Charts for estimating the hovering endurance of a helicopter Page: 3 of 16

                                
2                                                           NACA TN 3810
SYMBOLS
a           slope of curve of section lift coefficient plotted against
section angle of attack (radian measure), assumed to be
5.73
B          tip-loss factor, assumed to be 0.97; blade elements outboard
of radius  BR  are assumed to have profile drag but no lift
b          number of blades per rotor
CL         rotor mean lift coefficient, 6.C
a
CT          thrust coefficient; for hovering helicopter,      W
R2p(aR)2
CQ         torque coefficient,
xKR2p(QR)2R
c          blade chord, ft
cd;o       section profile-drag coefficientV
f   cr2dr
ce         equivalent blade chord, -M ft
R, r24,
E          hovering endurance, r
E        hovering-endurance parameter,   ()(sfc) E
550 --
P          horsepower required for helicopter to hover, hp
Q          rotor torque, lb-ft
R          blade radius, ft
r          radial distance to a blade element, ft
afe        specific fuel consumption, lb/(rotor hp)/hr                            V