Modern Design Concepts Chapter 10 Second Half Last Lecture of the Semester

Modern Airfoil Design NASA looked at developing an airfoil for general aviation that combine the high lift of the early 4-digit airfoils and the low drag of the 6- digit airfoils. –The key was the achievement of true laminar flow over a significant portion of the airfoil strictly by the shape. No external blowing or artificial means of preserving the laminar boundary layer

Natural Laminar Flow Airfoils These new airfoils were called natural laminar flow airfoils The old NACA airfoils could only be altered one parameter at a time The new approach that NASA used was to first specify the desired characteristics that a particular airfoil required; then design it to meet those requirements. – This was called the inverse design.

NASA NASA worked with the Eppler method which began with a prescribed pressure disturbance over the airfoil, and applied various aerodynamic theories to analyze the flow and establish the boundary layer characteristics

Eppler Method The Eppler method had provisions to account for altitude at gross weight. This method allowed NASA to account for a variety of considerations

First Airfoil Intended for Light Single Engine Airplanes The first airfoil intended for light single engine airplanes was the NASA NFL (1) –The fist two numbers(04) signify a design lift coefficient of 0.4 and the 16 refers to a maximum thickness of 16% of the chord. –The 1 in parenthesis refers to the first generation of such airfoils

Newer Design Details Swept vertical Fins & T-tail arrangements Winglets, improved cowl shapes, carefully designed fillets *** All these aerodynamic refinements are quite beneficial

Potential Airliner Designs Engine Efficiency/Aerodynamic efficiency –higher aspect ratios Very Narrow Chord Wings –reducing skin friction drag, increasing favorable pressure gradient; increasing laminar flow at higher speeds Span Loading –distributing the payload over all of the span

Potential General Aviation Designs Composite structures –can be molded & bound for very smooth aerodynamic surfaces –boron or carbon fibers give high strength with little weight –composites smoother & stronger

Potential General Aviation Designs Development in Propulsion systems Rotary/Wankel engine –an internal combustion engine without pistons –the combustion process drives the rotor in continuous, smooth, rotating manner –can run on a variety of fuels –it does not produce a tremendous amount of power for its weight

Potential General Aviation Designs Development in Propulsion systems Turboprops –prime performance for business & commuter planes –single and multi engine –pictures on pages

Quiz on Chapter 10 Take out a sheet of paper Include today’s date and your name

Quiz on Chapter 10 How has the study of aerodynamics affected modern aircraft design? Support your answer with an example.