Deflected slipstream
Deflected slipstream is an approach to creating an aircraft that can take off and land vertically (VTOL), or at least with a very short runway (STOL).
The basic principle is to deflect the slipstream from one or more propellers approximately 90 degrees, to create an upward thrust for vertical takeoff and a downward air cushion for landing.
[2] In 1956 Robert Kirby explored the effectiveness of wings with large-chord flaps in deflecting propeller slipstream downward through the large angles needed for vertical takeoff.
Other wind tunnel studies of deflected slipstream VTOL mechanics were conducted in 1955 and 1956 by Richard Kuhn and John Draper at the NACA Langley Research Center.
In Technical Note 3360,[4] Kuhn and Draper discussed their goal: An investigation of the effectiveness of monoplane wings and flaps in deflecting propeller slipstreams downward is being conducted at the Langley Aeronautical Laboratory.
This reference to a "diving moment", meaning pitching forward of the model as it approached the ground while hovering indicated one of the challenges facing the construction of full-scale prototypes that used the deflected slipstream principle.
Three different craft were built in the late 1950s and early 1960s that utilized deflected slipstream as the means of achieving vertical or short takeoffs.
Results of the testing of this craft were first published November 1959 in the NASA TN D-89 [5] of the Ames Research Center at Moffett Field, California.
They found that a diving moment materialized as the aircraft in hover mode approaches the ground from 16 feet (4.9 m) or less, even if the flaps are not fully employed.
NASA Technical Memorandum, TM SX-805,[7] authored by Marvin P. Fink describes the results of the testing of this deflected slipstream aircraft at the Langley wind tunnel.
A third attempt to utilize deflected slipstream to give an airplane VTOL capabilities was built by the Robertson Aircraft Corporation in 1956 and 1957.
Since only the Ryan VZ-3RY left the ground and its did not perform well in purely vertical operations, no true VTOL craft based on the deflected slipstream was developed during the period of NACA and NASA research in the 1950s and 1960s.
His son William D. Bertelsen, continues to experiment with the deflected slipstream method of vertical flight, and has built small models, kites, parasails and ultra lights as part of his research.
