Aircraft Design Work Outline
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• See A/P Design Part I

1. Determination of takeoff, empty, and fuel weights using fuel fractions
2. Determination of takeoff weight sensitivities to:

1. range
2. endurance
3. lift to drag ratio (L/D)
4. specific fuel consumption (sfc)
5. empty weight
6. payload weight

• See A/P Design Part I and Airplane Aerodynamics and Performance (Roskam and Lan)

1. Use the following constraints as applicable to select wing loading (W/S) and thrust to weight ratio (T/W) or power loading (W/P)

1. stall speed
2. takeoff and landing ground roll
3. carrier compatibility
4. climb with all engines operating (AEO) and one engine out (OEI)
5. cruise speed
6. maximum speed

• See A/P Design Part II

1. Overall configurations possible - conventional, flying wing, canard/tandem wing, three surface, joined wing
2. Fuselage configurations - conventional, twin fuselage, twin boom with center fuselage, Burnelli
3. Consider propulsion type/installation

• See A/P Design Part III

1. Develop overall fuselage layout in conjunction with configuration selection
2. Layout cargo hold and cabin layout
3. Cockpit layout

1. verify compliance with visibility requirements

4. Preliminary structural layout

• See A/P Design Part II

1. Wing

1. clean wing (pp. 141-166)

• decide on overall structural configuration - high/low/mid, strut braced or cantilever
• determine span based on geometric constraints
• select sweep, thickness ratio (t/c)
• airfoil selection / design
• select taper ratio
• layout lateral control devices (ailerons, spoilers ?)
• locate spars in conjunction with structures and control surfaces/high lift
• estimate wing fuel volume
• select/compute wing dihedral, incidence, and twist
• determine maximum clean lift coefficient for wing

2. high lift (pp. 167- 186)

• obtain values of maximum takeoff and landing lift coefficients from performance constraint analysis
• determine incremental values of lift coefficient high lift devices have to provide
• locate high lift devices on leading/trailing edge to achieve the incremental lift coefficients needed
• make sure high lift devices and control surfaces on trailing edge do not conflict

2. Empennage (pp. 187 - 216)

1. decide on empennage configuration in conjunction with overall configuration selection
2. estimate empennage moment arms from c.g. in conjunction with weight & balance
3. use volume coefficient method to do preliminary sizing of empennage
4. determine planform geometry in manner similar to that for the wing - sweep, taper, thickness, etc.
5. layout control surfaces
6. design very likely to be iterated during stability & control analysis

• See A/P Design Part II (pp. 123 - 140)

1. determine type of powerplant (turbofan, turboprop)
2. obtain values of maximum installed power/thrust from performance constraints
3. decide on number of engines and find engines which meet power/thrust requirements
4. select engine(s) and get geometry, weight, and performance data
5. for props/rotors: determine prop/rotor diameter and number of blades
6. decide on propulsion installation in conjunction with overall configuration selection
7. check Foreign Object Damage (FOD) and clearance requirements in conjunction with landing gear layout

• See A/P Design Part V

1. Class I weight and balance (pp. 237 - 258 of Part II)

1. Determine component weights (pp. 3-16 and Appendix of Part V, AAA)
2. Balance & c.g. excursion

2. Class II weight estimation

1. Make Speed-Load Factor (V-n) Diagram to determine airplane loads (pp. 31-45 of Part V)
2. Class II weight predictions
3. Balance & c.g. excursion
4. Moments/Products of inertia

• See A/P Design Part IV and Aircraft Landing Gear Design (Currey)

1. decide on type (fixed or retractable)
2. select configuration (tricycle, tail dragger, tandem, etc.)
3. use preliminary weight & balance to estimate required gear disposition
4. calculate maximum static load per strut
5. decide on number and type of wheels to use
6. make sure gear can be retracted into assigned volume (note that tires expand with use)
7. layout retraction kinematics
8. verify compliance with tipover & clearance requirements, weight percentage on nose gear

• See A/P Design Part VI and AA241 course notes

1. Parasite Drag

1. Wing
2. Empennage (h. and v. tail)
3. Fuselage
4. Nacelle/Pylon
5. Trim
6. Flap
7. Landing Gear

2. Induced Drag
3. Compressibility
4. Drag polar

• See A/P Design Part IV

1. Flight control system

1. Reversible or irreversible ?
2. layout of primary controls (elevator, aileron, rudder, spoilers)
3. secondary controls (engine, high lift, ??)

2. Fuel systems

1. Verify that all fuel can be contained in the tank(s)
2. Layout of fuel lines, pumps, etc.
3. Verify compliance with guidelines in A/P Design Part IV

3. Hydraulic systems

1. Size hydraulic system - # of independent systems needed, capacity, etc.
2. Layout of hydraulic line(s) to various systems (engines, brakes, flaps, etc.)

4. Electrical and avionics systems

1. Need for Auxiliary Power Unit (APU) or Ram Air Turbine (RAT) ??
2. Size generators based on electrical needs
3. Layout of major electrical distribution lines

5. Water and waste systems

1. Storage tanks for fresh and waste water, etc.

6. Anti/De-Icing System
7. Conflict Analysis

• See A/P Design Part VI, VII and Airplane Flight Dynamics and Automatic Flight Controls (Roskam)

1. Determination of aerodynamic center
2. Trim diagrams (will need c.g. excursion from W & B)
3. Takeoff rotation analysis
4. Longitudinal stability derivatives
5. Longitudinal control derivatives
6. Lateral-Directional stability derivatives
7. Lateral-Directional control derivatives
8. OEI control
9. Flying/Handling qualities check against FAR/MIL regulations

• See A/P Design Part VI and Airplane Aerodynamics and Performance (Roskam and Lan)

1. Installed thrust and fuel consumption
2. Specific range and verification of range requirements
3. Payload-range
4. Takeoff and landing distances - verification of design requirements
5. Climb & driftdown performance

• See A/P Design Part VIII

1. Research, Development, Test, and Evaluation (RDTE) cost (pp. 21-44 of Part VIII)
2. Manufacturing and acquisition cost (pp. 45-66)
3. Operating costs

1. Commercial airplanes (pp. 67-144)
2. Military airplanes (pp. 145-176)

4. Life Cycle Cost (LCC)

• Develop Subsystem Codes

• Rewrite Subsystem Codes as functions

• Write Optimization Code--calls all functions in one iteration

• Choose Optimization Algorithm

• Run Optimization

• Return Optimal Design Point to Subsystems