Wind-tunnel tests and analysis of two 10-foot-diameter six-blade dual-rotating tractor propeller differing in pitch distribution

An investigation was conducted at the Langley propeller=reae~ch tunnel to determine the efficiency at low tip speeds of two l&footdiameter six-blade dual=rotating propellers differing only in pitch distribution.IYopeller forces were determined from witi-tunnel tests were also calculated by an analytical method by use of two-dhensional airfoil section data.Wake surveys were made in order to compare the measured thrust loadings with the calculated thrust loadings.Comparison were made between the experhmntal and analytically derived efficiency, blade loading, thrust, and torque characteristics of the two propellers for a wide range of operating conditions.The -SiS included the detemnation of the enqg losses due to induced flow and to profile drag for several representative operating conditions.Satisfactory agreement was obtained letween test data and calculateci data.A dual-rotating propeller of low design pitch maintain.edhignefficiency at advance ratios greater than '2.5as contrasted with the serious losses resulting from operation of a dmiler single+rotating propeller in the same range.The induced efficiency of dual-rotating propellers near peak that high efficiency was relatim4_y independent of blade load distribution..-. -.-.