Correlation of predicted and experimental lateral oscillation characteristics for several airplanes Page: 3 of 34
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If deAirable-staIity characteristics, so the prediction of these
I stability characteristics me-mOrt mportat.
The purpose of this investigation was to find if a currently used
method of calculation of the lateral oscillation characteristics of an
airplane is sufficiently accurate. This study concentrated on the short
period oscillation, commonly referred to as the "Dutch roll" mode, and
did not include the investigation of snaking which might appear on some
aircraft. The calculated values of period and time to damp to half
amplitude of the lateral oscillations (controls held fixed) were compared
with experimental flight-test values to see how closely these motions
could be predicted. Any discrepancies which appeared between calculated
and experimental data were examined for possible causes such as aero-
elasticity, unknown Mach number or altitude effects, aerodynamic lag, or
incomplete derivative estimation.
It was decided to concentrate, in this investigation, on the smaller
fighter-type airplanes presently flying. At the beginning of the inves-
tigation published data were not complete on most of the aircraft.
Therefore, it became necessary to gather flight data from the manufac-
turers of the individual airplanes. In addition, wind-tunnel, geometric,
and mass data for the comparable configuration were requested. The
flight data used were obtained from tests conducted by the Armed Services,
by the manufacturer, and by the NACA. The wind-tunnel data with the
inertia and geometric characteristics were analyzed by a more or less
standard calculation procedure.
The methods of calculation and the results of this survey are
DESCRIPTION OF AIRPLANES
Geometric and mass characteristics and aerodynamic derivatives for
each airplane studied are listed in table 1 for two altitudes and one
Mach number. Two-view silhouettes are presented in figure 1.
The airplanes studied have jet engines. Airplanes A, D, E, F, and
H are twin engined, while the rest have single engines. As can be seen
in figure 1, the nine airplanes exhibit a variety of wing plan forms and
fuselage shapes. Airplanes A, C, D, and E have straight wing and tail
surfaces. The vertical stabilizer of airplane C has a swept-back leading
edge. Airplane B has straight surfaces except for the horizontal tail,
which is swept back 350. Airplanes F, G, and K have all surfaces swept
back approximately 350. Airplane H is a semitailless design having no
horizontal tail surfaces and with vertical surfaces on the wing. Air-
plane I has an inverse taper. wing swept back 400 at the midchord line.
NACA RM A52J06
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Heinle, Donovan R. & McNeill, Walter E. Correlation of predicted and experimental lateral oscillation characteristics for several airplanes, report, December 15, 1952; (https://digital.library.unt.edu/ark:/67531/metadc59423/m1/3/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.