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Altitude Wind Tunnel Investigation of Performance of Several Propellers on YP-47M Airplane at High Blade Loading - II - Curtiss 838-1C2-18R1 Four Blade Propeller

An investigation of the performance of several propellers on the
YP—47M airplane at high blade loadings has been conducted in the
Cleveland altitude wind tunnel at the request of the Air Materiel
Command, Army Air Forces. As part of the program, a study was made
of a Curtiss 858-102-1831 four-blade propeller. The results and a
brief discussion of the characteristics of this propeller are pre-
sented.

The investigation.was made for a range of power coefficients
between 0 .50 and 1.00 at free—stream Mach numbers of 0. 40 and O. 50,
density altitudes from 20, 000 to 45, 000 feet, engine powers from
150 to 2500 brake horsepowar, and engine speeds from 1100 to 2900 rpm.
The propeller efficiencies, as in reference 1, were determined from
force measurements; blade thrust distribution was obtained from pres-
sure surveys in the propeller slipstream.

The activity factor is nondimensional function of the propeller
plan form designed to express the integrated capacity of the
propeller blade elements for absorbing power (reference 1).

The propeller blade—form characteristics are giVen in. figure 1.
The Curtiss 838-102-1831 propeller blade is shown in figure 2.

The assembled propeller as installed on the BEE—47M airplane in
the 20-foot diameter test section of the altitude wind tlmnel is
shown in figure 3. The test equipment is described in reference 1.

Force measurements and slipstream surveys were taken for power
coefficients from 0.50 to 1.00 at a. free-stream Mach nwnbe‘r of 0.40
and for power coefficients from 0.40 to 1.00 at a free-stream Mach
writer of 0.50. Density altitudes from 20,000 to 45,000 feet were
simulated for engine powers from 150 to 2500 brake horsepower, and
for engine speeds from 1100 to 2900 rpm.

The method of data reduction was identical to that described in
reference 3,. The. force measurements were analyzed in terms of the
variation of the propeller efficiency with the propeller power
coefficient.