wing decreases as it gains altitude.

Explanation:

• The lift on an airplane wing is generated due to the the difference in the pressure on the top of the wing and the bottom of the wing in accordance with the Bernoulli's Principle.

• The pressure on the lower part of the wing is higher due to the low velocity stream of air than on the upper part of the wing.

The governing equation of the Bernoulli's Principle is:

$\frac{P}{\rho.g} +\frac{v^2}{2g} +z=constant$

where:

P = pressure of the fluid

g = acceleration due to gravity

$\rho=$ density of fluid

v = velocity of the fluid

z = height of fluid from the datum

But the lift force on the wings depends upon several aerodynamic factors given mathematically as:

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

where:

cl = experimental constant

$\rho=$ density of air

A = area of wing

v = velocity of the air

As we move up in the atmosphere the density of air reduces and thus the force of lift will eventually decrease, that is the reason why airplanes have a flight ceiling, an altitude above which it cannot fly.