Investigation of the Dynamic Longitudinal Stability of Two Equal Size Models Coupled in Tandem with a Single Joint: Preliminary Model Flight Tests Page: 2 of 15
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NACA RM LEOH17
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
INVESTIGATION OF THE DYNAMIC LONGITUDINAL STABILITY
OF TWO EQUAL-SIZE MODELS COUPLED IN
TANDEM WITH A SINGLE JOINT
PRELIMINARY MODEL FLIGHT TESTS
By Robert E. Shanks and David C. Grana
An investigation is being made in the Langley free-flight tunnel
to study the dynamic longitudinal stability of equal-size models
coupled in tandem with a single joint which provides freedom in pitch
between the models. This paper presents the results of some prelimi-
nary flight tests in which the joint was approximately equidistant from
the centers of gravity of the two models and the models had a mechanical
linkage which moved the elevator of the rear model so as to produce
pitching moments tending to oppose relative displacement in pitch of
the two models. All the flight tests were made for conditions which
would have been statically stable if the combinations were rigid.
The flight tests showed that the behavior of the models was satis-
factory in some conditions and that the stability of the combination was
decreased as the elevator gearing ratio (ratio of elevator deflection to
relative pitch angle) was decreased, as the ratio of the weight of the
rear model to that of the front model was increased, or as the center of
gravity of the front model was moved rearward.
An investigation is being conducted in the Langley free-flight
tunnel to determine the dynamic longitudinal stability characteristics
of two models of equal size coupled together in tandem with a single
joint. This arrangement would facilitate in-flight refueling by
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Shanks, Robert E. & Grana, David C. Investigation of the Dynamic Longitudinal Stability of Two Equal Size Models Coupled in Tandem with a Single Joint: Preliminary Model Flight Tests, report, November 13, 1950; (digital.library.unt.edu/ark:/67531/metadc58584/m1/2/: accessed February 21, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.