Dependence of Propeller Efficiency on Angle of Attack of Propeller Blade Page: 3 of 9
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is the efficienoy due to the slip.
For the stationary test the formula is simplified to
Vpr / lyF
In the above formulas
g is asooeleration due to gravity,
y is weight of I ou.m. of air in kg.,
S is thrust measured in kg.,
F is propeller disk in sq.m.,
VF is flight speed with reference to the air.
In order to be independent of the propeller slip, the total
effiolenoy is divided by the slip effiaiolenoy, and thus the me-
ohanical effioiency of the propeller is determined with relation
to angle of attack. (See B6rck, "Zeitschrift fur Sohiffbau,"
1919, Vol. XX, pp. 161 and 199.)
For the practical propellers unde= consideration, there
would have been no object in carrying the analysis of engine
ne experimental results rest on:
i. Eerinents b the writer at the "Flugzeugmeisterei"
(Technioal'Section of the Air Service);
2. Experiments performed by Dr. Schaffran with air pro-
peller models.in.the water at the institute for
hydrodynamios and ship building rider orders of
the inspector of the air forces.
3. Experiments with an "Eta" propeller on the propelled
testing stand at Fisohamend near Vienna, the re-
sults of which were played at my disposal by the
Eta propeller factory.
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Borck, Hermann. Dependence of Propeller Efficiency on Angle of Attack of Propeller Blade, report, December 1921; (digital.library.unt.edu/ark:/67531/metadc53653/m1/3/: accessed February 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.