Tank Tests of a 1/7-Size Dynamic Model of the Grumman XJR2F-1 Amphibian to Determine the Effect of Slotted- and Split-Type Flaps on Take-Off Stability - NACA Model 212, TED No. NACA 2378 Page: 4 of 22
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NACA RM No. L7A07 3
Position of center of gravity
Vertical position, 16.06 inches above keel at step
Horizontal position, 25-percent M.A.C.
.Full power, 7100 rpm, 12 blade angle at 3/4 radius
Nosewwheel drains sealed
Step vented to interior of hull through main wheel
The trim was referred to the base line of model
Moments -tending to raise the bow were considered positive
A gross load of 65.2 pounds corresponding to full-scale design
gross load was used for all of the take-off stability tests. The
forward limts for stable positions. of the center of gravity during
take-off were determined with full power and-elevators deflected -300,
Records were taken of the time history of trim and speed -during
take-off:. Where possible these records were supplemented by visual
observations of maximum amplitude of porposing and. trim. Al1l center
of-gravity limits were determined for two rates of acceleration,
1.1 and 4.8 ,feet per second per second, At .the higher rate of
acceleration, it was sometimes difficult to determine whether or not
the model was starting a cycle of porpoising.. .The motion was not
considered porpoising unless a complete oscillation in trim occurred.
For the aerodynamic tests, which were made with full power,
the aerodynamic lift and pitching moments were determined for a
range of speeds from 22 to 35 feet per second.
RESULTS AND DISCUSSION
The variation of the trim with speed during take-off with the
slotted flaps deflected 5, 150, 200, and 450 is presented in
figures 2 to 5, respectively. As the flap deflection was increased,
the free-to-trim tracks were lowered and, with flaps deflected 450
and the center of gravity at 32-percent mean aerodynamic chord, lower
limit porpoising occurred over most of the take-off run. Since the
elevators were already full up, a recovery from this porpoising was
not possible. .
The variation of the trim with speed for split flaps deflected
450 is presented in figure 6. At positions of the center of gravity
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Land, Norman S. & Zeck, Howard. Tank Tests of a 1/7-Size Dynamic Model of the Grumman XJR2F-1 Amphibian to Determine the Effect of Slotted- and Split-Type Flaps on Take-Off Stability - NACA Model 212, TED No. NACA 2378, report, February 6, 1947; (digital.library.unt.edu/ark:/67531/metadc64241/m1/4/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.