Additional studies of the stability and controllability of an unswept-wing vertically rising airplane model in hovering flight including studies of various tethered landing techniques Page: 11 of 27
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th tim of th oste st The ~ center fravit lcn i I F n ai~pl
flight tests, therefore, force tests were wade to determine the location
of the N rody...amic cente... of the model so that the center of gravity...
could be located in a position that would give a reasonable degree of
stab ility at low angles of a-;ttack. The results of these tests with the
center a gravity located . a. t te eating edge of thi wing are presented
in figure 6, Although these data do not show the static stability exactly
because the model was not properly trimmed, they indicate that the aeo-
dynamic center of the model was about 30 percent of the chord behind tie
leading edge of the wing. This indication was obtainedfroma the slope
of t1he pitching- moment curve s for thrust cotfficints of 0.03 and 034
at the normal-force coefficients 4010 and 056, respectively, for which
these power conditions represent full power. Since the static longi-
tudinal stability of the model was not unreasonably large when ithe
center of gravity was located at the leading edge of the wing (which
was ione of the locations covered in. th tests described in references 1
and 2) this location was chosen for the present series of flight tests
so that these test results would be directly ceiomparable with those of
the previouf0ts tests,
Motion picture s illustrating the results of several flights of th
mode in the configurationst discussd herein reae avai lable on loan from
the NAGA headquarters, Washington, t . C. The results of this invest-
gation are illustrated more graphically by the flight scenes of this
motion picture than is possible by a written presentations
ffect of rate-sensitive autopilot on pitching motion. The results
of the originals tests pressented in reference show thae. the uncontrolled
pitching motio n of the model consisted of a fairly long period unstable
osciliatIon0 Although this oscillation could be controlled fairly
easily, the instability might be considered undesirable for certain
operations requiring long periods of hovering flight. The tests of the
model with the ratoegyro stabilizing device were made, therefore, to
determine whether the stability: .C of pitching motions could be made ati-
factory with an automatic stabilizing device or pitch damper similar to
the rategyro yaw dampers now being used on a number of airplanes i s
pointed out previously, this pitch damper moved the elevator to oppose
the pitching velocity of the model Several flight tests were made
using progressively lager degrees of control response without any
improvement in the sabiity of the t pitching motions of the model being
nothiceabie to the pilot. Finally to etermine whether the pitch (amper
wonulet have any noticelye efft ev n with extremiy hlh control
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Bates, William R.; Lovell, Powell M., Jr. & Smith, Charles C., Jr. Additional studies of the stability and controllability of an unswept-wing vertically rising airplane model in hovering flight including studies of various tethered landing techniques, report, November 6, 1951; (digital.library.unt.edu/ark:/67531/metadc58981/m1/11/: accessed May 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.