The High-Speed Characteristics of Several Flaps and Spoilers on the Upper Surface of the Horizontal Stabilizer of a Model of a Radial-Engine Pursuit Airplane Page: 12 of 194
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MR No. A5L07
tests of the 12-inch-span flaps so that the projected area
was determined by the deflection of the flaps. Since the
solid curves include no data from tests with small flap
deflections, the characteristic reversal is not shown.
The power of the flaps to produce a download on the
tail increased with Mach number up to a value of 0.S15, and
the maximum change of elevator floating angle was about
25 percent less at a Mach number of 0.S15 than it was at
low speed. Nevertheless, above the lift coefficient and
Mach number at which the pitching-moment characteristics of
the standard model diverged widely (fig. 9) the power of
the flaps and spoilers to balance the model was greatly
reduced. For example, at a Mach number of O0.60, a 45
deflection of the 1.2- by 12-inch flaps trimmed the model
at a lift coefficient of about 0.82; at a Mach number of
0.815 the trim lift coefficient was only 0.39. Similarly,
only 1.80 travel of the elevators was required at low
speed in order to increase the balance lift coefficient
of the standard model from 0.00 to 0.30; whereas 8.O0
travel was required at a Mach number of 0.815. This
increase is due almost entirely to the increased static
longitudinal stability of the model at high speed, and
demonstrates clearly the need for additional control.
The results of tests of the modified flaps are shown
in figure 34 as single points, since each modification was
tested with only one deflection. Hinging the flap at its
trailing edge had very little effect upon its character-
istics, at least for the deflection tested. The 33-percent
gap, however, reduced the elevator-fixed effectiveness
slightly, and diminished the effect on the elevator floating
angle about 50 to 60 percent, the over-all effect of the
gap being to reduce the trim lift coefficient by about 0.06
at all Mach numbers from 0.60 to 0.815. The gap, although
detrimental to the effectiveness of a device of this type,
may alleviate the violent turbulence in the flap wake so as
to be desirable for reducing tail buffeting. Unfortunately,
the mass and rigidity of the model prevented observations
concerning tail buffeting during the present tests.
Compared on a basis of the projected area of the device
normal to the stabilizer surface, the 0.6- by 12-inch flaps
and the .2-inch-span, constant-percent-chord spoilers wore
slightly more effective than the remainder of the flaps and11
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Boddy, Lee E. The High-Speed Characteristics of Several Flaps and Spoilers on the Upper Surface of the Horizontal Stabilizer of a Model of a Radial-Engine Pursuit Airplane, report, January 21, 1946; (https://digital.library.unt.edu/ark:/67531/metadc61515/m1/12/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.