Aircraft Design: A Systems Engineering Approach, M. Sadraey, Wiley, 2012 Chapter 3 Aircraft Conceptual Design Tables No Component Primary function Major areas of influence 1 Fuselage Payload accommodations Aircraft performance, longitudinal stability, lateral stability, cost 2 Wing Generation of lift Aircraft performance, lateral stability 3 Horizontal tail Longitudinal stability Longitudinal trim and control 4 Vertical tail Directional stability Directional trim and control, stealth, 5 Engine Generation of thrust Aircraft performance, stealth, cost, control 6 Landing gear Facilitate take-off Aircraft performance, stealth, cost 7 Control surfaces and landing Control Maneuverability, cost Table 3.1. Aircraft major components and their functions 1
No Component Configuration alternatives 1 Fuselage - Geometry: lofting, cross section - Seating arrangement - What to accommodate (e.g. fuel, engine, and landing gear)? 2 Wing - Type: Swept, tapered, dihedral; - Installation: fixed, moving, adjustable - Location: Low-wing, mid-wing, high wing, parasol 3 Horizontal tail - Type: conventional, T-tail, H-tail, V-tail, inverted V - Location: aft tail, canard, three surfaces 4 Vertical tail Single, twin, three VT, V-tail 5 Engine - Type: turbofan, turbojet, turboprop, piston-prop, rocket - Location: (e.g. under fuselage, under wing, beside fuselage) - Number of engines 6 Landing gear - Type: fixed, retractable, partially retractable - Location: (e.g. nose, tail, multi) 7 Control surfaces Separate vs. all moving tail, reversible vs. irreversible, conventional vs. non-conventional (e.g. elevon, ruddervator) Table 3.2. Aircraft major components with design alternatives 2
No Configuration Configuration alternatives parameter 1 Conventionality 1. Conventional, 2. Non-conventional 2 Power 1. Powered, 2. Unpowered 3 Propulsion 1. Turbojet, 2. Turbofan, 3. Turboprop, 4. Piston prop, 5. Rocket 4 Number of Engine 1. Single engine, 2. Twin engine, 3. Tri-engine, 4. Four-engine, 5. Multi-engine 5 Engine and aircraft cg 1. Pusher, 2. Tractor 6 Engine installation 1. Fixed, 2. Tilt-rotor 7 Engine location 1. Under wing, 2. Inside wing, 3. Above wing, 4. Above fuselage, 5. Beside fuselage, 6. Inside fuselage, 8 Number of wings 1. One-wing, 2. Biplane, 3. Tri-plane 9 Wing type 1. Fixed-wing, 2. Rotary-wing (a. helicopter, b. gyrocopter) 10 Wing geometry 1. Rectangular, 2.Tapered, 3. Swept, 4. Delta 11 Wing sweep 1. Fixed sweep angle, 2. Variable sweep 12 Wing setting angle 1. Fixed setting angle, 2. Variable setting angle 13 Wing placement 1. High wing, 2. Low wing, 3. Mid-wing, 4. Parasol wing 14 Wing installation 1. Cantilever, 2. Strut-braced 15 Tail or canard 1. Tail, 2. Canard, 3. Three-surfaces 16 Tail type 1. Conventional, 2. T shape, 3. H shape, 4. V shape, 5. + shape, 17 Vertical tail 1. No vertical tail (VT), 2. One VT at fuselage end, 3. Two VT at the fuselage end, 4. Two VT at the wing tips 18 Landing gear 1. Fixed and faired, 2. Fixed and un-faired 3. Retractable, 3. Partially retractable 19 Landing gear type 1. Nose gear, 2. Tail gear, 3. Quadricycle, 4. Multi-bogey, 20 Fuselage 1. Single short fuselage, 2. Single long fuselage, 3. Double long fuselage, 21a Seating (in two-seat) 1. Side-by-side, 2. Tandem 21b Seating (in higher number 1. 1 n, 2. 2 n, 3. 3 n,, 10 n. (n: number of rows) of passengers) 22 Luggage pallet Based on types of luggage and payload, it has multiple options 23 Cabin or Cockpit 1. Cabin, 2. Cockpit 24 Horizontal tail Control 1. Tail and elevator, 2. All moving horizontal tail surfaces 25 Vertical tail Control 1. Vertical tail and rudder, 2. All moving vertical tail surfaces 26 Wing control surfaces 1. Aileron and flap, 2. Flaperon 27 Wing-tail control surfaces 1 Conventional (elevator, aileron, rudder), 2. Ruddervator, 3. Elevon, 4. Split rudder, 5. Thrust-vectored 28 Power system 1. Mechanical, 2. Hydraulic, 3. Pneumatic, 4. FBW 1, 5. FBO 2 29 Material for structure 1. Full metal, 2. Full composite, 3. Primary structure: metal, secondary structure: composite 30 Secondary control 1. Trailing edge Flap, 2. Leading edge slot, 3. Leading edge slat surfaces Table 3.3. Configuration parameters and their options (set by designer) 1 Fly-By-Wire (Electric signal) 2 Fly-By-Optic (light signal) 3
No Group Design requirements and constraints 1 Standard, nonstandard 1. Standard, 2. Homebuilt (or garage-built) 2 General type 1. Military (MIL-STD), 2. Civil - Transport (FAR 3 25), 3. Civil - General Aviation or GA (FAR 23), 4. Very Light Aircraft (VLA), 3 Maneuverability 1. Normal or non-aerobatic, 2. Utility or semi-aerobatic, 3. Aerobatic or acrobatic, 4. Highly maneuverable (e.g. Fighters and anti-missile missiles) 4 GA mission 1. General purpose, 2. Hang glider, 3. Sailplane or glider, 4. Agricultural, 5. Utility, 6. Commuter, 7. Business, 8. Racer, 9. Sport, 10. Touring, 11. Trainer, 12. Maneuver, 13. Model 5 Military mission 1. Fighter, 2. Bomber, 3. Attack, 4. Interceptor, 5. Reconnaissance, 6. Military transport, 7. Patrol, 8. Maritime surveillance, 9. Military trainer, 10. Stealth, 11. Tanker, 12. Close support, 13. Trainer, 14. Anti-submarine, 15. Early warning, 16. Airborne command, 17. Communication relay, 18. Target, 19. Missile, 20. Rocket 6 Density 1. Lighter-than-air craft (a. balloon, b. airship), 2. Heavier-than-air craft 7 Pilot control 1. Manned aircraft, 2. Unmanned aircraft, 3. Remote Control (RC) 8 Weight 1. Model (less than 30 lb), 2. Ultra light aircraft (less than 300 kg), 3. Very light (less than 750 kg), 4. Light (less than 12,500 lb), 5. Medium weight (less than 100,000 lb), 6. Heavy or Jumbo (above 100,000 lb) 9 Producibility 1. Kit form, 2. Semi-kit form, 3. Modular (conventional) 10 Take-off run 1. Short Take Off and landing (STOL) (runway less than 150 m), 2. Vertical Take Off and landing (VTOL), 3. Regular 11 Landing field 1. Land-based, 2. Sea-based, 3. Ship-based, 4. Amphibian, 5. Shoulder based 12 Stage 1. Model, 2. Prototype, 3. Operational 13 Term of use 1. Long term (Regular), 2. Experimental (X aircraft) or Research 14 Payload 1. Number of passengers, 2. Payload weight, 3. Store, 15 Aircraft 1. Air condition, 2. Weather radar, 3. Parachute, subsystems 16 FAR, and MIL 1. Number of crew, 2. Ejection seat, 3. Reserve fuel, requirements 17 Performance 1. Max speed, 2. Range, 3. Ceiling, 4. Rate of Climb, 5. TO run, 6. Endurance, 18 Maneuverability 1. Turn radius, 2. Turn rate, 3. Load factor Table 3.4. Design constraints and requirements (set by customer) 3 Federal Aviation Regulations 4
No Design requirements Aircraft component that affected most, or major design parameter 1a Payload (weight) requirements Maximum take-off weight 1b Payload (volume) requirements Fuselage 2 Performance Requirements (Range and Maximum take-off weight Endurance) 3 Performance requirements (maximum Engine; Landing gear; and Wing speed, Rate of climb, take-off run, stall speed, ceiling, and turn performance) 4 Stability requirements Horizontal tail and vertical tail 5 Controllability requirements Control surfaces (elevator, aileron, rudder) 6 Flying quality requirements Center of gravity 7 Airworthiness requirements Minimum requirements 8 Cost requirements Materials; Engine; weight, 9 Timing requirements Configuration optimality Table 3.5. Relationship between aircraft major components and design requirements 5
No Figure of Merit Military designer Large Civil Transport designer Small GA designer Homebuilt designer 1 Cost 4 2 1 1 2 Performance 1 3 2 3 3 Flying qualities 2 1 3 7 4 Period of design 5 9 8 6 5 Beauty (or scariness) 10 7 4 5 6 Maintainability 7 5 6 9 7 Producibility (Ease of 6 6 7 4 Construction) 8 Aircraft weight 8 4 5 2 9 Disposability 9 7 9 8 10 Stealth 3 0 0 0 Table 3.6. Design objectives and an example of the priorities for various aircraft designer 6
No Figure of Merit Priority Designer # 1 (%) Designer # 2 (%) Designer # 3 (%) 1 Cost 4 8 9 9 2 Performance 1 50 40 30 3 Flying qualities 2 10 15 20 4 Period of design 5 7 7 8 5 Scariness 10 1 1 2 6 Maintainability 7 4 5 5 7 Producibility 6 6 6 7 8 Weight 8 3 4 4 9 Disposability 9 2 2 3 10 Stealth 3 9 11 12 Total 100 100 100 Table 3.7. Three scenarios of weights (in percent) for a military aircraft designer 7
No Criteria Objective 1 Cost Minimum direct operating cost Minimum total manufacturing cost Minimum system cost over X years (life-cycle cost) Maximum profit Maximum return on investment Maximum payload per $ 2 Performance Maximizing cruise speed Maximizing range Maximizing endurance Maximizing absolute ceiling Minimizing take-off run Maximizing rate of climb Maximizing maneuverability 3 Weight Minimum take-off weight Minimum empty weight Maximum fuel weight 4 Flying qualities (stability and control) Most controllable Most stable Highest flying qualities Most luxurious for passengers 5 Size Smallest wing span Smallest fuselage length Smallest aircraft height Most specious fuselage 6 Beauty or scariness Most attractive (civil) or most scariest (fighter) 7 Systems engineering criteria 8 Design and operation duration Most maintainable Most Producible Most disposable (environmental compatibility) Most flight testable Most stealth Most flexible (growth potential) Most reliable Minimum duration of design Minimum duration of manufacture Maximum aircraft operating life Table 3.8. Optimization criteria at group level 8
Design parameter Cost Performan ce Flying qualities Period of design Short (10) Long (1) Criterion Beauty Maintain ability Producibil ity Weight Disposa bility Fixed Cheap (1) Worst (1) Best (10) Worst (1) Best (10) Best (10) Light (10) Better (8) Retractable Expens Best Worst Best Worst Worst Heavy Worse ive (10) (1) (10) (1) (1) (1) (3) (10) Partially Middle Middle Middle Middle Middle Middle Middle Middle Middle retractable (5) (5) (5) (5) (5) (5) (5) (5) (5) Table 3.9. The relationship between landing gear design options and the design criteria 9
No Criteria Must be Priority (%) Configuration A B C 1 Cost minimized 9 115 183 210 2 Weight minimized 4 136 163 94 3 Period of design minimized 7 190 176 217 DI min 20 20.1 35.3 37.8 4 Performance maximized 40 210 195 234 5 Flying qualities maximized 15 183 87 137 6 Scariness maximized 1 87 124 95 7 Maintainability maximized 5 95 83 68 8 Producability maximized 6 215 184 164 9 Disposability maximized 2 246 254 236 10 Stealth maximized 11 65 36 42 DI max 80 142 116.5 137.7 Table 3.10. Evaluation of three presumptive configuration alternatives for a fighter 10
No Attribute Boeing 747 McDonnell Douglas F-15C Eagle Stampe- Vertongen Rutan 33 VariEze 1 Standard FAR 25 MIL-STD Homebuilt Nonconventional 2 Runway Land Land Land Land 3 Materials Mostly metal Metal Metal Composite materials 4 Manufacture Modular Modular Modular Kit-form 5 Engine type Turbofan Turbofan Piston-prop Piston-prop 6 Seating (in a row) 10 seat single seat Two tandem seats 7 Landing gear type Multi-gear Tricycle Tail-gear Tricycle 8 Fixed or retractable Retractable Retractable Fixed Partially retractable 9 Pusher or tractor Pusher Pusher Tractor Pusher 10 Engine location Under wing Inside fuselage Fuselage nose Rear fuselage 11 Number of engines 4 2 1 1 Two tandem seats 12 Flap Triple slotted Plain flap Plain flap Plain flap flap 13 Door 10 cabin door Cockpit No door Cockpit 14 Tail or canard Aft tail aft Aft tail Canard 15 Number of wings Monoplane Monoplane Biplane Monoplane 16 Wing location Low wing High wing Low + parasol Mid-wing 17 Wing attachment Cantilever Cantilever Strut-braced Cantilever 18 Tail configuration Conventional Conventional Conventional Canard + twin VT 19 Wing fixed or Fixed-wing Fixed-wing Fixed-wing Fixed-wing 20 Wing configuration Swept back Swept back Elliptic Swept back 21 Tail attachment Adjustable All moving Fixed Fixed 22 Control surfaces Elevatoraileron-rudder Elevatoraileron-rudder Elevator-aileronrudder Elevator-aileronrudder 23 Power transmission Hydraulics Hydraulics Mechanical Mechanical 24 Fuel tank Inside wing Inside wing Inside fuselage Inside fuselage and fuselage and fuselage 25 Vertical tail A VT Twin VT A VT Twin VT on wingtip 26 Spoiler/tab Spoiler and 3 tabs No tab No tab No tab Table 3.11. The configuration features for four aircraft of Example 3.2 --------------------------------------------------- 11
Figure of Merit Weight (%) Monoplane Biplane X-wing Blended wing Weight 20 1-1 -1 1 Strength 20 0 1 1 1 Span 10 0 0 0 0 Take-off Capability 10 0 1 1 1 Stability & Control 10-1 1 1-1 Interference 10 1 1-1 1 Manufacturability 10 1 1 1-1 Reparability 5 1 1 1-1 Familiarity 5 1 0 0-1 Total 100 0.4 0.45 0.25 0.3 Table 3.12. Wing Figures of Merit 12