Investigation of effectiveness of large-chord slotted flaps in deflecting propeller slipstreams downward for vertical take-off and low-speed flight Page: 2 of 43
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TECH LIBRARY KAFB, NM
NATIONAL ADVISORY COMMITTEE FOR AERONA 0065945
TECHNICAL NOTE 3364
INVESTIGATION OF EFFECTIVENESS OF LARGE-CHORD SLOTTED
FLAPS IN DEFLECTING PROPELLER SLIPSTREAMS DOWNWARD
FOR VERTICAL TAKE-OFF AND LOW-SPEED FLIGHT
By Richard E. Kuhn and John W. Draper
An investigation of the effectiveness of a wing equipped with large-
chord slotted flaps in rotating the thrust vector of propellers through
the angles required for vertical take-off and for flight at very low speeds
has been conducted in the facilities of the Langley 300 MPH 7- by 10-foot
Under conditions of static thrust and with zero incidence between the
thrust axis and the wing chord plane, the slotted flaps were effective in
rotating the thrust vector upward about 6350 with a loss of ,slightly less
than 10 percent of the thrust. When an auxiliary vane was added above the
wing, the thrust vector was rotated upward 740 with a loss of only about
10 percent of the thrust. With this vane configuration, vertical take-off
could be achieved with an initial attitude of 160 and at airplane weights
up to 90 percent of the total propeller thrust. The addition of 100 inci-
dence between the thrust axis and the wing increased the upward rotation
of the thrust vector about 100. For the same turning angle, the diving
moments associated with the slotted-flap configurations were approximately
twice as large as the diving moments of the configurations with plain
flaps and two auxiliary vanes.
The practical utilization of the helicopter has indicated the useful-
ness of aircraft that are capable of operating from very small bases. The
advantages to be gained with an airplane that incorporates both the small-
field capabilities of the helicopter and the high-speed potential of con-
ventional airplanes are readily apparent. One possible means of achieving
these advantages would be to provide an engine-propeller combination that
is capable of providing static thrust in excess of the gross weight. The
lift for vertical take-off could then be obtained by deflecting the pro-
peller slipstreams downward by means of wing flaps or both flaps and vanes.
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Kuhn, Richard E. & Draper, John W. Investigation of effectiveness of large-chord slotted flaps in deflecting propeller slipstreams downward for vertical take-off and low-speed flight, report, January 1955; (digital.library.unt.edu/ark:/67531/metadc56039/m1/2/: accessed November 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.