Landing Characteristics of a Model of a Flying Boat With the Depth of Step Reduced to Zero by Means of a Retractable Planing Flap Page: 4 of 10
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.3
RESULTS AND DISCUSSION
Stability tests.- Figure 2 shows the variation of
trim with speed when the model was accelerated from rest
to get-away speed at a constant rate of 1 foot per second
per second. The trim of a similar model with a depth of
step equal to 5 percent of the beam is included in fig-
ure 3(b) for comparison. A notable result obtained with
zero depth of step is that the trim was not affected at
any speed by more than approximately 80-when the center
of gravity was shifted from 24 to 38 percent mean aero-
dynamic chord. Manipulating the elevators from full down
to full up was also relatively ineffective in changing
the trim. Even though the slipstream and the thrust were
not reproduced on the model, it appears that the hydro-
dynamic moments would predominate throughout the landing
run in controlling the trim of a flying boat with the step
retracted and that the location of the center of gravity
would have no great effect. The variation of trim with
speed during accelerations to get-away speed was practi-
cally the same as that obtained during the decelerations
after landing.
Landing tests were made with the center of gravity
at 34, 30, and 38 percent mean aerodynamic chord. The
model exhibited almost no tendency to skip or to porpoise
when landed at any trim from about 5.50 (afterbody
horiszntal) up to and including a full-stall landing at
12. After landing, the trim would decrease quickly to
about 50 and, as the speed decreased, the trim would vary
approximately as shown in figure 2 for take-off. When
landings were made at trims below 50, the stability char-
acteristics depended upon the rate at which the carriage
was decelerated. With a rate of deceleration of 1 foot
per second per second the model increased trim after con-
tact and left the water. With very rapid decelerations,
which were not measured but were believed to be about 12
feet per second per second, the model remained on the
water after landing at trims less than 50
Resistance teets.- The resistance of the full-sige
flying boat represented by the model with zero depth of
step is compared in figure 3 with the resistance of a
similar model having a depth of step equal to 5 percent
of the beam. The resistance with sero depth is excessive
for a normal take-off. For a landing the high resistance
may be of value in reducing the length of the landing run.
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Benson, James M. & Freihofner, Anton. Landing Characteristics of a Model of a Flying Boat With the Depth of Step Reduced to Zero by Means of a Retractable Planing Flap, report, February 1944; (https://digital.library.unt.edu/ark:/67531/metadc61760/m1/4/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.