Question

An aircraft increases its speed by 2% in straight and level flight. If the total lift remains constant determine the revised CL as a percentage of its original value to three significant figure

Answer 1

96.1%

Step-by-step explanation:

We know that lift force

`F_L=(1)/(2)C_L\rho AV^2`

------------(1)

Where
`C_L` is the lift force coefficient .

ρ is the density of fluid.

A is the area.

V is the velocity.

Now when speed is increased by 2 % and all other parameter remains constant except
`C_L` .

Let;s take new value of lift force coefficient is
`C_L'` .

`F_L=(1)/(2)C_L'\rho A(1.02V)^2`

-----------(2)

Now from equation 1 and 2

`C_L* V^2=C_L'*1.0404 V^2`

⇒
`C_L'=0.961C_L`

So we can say that revised value of lift force coefficient is 96.1% of original value.