The two most important factors that influence the efficacy of a product onto the target are the application volume and the droplet size.

The aircraft speed over the ground varies greatly as the job progresses. Because it is fully loaded and heavy at the start of the job it flies slower. Towards the end of the job when it is much lighter it goes a lot faster. The wind also has an effect. When the aircraft is flying with the wind behind it it is going faster over the ground. When it turns around to do the next path it is flying into the wind and is flying slower. The combination of these two factors means the ground speed of the aircraft can vary by as much as 30% over the course of a job. If the application volume varies, the incorrect amount of product is applied. If a constant pressure in the boom is used then as the ground speed is varied then the application volume is altered. The Spray Boom boom includes a variable flow meter which monitors the speed of the aircraft over the ground and adjusts the flow of product to ensure an even application.

Droplet size is very important to the efficacy of the product on the target. Too fine a droplet may drift off the target and be lost, and a too large a droplet may not give the desired coverage. A small droplet size may affect the job quality. The droplet is formed by the speed of the air flowing over the nozzle and shattering the product stream into droplets. The bigger the angle the finer the droplets. The faster the air stream the finer the droplets.

Pilots are able to adjust the angle of the nozzle at any time by rotating the boom. For example he may wish to create large droplets where off target drift is an issue. At other times he may wish to make a finer droplet where pesticide penetration into the crop canopy is more desirable. He is able to do this during flight from the cockpit.