Charts for Helicopter-Performance Estimation Page: 27 of 73
This report is part of the collection entitled: National Advisory Committee for Aeronautics Collection and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
26 M NACA ACR No. L5E04
Section 7
and equal to the value near the tip. This approximation
is suggested by the relatively small charge with radius
of the average angle of attack per revolution indicated
by the contour plots of reference 7. Use of the tip-
drag coefficients as representative is further suggested
by the fact that the drag power loss is predominantly
determined by the tip drag coefficients, as is shown by
the weighting curves presented in figure 8 of reference 7.
The drag power loss is also shown by equation (8) to
increase with nearly the cube of the radius for constant
blade drag coefficient.
The rethbd presented herein for determining 8 is
based on approximations suggested by the foregoing con-
siderations. The determirnation of 5 is made first for
untwisted rectangular blades neglecting axial inflow, in
which case the angle of attack a is constant along the
radius but varies with azimuth ,- and tip-speed ratio p.
The effects of inflow and blade shape are then briefly
considered. The method consists in calculating values
of the blade-element lift coefficient o as a function
of aYt2, V, and J and using c to read ed from
the airfoil nolar. The values of do thus obtained
are then multiplied by weighting factors and integrated
graphically to find 6. in order to find ct, the value
of Ex is first obtained from: equation (57) for x = 1
Y=l =6t- 82 sin 4t (65)
where
%x=1 blade pitch angle at tip and at azimuth 4
6t blade pitch angle at tip and at azimuth I = 0
82 amplitude of harmonic pitch control for lateral
balance of the rotor
Also, from equation (61), for B = 0, k = 1, and - = 0,
16e
= (66)
2 6+9 2n.
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Talkin, Herbert W. Charts for Helicopter-Performance Estimation, report, August 1945; (https://digital.library.unt.edu/ark:/67531/metadc61830/m1/27/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.