Ditching Investigation of a 1/18-Scale Model of the North American B-45 Airplane Page: 4 of 25
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, NACA RM SL9L22a 3
Test Methods and Equipment
/ The model was ditched by catapulting into the air to permit a
*, free glide onto the water. The model left the launching carriage at
,* scale speed and at the desired landing attitude. The control surfaces
were set so that the attitude did not change appreciably in flight.
The behavior was recorded by a motion-picture camera, a single-
component time-history accelerometer, and from visual observations.
The accelerometer had a natural frequency of 20 cycles per second
and was damped to about 65 percent of critical. The reading accuracy
of the instrument was 1g. It was installed in the pilots' compartment
and both vertical and horizontal components of acceleration were
measured by rotating the instrument and repeating the runs.
(All values are full scale.)
Weight.- The design gross weight of 82,600 pounds was simulated
in the investigation.
Moments of inertia.- The moments of inertia corresponding to the
design gross weight were specified as follows:
Roll, slug-feet2 ....................... 540,000
Pitch, slug-feet2 . . .....................310,000
Yaw,. slug-feet2........................ 830,000
At the start of the tests the model was ballasted to obtain these
Center of gravity.- The center of gravity was located at 28.8 per-
cent of the mean aerodynamic chord and 18.5 inches above the thrust
line of the engines.
Landing attitude.- Two attitudes were used in the investigation.
The 60 attitude is near the stall angle and the 20 attitude is approxi-
mately the static ground attitude. The attitude was measured between
the fuselage reference line and the smooth-water surface.
Flaps.- All tests were made with the landing flaps in the down
position attached at scale strength. The model was not tested with
flaps up because of the correspondingly higher landing speed.
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Fisher, Lloyd J. & Thompson, William C. Ditching Investigation of a 1/18-Scale Model of the North American B-45 Airplane, report, December 22, 1949; (https://digital.library.unt.edu/ark:/67531/metadc65517/m1/4/: accessed April 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.