What Is the Correct Equation to Calculate Lift in RC Helicopters?

[hbooth93]

Homework Statement

I've been trying to find a simple equation for calculating the lift (or thrust) of a RC helicopter and I've found a few that are different.

Homework Equations

1) Lift = circular area swept by rotor blades \times density of air \times velocity of air exiting disk \times velocity of air exiting disk

2) Thrust = 2 \times air density \times length of rotor blades ² \times induced velocity

The Attempt at a Solution

I am unsure which is the correct equation. Also, can someone explain what 'induced velocity' is please?

thanks!

 

[NascentOxygen]

Homework Statement

I've been trying to find a simple equation for calculating the lift (or thrust) of a RC helicopter and I've found a few that are different.

Homework Equations

1) Lift = circular area swept by rotor blades \times density of air \times velocity of air exiting disk \times velocity of air exiting disk

2) Thrust = 2 \times air density \times length of rotor blades ² \times induced velocity

The Attempt at a Solution

I am unsure which is the correct equation. Also, can someone explain what 'induced velocity' is please?

thanks!

The equations seem very similar. Each contains a term having units of length² (we call that area), and density of air and velocity of air column. So I'd say you are in error in having velocity appearing twice in the first equation. This leaves us with two equations almost identical, except for a Pi and I'd surmise that you may have accidently left that out, too.

So I'd conclude that induced velocity is the downdraught, the velocity of the air below the disk.

Have you decided what units you would expect this 'thrust' to have? Do the units of the terms on the right hand side of the equations seems to amount to that?