Aerodynamic Tests of an NACA 66(215)-116, a=0.6 Airfoil With a 0.25c Slotted Flap for the Fleetwings XA-39 Airplane Page: 7 of 39
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6aR No. L14.21
improvement due to the use of-the long lip at low
deflections and,in fact,. at&elower'in some cases.
An examination of the moment characteristics for
pivot points 4 and 5 .in figures 4(b) and )(c) shows
that the moments are in no case excessive. At the
lower deflections, both the lift and the moment curves
for the two pivot points agree fairly well. At
deflections above 300 about pivot point 5, however,
the flap effectiveness decreases and the moment charac-
teristics are very nearly the same for all the higher
flap deflections. For deflections about pivot point 4
both the lift and the moment characteristics show
Increases with flap deflection up to the maximum.
Determination of optimum 'confiurations.- The
charac oeristi~d considered desirable for this wing-flap
combination were a high maximum lift at a high flap
deflection; reasonably high lifts with low drags at
6f = 300; and a positive lift coefficient with low
drag at a negative an3le of attack for a flap deflection
of 150. It was not considered necessary to use a single
flap pivot po.ition.
Figure 6 shows the variation in the increment of
section maximum lift coefficient with flap deflection
about several pivot points at both Reynolds numbers.
Pivot point 4 gives the highest values of maximum
lift coefficient at both Reynolds numbers. For a
flap deflection of 550 about pivot point 4, the maximum
lift cgefficient was 2.70 at a Reynolds number of
6 x I0'.
lIn figure 7 lift and drag characteristics at the
higher lift coefficients are plotted for a flap
deflection of 300 about various pivot points. The
values of the drag coefficient obtained at this flap
deflection above a lift coefficient of about 1.3 were
not accurate and so are not included. This figure
indicates that the drag coeficients at the higher
lift coefficients would probably be lowest for pivot
point 3. There is very little.difference in the lift
characteristics for the various pivot points.
A section lift coefficient 'of.0.18 was assumed
as a reasonable voint for the comparison of the various
configurations at the 15o flap-defletion, Lift
curves are shown in figure 4(c) for the slot both sealed6
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Cahill, Jones F. Aerodynamic Tests of an NACA 66(215)-116, a=0.6 Airfoil With a 0.25c Slotted Flap for the Fleetwings XA-39 Airplane, report, November 1944; (https://digital.library.unt.edu/ark:/67531/metadc61411/m1/7/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.