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Critical Design Review

Critical Design Review. Brian Barnett Rob Benner Alex Fleck Ryan Srogi John Keune. Preliminary Design. Initial Weight Estimation (Historical Data) Payload = approx 1.18 lb 3 Battery Cells Rate Gyro Weight = approx 5 lb. Preliminary Design. Equations of Constraint (Roskam)

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Critical Design Review

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  1. Critical Design Review Brian Barnett Rob Benner Alex Fleck Ryan Srogi John Keune A&AE 451 - Fall, 2001

  2. Preliminary Design • Initial Weight Estimation (Historical Data) • Payload = approx 1.18 lb • 3 Battery Cells • Rate Gyro • Weight = approx 5 lb. A&AE 451 - Fall, 2001

  3. Preliminary Design • Equations of Constraint (Roskam) • Loiter Velocity • Turn Radius • Climb Angle A&AE 451 - Fall, 2001

  4. Preliminary Design • Equations of Constraint (Roskam) • Ground Roll • Stall A&AE 451 - Fall, 2001

  5. Preliminary Design W/P = 23 lb/hp W/S = 0.55 lb/ft2 With AR=6, S = 9.1 ft2 b = 7.4 ft c = 1.2 ft • Constraint Diagram A&AE 451 - Fall, 2001

  6. Aerodynamics • Airfoil Selection • Best endurance when CL3/2/CD is maximized • Selig airfoils for low Re flight • 2-D Data readily available online (www.nasg.com) • Compared 13 Selig airfoils • Roskam method used to generate CL and CD values A&AE 451 - Fall, 2001

  7. Aerodynamics Selig S1210 Airfoil A&AE 451 - Fall, 2001

  8. Aerodynamics • Twist for elliptical loading • Elliptical Loading • 12º total twist • Very high da/dy near wing tips • Twist for elliptical loading very difficult to manufacture • Linear Twist • 3º twist is sufficient to ensure initial stall at root • Angle of incidence • CL3/2/CD peaks at 3º A&AE 451 - Fall, 2001

  9. Aerodynamics Aerodynamics • Vertical Tail Sizing (Roskam) A&AE 451 - Fall, 2001

  10. Aerodynamics Longitudinal Xplot SM = 15% Horizontal Tail Area = 1.7 ft2 Xcg = 0.37c Xac = 0.52c A&AE 451 - Fall, 2001

  11. Propulsion Preq= Ppout= Ppin* hp Ppin= Pgout Pgout= Pgin * hg Pgin = Pmout Pmout = Pmin * hm Pmin = Pbout Pbout = Pmin Pmout = Pgin Pgout = Ppin Ppout Battery Speed Controller Motor Gearbox Propeller hg hp hm PowerAnalysis A&AE 451 - Fall, 2001

  12. Propulsion Propeller Selection • Power required from aerodynamics • 8.6 ft*lbf/sec • Gold matlab code • 15 x 10 propeller was chosen hp = .766 n = RPM/60 = Hz D = propeller diameter A&AE 451 - Fall, 2001

  13. Propulsion Effect of Differing Prop Diameter with Pitch = 10” Power Required=8.6 RPM =1910 Eta =.766 Prop Eta D=18” Ground Clearance Constraint (15”) D=16” D=14” D=12” D=10” D=8” Power Out (ft*lbf/sec) A&AE 451 - Fall, 2001

  14. Propulsion Gearbox Selection • Ppin= Pgout = 11.23 ft*lbf/sec • Pgin = Pgout / .95 = 11.82 ft*lbf/sec • Gear ratio = 3:1 hg = .95 A&AE 451 - Fall, 2001

  15. Propulsion • Propeller Selection • Power required from aerodynamics • 8.6 ft*lbf/sec • Gold matlab code • 15 x 10 propeller was chosen n = RPM/60 = Hz D = propeller diameter J = V/(n*D) hp = Ct*J/Cp = .766 A&AE 451 - Fall, 2001

  16. Propulsion Motor Selection • Pgin = Pmout = 11.82 ft*lbf/sec • RPM = 1910 • Matlab script was run for 615 motors • Motor was chosen for highest efficiency using three battery cells • Efficiencies hm = .519 hg = .95 hp = .766 htot = .378 A&AE 451 - Fall, 2001

  17. Propulsion Motor Performance Motor Current (amperes) A&AE 451 - Fall, 2001

  18. Propulsion • Battery Selection • 3 x Panasonic NiMH batteries • 3000 mAh • 1.2 V/cell • 57.4 g/cell A&AE 451 - Fall, 2001

  19. Propulsion • Maxx Products Cobalt 400 14T • Kv = 2290 RPM/V • Io = 2.5 A • Imax = 20 A • Rm = .108 Ohm • $70.00 • Maxx Products Ball • Bearing Gearbox • Ratio 3:1 • $22.50 A&AE 451 - Fall, 2001

  20. Structures All Spars 3/8” 3/8” 1/8” Finite Element Methods Modeling Moment of Inertia: I = 2(Aflange x d2) + 1/12 (bweb x h3web) A&AE 451 - Fall, 2001

  21. Structures • Bending Load Carried in Spars • Huge percentage of bending moment transmitted to all spars • Max stress: smax = Mmaxy I Uniform Pressure Load: 2.5 lbs x 2.5 g’s = 6.25 lbs 6.25 lbs x 1.5 safety factor = Applied Load = 9.38 lbs Divided by ½ Wing Area: 9.38 lbs / 648 in2 = Distributed Pressure Load = .0145 psi A&AE 451 - Fall, 2001

  22. Structures Exaggerated Wing Deflection FEM Results: smax = 273.3 psi dmax = .34” Balsa Properties: syield = 1725 psi(WT team, Spring ’99) FEM Calculated Weight: .56 lbs for ½ wing A&AE 451 - Fall, 2001

  23. Structures • Buckling Load: • FEM calculates Eigenvalue of stability problem • This value is a load multiplier for buckling to occur Wing Spar Buckling Point Evalue = 5.443 Applied Load = .0145 psi Buckling Load = .0789 psi A&AE 451 - Fall, 2001

  24. Structures Fuselage Structure • Employing bulkheads/stringers for ease of manufacturing • Tail-boom to be captured through reinforced bulkheads • Terminates at wing bolt-down block • Pinned to prevent rotation • Removable at fuselage • junction A&AE 451 - Fall, 2001

  25. Structures Tail Structure • Built on a box design • Hole drilled into box to allow tight fit of tail-boom • Pinned design prevents rotation • Stabilizer assembly removable • from boom • Stabilizers manufactured from • sheet balsa with lightening holes A&AE 451 - Fall, 2001

  26. Structures Landing Gear Structure • Steerable nose-wheel mounted to internal firewall • Main gear mounted to internal/external • sandwich plate • Bolt holes run vertically • between stringers • Minimize damage if • shear-off occurs • Easily replaceable A&AE 451 - Fall, 2001

  27. Dynamics & Control Control Surface Sizing Class I sizing based on historical data A&AE 451 - Fall, 2001

  28. Dynamics & Control Dihedral and Static Margin • 2º dihedral recommended for high-wing model aircraft with ailerons and no sweep. • ‘The Basics of R/C Model Aircraft Design’ • 15% Static Margin • Mark Peters recommends 18% • Previous 451 designs have gone as low as 10% • Adjustable by moving internal components A&AE 451 - Fall, 2001

  29. Dynamics & Control Pilot Input Servo Transfer Function Aircraft Transfer Function e(s) q(s)  He(s) q(s)/e(s) + - Rate Gyro Transfer Function Feedback Gain K Hg(s) Loop Closure A&AE 451 - Fall, 2001

  30. Dynamics & Control Transfer Functions Aircraft Transfer Function (Short Period Approximation) Natural Frequency and Damping Ratio = 6.63 rad/s = 1.146 A&AE 451 - Fall, 2001

  31. Dynamics & Control Transfer Functions Futaba S-148 Servo Transfer Function (2nd Order Approximation) Airtronics SG-1 Gyro System Gain K (abs value) < 1.3 deg/(deg/sec) A&AE 451 - Fall, 2001

  32. Dynamics & Control Root Locus A&AE 451 - Fall, 2001

  33. Dynamics & Control Bode Plot A&AE 451 - Fall, 2001

  34. Dynamics & Control Nyquist Plot A&AE 451 - Fall, 2001

  35. Flight Testing • Schedule of Events A&AE 451 - Fall, 2001

  36. Flight Testing Component Testing • Test boom for structural strength with point load at end of boom • Test wing with uniform load distribution • Landing gear test for impact load carrying • Provides time to add strength if needed before flight • Engine test on stand, check operation • Control Surface test, check operation A&AE 451 - Fall, 2001

  37. Flight Testing • Ground Testing • Phase 1 (AR 106) • Ground Stability Check • Phase 2 (Black IM Fields) • Running takeoff, feedback off, turns, climbs, descents, approaches to landing • Rolling Takeoff • Phase 3 (Smooth Surface Strip) • Stabilizing feedback on, turns, climbs, descents, approaches to landing • Phase 4 (Smooth Surface Strip) • Destabilizing feedback, turns, climbs, descents, approaches to landing • Phase 5 (Smooth Surface Strip) • Confined space practice, endurance test • Phase 6 (Mollenkopf) • Stabilizing and destabilizing feedback, indoor endurance test A&AE 451 - Fall, 2001

  38. Cost & Economics • Approximate cost for boom $25 • This is available at Hobby Time • Approximate cost for landing gear $20 • This is available at Tower Hobbies Brings total cost to approximately $198 A&AE 451 - Fall, 2001

  39. Cost & Economics Man-hours devoted • Total hours spent: 985 hrs • Man hours per person per week: 17.9 hrs • Project 600 man hours for construction Includes time spent in classroom. A&AE 451 - Fall, 2001

  40. Cost & Economics • $75.00 per hour labor cost • Kit Price = $198.00 • Prototype Cost: $119,073 • 985 design hours + 600 construction hours • 1585 prototype development hours • Further Production Cost: $257.54 • Sell 2000 aircraft kits • Prototype costs/2000 kits + kit price A&AE 451 - Fall, 2001

  41. Questions? A&AE 451 - Fall, 2001

  42. Appendix • 3-View Drawing A&AE 451 - Fall, 2001

  43. Appendix • Roskam Method: A&AE 451 - Fall, 2001

  44. Appendix A&AE 451 - Fall, 2001

  45. Effect of Differing Prop Diameter with Pitch = 6” Power Required =8.6 RPM =2430 Eta =.757 Prop Eta Ground Clearance Constraint (15”) D=18” D=16” D=14” D=8” D=10” D=12” Power Out (ft*lbf/sec) A&AE 451 - Fall, 2001

  46. Power Required=8.6 RPM =2140 Eta =.765 Prop Eta D=18” Ground Clearance Constraint (15”) D=16” D=14” D=12” D=10” D = 8” Power Out (ft*lbf/sec) Effect of Differing Prop Diameter with Pitch = 8” A&AE 451 - Fall, 2001

  47. Effect of Differing Prop Diameter with Pitch = 12” Power Required=8.6 D=18” Ground Clearance Constraint (15”) Prop Eta D=16” D=14” D=12” RPM =1750 Eta =.760 D=10” D=8” Power Out (ft*lbf/sec) A&AE 451 - Fall, 2001

  48. Dimensional Derivatives A&AE 451 - Fall, 2001

  49. Stabilizing Root Locus A&AE 451 - Fall, 2001

  50. Stabilizing Bode Plot A&AE 451 - Fall, 2001

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