Critical Design Review 24 March, 2005 Team One Purdue University AAE 451 Critical Design Review 24 March, 2005 Agenda: Design Concept Aerodynamics Structures Propulsion Dynamics and Controls Design Code John W Apostol Michael S Carpenter Christopher L Grupido Jeeyeon Hahn Daniel J Halla Douglas K Klutzke Christopher E LaMaster Joshua T Mook Todd M Mostrog Thomas B Shaw

DR&O Requirements Create a Stylish, Remotely Piloted Aircraft Operable Airspace Within football field 6-30 ft vertical Takeoff / Landing Less than 100 ft Flight Angles Climb Angle of 30o Descent Angle of -5.5o Velocities Loiter at less than 30 ft/s Stall at less than 20 ft/s Maximum greater than 40 ft/s Turn 30 ft Radius Endurance Greater than 8 minutes Feedback Controller

Design Concept

Original Concept Original Concept Areas of Concern Center of Gravity Location Low Aspect Ratio Wing Possible Tail Strike Aerobatic Capabilities Marketability/Expense How do we increase performance capabilities without compromising unique visual appeal?

Final Design Final Design Modifications Single-engine configuration Shortened tail boom Moved leading edge Design kept as close to original concept as possible Achieved higher performance, possibly aerobatic design that still maintains a unique shape and style. Two motors with pusher props. Stability Concerns. Performance Concerns. Marketability Concerns. Shorter tail boom length. Increases static margin. Reduces take-off problems. Modifying the planform. Performance aspects of aerobatic Extra 300 wing incorporated. Design kept as close to original concept as possible. Leading edge moved back.

Final Design Original Concept Final Design

Style Features Tapered wing planform Provides appealing look Unique polyhedral wing design Combines distinctive visual styling cues Winglets Provide finished look to polyhedral theme Hybrid fuselage/boom structure Creates distinctive profile Polyhedral tail design Maintains consistency of aircraft appearance

Constraints Wing Loading of 0.59 lbf/bhp Power Loading of 20 lbf/ft2 Design Point

Overview Aircraft Horizontal Tail Weight = 2.05 lbf Area = 0.68 ft2 Wing Area = 3.4 ft2 Span = 4.6 ft Root Chord = 0.97 ft Tip Chord = 0.52 ft Fuselage Length = 2.8 ft Max Diameter = 0.33 ft Horizontal Tail Area = 0.68 ft2 Span = 1.65 ft Root Chord = 0.47 ft Tip Chord = 0.36 ft Vertical Tail (per tail) Area = 0.13 ft2 Span = 0.52 ft Root Chord = 0.36 ft Tip Chord = 0.22 ft

Aerodynamics

Airfoil Selection Analyze airfoils from NASG database: Based on operating Reynolds Number

Geometry Selection Selig 2091 Simple shape Acceptable t/c ratio Best balance of aerodynamic characteristics NACA 0009 chosen for tail Suitable lift to trim aircraft Acceptable aerodynamic characteristics The Selig 2091 was the chosen section. It has a shape that will be easy to manufacture and the thickness ratio allows enough room for equipment to be stored within it near the fuselage. It had a good balance of aerodynamic characteristics with a low drag bucket and a higher Cl,max. The tail geometry was more concerned with trimming the aircraft. The NACA 0009 provides suitable characteristics for lift and drag. Its symmetric shape will be easy to manufacture and the small thickness will give a smaller weight increase for the rear part of the aircraft. * The stall characteristics will need to be checked for the tail as it is necessary for the tail to stall after the wing, so the pitch control surfaces can recover the aircraft to a stable flight configuration. The stall characteristics will be modified by changing the aspect ratio of the tail for suitable stall characteristics.

Market Study How to balance ‘style’ versus aerodynamic performance? Sampled 25 random people on style parameters Sweep Angle Aspect Ratio Dihedral Angle Taper Ratio Winglets Weighted Market Study versus Aerodynamics

Aspect Ratio Market Study Original Design AR = 6.2 44% votes Modified Design AR = 7.6 56% votes

Aspect Ratio Performance Advantages Increases CL Decreases CDi Disadvantages Earlier stall angle Increased wing weight Trade study Used box beam Corresponds to AR = 6-7 Chose Aspect Ratio = 6.2

Dihedral Marketability Original Design Θ = 4 degrees Modified Design Θ = 0 degrees 76% votes 24% votes

Dihedral Angle Polyhedral Wing Design Dihedral Angle measured using Effective V-Dihedral Method (EVD) Wing Taper also affects EVD Self corrects roll For Aerobatic aircraft typical EVD = 0°- 2° Market Study suggests EVD = 4° EVD = 3.0° A = -25° B = 25° C = 4.5° x1 = 0.18 (ratio of wing span) x2 = 0.32 (ratio of wing span) Chose EVD = 3°

Sweep Marketability 48% votes 52% votes Modified Design Λ = 0 degrees Original Design Λ = 3.0 degrees 48% votes 52% votes

Sweep Performance Λ Lift Reduction 3 0.3% 5 0.8% 10 3.0% 20 11.7% 40 41.3% Chose Λ = 3 degrees

Taper Ratio Market Study Original Design TR = 0.58 Modified Design TR = 0.8 96% votes 4% votes

Taper Ratio Performance Brings planform closer to an elliptical shape Desire λ = 0.4 - 0.5 Increases AR, decreases area Chose λ = 0.5

Winglets Market Study No Winglets Winglets

Winglets Market Study 1.5” 3” 6”

Chose Winglet Height = 3 inches Winglets Penalty? Winglet Height Drag Penalty 1.5" 2.4% 3" 4.5% 6" 8.2% Chose Winglet Height = 3 inches

Lift Lift slope equation: Maximum Wing Lift Coefficient: Coefficients for the lift slope equation where calculated using FlatEarth Predator code CLmax estimation was referenced from Raymer CLo for the aircraft was determined using FlatEarth *********************** maybe tabulate CLmax, CLo and CLa into a table for sectional, finite wing, and whole aircraft *********************************************

Parasite Drag K = form factor Q = interference factor   K Q Cf Swet Sref CDp Wing 1.21 1 0.0066 7.10 3.50 0.0162 Horizontal Tail 1.19 0.0074 1.70 0.0043 Vertical Tail 1.18 0.0077 0.60 0.0016 Fuselage 1.06 0.0050 1.57 0.0024 Winglets 0.0073 0.24 0.0012 Components - 0.0251 K = form factor Q = interference factor Cf =skin friction coefficient Swet = wetted area (ft2) Sref = wing plan form area (ft2) Internal Antenna Landing Gear Drag: 0.0021 Tom’s Slide: parasite drag build up calculation Summation of all components results in total parasite drag * parasite drag includes the following drag parameters: pressure (form) drag, friction drag and miscellaneous drag (these drags are present in sectional curve) * miscellaneous drag includes things such as control surface gaps, base area, or other items that were looked over in the other drag calculations Miscellaneous Drag: 10% CDo Schlicting Formula

Drag 3-D accounts for build up of all drag components: Pressure, friction, induced, and miscellaneous Drag Equation: This plot includes parasite drag that was covered in previous slide. For the aircraft, induced drag is also added as a parameter. The drag profile is a good estimate of the efficiency of the aircraft. Lower drag for higher values of lift will give a more efficient aircraft ******************************** it may be good to show the point where our aircraft will be operating for the majority of flight ********************************* i.e. Vloiter like lift, it may be nice to tabulate Cd, Cdo, and Cdi for sectional, wing, and whole aircraft

Structures

Load Factors Load Factor Analysis V-n Diagram for CLmax Turn-Radius Load Factor of 2.26 for Loiter Speed Turn-Radius 60o Bank Angle Load Factor of 2.0 Turn Radius is 11.21 ft Vertical Turn / Loop Considered for Loiter Speed Pull-Up : 19.97 ft Upside Down : 11.65 ft Pull-Down : 8.22 ft Conclusions Load Factor of 2.26 chosen Aerobatics Performed at Loiter Speed or Below Max Speed for Level Dash Only

Structural Analysis For Maximum Load Factor of 2.26 and Weight of 2.0 lbf Maximum Load = 4.5 lbf Lift Distribution on Wing is 83% Elliptical Centroid of Elliptical Parabolic Semi-segment: x = 3/8 base Assumed Resultant Loading at ½ Wing Section Span: x = 1.15 ft Maximum Bending Moment at Root Chord M = 31.85 in-lbf = 2.65 ft-lbf Load Modeling Assumptions Uses Bending Moment and Euler Buckling Criteria Number of Stringers of Wing and Fuselage Design Based on Max Load Case and a Safety Stress Factor Constant Size Spars Favorable Effect of Landing Gear Weight Ignored

General Construction Medium Grade Balsa Wing, Fuselage, & Horizontal Tail Traditional rib and stringer construction Balsa leading edge All stringers are 3/16 in2 Vertical Tails Solid Balsa Monokote Covering

Structural Properties Wing 0.25 lbf Weight 0.6 in Max Deflection 2 Spars 26 Ribs 2.2 in Separation 2 Stringers Horizontal tail 0.04 lbf Weight 12 ribs 2.34 in Separation 1 Spar 2 stringers Fuselage Weight = 0.05 lbf Max Moment = 152 in-lbf 0.04 degrees/inch of twist 2 Spars 12 Bulkheads 2.8 inches of Separation 6 Stringers

Fuselage Properties

Landing Gear Two 21/16 in diameter foam wheels Fixed to wing ribs Top half hidden in wing section Designed for no failure Forward landing gear in wing Simple structure attachment Reduce drag Aft landing gear on tail Rudder mounted for ground directional control Four points of contact Increases on ground stability 8o 10o

Propulsion

Constraints Effect of increased climb angle Decreases power loading 25.5 to 18.6 lbf/bhp 0.12 bhp needed to meet DRO Climb Angle = 20o Climb Angle = 30o

Mission Analysis Warm up/Taxi 45 seconds , 50% power 96 mA-h Take off roll/Climb 10 seconds, 100% power 49 mA-h Loiter 4 min turning, 100% power 1174 mA-h 4 minutes straight, 75% power 880 mA-h Descend and Land Unpowered Landing Warm up/ Taxi Take off Climb Loiter Descent TOTAL = 2200 mA-h

Motor Selection Graupner SPEED 600 7.2V 0.43 lbs (6.88 oz) 0.178 shaft horsepower 0.12 useful horsepower 69% motor efficiency 65% propeller efficiency at loiter 22 amps max 12 amps nominal loaded 7.2 volts 8600 Loaded RPM Small Propeller Size (No Gearbox)

Batteries and Controller Kokam Li-Poly 2 cell 1250 mAh 7.4 volts 2.92 oz 1.65” by 3.1” by .43” Castle Creations Sprite-25P 25 amp .5 oz .9” by .7” Flight Time = 15 minutes

Propeller Selection Physical Characteristics Small Propeller Short landing gear Graupner Scimitar Folding Prop 8” Diameter 6” Pitch .48 oz Multiple Propeller Testing 8” by 6” two blade 8” by 4.5” two blade 8” by 6” three blade Landing Concerns Prop Clearance if Pitched Forward Test Folding Propellers for Clearance Safety

Dynamics & Controls

Parts Location Number Part Motor Batteries Wheels Aileron Servos Speed Controller Gyro Receiver Tail Servos Tail Gear

Center of Gravity Center of Gravity: 0.25*Aircraft Length Motor Batteries Wing Aileron Servos Landing Gear Fuselage Elevator & Rudder Tail Increasing Weight This is an artist representation of the center of gravity of the aircraft. The farther the blue arrow points down, the greater the weight of that component. The CG was calculated by first identifying the location of each component and it’s corresponding CG. Then the sum of the x-distance times the weight divided by the sum of the weight results in a CG location as a percent of aircraft length. Center of Gravity: 0.25*Aircraft Length 0.30*Mean Chord

Class II Tail Sizing Longitudinal X-Plot Directional X-Plot Xcg Leg Determined from Weight of Design Xac Leg Determined by Methods in Roskam Part II, Chapter 11 Directional X-Plot Determined from Yawing Moment Due To Sideslip Derivative Cnβ For stable aircraft, Roskam’s book sets Cnβ to 0.001 per degree.

Tail Sizing Roskam method implemented in code Determined By Coefficient Ratio Equation Static Margin = 12.63% AC CG

Control Surface Sizing Determined Using Historical Data Verified adequate in FlatEarth Rudder Aileron Elevator

Incidence Angles Wing incidence defined by necessary level flight lift condition Tail incidence determined by trimming the aircraft to zero moment about the center of gravity Wing Incidence = 2.4° Tail Incidence = 5.0° Relative Tail Incidence to Local Flow = 2.1° Incidence angles were calculated to ensure the aircraft could attain the necessary lift and would be trimmed in a desirable orientation.

Aircraft Moments Moment about C.G. Equation: Cm = Cm0 + Cma*a + Cmde*de Determine elevator deflection for zero net moment Cruise Condition: CL = 0.56 de = 0o

Dynamic models Aircraft transfer function Rate gyro transfer function: 1 Actuator transfer function: 1 Control Law Laplace Transform:

Feedback Control Lateral-Directional feedback Poles = 0 0.30452 -79.325 Negative Gain Longitudinal Poles Stable at zero gain except for spiral mode which is slightly unstable--- alert pilot to Can have basically any negative damping, but don’t want anything too large because we don’t want a slow response. Can have a slightly positive gain, but not too much, or the aircraft will become unstable. Examine the effects of changing the gain xxxxxxx Spiral Mode Dutch-Roll Roll -3.525e-005 -0.16509 + 0.66192i -0.16509 - 0.66192i -9.7055 -78.001 Positive Gain

Design Code

Design Code User Excel Input File Design Cycle Constraints Weight Build-up Main Wing Size Static Margin Horizontal Tail Size Side Slip Derivative Vertical Tail Size Aero Performance Structures Take Off Zero AOA Lift Wing Incidence Zero AOA Moment Tail Incidence Output File FlatEarth