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National Advisory Committee for Aeronautics, Research Memorandum - Altitude Wind Tunnel Investigation of Performance of Several Propellers on YP-47M Airplane at High Blade Loadings - V - Curtiss 836-14C2-18R1 Four-Blade Propeller

An altitude wind tunnel investigation has been made to deter-
mine the performance of a Curtiss 836—1402-1831 four-blade propel—
ler on a Y-41M airplane at high blade loadings and high engine
powers. The study was made for a range of power coefficients from
0.10 to 1.00 at free-stream thh numbers of 0.50, 0.40, and 0.50.
The results of the force measurements indicate primarily the trend
of propeller efficiency for changes in power coefficient or
advance-diameter ratio, inasmuch as no corrections for the effects
of tunnel-wall constriction on the installation were applied.
Slipstream surveys are presented to illustrate blade thrust load
distribution.for several operating conditions.

For the range of advance-diameter ratios investigated at a
free—stream mach number of O.50, highest efficiencies were obtained
at power coefficients from 0.10 to 0.30 and flow breakdown was
evident for power coefficients abote 0.40.

The maximum efficiencies et'a free—stream Mach number of O. 40
were obtained for power coefficients from 0.20 to' 0.40, between
advance-diameter ratios of 1.50 and 3.10. The envelope of the
efificiency curves decreased about 15 percent between advance-
diameter ratios of 0.2 20 and 5.80.

At a free-stream Mach number of 0.50, maximum efficiency in
the low range of advance—diameter ratios was obtained for a power
coefficient of 0. 50, and in the high range of advance—diameter ratios
at a power coefficient of 1.00. There was about a 4 percent decrease
in the enrelope of the efficiency curves between advance-diameter
ratios of 2.20 and 3.60.

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 requests: the Air Materiel
Command, Army Air Forces. As part of tlie program, a study was made
of a Curtiss 856—1402 propeller.

The investigation was made for a range of power coefficients
from 0.10 to 1.00 at free-stream Mach _numbers of O. _30, O. 40, and 0.50
for density altitudes from 10, 000 to 45, 000 feet, engine powers frm
150 to 2500 brake.horsepOWer, and for engine speeds from 1000 to
2900 rpm.