• Version
• 100 Downloads
• 2.34 MB File Size
• 1 File Count
• January 31, 2017 Create Date
• January 31, 2017 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Wind Tunnel Investigation of External-Flow Jet-Augmented Double Slotted Flaps on a Rectangular Wing at an Angle of Attack of 0° to High Momentum Coefficients

A preliminary investigation of external-flow Jet-augmented double
slotted flaps on a rectangular wing with an aspect ratio of 6 has been
made in the Langley 300 MPH T— by 10-foot tunnel. High-momentum air was
blown from one and two nacelles over the double slotted flaps of 30 per-
cent wing chord incorporating vanes of either 58.5 percent or 20 percent
of the flap chord.

Lift coefficients larger than the Jet reaction in the lift direction
were attained with the external-flow Jet-augmented double slotted flaps.
Over the lift-coefficient range investigated, these flaps produced about
80 percent of the lift produced by the Jet-augmented plain flap investi-
gated in NACA Technical Note 5865. The lift coefficients for configura-
tions incorporating an inboard nacelle, a midspan nacelle, or twin nacelles
were about the same throughout the mementum~coefficient range tested.

With the center of moments at 25 percent wing mean aerodynamic chord,
large negative pitching moments were found to exist for the double-slotted-
flap configuratibns which were comparable with those produced by the Jet-
augmented plain flap previously investigated. The loss in lift needed to
trim these pitching moments for a tail located 2 wing chords behind the
wing was estimated to range from 7.5 percent to 27.5 percent of the total
wing lift.

Considerable emphasis is being placed on methods of increasing the
lift of airplane wings to reduce the landing and take-off distances and
velocities. One such method, which employs the jet flap, consists of
directing a thin, high-momentum, jet sheet of air downward from a continuous
slot in the wing trailing-edge region (ref. 1) and, thus, greatly augments
the lifting capabilities of a wing. Investigations (refs. 2 and 5) in
which the air Was ejected from a slot on the upper surface of the wing and
thence downward over a round trailing edge indicated even greater lift
augmentation.