Ae SK P O BOX 758 00517 NAIROBI

Ae. SK, P. O. BOX 758 -00517, NAIROBI, KENYA Ae. SK LECTURE on AIRCRAFT DESIGN by Dr. Faustin Ondore Chartered Engineer, MAe. SK, MRAe. S, MIMech. E, 17 May 2013 Kenya Aeronautical College Nairobi

AIRCRAFT TYPES 6/13/2021 © FA Ondore 2

AIRCRAFT DESIGN I Introduction – Objective, Definitions, Stake-holder map. II Systems Engineering V-Diagram Model – concept, requirements capture, architecture, design, implementation, to service acceptance III Aircraft Design Procedures- Safety V-diagram, constraints, processes, certification specifications (airworthiness code & acceptable means of compliance) IV Problems (Airbus 380, Boeing 787, etc) V Conclusion VI Discussion - Question and Answer Session 6/13/2021 © FA Ondore 3

AIRCRAFT DESIGN purpose of lecture I Introduction – • Generate the understand the key features of design and their impact on performance; • Gain an insight into links between design and other life cycle characteristics (e. g. in-service reliability); • Acquire more complete multi-dimensional knowledge about aircraft; • Appreciate the need to link all life cycle activities (e. g. maintenance and operations) ; • Hopefully, support the production of Kenyan Aircraft Designers (& Manufacturers) 6/13/2021 4

I Introduction - definition Design is the process of creating a plan or convention for the construction of an object or a system • Presentation examples – calculations, experimental reports, engineering drawings, architectural blueprints, project process, graphics etc. ) • A Rational Design model was developed: - designers attempt to optimize a design candidate for known constraints and objectives; - the design process is plan-driven; - the design process is understood in terms of a discrete sequence of stages. 6/13/2021 5

I Introduction -Stake-holder map Air travelers- tourists; business people; farmers; enthusiasts; sports; recreation Aviation business – airlines; MROs; lessors; 6/13/2021 Producers Design and Production Organisations AIRCRAFT People safety & environment Regulators – ICAO; national airworthiness authorities; Governments – defense & security; police; wildlife protection; Banks & other financial institutions; 6

II System Engineering V-Diagram model (ISO/IEC 15288: 2008) for Product Life Cycle Analysis 6/13/2021 7

II Systems Engineering V-Diagram Model – Requirements Capture • Detailed analysis and documentation of all requirements – tool (DOORS) – Design Object Orientation Requirements System; • Use of Customer Focus Groups (CFGs) to solicit requirements(manufacturers/airlines with NAAs); • Customer Requirements Document (CRD) – documents all customer and other stake-holder requirements; • Systems Requirements Document (SRD) – documents all systems requirements CRD SRD AIRCRAFT DESIGN IMPLEMENTATION 6/13/2021 8

III Aircraft Design Procedures- Safety V-diagram 6/13/2021 9

III Aircraft Design Procedures - constraints • Purpose The design process starts with the documentation of aircraft's intended purpose. -Commercial airliners are designed for carrying a passenger or cargo payload, long range and greater fuel efficiency; -Fighter jets are designed to perform high speed manoeuvres and provide close support to ground troops • Aircraft regulations – airworthiness, safety & operational aspects; • The market and financial factors – projections of market demands and hence project viability • Environmental factors – noise, carbon emissions & hence need for fuel efficiency • Safety- high speeds, fuel tanks, atmospheric conditions at cruise altitudes, natural hazards (thunderstorms, hail and bird strikes) and human error are some of the many hazards that pose a threat to air travel 6/13/2021 10

III Aircraft Design Procedures- process Conceptual Design • First design step, entails the sketching a variety of possible configurations that meet the required design specifications. • Determines the design configuration that meets all requirements and is aligned to factors such as aerodynamics, propulsion, flight performance, structural and control systems. • Also called Design Optimization • Fundamental aspects such as fuselage shape, wing configuration and location, engine size and type are all determined at this stage. • Constraints to design like those discussed earlier are all taken into account at this stage as well. The final product is a layout of the aircraft configuration on paper or computer screen, ready for review other by engineers and designers. 6/13/2021 11

III Aircraft Design Procedures- concept 6/13/2021 12

III Aircraft Design Procedures- process Preliminary design • The design configuration arrived at in the conceptual design phase is then tweaked and remodelled to fit into the design parameters. • Wind tunnel testing and computational fluid dynamics (cfd) calculations of the flow field around the aircraft are accomplished at this stage. • Major structural and control analysis is also carried out in this phase. Aerodynamic flaws and structural instabilities if any are corrected and the final design is drawn and finalized. • Then after the finalization of the design lies the key decision with the manufacturer or individual designing it whether to actually go ahead with the production of the aircraft. • Several designs, though perfectly capable of flight and performance, have been opted out of production if economically unviable 6/13/2021 13

III Aircraft Design Procedures - process Detail design Deals with the fabrication aspect of the aircraft to be manufactured. It determines the number, design and location of frames, formers, spars, ribs and skin sections and other structural elements. All aerodynamic, structural, propulsion, control and performance aspects have already been covered in the preliminary design phase and only the manufacturing remains. Flight simulation strategies are implemented at this stage. Computer Aided Design (CAD) The use of numerical methods tools – Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA)- to experimental testing methods to achieve cost efficient design in shorter time scales. 6/13/2021 14

III Aircraft Design Procedures - process DESIGN TOOLS • Experimental : wind tunnel tests - for aerodynamics - Numerical: cfd, finite element analysis - CAD 6/13/2021 15

III Aircraft Design Procedures – process -Major elements Aerodynamics; Propulsion; Controls; Mass; Structure; Systems ; Avionics 1. Wing design - The wing design depends on many parameters such as selection of aspect ratio, taper ratio, sweepback angle, thickness ratio, section profile, washout and dihedral; 2. Fuselage - the part of the aircraft that contains the cockpit, passenger cabin or cargo hold; ultimate safe loads, wing/engine integration, emergency configuration/equipment; 3. Propulsion - Maximum engine thrust available; fuel consumption; engine mass; engine geometry; single engine operation; effects on take-off and stalling speeds; 4. Weight -weight of the aircraft is the common factor that links all aspects of aircraft design such as aerodynamics, structure, propulsion together. - derived from various factors such as empty weight, payload, useful load, etc. - the various weights are used to then calculate the centre of mass of the entire aircraft. - The centre of mass must fit within the established limits set by requirements; 5. Structure - focuses not only on strength, but also on fatigue, fail-safety, corrosion, maintainability and ease of manufacturing. Must be able to withstand the stresses caused by cabin pressurization system (if fitted), turbulence and engine or rotor vibrations; 6. Systems and Avionics – general systems, communication and navigation systems. 6/13/2021 16

III Aircraft Design Procedures- Certification Specifications (airworthiness code & amc) Example: EASA - AMC-20 (General Acceptable Means of Compliance for Airworthiness of Products, Parts and Appliances • Acceptable Means of Compliance (AMC) with design & other requirements; • Based on – FAA (FARs), EASA (Certification Specification Documents – CS-23; CS – 25 ; CS – E; etc • Basis of Aircraft Certification (and issue of Certificate of Airworthiness) • Driver for Aircraft Maintenance Programme Examples: - Structural : materials processes, strength, fatigue resistance; - Systems: designed to comply with structural and mission requirements; - Performance: system performance must exceed the mission mandates; 6/13/2021 - Environmental Protection Requirements (especially for EASA) 17

IV Problems (Airbus 380, Boeing 787, etc) • A 380 delay - different French vs German wiring codes; - electric cables too short to connect across fuselage sections; - production and connection of new - Production delayed for over 1 year + millions lost • B 787 battery overheating (causing fire) problems (a/c grounded) - 6/13/2021 18

V Conclusions Design flaws mainly originate with: - 1. Poor requirements capture (especially failure to fully accommodate all stakeholder concerns) 2. Inadequate system integration 6/13/2021 19

VI Discussion - Question and Answer Session 1. 2. 3. 4. 5. What is the certification procedure ? 6/13/2021 20