Summary report of results obtained during demonstration tests of the Northrop X-4 airplanes Page: 3 of 48
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2 ' f 9\- NACA RM A50I01
The damping of the lateral oscillation does not meet the Air Force
requirements for satisfactory handling qualities over the Mach number
range covered. The data indicated decreased damping as the flight Mach
number was increased above about 0.5, and at high Mach numbers (M>0.8)
and at high altitudes the X-4, in comnnon with other transonic research
airplanes, experienced a small amplitude undamped lateral oscillation.
The dynamic lateral-stability characteristics were estimated fairly
well by theory at low Mach numbers and at a pressure altitude of 10,000
feet. At 30,000 feet, however, at Mach numbers above about 0.6, the
theory again indicated a higher degree of stability than was actually
obtained.
For the conditions covered in these tests the stalling characteris-
tics of the X-4 airplane, as measured in stall approaches in straight
flight and in an accelerated stall to about 1.6g, were, in general,
satisfactory. Both the stall approaches and the stall were character-
ized by a roll-off to the right.
The X-4 buffet boundary showed a sharp drop-off in the normal-force
coefficient for the onset of buffeting as the flight Mach number exceeded
0.8. The boundary was almost identical to that obtained for the D-558-II
research airplane at comparable Mach numbers.
INTRODUCTION
The X-4 airplane was constructed as part of the joint NACA - Air
Force - Navy research airplane program to provide research information
on the stability and control characteristics of a semitailless config-
uration at high subsonic Mach numbers.
In the course of the demonstration flight tests of the airplane by
Northrop Aircraft, Inc., at Edwards Air Force Base, Muroc, California,
limited stability and control data up to a Mach number of about 0.80
were obtained and reported in references 1 through 7. The present
report consolidates the previous results and presents a limited analysis
of these data. Additional information is also provided on the
longitudinal-stability characteristics up to a Mach number of 0.88, the
characteristics in steady sideslip at a Mach number of about 0.50, and
the buffet boundary at low (M0.30) and at high (M:0.80 to 0.88) Mach
numbers.
SYMBOLS
Vi indicated-airspeed, miles per hour
hp pressure altitude, feet.
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Sadoff, Melvin & Sisk, Thomas R. Summary report of results obtained during demonstration tests of the Northrop X-4 airplanes, report, December 13, 1950; (https://digital.library.unt.edu/ark:/67531/metadc58656/m1/3/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.