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Variable Camber Continuous Trailing Edge Flap Testing Demonstrates High-Lift Capability
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Variable Camber Continuous Trailing Edge Flap Testing Demonstrates High-Lift Capability

High-lift wind-tunnel testing of the Variable Camber Continuous Trailing Edge Flap (VCCTEF) on the flexible wing Generic Transport Model (GTM) configuration at the University of Washington Aeronautical Laboratory (UWAL) was conducted from July 16 – 25. The VCCTEF is an advanced adaptive aeroelastic wing-shaping control concept originally developed by the Intelligent Systems division at NASA Ames Research Center and further refined by the Boeing Company. The initial high-lift design encountered aerodynamic issues with premature flow separation at the wing outboard due to incorrect rigging of the Krueger leading edge device. By adjusting the rigging angle of the Krueger slat using shims, improved high-lift performance was attained. A maximum lift coefficient (CLmax) of 2.1 is achieved with the single element high-lift flap. This CLmax is close to the desired CLmax for the Boeing 757 landing configuration. This confirms that the high-lift design for the VCCTEF may be capable of providing sufficient high-lift performance.

In addition, a circular-arc cambered high-lift flap was also tested. The cambered high-lift flap achieves a 2% decrease in CLmax, but at the same time improves aerodynamic efficiency (L/D) by 7% over the single-element high-lift flap. Sensitivities due to the VCCTEF span-wise deflection shape, Reynolds number (Rn) effect, and Fowler gap were studied. 2% Variations in CLmax and L/D were noted among four different VCCTEF deflection shapes, with uniform span-wise deflection achieving the highest CLmax but also the lowest L/D. The Reynolds number effect was studied at various dynamic pressures (Q’s) up to 5.8 times the baseline Q. Test results show increasing CLmax and decreasing drag (CD) with an increasing Rn. Test results for Fowler gaps from 0.25” (baseline) to 0.5” show the largest CLmax is achieved at the 0.25” gap. In summary, the objective of the high-lift test was met and the test results demonstrate high-lift capability and L/D improvement of the VCCTEF.

BACKGROUND: Today’s aircraft employ lightweight flexible wing constructions. As wing flexibility increases, aircraft aerodynamics at off-design operating conditions become significantly degraded due to non-optimal span loading. Modern aircraft design addresses this problem through aerodynamic re-optimization using wing-twist control devices. The VCCTEF addresses this problem in two ways: 1) variable camber design that enables mission-adaptive wing performance, and 2) adaptive aeroelastic shape control via re-twisting flexible wings to achieve optimal span loading. The VCCTEF also must be capable of high-lift performance for it to be considered as a viable aerodynamic control device candidate. A variable camber flap improves L/D over a plain flap, but at an expense of a reduction in lift at the same angle of attack. The purpose of the high-lift wind tunnel test is to assess the high-lift capability of the VCCTEF as an important aircraft technology validation step to meet take-off and landing design requirements.

TEAM: CODE TI: Tung Dao, Greg Hornby, Abe Ishihara, Sonia Lebofsky, Nhan Nguyen, Sean Swei, Eric Ting, Ezra Tal, Joe Totah, and Khanh Trinh; CODE TNA: Michael Aftosmis, Dogus Akaydin, Jeff Housman, James Jensen, Upender Kaul, Cetin Kiris, Shayan Moini-Yekta, Marian Nemec, and David Rodriguez

BOEING / UWAL: Eric Dickey (BR&T Huntington Beach), John Dykman (BR&T Seal Beach), Brian Foist (BR&T Seal Beach), Eli Livne (UWAL), Marat Mor (UWAL), Lee Mayer (BR&T St. Louis), Charles Morris (BR&T St. Louis), Chester Nelson (BCA Seattle), Nathan Precup (UWAL), Jack Ross (UWAL), Hieu Truong (BR&T Huntington Beach), and Jim Urnes, Sr. (BR&T St. Louis)

COLLABORATORS: Boeing Research & Technology (BR&T), Boeing Commercial Airplanes (BCA), and the University of Washington Aeronautical Laboratory (UWAL)

NASA PROGRAM FUNDING: Fixed-Wing Project, Fundamental Aeronautics Program (FAP), Aeronautics Research Mission Directorate (ARMD)

Contact: Nhan Nguyen

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