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Low Fare Airline – Design Project 2006-2007

P Bradshaw. Skill Group Leader Airbus Future Projects. Low Fare Airline – Design Project 2006-2007. University of Southampton 3rd November 2006. Design Project Aim. Enable design teams : To bring together knowledge of individual engineering disciplines into a complete aircraft project

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Low Fare Airline – Design Project 2006-2007

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  1. P Bradshaw Skill Group Leader Airbus Future Projects Low Fare Airline – Design Project 2006-2007 University of Southampton 3rd November 2006 EDXCW/PR/PB/20808A

  2. Design Project Aim Enable design teams: • To bring together knowledge of individual engineering disciplines into a complete aircraft project • To combine ‘conceptual design’ with some more focussed engineering. • To work efficiently in teams – Compete with other teams, not each other • Develop process of working, managing and controlling the Project Design for an aircraft. EDXCW/PR/PB/20808A

  3. The Problem Background: • Current short-range aircraft developed to meet the requirements of flag carriers. • Next generation of SR aircraft will probably be operated by Low Fare Airlines The Task ? • Design a SR aircraft to meet the specific requirements of LFA’s • Two aircraft family: • 150 pax HD • 1800nm and 3000nm versions EDXCW/PR/PB/20808A

  4. Objective • Each team is to propose a short-range aircraft primarily designed for Low Fare Airlines. • EIS 2015 • Generate initial technical specification to support a possible launch decision. Based on current and emerging technology and materials Novel configurations are not excluded Realistic approach to technology and risk EDXCW/PR/PB/20808A

  5. Design Targets • Performance (P, R, Mcr, TOFL, TAT) • Manufacturing and Assembly considerations ? • Reliability and Maintenance • Cost • To Manufacturer • Non-Recurring Cost - NRC • Recurring Cost - RC • To Customer • Operating Cost (direct and indirect) • Life Cycle Costs • Timescale • Design and Development • Manufacturing Cycle Time – Build rate ? • Marketability: • What appeals ? • Business Case: • IRR vs Investment • Expected MSN to break even ? EDXCW/PR/PB/20808A

  6. The Design Specification UB2007-SR UB2007-ER Passenger Capacity (1-cl HD) - 150 Design Range (still-air) nm 1800 3000 Design Cruise Speed Mach 0.80 Take-Off Field Ln. (MTOW at S-L, ISA+15) m 2000 Time To Climb (1500ft to ICA at ISA+10) min Result  25 Initial Cruise Altitude (ISA+10) ft 35000 Maximum Cruise Altitude ft 41000 Approach speed (MLW, S-L, ISA) kts CAS 135 Landing Field Length (MLW, S-L, ISA) ft 1600 One Engine Inoperative Altitude ft Result Result VMO / MMO kts CAS / Mach 360 / 0.84 Equivalent Cabin Altitude (at 41000ft) (4.9) ft 8000 Turn-Around Time - Minimum Minimum Airport compatibility limits - ICAO Code ‘C’ ACN (Flexible B) - 40 DOC target $/seat-nm Minimum Minimum ETOPS capability (at EIS) mins 90 EDXCW/PR/PB/20808A

  7. What are Customers’ Needs ? • Future concept selection will be chosen to fulfill the requirements to be met………… 4Range 4Payload 4Noise 4Safety 4Operating cost – (Profit for airlines !) 4Manufacturing Cost (Profit for us !) 4Cheap to maintain (DMC) 4Reliable etc etc etc (OI, MMEL) •That means understanding the options available to us, and the challenges ahead – does the latter infer that particular technologies have to be used, whether we like it or not ?? EDXCW/PR/PB/20808A

  8. Method of Working • Initially you will be ‘swamped’ with information - don’t panic. • Things will get clearer as all topics are delivered and you will see how they fit together. THEN: • Organise yourselves: • Everyone cannot do everything, so allocate responsibilities • Ensure everyone knows their roles and tasks (and is fully aware of the roles and tasks of others) – focus on problems early – support eachother. • Plan your project: • Identify major deliverables (internal / external), dates and owners • Identify activities with realistic timescales • Keep the plan current & feasible. • Ensure everone agrees & aims to adhere to it • Communicate • Share information early – decide what’s improtant/ what isn’t • Single failure=Collective failure EDXCW/PR/PB/20808A

  9. General Tips – Some Do’s and Don’ts • Understand the question: • Differentiate between the “hard” and “soft” requirements • Identify key drivers • Assess the ‘cost’ of each requirement • Challenge if appropriate - • Understand the importance of a design decision – Ensure technical evidence justifies it. • Ensure design solutions are driven by the requirements • Be realistic in your assessment of risk – Wild arsed guesses may kill your product. EDXCW/PR/PB/20808A

  10. General Tips – Some Do’s and Don’ts • If you go for an unconventional design, always assess against an equivalent conventional design. • Only include technology if it buys it’s way onto your aircraft. • Focus on the engineering – The marketeers will do the marketing (…..and understand the difference between the two) • Always be aware of the regulations and ensure your design meets them (eg minimum ROC margin @ top of climb, Vapp rules in terms of Vst....). EDXCW/PR/PB/20808A

  11. General Tips – Some Do’s and Don’ts Always reference your design against a known solution • Sanity check • Calibration • Gain a feel for the configurational influences and exchange rates. • Don’t squeeze the last drop from your design – you’ll regret it later on ! EDXCW/PR/PB/20808A

  12. General Tips – Some Do’s and Don’ts • Ensure you draw, maintain and use a GA of the aircraft • Gives design change traceability • Assists in understanding of scale & ‘fit’ • Unique definition of the configuration and geometry EDXCW/PR/PB/20808A

  13. General Tips – Some Do’s and Don’ts • Use methods appropriate to the stage of the design and the input data available • Don’t obsess with accuracy of numbers – the nth decimal place is completely unrealistic – Get OM understood. • Use quick and dirty methods where appropriate • Always ‘sanity check’ results – does it look/ feel right ? "Tools don't design aircraft, engineers do” EDXCW/PR/PB/20808A

  14. Presentation of Results • Ensure content, style and level of detail are appropriate. • Clearly describe the main features of the aircraft and its components. • Justify all design decisions made. • Demonstrate the multidisciplinary balance and integration of your design. • Describe the process by which you approached the design. • Demonstrate: • Good team working • Good project management • Good control of the project design • Make your points as clearly as you can – peer review your chapters before submission. EDXCW/PR/PB/20808A

  15. The Question Max Payload Limit Fuel Volume Margin MTOW Limit Fuel Volume Limit • Requirements drive the solution • Payload and Range define some major aircraft parameters • e.g. 150 pax / 3000nm • These will form a significant part of the design drivers Payload Design mission should be typical Max Payload by HD mission Fuel Volume by design mission fuel or other requirement (e.g. approach speed) MTOW driven by design mission Range EDXCW/PR/PB/20808A

  16. Design Process • Design is iterative • You can’t unpick the ends to untie the knot • You can’t work out a solution from the question in a straight line • ‘Cut the Gordian Knot’ • Choose a concept • Analyse it • Assess it • Change it • Start again… EDXCW/PR/PB/20808A

  17. The Iterative Design Process Component Weights Component Weights Aerodynamics Aerodynamics Initial Cardinal Geometry Configuration: Size, Position ... Design Weights, Engine Size, CLmax, Minimise Cost Space Allocation (Fuel Volume, LG, Hi-Lift...) Refine Config ‘Actual’ V ‘Targets’ (Wing area,  MTOW, ..) Performance & Cost Performance & Cost No Yes OK? EDXCW/PR/PB/20808A

  18. Example of Simplified Calculation Wing Area or Thrust T/Off Dist. Weight T/Off Dist. Take-Off Dist = aP + b Parametric No (P) • Take-Off Field Performance EDXCW/PR/PB/20808A

  19. Sizing Process - Design Weights • MTOW = ZFW + Fuel • ZFW = Payload + OWE • MLW = z * MZFW • 1st order: MTOW/OWE = fn(Range) • Range (Breguet)= y * (V*(L/D)/sfc) * log (MTOW/ZFW) • Initial L/D value: Compare with other a/c • Calibrate z & y against known aircraft EDXCW/PR/PB/20808A

  20. Sizing Process: Component Sizing • Wing Area = fn (MLW, CL, Vapp) or fn (MTOW, CL, TOFL, Thrust) or fn (Cruise Weight, CL, Height, Speed) or fn (Fuel Volume) • Wing Sweep, t/c => see aerodynamics section • Fin Area = fn (Wing Area, Span, Moment Arm) • Tail Area = fn (Wing Area, Chord, Moment Arm) • Thrust = fn (MTOW, CL, TOFL, Thrust) or fn (Cruise Weight, Height, Speed, L/D) EDXCW/PR/PB/20808A

  21. Sizing Process: Component Weights • Fuselage = fn (Length, Cross-Section) • Wing = fn (Area, MTOW, Sweep, Span, t/c, MZFW) • Fin & Tail = fn (Area) • Engines = fn (Thrust) • Undercarriage = fn (MTOW) • Systems = Fixed • Furnishings = fn (Length, Cross-Section) • Operator’s Items = fn (No Pax) EDXCW/PR/PB/20808A

  22. Sizing Process: Aerodynamics • CD = CD0 + K.CL² +CDM • CD0 = fn (Surface Area)= fn (Fuse len. & diam., wing, fin & tail area, eng. size) • K = fn (AR, sweep) • CDM = fn (AR, sweep, t/c) • CLmax = fn (flap type) EDXCW/PR/PB/20808A

  23. Sizing Process: Performance • Range = y * (V*(L/D)/sfc) * log (MTOW/OWE) • Vapp = fn(Wing Area,MLW, CL) • TOFL = fn (Wing Area, MTOW, CL, TOFL, Thrust) • Thrust = fn (MTOW, CL, TOFL, Thrust) or fn (Cruise Weight, Height, Speed, L/D) EDXCW/PR/PB/20808A

  24. Fuselage & Cabin • Preliminary – scale from existing known aircraft • Define seat-abreast and cross-section (incl. number of decks) • Calculate required number of: • Seats (by class) • Galleys / Lavatories / Attendants / Crew rest areas etc • Doors (based on highest density layout) • Layout cabin to determine length (and iterate) • Add nose and tail (length based on scaling of existing aircraft) EDXCW/PR/PB/20808A

  25. Door distribution requirements A380 due to • certification requirements max. door spacing is 60ft=18m uniform distribution of exits due to passenger distribution in the cabin EDXCW/PR/PB/20808A chart 25 EDXCW/PR/PB/20808A

  26. Door distribution requirements due to • certification requirements • emergency slide function spacing to flaps min. door spacing= 4.5m spacing to engines EDXCW/PR/PB/20808A EDXCW/PR/PB/20808A

  27. Landing gear definition • Functions: • carry aircraft max gross weight to take off runway • withstand braking during aborted take off • retract into compact landing gear bay • damp touchdown at maximum weight- and sink rate-landing • Characteristics: • size and number of wheels • retraction path / stowed position • impact on ground surface (cracks, damage and fatigue) • maximum braking energy capability Main parameters fix the development potential quite early. Small changes can be introduced later in the programme EDXCW/PR/PB/20808A

  28. LG continued • Ensure wing & LG integration with rest of aircraft; 4NLG impact on high speed landing (A/C attitude too nose down on touchdown?) – resolve through body setting angle or more powerful high lift devices ? 4Tail tip on loading – MLG too far forward. 4Wing (& MLG) too far aft – rotation @ T/O may be difficult. 4Longitudinal constraints: Tail-scrape on rotation (LG length or longitudinal position/ rear fuselage shape/ ‘Power’ of High Lift Devices) 4Lateral constraints: x-wind landing, turnover angle theta < 30 degrees typically 4Position NLG & MLG to retain at least 5% MTOW over NLG in static balance about CG, to ensure steering feasibility. EDXCW/PR/PB/20808A

  29. LG • Ensure LG leg integration feasibility • NLG, BLG, MLG volume requirements for sensible leg positions & tyre quantity & size (family growth version ?) • ACN – pavement loading – set by Airfield classification (requirement). –Greater root chord? –Inner TE kink? –Thicker section @ root? –Re-twist at root? EDXCW/PR/PB/20808A

  30. Standard Clearances for LG Concept Studies • Weight:- Total LG weight typically 3% of MTOW for commercial airliners • Tyre clearances:- Spinning Tyre to airframe = 80mm minimum for nominal static structure (50mm after tolerances and deflections) Landing gear structure to airframe = 50mm minimum for nominal static structure (25mm after tolerances and deflections) • Airframe skin thickness:- Wing skin thickness = 50mm Belly fairing thickness = 100mm Nose bay skin thickness = 100mm EDXCW/PR/PB/20808A

  31. Results in an Envelope for LG Fairing Sizing Tyre clearance illustration for stowed Main Gear. Spinning tyre +80mm clearance to structure +100mm belly fairing thickness +180mm total offset Structure +50mm clearance to structure +50mm Wing skin thickness +100mm total offset EDXCW/PR/PB/20808A

  32. Section through stowed leg in wing Wing surfaces EDXCW/PR/PB/20808A

  33. Landing Gear - Aerodrome reference code • The purpose of the Aerodrome reference code is to match aerodrome facilities to the A/C. It is a two part code. • The first part relates to the A/C reference field length • The second to the A/C wing span and L/G outer wheel span. • The details regarding the aerodrome reference code for L/G outer wheel span can be found in the ICAO aerodrome design manual Part 2 Chapter 1 (Taxiways). • The code elements are reproduced as follows; EDXCW/PR/PB/20808A

  34. Landing gear layout “equivalent single wheel load” to estimate impact on ground surface by scaling of pavement test results (number, size , pressure & spacing) retraction into compact landing gear bay including free-fall capability (number, size & spacing) load per wheel under nominal and special conditions to be less than tire’s allowables (number, size & ply rating) attachment to wing & fuselage to guide static and braking loads (available space between spars & flaps) volume for brake discs inside wheel (number & size) EDXCW/PR/PB/20808A

  35. Landing gear characteristics number of wheels load / wheel / diameter / width 20 50 maximum “ground pressure” 16 40 12 30 8 20 20-30t per wheel 4 10 0 0 0 100 200 300 400 500 600 0 100 200 300 400 500 600 MTOW [t] MTOW [t] Number and size of wheels driven by max gross weight and ground impact requirement EDXCW/PR/PB/20808A

  36. Powerplant Positioning & Integration 4Powerplant position: – Gulled wing ? (local increase in dihedral at root) –+/ - 5 degree disc burst cones for fuel tank boundaries and feeds to Engine. –MLG longitudinal position on NLG collapse to ensure engine clearance. EDXCW/PR/PB/20808A

  37. Engine installation constraints 17.5° Door 7 slide 2.0 m Toe-in 1.7° 110mm margin 5° 3° Door 7 position • Fan burst criteria : • 3° opposite wing side fan burst trajectory / rear I/B pick-up point • 5° same wing side fan burst trajectory / rear I/B pick-up point Safety requirements bound optimisation window EDXCW/PR/PB/20808A

  38. Wing planform definition • Wing aerodynamic performance depends on • Sectional shape • Wing area, span, sweep, thickness, taper • Spanwise lift distribution • Flap size and type • Wing weight depends on • Design weights • Design speed • Wing area, span, sweep, t/c, taper • Spanwise lift distribution • Box size / flap size and type • Weight & drag require different planforms • The wing must also carry landing gear & engines, and integrate into the fuselage We must find the best balance for the overall aircraft EDXCW/PR/PB/20808A

  39. Wing Sizing • Develop understanding of component level sizing & links to OAD; •Wing planform versus drag & economics; • 4TR, Span, t/c, S – which gives the best multidisciplinary balance ? • Span versus Area • Sweep versus t/c • TR versus CoP • 4Check fuel volume requirement is met in wing. • 4Value of Weight versus Drag for Economics terms – Which most influences ? • 4Is aero benefit of elliptical lift distribution more powerful than BM relief due to • more inboard position of CoP ? EDXCW/PR/PB/20808A

  40. Wing Area Selection constant AR • Lower wing weight • Lower drag • Lower cost • Smaller fin & tailplane • Fuselage integration easier • Increased fuel volume • Increased high speed lift • (better buffet margin) • Increased low speed lift • (lower approach speed) • Gear installation easier Minimum Area for capability and growth potential EDXCW/PR/PB/20808A

  41. Aspect Ratio (AR) Definition constant wing area • Possibly tip stall problems • Quieter aircraft • Improved aerodynamic performance: • Induced drag = fn(span –2) • More fuel volume • Better engine & gear installation • Lower wing weight: • Wwing = fn(span3) Balance between aerodynamic performance and wing weight depends on aircraft requirements (range etc.) EDXCW/PR/PB/20808A

  42. Sweep Angle Selection constant wing area and AR • Improved high speed performance • Easier engine segregation • Easier gear installation • Improved low speed performance • Lower wing weight Balance between high speed and low speed performance EDXCW/PR/PB/20808A

  43. Spanwise Lift Distribution Triangular • Higher induced drag • Lower wing weight Elliptical • Minimum induced drag Optimum depends on the requirements –Range in particular EDXCW/PR/PB/20808A

  44. Span vs Area vs Block Fuel Span and Area Trades Mission Efficiency 6 15 Design Mission (500 nm) 4 10 Area Span Vapp limit 2 5 const. AR 33.4m Baseline DOCM Block Fuel Change [%] 0 0 TTC limit 2 145m -2 -5 -4 -10 38.7m 2 125m Fuel limit boundary 3500nm -6 -15 EDXCW/PR/PB/20808A

  45. Weight and Drag Balance +5dc datum +2t +1t drag datum -1t MWE -5dc -2t Minimising Operating Cost means balancing weight and drag benefits EDXCW/PR/PB/20808A

  46. Span vs Area vs DOC/ Weight Span and Area Trades Weight 15 10 Span 5 Wing Weight Change [%] 0 -5 -10 Area 38.7m Baseline 2 145m wing weight for iso Vapp 33.4m 2 125m Span and Area Trades Operator Cost 0.7 Design Mission (500 nm) • Other key trades include: • DOC vs A/C price vs Fuel price • Fuel margin vs Area vs Span • Aircraft Price vs Area vs Span 2 145m 0.6 6 Span 0.5 0.4 4 CoC 0.3 0.2 2 EDP Change [%] 0.1 0 0 Baseline -0.1 Area 2 125m -0.2 -2 33.4m -0.3 38.7m Fuel Price assumened at 0.7 $/Gal -0.4 -4 EDXCW/PR/PB/20808A

  47. Requirements for High Lift Devices Clmax limit Vapproach = 1.23 x Vs1g + 5 kts CLapproach = f(CLmax) Vapproach = 1.23 x Vs1g + 15 (20) kts cruise • Provide sufficient lift to meet Vapp • Avoid tail-strike @ touch down • Avoid NLG first impact @ touchdown for High speed landing Max Alpha case - Tailscarape CL Overspeed cases – Alpha min CL0 NLG First Impact Tailstrike Alpha EDXCW/PR/PB/20808A

  48. Useable Rotation Angle – Take-off & Landing • For landing, the compressed main gear is a useful • de-rotation axis for measuring allowable alpha • For take off, calculation benefits can be drawn from taking the extended main gear (including rocking bogie) as the rotation axis for measuring allowable alpha and calculating safe lift off speed EDXCW/PR/PB/20808A

  49. Different Ways to Meet LS Targets Trailing Edge: Split Flap Plain Flap Single Slotted double Slotted Triple Slotted Improved Aerodynamics Increased Weight, Cost, Maintenance Leading Edge: Plain Slat Krueger Hinged EDXCW/PR/PB/20808A

  50. Actuation Mechanism Trailing Edge - Three principle mechanism types: Drop-hinge (pure rotation) Low weight Low cost Limited deployment Poor lap & gap Track & Lever Heavier weight Higher cost Excellent deployment Excellent lap & gap control 4-Bar Link Medium weight Medium cost Good deployment Good lap & gap control Selection is a balance of all characteristics at the aircraft level EDXCW/PR/PB/20808A

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