naca-tn-1060
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National Advisory Committee for Aeronautics, Technical Notes - An Investigation of Additional Requirements for Satisfactory Elevator Control Characteristics
Rests of three airplanes have been conducted in an
effort to develop elevators that would provide stick Ti
forces in steady turns within the limits required by the
Army and Navy handling-qualities specifications over a___ ._n
large range of center—of—gravity positions (about 10 per— "
cent of the mean aerodynamic chord)?’ In order to obtain' "i
the desired stick forces in steady turns, closely balanced "
elevators were used in conjunction with bobweights or with
types of balance that gave the elevators a tendency to
float against the relative Wind. Although.the desired
stick forces in steady turns were obtaine , the control
characteristics were considered unsatisfa tory by the
pilots because ofathe lightness of the forces required in-
rapid pulleups and because of the uncertainty of the con- .
trol in rough air. These tests indicate that the desire -“
to provide stick forces in steady turns within specified
limits over a large center—of-gravity range tends to con-
flict with the need for sufficiently heavy stick forces
in maneuvers involving rapid stick movements, Several _
factors that may limit the degree of elevator balance '"""
permissible (and hence set a limit on the allowable reduc—
tion in variation of force per g with center-of—graVity
position) are discussed.
Sis a result of the tests, requirements have been added
to the Army and Navy stability and control requirements for
airplanes that the gradient of elevator control force
per g in quick pull-ups shall never be less than in steady
turning flight under_the same conditions; Further
research is needed to determine whether a more severe
restriction is desirable and to investigate flight test
procedures for studying control characteristics in quick
maneuvers.
Requirements for the elevator-control characteristics
in maneuvers were first established on the basis of the
stick force required per g normal acceleration in steady
turns (reference 1). Tests at the Langley Laboratory of
the NACA have shown that an airplane designed to have
sticknfcrce gradients within the required limits over the
allowable center—qf—gravity range may still be considered
unsatisfactory because of undue lightness of the control
force required for rapid movements of the stick. Limita—
tions on the degree of elevator balance that may be
required to provide satisfactory characteristics in this
respect are therefore discussed.
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