# Determining Volumetric Airflow Rate for a Hovering Helicopter

## How can we determine the volumetric airflow rate downdraft that a hovering helicopter generates?

An unloaded helicopter hovers at sea level while being loaded, causing an air mass to move downward. A load is added, and the helicopter slowly rises. What factors do we need to consider in determining the volumetric airflow rate downdraft?

## Factors to Consider in Determining Volumetric Airflow Rate:

When calculating the volumetric airflow rate downdraft that a hovering helicopter generates, several factors come into play:

- Area of the rotor disc
- Mass flow rate of air through the rotor
- Density of the air
- Velocity of the air

First, let's determine the area of the rotor disc. Given that the rotor diameter is 18 meters, the radius would be 9 meters. The area of a circle can be calculated using the formula A = πr∧2, resulting in 81π square meters as the area of the rotor disc.

Next, the mass flow rate of air through the rotor disc can be calculated by multiplying the density of air with the area of the rotor disc. In this scenario, the velocity of the air approaching the blades is considered negligible, simplifying the calculation to the product of air density and rotor area.

Although the question does not provide the specific density of air, it mentions taking the density of atmos. However, since the details are not fully provided, the exact volumetric airflow rate downdraft cannot be calculated. The time taken for the helicopter to rise after the load is added is crucial in this calculation.

In conclusion, the determination of the volumetric airflow rate downdraft that a hovering helicopter generates requires considering various factors, including the rotor disc area, air mass flow rate, air density, and air velocity.