Technical memorandums Volume 43-279

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ...for test. The airplane propeller was driven by its own engine and delivered a slip stream parallel to the slip stream of the propeller under test-the wind being controlled to some extent by screens-at an average velocity of 4l.9 miles per hour as indicated by a Pitot tube. The results obtained from this method, although reasonably substantial, are not considered as having the accuracy of those of wind tunnel tests. The comparative results of thrusts and velocities of a fourblade, 4-fcot propeller from tests in a wind, similar to that just described with those of a wind tunnel are given in Fig. l3. Referring to Series 3, the practical test, nine different propellers were made and used on airplanes in flight: one, the D-4 on a Curtiss J.N., 0.X.5, 75 HP engine, Fig. 1; another, first on a Curtiss Standard K-6, l50 HP engine, and afterward on a Curtiss 0riole, l60 HP engine, Fig. 2; two others on Curtiss 0rioles, and one on an Air Mail 400 HP Liberty engine. In the first four cases /' Re eo. the/propeller proved the more efficient when compared with a wood propeller while with the Liberty engine, the pitch being purposely too low for full speed, the flight was made with engine throttled, the propeller turning at about l900. The D-l and D-2 were tested statically at McCook Field and proved a success. D-l had been flown several times on a l60 HP engine and also endured a 30-hour test successfully. The D-6 was flown a number cf times, twice with a passenger, attaining an air speed of between l06 to l08 m. p. h., the usual wood propel3=r accomplishing a speed of 96 m.p.h. It was again flown on an Oriole, in a race during the spring meet at the Curtiss Field and won easily against several competitors. It was then given to Amundsen fcr an 0riole taken on the Arctic ...