INSECTICIDES AND REPELLENTS 



45 



600 feet, and for a deposit of 0.1 gallon per acre, 342 feet. The mass 

 median diameter of the droplets was estimated to be 100 to 165 

 microns, with 75 percent of them less than 226 microns in diameter. 



One of the simplest installations that has been used in cargo planes 

 and medium bombers consists of a straight discharge pipe that 

 extends about 3 feet below the belly of the fuselage (fig. 16). The 

 pipes vary from about % to 3 inches in diameter, depending on the 

 desired output, and may be enclosed in a streamlined fairing. The 

 lower ends of the pipe and fairing are cut at an angle of about 45°, to 

 increase the atomization of the liquid. The insecticide is discharged 

 by gravity from the storage tanks in the cargo compartment. The 

 installation between the storage tanks and outlet pipe of a smaller 

 tank with a float valve to maintain a constant head provides an even 

 flow of the liquid. However, the pressurized boom-type equipment 

 is much superior from the standpoint of atomization and effective 

 swath width. 



In another modification of the equipment for use with the PT-17, 

 a 75-gallon auxiliary fuel tank suspended from a bomb shackle beneath 

 the fuselage served as the insecticide container (fig. 17). This equip- 

 ment was employed for experimental work at Orlando and also to a 

 limited extent in civilian mosquito-control operations. The tank could 

 be quickly attached or detached, and the two cockpits left free for 

 normal use. A wind-driven gear pump was mounted on one of the 

 landing-gear struts, or a centrifugal pump and propeller on a special 

 bracket on the front end of the tank, the latter for use with suspensions 



Figure 16. — A streamlined straight discharge pipe attached under the bomb bay 



of a B-25 plane. 



