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National Advisory Committee for Aeronautics, Report - The Estimation of Maximum Load Capacity of Seaplanes and Flying Boats

The maximum load that can be taken into the air by
a seaplane or flying boat is a matter of general interest
and, in some cases, of considerable importance. It
may be obtained either by calculation or by direct
experiment. However, the calculation requires model
basin data not always available, while the direct deter-
mination with gradually increased loads is often out
of the question, due to the time and expense involved.
Consequently, very little .data are available on the
ability of seaplanes to take ofl? with heavy loads.
This paper is concerned with the study of take-01f data
and the development of a simple method for the esti-
mation of maximum load.
Observed times for take-off with a progressive
increase in gross weight are given in Table I. These
data are for a typical flying boat fitted with two
engines developing 540 b -hp each, according to
calibration tests. The conventional plot of take—OE
time against gross welght ls given in Figure 1.
A test was also made on another flying boat substan-
tially identical with the above except that it was fitted
with two calibrated engines developing 620 b~hp each,
and the time for take-off was found to be 30 seconds
with a gross load of 17,184 pounds. This point is also
plotted on Figure 1. The question then arises as to
what is the maximum load that can be taken ofl with
the second flying boat. It is obvious that the plotting
method used in Figure 1 is unsatisfactory for this
purpose.