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National Advisory Committee for Aeronautics, Technical Notes - Water Landing Investigation of a Model Having a Heavy Beam Loading and a 30° Angle of Dead Rise

A model having a heavy beam loading and an angle of dead rise of 30°
was subjected. to smooth—water impacts in the Langley impact basin. The
tests were made at fixed trims of 6°, 15°, 30°, and 15° for a range of
flight—path angles from approximately 2° to 22°. The beam—loading coef—
ficient (18.8) was constant throughout the test.

Time histories of horizontal and vertical displacements, vertical
velocity, vertical acceleration, and pitching moment were obtained. The
results are presented as plots showing the variation of the experimentally
determined quantities converted to nondimensional coefficients with the
flight—path angle at water contact. Throughout the tests maxim accel—
eration occurred subsequent to chine immersion. The impact lift coeffi—
cient increased with trim up to 30°; however, no change was apparent
between the trims of 30° and M50. Throughout the range of these tests
the draft appeared to be solely a function of flight—path angle.

Interest in the hydrodynamic characteristics of configurations
having heavy beam loadings has been stimulated recently by both the
development of high—length—beam—ratio flying boats and the considera-
tions being given to the use of hydroflaps as a means for alleviating some
of the take-off and landing problems posed by high—speed aircraft.
Theoretical considerations indicate that landings associated with heavy
beam loadings will exhibit greater depths of immersion in order to dis—
sipate the vertical momentum. Development of the equations necessary
to predict the loads resulting from immersion of such configurations
has been handicapped by the lack of pertinent experimental data. Even
though the theory developed in reference 1 is very general and indicates
that the maxim load occurs subsequent to chine immersion for the heavy—
beam—loading case, the equations and coefficients developed in refer—
ences l and 2 are limited to landings in which maximum load occurs
before or within a limited range subsequent to chine immersion. In
order to convert the equations to a form valid for the heavy—beam—loading
case, the theory must be evaluated on the basis of pertinent experi—
mental data to determine the relative importance of the various quan—
tities. The purpose of this paper is to present experimental data that
can be used in extending the range of the equations to include substan—
tial amounts of chine immersion.