• Version
• 242 Downloads
• 917.92 KB File Size
• 1 File Count
• August 31, 2016 Create Date
• August 31, 2016 Last Updated

National Advisory Committee for Aeronautics, Report - Formulas for Propellers in Yaw and Charts of the Side Force Derivative

General formulas are girenfor propellers for the rate of change
of side—force coefficient with angle of yaw and for the rate of
change of pitching—moment coefficient with angle of yaw.
Charts of the side force dcriratire are giren for two propellers
of difierent plan form. The charts cocer solidifies of two to sic:
blades and single and dual rotation. The blade angles range
from 15° or 20" to 60°.

The equations and the charts computed from the equations
are based on an unpublished analysis that incorporates
factors not adequately corered in previously published work and
gives good agreement with experiment orer a wide range of
operating conditions. A study of the equations indicates that
they are consistent with the following physical interpretation:
In dereloping side force, the propeller acts like a fin of which
the area is the projected side area of the propeller, the effective
aspect ratio is of the order of 8, and the efectire dynamic pres-
sure is roughly that at the propeller disk as augmented by the
inflow. The variation of the inflow relocity, for a fixed-pitch
propeller, accounts for most of the variation of side force with
advance—diameter ratio.

The charts may be applied to obtain the rate of change of
normal-fora coefl'icient with angle of attack of the axis of rota-
tion if proper account is taken of the upwash or downwash from
the wing.

There has been a need in stability analyses for a systematic
series of charts for the estimation of the rate of change of
propeller side force with angle of yaw. Although the formula.
developed by Harris and Glauert in references 1 and 2 and
discussed in reference 3, which expresses the side force in
yaw in terms of coefiicients for the unyawed propeller, is
fairly satisfactory, there has been no adequate formula based
primarily on the geometry of the propeller blades. An
unpublished analysis has resulted in such a. formula.