Charts for Helicopter-Performance Estimation Page: 3 of 73
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2 NACA ACR No. L5E04
The primary purpose of the report is to present,
for numerical application, the relations among the
aerodynamic design and performance parameters. The actual
porformance of a given helicopter is influenced by a
number of secondary parameters, eny one of which has only
a small effect on the over-all performance but the
quantitative estimation of which presents great diffi-
culties. When the design variables have been selected
for a given helicopter, however, it is only by means of
the secondary parameters that the efficiency of the heli-
copter can be imoroved. For this reason the secondary
parameters or efficiency parameters are the proper subject
of basic helicopter research. Since the efficiency
paramoters used herein are for the most part idealized
or neglected, tile numerical results obtained are con-
sidered to be only approximate in absolute value but to
give a true representation of the relations among the
design parameters. The results should therefore be of
practical assistance in comparative performance studies.
The accuracy with which the performance must be predicted
in a given case will determine the extent to which the
efficiency parameters should be investigated. At a
number of olaces in the report secondary parameters have
been briefly discussed. Only the following should be
considered design parameters:
Y helicopter speed parameter
Yt blade tip-speed parameter
F rotor-power losing parameter
6 average effective blade-element dra coefficient
CDf fuselage drag coefficient
a rotor solidity
The text of this pcper is divided, for convenience,
into r2ubered sections. In section 1 & general equation
for the aerodynamic performance of helicopters in steady
flight is derived from familiar helicopter theory. In
sections 2 to 5 the general equation is applied to the
construction of graphs for the solution of problems in
hcriscutal flight and climb and the numericl applica-
tion or the charts is explained. The special problem
of the conditions for blade stall in horizontal flight
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Talkin, Herbert W. Charts for Helicopter-Performance Estimation, report, August 1945; (digital.library.unt.edu/ark:/67531/metadc61830/m1/3/: accessed December 9, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.