Charts for estimation of the characteristics of a helicopter rotor in forward flight I: profile drag-lift ratio for untwisted rectangular blades Page: 3 of 25

                                
NACA ACR No. L4H07

INTRODUCTION
Because of the pressing requirements of procurement
agencies for a rational method for evaluation of heli-
copter proposals and because of the requirements of
helicopter designers for a basis for choosing the
optimum combination of variables, it was felt that a
need existed for design charts summarizing the effect
of changes in the major variables on the characteristics
of a powered rotor in forward flight. The method of
analysis of reference 1 accordingly was used to prepare
summary charts that are generally similar to figure 3
of reference 1 but cover various amounts of shaft power
input. The present report has, for simplicity, been
restricted to the basic case of zero blade twist.
METHOD OF ANALYSIS
Parameter for shaft power input.- The primary modifi-
cation made herein  in the method of reference 1 is the
introduction of a new parameter   P/L  for rotor-shaft
power input. The symbol P represents the drag that
would absorb the same power, at the velocity along the
flight path, as the power being supplied through the
rotor shaft. The parameter    P/L  is therefore equal to
the total drag-lift ratio, or
P   /D\     D      D      'D
L  =  -  +   -m  + A   +  -           (1)
L    L      L(i    L P    Le
where
(LI     profile drag-lift ratio
IL ,i  induced drag-lift ratio
(DI    parasite drag-lift ratio
p
)      drag-lift ratio representing angle of climb;
L       that is, rate of climb divided by velocity
along flight path

Sm

- -       -- -
--        .*- ---   r-l I

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