Static and Dynamic Analysis of an unconventional plane - flying wing

Static and Dynamic Analysis of an Unconventional Plane: Flying Wings Sergio Esteban Department of Mechanical and Aerospace Engineering and Engineering Mechanics University of Missouri-Rolla AIAA Region V Student Conference April 27 & 28, 2000, Wichita, Kansas Outline Introduction Motivation Analysis Results Conclusions Future Work Video Questions Introduction –What is a flying wing? Tailless airplane where all the surfaces are effectively used for lift. –Why are they a hot prospect? Maximizing all lifting surfaces. Increase range and decrease the thrust requirements. Increase cargo weight. –Present interest: Reconnaissance. Civil transport. Motivation –Senior design Request to build and fly an unconventional reconnaissance plane. –Need for prediction of longitudinal and lateral characteristics for unconventional planes. Challenges –General literature approximates most stability derivatives with the tail contribution. –Need for decoupling the derivative coefficients into wing and vertical surfaces contributions. –Creation of automated code to analyze stability for unconventional planes. Analysis Approach Analysis Approach –Decoupling stability derivatives. Extensive literature research (Smetana & Roskam). Wing, fuselage and vertical surfaces contributions. –Determine stability requirements. –Analysis of stability: MATLAB automated code (+15000 lines of code). Pure flying wings – no winglets. Flying wings with winglets. –Determine winglets influence on lateral stability. –Optimize winglets size and location to achieve stability. Ala-Voladora MATLAB Code Receive input from user. Initialize program. Iterative process. Solve equations of motion. Extract data. Output results. Static Longitudinal Stability Criteria –Conditions for static longitudinal stability: CM0must be positive. CMmust be negative. –To satisfy the above criteria: Sweep. Symmetric airfoils. Geometric twist. Reflex airfoils. Influence of Winglet Geometry on Damping and Natural Frequency Given target Dutch Roll damping ratio and natural frequency, the following parameters can be used to determine winglet dimensions: –Winglet taper ratio. –Distance from the Xcg to the vertical tail aerodynamic center. –Winglet leading edge sweep. –Distance from the vertical tail aerodynamic center to the wing center line. Dutch Roll Damping Ratio vs. Normalized Surface Area of Winglets 510 15 20 25 30 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 Dutch Roll Damping ratio vs. % Sw for sweep 40 deg %Sw Damping ratio taper 0.2 taper 0.4 taper 0.6 taper 0.8 Dutch Roll Natural Frequency vs. Normalized Surface Area of Winglets 510 15 20 25 30 2 4 6 8 10 12 14 16 18 Dutch Roll Natural Frequency vs. %Sw for sweep 40 deg %Sw Natural frequency taper 0.2 taper 0.4 taper 0.6 taper 0.8 Lateral Results with Winglets Lateral Stability Results for Flying Wing with Winglets –Cl= -0.026 –Cn= 0.049 per degree. –Dutch Roll poles = -1.37 7.09i Damping ratio: D = 0.19 Natural frequency: nD = 7.22 rad/sec Dutch Roll Response With and Without Winglets 0 5 10 15 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 Dutch Roll Impulse Time Response Time (sec) Amplitude No Winglets Winglets for Dutch damping ratio=0.19 Winglets for Dutch damping ratio=0.25 Dutch Roll Response for Several Winglets 00.5 11.5 22.5 33.5 44.5 5 -0.1 -0.05 0 0.05 0.1 0.15 Dutch Roll Impulse Time Response Time (sec) Amplitude Winglets for Dutch damping ratio=0.15 Winglets for Dutch damping ratio=0.19 Winglets for Dutch damping ratio=0.25 Conclusions Conclusions –Dynamic and static longitudinal stability achieved without winglets, however to achieve lateral stability winglets were required. –Longitudinal stability can be achieved by: Proper location of center of gravity. Proper wing geometry –Lateral stability can be achieved by: Proper winglet sizing (lv, v, Sv& zv). –Dutch Roll lateral stability can be achieved without augmentation of flight controls. Final Conclusion The present stability analysis was implemented on an actual flying wing: Flew successfully on April 1999. Highly maneuverable. Numerous acrobatic maneuvers: –Barrel rolls. –Hammer heads. –Loops.