3.0 
PROPELLER 4681 
v= 10 DEG 
NO SCREEN 
AM! Fy/Fy. Ma My 
F IF, My/My, Fy/Fy, 
POSITION ANGLE, 8 (deg) 
PROPELLER 4661 
v =0DEG 
WITH SCREEN 
J= 1.26 
FJ. My/My, Fy/Fy, My MM. F,/E,. MyM 
1of- 2 
pam | 
ty Say \ 
era N 
Pale ni 
3.0 
0 as 90 3 180 72 270 316 360 
POSITION ANGLE. 6 (deg) 
Fig. 4 — Experimental Variation of Loading Components with Blade Angular Position 
paper only the hydrodynamic component of 
blade loading is presented. Centrifugal 
and gravitational loads were measured 
soley to permit the hydrodynamic loads 
to be determined by subtracting the 
centrifugal and gravitational loads from 
the total experimental loads. 
Centrifugal and Gravitational Loads 
Centrifugal and gravitational loads 
were determined from air-spin experi- 
ments with each flexure over a range of 
rotational speed n for ¥ = 0, 10, 20, 
and 30 deg. The centrifugal load, which 
is a time-average load in a coordinate 
system rotating with the propeller, 
should vary as n2 and be independent 
of ~. The time-average experimental 
data followed these trends closely. The 
gravitational load, which is a first 
harmonic load in a coordinate system 
rotating with the propeller, should vary 
with and be independent of n. The 
first harmonic experimental data 
followed these trends closely. 
The centrifugal and gravitational 
loads measured during these experiments 
agreed with the values previously 
reported in References 3 and 4 and the 
gravitational loads agreed with values 
deduced from the weights of the blades 
and associated flexures. Therefore, 
these results will not be repeated here. 
Variation of Loads with Angular Position 
Figure 4 shows the variations of 
the loading components with blade 
angular position for Propeller 4661 for 
operation with 10 degrees shaft 
inclination with no screen and for 
operation behind the wake screen with no 
shaft inclination. These plots present 
typical results obtained in inclined 
flow and behind the wake screen. For 
other conditions evaluated in inclined 
flow and behind the wake screen the 
trends are basically the same as shown 
in Figure 4, but the magnitude of the 
unsteady loading varies with 
experimental conditions. 
The variations of the primary load 
components, Fy and M, with blade 
angular position in inclined flow and 
behind the wake screen follow patterns 
approximately similar to the tangential 
and the longitudinal velocity profiles 
of the respective wakes shown in Figure 
3. The variation of the loads behind 
the wake screen implies that the high 
velocity region covers a smaller portion 
of the propeller disk than the low 
velocity region, which agrees with the 
measured wake data. 
Effect of Plate Clearance 
Figure 5 shows that the periodic 
blade loads in inclined flow are fairly 
insensitive to the presence of a nearby 
flat boundary parallel to the flow for 
tip clearance to propeller diameter (tip 
clearance ratio) as small as 0.1. The 
ratios of the periodic to the time- 
average loading components at tip 
clearance ratio of 0.1 are no greater 
than 10 percent larger than the 
05 —— Sla h Eo  lh lea Lae aa] 
O (Fp)q/lF I PROPELLER 4402 
v = 10 DEG 
OD (My) ,/iMy) NO SCREEN 
© (Fy) /IFyI 
D (My), /iMy! 
o4- OQ 4 
0.3 4 
FIRST HARMONIC LOAD/TIME - AVERAGE LOAD 
0.0 0.2 0.4 06 08 1.0 1.2 14 16 
TIP CLEARANCE/PROPELLER DIAMETER, z,/D 
Fig. 5 — Effect of Plate Clearance on First Harmonic Loading 
in Tangential Wake 
