UCSD/General Atomics Design Project: Aeroelastic Wing Enhancement Jose Panza, Project Sponsor Jose Panza, Project Sponsor Dr. James D. Lang, Project Advisor Dr. James D. Lang, Project Advisor Jonquil Urdaz, Team Leader Jonquil Urdaz, Team Leader Sean Summers Sean Summers Steve Ringel Steve Ringel Jorge Mendoza Jorge Mendoza

Presentation Outline:  Goals, Schedule, & Actual Cost  Active Camber Change –Aircraft Characteristics –Aircraft Initial Performance –Methods of Altering Airfoil –Effects of Altering Airfoil –Final Performance –Propulsion  Control Reversal –Stability & Control –Materials & Structure  Cost Estimates  Conclusions  References & Acknowledgements

Goals:  Originally: Create flutter suppressant design  After research and advice from Professors-new goal  New Goals: Increase performance and roll efficiency with active camber change and control reversal

Schedule:  Flutter research (3 weeks)  Thunder and control reversal research (3 weeks)  Analysis and data collection (2 weeks)  Finalize analysis, conclusions, and presentation preparation (2 weeks)

Current Cost  Engineering hours and transportation costs  Total current cost $37,863.00

Active Camber Change: Original Airfoil Positively Deflected Airfoil Negatively Deflected Airfoil

Aircraft Characteristics:  TOGW = 10,500 lbs  T/W = 0.14  W/S =  Span = 84 feet  Sweep = 2.36 degrees

Aircraft Initial Performance:  Max Air Speed = 220 knots  Cruise Velocity = 144 knots  Loiter = 127 knots Cruise Out 4,000 nm Loiter 38 hours Cruise Back 25, 000 feet 52,000 feet 3,900 nm

Aircraft Initial Performance:

Methods of Altering Airfoil:  Less power required to actively change camber  Compact  Easy to Install  Alternative = Spar Twisting Thunder-Piezoelectric Actuator

Airfoils: Tip Original Airfoil Positively Deflected Airfoil Negatively Deflected Airfoil Max thickness: t/c = 0.15 Camber = Max thickness: t/c = 0.16 Camber = Max thickness: t/c = 0.14 Camber =

Airfoils: Root Original AirfoilPositively Deflected Airfoil Negatively Deflected Airfoil Max thickness: t/c = 0.17 Camber = Max thickness: t/c = 0.19 Camber = Max thickness: t/c = 0.15 Camber =

Effects of Altering Airfoil: Theoretical Lift Coefficient vs Angle of Attack

Effects of Altering Airfoils: CD0 vs Mach Number At 25,000 feetAt 52,000 feet

Effects of Altering Airfoil: K vs Mach Number At 25,000 feet At 52,000 feet

Effects of Altering Airfoil: Drag Polar 52,000feet - Loiter Speed Drag Polar 25,000feet- Cruise Speed

Effects of Altering Airfoils: CL vs L/D at CruiseCL vs L/D at Loiter

Effects of Altering Airfoils: Fuel Burned vs. Drag At 25,000 feet At 52,000 feet

Final Performance:  Increased Performance: –Loiter time = +1 hour –Cruise Back = +400 nm –Fuel = -200 lbs. to complete initial mission profile Cruise Out 4,000 nm Loiter 39 hours Cruise Back 4,300 nm 25,000 feet 52,000 feet

Propulsion: Turboprop Engine  Based on Assumptions from Raymer: Engine CharacteristicsUninstalled Actual Thrust32,000 Scaled Thrust1950 Actual Power6500 Scaled Power396 Scale Factor (SF) Actual Weight2600 Scaled Weight Actual Length Scaled Length Actual Diameter Scaled Diameter

Control Reversal Increasing Roll Effectiveness Utilizing Wing Twist due to Control Surface Reversal

Stability and Control  Control reversal  Roll effectiveness  Lateral control governed by control system  Control surface sizing  Aerodynamic center  Divergence speed  Flutter speed

Control Reversal  Actively control wing twist  Increase roll-rate performance  Damp out potential flutter excitations  Decrease deflection of wing  Specific applications of AAW in recent design studies have shown AAW technology to provide a 7 to 10% reduction in aircraft takeoff gross weight (TOGW) for subsonic cruise and Joint Strike Fighter type configurations, while a 20% reduction can be realized in TOGW for a supersonic cruise configuration.

Control Reversal: Negative Twist using Flaps and Ailerons Positive Twist using Ailerons and Slats

Control Benefits/Issues of AAW  If AAW works, then structural weight can be removed that was otherwise needed to make the wing stiff. Also, the wing could have a higher aspect ratio, which would normally make it too flexible. Higher aspect ratio should reduce drag, and combined with lower weight should improve payload-range performance. Boeing Sonic Cruiser officials have shown interest in the technique.  The lurking concern is flutter. This is a reason the preproduction F-18A design was chosen; its flight test showed that even though the wing was flexible, it did not have a flutter problem--hopefully removing this concern from the AAW. There is no active flutter suppression in the planned AAW control laws.

Roll Performance  Less lateral moment of inertia of wing due to lighter wing  Twisting wings will allow better flow control over wing surface thus generating more lift and reducing drag  Creates a more efficient wing during maneuvering  Decreases the parasitic drag caused by control surfaces with rigid wing  Uses traditional roll generation methods until dynamic pressures are high enough to twist wing with control reversal  Above switch occurs in control law (future work)

Block Diagram

Control Surface Sizing  Must generate enough torque to twist the wing as desired  Control surfaces will be used to damp out excitations that could lead to flutter  Leading edge and trailing edge devices used in main part of wing  Trailing edge surface only on wingtip

Aerodynamic Center  Aerodynamic center is reference point for pitching moment calculations  Flight conditions are always subsonic for Mariner  Aerodynamic center can be assumed to be located at quarter-chord of Mean Aerodynamic Chord.

Divergence Speed  Designed new wing to have the same divergence speed as current design.  Sea level  Safety factor = 1.25 Current divergence speed 426 feet per second New divergence speed 370 feet per second

Flutter Speed New design flutter speed at sea level: 370 ft/sec

Materials and Structures Material Selection Sources and estimates of limit loads Structural concept Wing shear and bending moment diagram approximations Ixx, Iyy, J

Material Selection  Similar materials as current design  95% of aircraft is composites  Composite properties  Utilize bend-twist coupling with layup  General dimensions of current design conserved

Finite Element Model

Aerodynamic Loads  Loads/Boundary Conditions  Flat plate Aero modeling

Structural properties  Wing approximated as cantilevered beam with constant cross- sectional area  Moments of inertia for airfoil cross section  Torsional Stiffness of Wing Ixx =.032 ft^4 Iyy =.637 ft^4 J =.669 ft^4 Current GJ = New 5,000,0003,698,400

Limit Loads  Maneuvering loads  Gust loads  Control deflection  Take-off and landing loads  Power plant loads  Load factors approximately 3 to 4

Shear & Bending Moment Diagrams  Lift load approximated as point load acting at aerodynamic center of wing.

Structural Geometry  Span  MAC  Spar locations  Set up (spars skin) no ribs or stringers Span 84 ft MAC 4.04 ft Main Spar 25% MAC Aft Spar 75% MAC LE Sweep 2.36 deg TE Sweep 2.00 deg Skin Thickness.25 in Spar Thickness.5 in

Material Cost  Cost of Thunder actuator per aircraft: $170, $170,861.48

DAPCA IV Model  Estimated Flyaway and RDT&E costs per aircraft for a 100 aircraft buy. RDT&E + Flyaway= $637, Price per aircraft = $6,375,058.50

System Configuration Improvements  Iterate to find optimal skin thickness  Determine optimal spar dimensions and locations  More improvements can be made after test results are considered and analyzed

Cost Improvement  Wait for the technology to mature  Make a special contract with supplier to purchase Thunder actuators at a lower cost  Lower drag will increase efficiency and lower operational costs

Conclusions:  Results: Not worth the extra cost for Mariner  Would be more profitable for a Hunter/Killer  Planes today do not operate at max efficiency – with increased technology this design will become the more profitable method to increase performance

Future Work Needed:  Active Camber Change: –Research into Angle of Attack vs. Laminar Flow  Control Reversal: –Finite Element Model and Analysis –Test article fabrication –Flight Testing –Active flutter suppression in the planned AAW control laws.

References & Acknowledgements:  Josh Adams  Dr. John Kosmatka  John Meisner  Raymer, Daniel P., “Aircraft Design: A Conceptual Approach”  Anderson, “Fundamentals of Aerodynamics”  NASA Paper  AIAA Paper  Beer, Ferdinand P., “Mechanics of Materials”