(3)Application of favorable interference principles.
Another advanced aerodynamic technique, development at the NASA-Langley Laboratory, has been applied to wing contours in regions affected by the pressure fields generated by the large under-wing nacelles. Research results on the SCAT-15F model and others showed that favorable interference effects could be attained by altering wing contours in this vicinity of the nacelles.
This allows positive pressure fields generated by the nacelles to fall on forward-facing slopes of the wing.
Shown in Figure 30, this design refinement is referred to as “wing reflexing ” and its effects of favorable nacelle-wing interference have been realized both in drag reduction and improved longitudinal trim.
(Little looks like compression lift?)
(4)Adoption of leading edge flaps.
Lift/drag ratio improvements have also been accomplished in other portions of the high-speed flight spectrum by use of the leading-edge flap.
Tests at Cornell Laboratory and the NASA-Ames Laboratory have shown that deflection of the leading-edge flap results in drag reduction at Mach numbers as high as 1.4.
As shown in Fig 31, test data at model scale show a direct improvement of a full unit in lift/drag ratio at a Mach number of 0.92.
Although improvement due to leading-edge flap are reduced at higher transonic speeds, they are still significance.
