26 BULLETIN 1204, U. S. DEPARTMENT OF AGRICULTURE. 
RATE OF DUST DELIVERY. 
A number of straightaway flights were made to obtain data on 
the rate of delivery of dust from the planes. One plane was loaded 
with a known quantity of dust and flown on a straight line across the 
fields, paralleling a straight road several miles long. The feeder 
valve was opened at a certain starting point marked on the ground, 
and dust delivery was continued until the hopper was empty. A 
second plane followed this one, flying perhaps 100 feet higher and 
carrying an observer who watched the behavior of the dust de- 
livered from the first plane, noting carefully with a stop watch the 
time from first delivery until the end of the dusting. In addition, 
the point at which the dust supply was exhausted was marked by 
the second plane, and the distance back to the point of starting was 
measured. In this way the time of delivery of a hopper charge, as 
well as the distance it would last, was determined. 
The first tests of this nature were conducted with the hand-crank 
hopper with the feed mechanism as at first designed. One hundred 
and twenty pounds of 100 cubic inch calcium arsenate were loaded 
into the hopper, and the dusting plane was flown straight away at 
full speed above the cotton plants. The type of dust cloud being put 
out can be judged from Figures 15 and 16, which were taken during 
one of these test flights. 
The average of these flights showed that it required 2 minutes and 
15 seconds to empty the hopper each time, and during this time the 
plane flew 3.3 miles. In other words, it was operating at an average 
rate of ground speed of 88 miles per hour, and the 120 pounds con- 
tained in the hopper lasted over a strip 17.424 feet long. 
The poundage per acre being delivered depends, of course, on the 
width of strip which can be considered as effectively treated. On the 
basis of the figures obtained on this flight, it would be necessary to 
take a strip only 50 feet wide with the plane to utilize the dust at an 
average rate of 6 pounds per acre, the rate at which calcium arsenate 
is usually applied in ordinary commercial dusting for boll-weevil 
control. Examinations made during these flights showed very plainly 
that an effective treatment was being obtained on a strip over 200 
feet wide, but reducing this to 150 feet as the average width of the 
strip would mean that only 2 pounds of poison was being used per 
acre. 
This rate of dust delivery was not considered sufficient for the 
maximum dust cloud desired, as, of course, every foot which could be 
added to the width of the strip at each trip by correspondingly in- 
creasing tin' dust delivery, would reduce 1 the number of trips neces- 
sary to poison a field of cotton, and, consequently, add much to the 
acreage capacity of a plane. 
The feeder opening of the same hopper was therefore enlarged to 
the maximum size which could be secured between the cross brace 
wires of the fuselage. This allowed an outlet about !) inches square, 
and the paddle wheel was correspondingly enlarged to cover this en- 
tire opening. At the same time the gear ratio of the sprockets used 
for driving the paddle wheel was changed from 1 to 1 to 2 to 1. so 
that the paddle wheel was operated twice as fast as by a simple hand 
ciank. 
Throughout this work an effort was made to maintain about the 
same speed of cranking, and the majority of the tests were conducted 
