TM 5-3740-218-13&P
Example: An application calls for 10 gpa at 50 mph with a swath width of 90 feet. The operator puts 50 gallons of water
into the hopper. How long should it take to spray this out?
TIME/Load = 495 x # Gal/Load
=
495 x 50
= 0.55 Minutes
10 x 90 x 50
# of Gal/Acre x SW x MPH
0.55 Minutes x 60 = 33 Seconds
Answer: It should take 33 seconds to spray out 50 gallons.
b. Swath Runs per Load Checks. This method is most commonly used by airplane operators. Before taking off with
a load, calculations should be made to find out how many swath runs can be made on a field without running out of
chemical. The following formulas apply:
Swath Runs/Load = Acre Load in Hopper
Acres per Swath Run
or
Swath Runs/Load = Acre Load in Hopper x 43560
Field Length x Swath Width
Example: An operator wants to apply 10 gpa and the system carries 100 gallons, which means 10 acres in the hopper.
The swath width is 90 feet and the field runs are 2,200 feet. How many passes can be made?
Swath Runs/Load = Acre Load in Hopper x 43560
10 x 43560
= 2.2 Swath Runs
2200 x 90
Field Length x Swath Width
Answer: The operator can make two passes and should not attempt three without adjustments. See the Acre/Swath
Chart.
c. PSI Setting. Although not commonly used as a means for accurate calibration, it should be mentioned as one
method to aid in calibration. The formula for this method is:
2
PSI =
(GPA x MPH x SW Ft)
X 30
495 x # NOZ x GPM/NOZ at 30 PSI
Example: An operator wants to apply 10 gpa at 100 mph with a swath width of 45 feet. The operator has 58 nozzles with
D-7 orifices in them. What should the boom psi be? From the chart for nozzle selection, it is given that a D-7 puts out
1.25 gpm/nozzle at 30 psi. Substituting for the above formula appears as follows:
2
(10 x 100 x 45)
X 30 = PSI
495 x 58 x 1.25
(1.25)2 x 30 = 47.2 PSI
Answer: The psi should be adjusted to 47.2.
G-3
