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National Advisory Committee for Aeronautics, Technical Notes - Wind Tunnel Investigation of Effect of Propeller Slipstreams on Aerodynamic Characteristics of a Wing Equipped with a 50% Chord Slotted Flap

An investigation of the aerodynamic characteristics of a wing
equipped with a 50-percent—chord sliding flap and a 50-percent—chord
slotted flap operating in the slipstreams of two large-diameter pro—
pellers has been conducted in the Langley 500 MPH 7- by lO—foot tunnel.

Large tunnel-wall effects for which there are no known correction
methods were encountered in the tests. However, because of the current
interest in and general scarcity of data applicable to aircraft designed
for vertical take—off and landing (VTOL) and for short take-off and
landing (STOL), the results (uncorrected) are presented herein with only
limited discussion. It was observed, however, that stalling would occur
in conditions approaching steady level flight at highapower conditions,
but that a leading-edge slat effectively delayed this stall.

An investigation of the aerodynamic characteristics of wing-
propeller combinations that may be applicable to aircraft designed
for vertical take-off and landing (VTOL) and short take—off and
landing (STOL) is being conducted in the Langley 300 MPH 7- by 10—
foot tunnel. The aerodynamic characteristiCS at low forward speed
of a wing-propeller combination without flaps (tilting-wing configura—
tion) at angles of attack up to 900 is reported in reference 1. Refer-
ences 2 and 5 report the characteristics of this same model equipped
with plain and slotted flaps, respectively.

In the present-investigation the aerodynamic characteristics of a
semispan-wing model equipped with a 50—percent—chord sliding flap, a
50-percent—chord slotted flap, a 50-percent-chord leading-edge slat,
and two large-diameter propellers have been investigated; The charac—
teristics of this model at zero forward speed are reported in reference h.

When a wing is located in the slipstream of a propeller, large
forces and moments can be produced even though the free—stream velocity
decreases to zero. For this condition, coefficients based on the free-
stream dynamic pressure approach infinity and become meaningless. 'It '
appears appropriatej—therefore, to base the coefficients on the dynamic
pressure in the slipstream. 'The coefficients based on this dynamic
pressure are indicated in the present paper by the use of a double prime.
The relations between the thrust and the dynamic pressure and velocity"
in the slipstream have been derived in reference 1. The positive sense
of forces, moments, and angles is indicated in figure 1. The pitching
moments are presented with reference to the center of gravity shown in
figure 2.