A Method for Studying the Transient Blade-Flapping Behavior of Lifting Rotors at Extreme Operating Conditions Page: 5 of 28
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NACA TN 366
u = U/R
ups = Ups/ i
UTs = Ups/R
v induced inflow velocity at rotor (positive downward), ft/sec
V velocity along flight path, ft/sec
x ratio of blade-element radius to rotor-blade radius, r/R
as angle between shaft axis and plane perpendicular to flight
path, positive when axis is pointing rearward, deg
ar blade-element angle of attack, measured from line of zero
blade flapping angle with respect to shaft at particular
azimnuth position, radians
),p first and second derivatives of 0 with respect to time t
pp first and second derivatives of P with respect to azimuth
7' mass constant of rotor blade, cePR4/Ih
80 collective-pitch angle at blade root, average value of
instantaneous blade-root pitch angle around azimuth, deg
e. 75 collective-pitch angle at 0.775 blade radius, deg
E1 difference between root and tip pitch angles, positive when
tip angle is larger, deg
8 instantaneous blade-section pitch angle; angle between line
of zero lift of blade section and plane perpendicular to
rotor shaft, 80 + lx - Al cos ' - B1 sin ', deg
V sin as - v
s, inflow ratio,
V cos as
ps tip-speed ratio,
E = e/R
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Gessow, Alfred & Crim, Almer D. A Method for Studying the Transient Blade-Flapping Behavior of Lifting Rotors at Extreme Operating Conditions, report, January 1955; (https://digital.library.unt.edu/ark:/67531/metadc56061/m1/5/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.