How a spraying drone works — why propeller airflow matters more than the pump

Most people see a spraying drone as a "flying spray tank", but what really makes drone spraying work differently from hand spraying is not the tank or the pump. It is the "downwash" created by the propellers.

What is downwash?

The drone's propellers push air downward to keep the aircraft in the air. This air does not disappear. It drives straight down into the crop canopy, and it is what carries spray droplets down into the lower layers of the plant and under the leaves, where many insects and diseases live.

This is why drones spray effectively while using far less water than traditional spraying. A backpack sprayer needs a lot of water so the product runs over the whole plant, while a drone uses the force of the air to carry the droplets instead.

What the spray system is made of

A tank for the spray solution, a pressure pump, delivery hoses and nozzles mounted under the drone's arms. The nozzles determine the droplet size and the volume per minute, while the pump keeps the pressure steady so the droplets do not vary between large and small.

The key: how three things relate

Flight speed, flight height and nozzle flow rate must all match each other. If you fly faster without increasing the flow rate, the product applied per rai drops immediately. If you fly too high, the downwash spreads out before reaching the crop, and more droplets drift out of the field.

Most newer drones calculate this automatically once you set the volume per rai, but users should understand the principle, because on the day the system is set wrong or a sensor is off, the person who knows the principle will notice before the spray is wasted across the whole field.

What a drone cannot do for you

A drone does not decide what to spray, when, or at what rate. Surveying the field, diagnosing diseases and pests, and choosing the product are still the work of farmers and agricultural specialists. A drone only makes "spraying" faster and safer for the person doing it.
Important note
This article explains general principles. It is not a recommendation for any specific chemical. Suitable mixing rates and timing differ by substance, crop, growth stage and field conditions. Always treat the product label as the authority, and ask our staff or an agricultural specialist before deciding.