# How can I calculate the minimum thrust to weight ratio required for a given takeoff distance?

I am building a plane and I have a take-off distance of 50ft, is there a way for me to estimate the thrust-to-weight ratio required for this constraint (even if it was in terms of say wing loading)?

Assuming you know the mass $$m$$ of the aircraft, the speed $$v_0$$ required to take off and the lift and drag associated.

Using basic dynamic and newton's second law you can calculate the average acceleration $$a$$ required to reach take off speed before the end of your runway:

$$a=\frac{v_0^2}{100\text{ft}}$$

Then using your drag generated at takeoff to be on the safe side

$$\text{Thrust} = m * a + \text{Drag}$$

Implying,

$$\frac{\text{Thrust}}{m}=a+\frac{\text{Drag}}{m}$$