Low fare airline design project 2006 2007
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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

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


Design project aim

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


The problem

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


Objective

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


Design targets

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


The design specification

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


What are customers needs

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


Method of working

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


General tips some do s and don ts

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


General tips some do s and don ts1

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


General tips some do s and don ts2

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


    General tips some do s and don ts3

    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


    General tips some do s and don ts4

    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


    Presentation of results

    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


    The question

    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


    Design process

    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


    The iterative design process

    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


    Example of simplified calculation

    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


    Sizing process design weights

    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


    Sizing process component sizing

    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


    Sizing process component weights

    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


    Sizing process aerodynamics

    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


    Sizing process performance

    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


    Fuselage cabin

    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


    Door distribution requirements

    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


    Door distribution requirements1

    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


    Landing gear definition

    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


    Lg continued

    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


    Low fare airline design project 2006 2007

    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


    Standard clearances for lg concept studies

    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


    Results in an envelope for lg fairing sizing

    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


    Section through stowed leg in wing

    Section through stowed leg in wing

    Wing surfaces

    EDXCW/PR/PB/20808A


    Landing gear aerodrome reference code

    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


    Landing gear layout

    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


    Landing gear characteristics

    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


    Powerplant positioning integration

    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


    Engine installation constraints

    Engine installation constraints

    17.5°

    Door 7 slide

    2.0 m

    Toe-in

    1.7°

    110mm margin

    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


    Wing planform definition

    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


    Wing sizing

    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


    Wing area selection

    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


    Aspect ratio ar definition

    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


    Sweep angle selection

    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


    Spanwise lift distribution

    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


    Span vs area vs block fuel

    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


    Weight and drag balance

    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


    Span vs area vs doc weight

    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


    Requirements for high lift devices

    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


    Useable rotation angle take off landing

    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


    Different ways to meet ls targets

    Different Ways to Meet LS Targets

    Trailing Edge:

    Split FlapPlain FlapSingle Slotteddouble SlottedTriple Slotted

    Improved Aerodynamics

    Increased Weight, Cost, Maintenance

    Leading Edge:

    PlainSlatKruegerHinged

    EDXCW/PR/PB/20808A


    Actuation mechanism

    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


    Some sanity checks 1

    Some Sanity Checks - 1

    • Effect of Engine wear: Equivalent to 4 – 6% FB increase.

    • Weights: (Check out Niu/ Raymer/ Roskam/ Shevell/ Torenbeek)

      • Covers Weight W/S, b3, c/t, / 

      • Top Cover: 7000 srs Al (550 Mpa FTU)

      • Bottom Cover: 2000 srs Al (300 MPa FTU) with fatigue reduction.

      • Covers approx 45% - 50% wing weight

      • Ribs & Spars approx 25% wing weight

      • FLE & Movables approx 5% - 10%

      • FTE & Movables approx 15% - 20%

    • Disk burst: All subject to rational analysis to decrease cone size if possible;

      • Turbine blades: +/- 15º

      • Compressor blades:

        • 1/3rd of a disk; +/ - 3 º

        • Intermediate fragment; +/ - 5 º

    EDXCW/PR/PB/20808A


    Some sanity checks 2

    Some Sanity Checks - 2

    • Fuel Volume Availability

      • Gross volume - Outside skin line

      • Nett Volume – What is available to use

      • Remember: Limiting mission + 200 nm diversion, 5% trip fuel

        allowance + 30 minute hold @ 1500 ft AGL +10% margin is what you will need.

      • Items that reduce fuel volume availability:

        • Structural volume

        • Thermal expansion

        • Unusable fuel

        • Trapped air

        • In-tank equipment (pumps, probes, pipes)

      • Gross – Nett: Should be approx 10 – 15% difference, subject to above items.

    EDXCW/PR/PB/20808A


    Economics

    Economics

    EDXCW/PR/PB/20808A


    Why we re producing aircraft

    Why we’re Producing Aircraft ?

    Making money

    is the reason why most

    companies are in the

    aerospace industry

    Operating Cost

    methods give engineers

    a useful multi-disciplinary

    assessment tool in the

    sizing process

    Operating Costs

    are an important criterion used by airlines when choosing new aircraft

    Consider economics throughout, not just as a result

    EDXCW/PR/PB/20808A


    Low cost operator tat hub vs destination

    Low Cost Operator TAT (Hub vs. Destination)

    • TAT process

    • TAT –time in between „blocks on“ and „blocks off“

    • Passenger deplaning/ boarding

    • Cargo unloading/ loading

    • Refuelling process

    • Catering

    • Cabin Cleaning

    • Freshwater service

    • Lavatory water service

    • Inspection/ maintenance

    • Security check

    • Deicing

    Data for many different airports and airlines available for analysis

    EDXCW/PR/PB/20808A


    Operating costs coc doc ioc 1 2

    Operating Costs - COC, DOC & IOC (1/2)

    Total Operating Cost (TOC)

    • Direct Operating Cost (DOC)

    • Financial Costs

      • Depreciation

      • Interest

      • Insurance

    • Indirect Operating Cost (IOC)

    • Ground Property & Equipment

      • Depreciation & Maintenance

    • Administration & Sales

      • Servicing administration

      • Reservations & sales

      • Advertising & publicity

      • General

    • Servicing

      • Passenger services

      • Aircraft services

      • Traffic services

    • Cash Operating Cost (COC)

    • Flying Costs

      • Fuel

      • Landing fees

      • Cockpit crew

      • Cabin crew

      • Navigation charges

    • Maintenance Costs

      • Airframe

      • Engines

    Dependent on aircraft design

    Dependent on airline operations

    EDXCW/PR/PB/20808A


    Operating costs coc doc ioc 2 2

    Operating Costs - COC, DOC & IOC (2/2)

    • Cash Operating Cost (COC):

      • Flight-related costs

         Highlights aircraft-use and variable cost trends – Useful to airlines

         Doesn’t account for aircraft cost - If used as the target function, it drives design to a high-tech solution to reduce fuelburn

    • Direct Operating Cost (DOC):

      • COC + Aircraft price (or cost) related costs

         Large price/cost component masks flight-related cost trends which are important for airlines

        Realistically accounts for the cost of aircraft design and technology

    • Indirect Operating Costs (IOC):

      • Airline infrastructure costs

         Highly airline dependent – No reliable quantitative method

    • Calculate COC for “airline” a/c comparisons

    • Calculate DOC for technical trade studies

    • Assess IOC issues qualitatively

    EDXCW/PR/PB/20808A


    Aea method inputs assumptions results

    AEA Method - Inputs, Assumptions & Results

    Inputs

    • Mission data:

      • Stage Length (nm)

      • Block Fuel [BF] (lb)

      • Block Time [BT] (hr)

      • Passengers [Pax]

    • Fuel Density = 6.7 lb/USgal

    • Labour Rate [R] = 66 $/hr

    • Financial Costs:

      • Depreciation [DEP]

      • Interest [INT]

      • Insurance [INS]

    • Weight data:

      • MTOW (t)

      • MWE (t)

      • Engine Weight (t)

    • Maintenance Costs:

      • Airframe Maintenance [AMC]

      • Engine Maintenance [EMC]

    • Engine parameters:

      • Number of Engines [NE]

      • SLST [T] (t)

      • Bypass Ratio [BPR]

      • Overall Pressure Ratio [OPR]

      • No. of compressor stages [NC]

    D

    O

    C

    C

    O

    C

    • Flight Costs:

      • Cockpit Crew [CPC]

      • Cabin Crew [CAC]

      • Navigation Charges [NAV]

      • Landing Fees [LAF]

      • Fuel [FUE]

    • Price data:

      • Engine Price [ENP] ($)

      • Manufacturers Study Price [MSP] ($)

      • Airframe Cost [AFC] ($)

      • Fuel Price ($/USgal)

    (All costs calculated as $/trip)

    Assumptions

    Results

    AEA DOC Method

    EDXCW/PR/PB/20808A


    Aea method study mission coc doc

    AEA Method - Study Mission(COC & DOC)

    Use the values from the following table:

    Note:

    DOC mission payload is usually the aircraft design payload (Standard Passenger Payload)

    The Study mission is not the same as the Design mission

    • Aircraft are sized by their Design mission Payload-Range requirements

    • Operational routes are typically much shorter than the Design mission

    • For representative operating costs it is important to use a representative (average) mission.

    For DOC, use Study Mission with Standard Payload

    EDXCW/PR/PB/20808A


    Aea method utilisation doc

    AEA Method - Utilisation (DOC)

    • Use the values from the following table for your aircraft’s study mission:

    Use your calculated turn-around time

    (The average of the three cases specified)

    Utilisation (U) = Number of trips in a year

    = Available hours in year / (Block Time + Turn Around Time)

    Where:

    Available Hours in year is not simply 24 hours ×365 days

    Turn Around Time [TAT] = fn(Loading, Maintenance, Refuelling, etc.)

    These values depend on the aircraft type and operation

    Increased utilisation = More trips = More fares = 

    EDXCW/PR/PB/20808A


    Aea method total investment doc

    AEA Method - Total Investment (DOC)

    Total Investment [TI] = Cost of aircraft and initial spares

    = Manufacturer’s Study Price [MSP]

    • Typically a study variable (see later)

      + Airframe spares

      = 10% of airframe price (or airframe cost)

      = 0.10 × (MSP – (Engine Price [ENP] × No. of engines [NE]))

      + Spare Propulsion Units

      = 30% of total engine price

      = 0.30 × (Engine Price [ENP] × No. of engines [NE])

    EDXCW/PR/PB/20808A


    Aea method financial costs doc

    AEA Method - Financial Costs (DOC)

    Total Financial Costs = Financial Overheads

    = Depreciation [DEP]

    = Depreciation of aircraft value

    = Total Investment/(14 × Utilisation)

    + Interest [INT]

    = Payment of aircraft financing

    = 0.05 × Total Investment / Utilisation

    + Insurance [INS]

    = Cost of insuring aircraft

    = 0.006 × Manufacturer’s Study Price / Utilisation

    EDXCW/PR/PB/20808A


    Aea method crew costs coc doc

    AEA Method - Crew Costs (COC & DOC)

    Total Crew Costs = Cost of current and reserve crews

    = Cockpit Crew Cost [CPC]

    = 380 × Block Time

    • Assumes a 2 person cockpit at $380 per block hour

      + Cabin Crew [CAC]

      = 60 × NCAB × Block Time

    • Assumes $60 per block hour per cabin crew member

    • For a commercial airliner, the number of cabin crew [NCAB] is a function of the comfort standard.

      • Typically 1 per 35 pax, rounded up to the next whole number

    EDXCW/PR/PB/20808A


    Low fare airline design project 2006 2007

    EDXCW/PR/PB/20808A


    Aea method af maintenance cost s coc doc

    AEA Method - AF Maintenance Costs(COC & DOC)

    Airframe Maintenance Costs [AMC]

    = Airframe Labour

    =

    • + Airframe Materials

    • = AFP × (4.2 +2.2 × (t - 0.25))

    • Where:

    • AFW= Airframe Weight (tonnes) = MWE less Weight of the Engines

    • R= Labour Rate = 66 $/hour

    • MWE= Manufacturers Weight Empty (tonnes)

    • t = Block time (hours)

    • AFP= Airframe Price = MSP less Price of the Engines ($M)

    EDXCW/PR/PB/20808A


    Aea method eng maintenance cost s coc doc

    AEA Method - Eng Maintenance Costs(COC & DOC)

    Engine Maintenance Costs [EMC]

    • The method depends on the engine type:

      Turbojet or TurbofanContra-Turboprop or Propfan

      Labour:LT = 0.21 × C1 × C3 × (1+T )0.4 × R LT × 0.152 × C3 × (1+N)0.4 × R[Core]

      LP = 0.072 × B × (1+N/2)0.4 × R[Props]

      Material:MT = 2.56 × (1+T)0.8 × C1 (C2+C3) MT = 1.65 × (1+N)0.8 × (C2+C3)[Core]

      MP = 0.56 × (1+N/2)0.8 × B[Props]

      Total:EMC = NE × (LT + MT) × (tƒ+1.3)EMC = NE × (LT+MT) × (tƒ+1.3)

      + NE × (LP+MP) × (tƒ+0.5)

    Where:

    C1 = 1.27 - 0.2 x BPR0.2A = 8.5 × (N / 3 × P + 28)0.5 + 0.9

    C2 = 0.4 × (OPR / 20)1.3 + 0.4B = (0.05 × P + 0.6) × (0.4 × (D / A) + 0.6)

    C3 = 0.032 × NC + 0.57

    T = Sea Level Static Thrust (tonnes) BPR = Bypass RatioN= Take Off SHP×10-3

    NC = No. of Compressor StagesOPR = Overall Pressure Ratio D= Prop Diameter (m)

    tƒ = Flight time = Block time - 0.25 (hrs)P = No. of Propeller Blades

    EDXCW/PR/PB/20808A


    Aea method fuel price coc doc

    AEA Method - Fuel Price (COC & DOC)

    Fuel cost [FUE]

    = Block Fuel (lb) / 6.7 × Fuel Price ($/USGal)

    • Assumed fuel density = 6.7 lb/USGal (~0.803 kg/l)

    • The price of fuel varies considerably

    • A tax on fuel is likely to be the method of taxing aircraft emissions in the future

    • Fuel price is typically considered a study variable (... see later)

    Current price

    >2 $/USgal

    Historic price

    ~1 $/USgal

    Source: IATA website, 03 October 2006 http://www.iata.org/whatwedo/economics/fuel_monitor/price_development.htm

    EDXCW/PR/PB/20808A


    Cost estimation understanding price cost

    Cost Estimation - Understanding Price & Cost

    • The Manufacturer’s Study Price [MSP] is a major DOC input

      = Airframe Price [AFP] + Engine Price [ENP]

      ( = Aircraft Cost + Manufacturer’s Profit)

    • The Priceiswhat the airline is willing to pay for the aircraft

      • Market driven, big discounts

    • The Cost is what it costs the manufacturer to build the aircraft

      = RC + (NRC/Number of a/c produced)

      Where:

      RC = Recurring Cost = Cost of building one aircraft. Includes materials,

      man-hours, transportation, bought items, energy, etc.

      NRC = Non Recurring Costs = Cost of design and set up for manufacture

      of a new aircraft. Includes design, jig & tools, testing, prototypes.

    Price is not the same as Cost

    EDXCW/PR/PB/20808A


    Cost estimation price prediction

    Cost Estimation - Price Prediction

    • The Priceiswhat airlines are willing to pay for the aircraft

      • Price is market driven and is dependent on the aircraft’s capabilities:

        • Primary effects: Range, Payload (passenger & freight)

        • Secondary effects:Speed, Comfort, Operating Cost

        • Tertiary effects:Fleet commonality, cross-crew qualification, etc.

      • Airframe price can beestimated by statistical assessment ofa/c list prices against combinations of their capabilities, i.e.

        Airframe price = fn(payload, range, speed, ...)

      • Engine price can be estimated in a similar way, assessed against relevant engine parameters:

        Engine price = fn(thrust, efficiency, ...)

      • Airlines rarely pay full price (... see next slide)

    Aircraft price is determined by the market place

    EDXCW/PR/PB/20808A


    Price list vs discounted

    Price - List vs. Discounted

    ... $51 million is a "basic price"...

    ... already discounted between 17 and 27 percent from the public list price of $61.5 million to $69.5 million...

    ... Boeing granted Ryanair "certain price concessions" ... that "will reduce the effective price of each aircraft ...

    Boeing will also provide a range of support services, and will install fuel-conserving winglets at no extra cost.

    ... a bargain price tag on Ryanair's jets of about $29 million ...

    In addition, the deal retroactively applies the newest, biggest discounts to 89 previously ordered jets that Boeing hasn't yet delivered

    "Even at these price levels, I still have to believe Boeing is making money"

    Boeing jet prices glimpsed in deal

    How much does Ryanair Chief Executive Michael O'Leary pay for his Boeing jets?

    His bare-bones, low-cost airline is one of Boeing's most important customers. But Boeing's prices are one of its best-kept secrets — Airbus would certainly like to know.

    Ryanair gave a glimpse of the answer yesterday in an unusual regulatory filing connected to its February order for 70 jets. The papers offer details of Boeing's commercial jet pricing that are not normally revealed.

    O'Leary's starting point for price negotiations is way below Boeing's public list price — and he gets deep concessions from there, according to the proxy document provided to shareholders.

    In addition, the deal retroactively applies the newest, biggest discounts to 89 previously ordered jets that Boeing hasn't yet delivered to Ryanair.

    Ryanair, one of the fastest-growing airlines in the world, has a fleet of 89 Renton-built Boeing 737s in service, with another 145 of the jets on firm order and options to buy a further 193. The order placed earlier this year needs shareholder approval in a May 12 vote — hence the proxy filing.

    Yesterday's filing said $51 million is a "basic price" for the 70 Boeing 737-800 airplanes ordered in February, including the engines and some optional features. Ryanair will also pay around $900,000 per aircraft for equipment from third parties that Boeing will install.

    That basic price is already discounted between 17 and 27 percent from the public list price of $61.5 million to $69.5 million given on Boeing's Web site.

    However, the filing adds that Boeing granted Ryanair "certain price concessions" in the form of credit and allowances that "will reduce the effective price of each aircraft to Ryanair significantly below the basic price."

    Boeing will also provide a range of support services, and will install fuel-conserving winglets at no extra cost.

    The document gives one further clue to Ryanair's price tag: It states that 454 million euros (or $593 million) will be required to fund the 29 jets to be delivered between now and March 2006, or about $20 million per aircraft.

    And elsewhere it says 30 percent of the price is required in advance of delivery, suggesting the $593 million will pay the remaining 70 percent.

    That works out to a bargain price tag on Ryanair's jets of about $29 million.

    For a hard-driving negotiator like O'Leary, $29 million for a 737-800 — less than half the public list price — is "not out of the realm of imagination," said industry analyst Byron Callan of Merrill Lynch.

    Callan said he'd heard of such prices being offered in the recent Iberia sales campaign that Boeing lost to Airbus.

    "Even at these price levels, I still have to believe Boeing is making money," Callan said.

    To persuade shareholders to approve the purchase, the filing gives the rationale for picking the 737 over Airbus' A320: Boeing offered the best price; its jet has lower per-seat operating costs; and the airline already operates an all-Boeing fleet.

    Source: Seattle Times, 23 April 2005http://seattletimes.nwsource.com/html/boeingaerospace/2002250601_ryanair23.html

    Discounts are unpredictable – Always use list price

    EDXCW/PR/PB/20808A


    Cost estimation rc prediction

    Cost Estimation - RC Prediction

    • The Recurring Cost [RC] is the cost of making one aircraft

      • Materials, man-hours, transportation, bought items, energy, etc.

      • Cost prediction can be harder than price prediction.

    • There are two main methods:

    • Top Down

      • Airframe cost = fn(Airframe Weight)

      • Method predicts light, high-tech structures are cheap (... rarely the case)

      • Fairly simple, good at OAD level, historical data driven - not particularly accurate – predicts yesterday’s cost tomorrow ?

    • Bottom up (Manufacturing process based)

      • Airframe cost = S(component costs)

      • Component cost = Material cost + Process Cost

        (Process cost includes man-hours, machining, energy, transportation)

      • Method correctly predicts heavy, simply machined components are cheap

      • More complicated, far more accurate, component & sub-component

        ... See note on next page

    Aircraft cost is determined by the aircraft design

    EDXCW/PR/PB/20808A


    Cost estimation n rc prediction

    Cost Estimation - NRC Prediction

    • Non-Recurring Cost [NRC] is the cost of design and set up for manufacture of a new aircraft

    • Consists of ...

      • Engineering: Main stream engineering will typically take ~5 years

      • Tests: Wind tunnel test program, Materials & structures tests

      • Jig and tooling costs

      • Static & fatigue test airframes

      • Flight test aircraft - Typically costs about 30% more than a normal production aircraft

        Note:

        RCs and NRCs, and hence aircraft cost, may already be a deliverable for the project Business Case chapter.

        • If so, use these values in the operating cost calculations

        • If not, a suggested NRC and RC estimation method can be found in:

          “Airplane Design, Part VIII: Airplane Cost Estimation” by Dr. J. Roskam

          ... and maybe use the updated factors from the “AAA” method

    EDXCW/PR/PB/20808A


    Results example coc doc input data

    Results - Example COC & DOC Input Data

    ExampleDesign

    Project

    Airframe Price$M 48.0 ?

    Engine Price (per engine)$M 6.0 ?

    Fuel Price$/USGal variablevariable

    Labour rate$/hr 66 66

    SPP Passengers 150 ?

    Stage Length (Study Mission)nm 500 ?

    Block Fuellbs 7189 ?

    Block Timehrs 1.602 ?

    MTOWT 75.5 ?

    MWET 38.0 ?

    Engine WeightT 3.5 ?

    Number of Engines 2 ?

    Sea Level Static Thrustklb 26500 ?

    Take-Off Shaft horsepowerSHP×10-3 n/a ?

    BPR 4.75 ?

    Propeller Diameterm n/a ?

    Propeller blades n/a ?

    Compressor Stages 14 ?

    OPR 27.4 ?

    EDXCW/PR/PB/20808A


    Results example coc doc results

    Results - Example COC & DOC Results

    Fuel Price$/USgal 1.0 2.5 4.0

    Financial Costs

    Depreciation$/trip 2567.44 2567.44 2567.44

    Interest$/trip 1797.21 1797.21 1797.21

    Insurance$/trip 189.18 189.18 189.18

    Maintenance Costs

    Airframe Maintenance$/trip 1046.58 1046.58 1046.58

    Engine Maintenance$/trip 421.36 421.36 421.36

    Flight Costs

    Cockpit Crew$/trip 608.76 608.76 608.76

    Cabin Crew$/trip 480.60 480.60 480.60

    Navigation Charges$/trip 568.94 568.94 568.94

    Landing Fees$/trip 453.00 453.00 453.00

    Fuel$/trip 1072.99 2686.46 4291.94

    Total COC Sector Cost$/trip 4652.23 6261.71 7871.19

    Total COC Seat-Mile Costscent/seat-nm 6.20 8.35 10.49

    Total DOC Sector Cost$/trip 9206.0710815.5412425.02

    Total DOC Seat-Mile Costcent/seat-nm 12.27 14.42 16.57

    Use these results to validate your method

    EDXCW/PR/PB/20808A


    Results example coc doc pie charts

    Results - Example COC & DOC Pie charts

    Current

    Fuel = 2.50 $/USgal

    The Future?

    Fuel = 4.00 $/USgal

    Airline analysis: Use COC

    Design studies: Use DOC

    Historic

    Fuel = 1.00 $/USgal

    COC

    DOC

    Blue = Financial Costs Green = Maintenance CostsRed = Flight Costs

    EDXCW/PR/PB/20808A


    Sensitivity analysis trade studies

    Sensitivity Analysis - Trade Studies

    • Price Variability Studies

      • Both fuel price and MSP are fixed by market forces, not the manufacturer, soinvestigate theireffect on COC

    • Technical Trade Studies

      • As part of your sizing loops, investigate the effect of aircraft configuration change on DOC

        • Geometric parameters, i.e. Wing area, Wing span

        • Use of technology, i.e. CFRP vs. Metallic

      • For technical trade studies it is important to use a Cost + Profit method (i.e. price variant), rather than assumed aircraft price.

    EDXCW/PR/PB/20808A


    Low fare airline design project 2006 2007

    This document and all information contained herein is the sole property of AIRBUS UK LTD. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document shall not be reproduced or disclosed to a third party without the express written consent of AIRBUS UK LTD. This document and its content shall not be used for any purpose other than that for which it is supplied.

    The statements made herein do not constitute an offer. They are based on the mentioned assumptions and are expressed in good faith. Where the supporting grounds for these statements are not shown, AIRBUS UK LTD will be pleased to explain the basis thereof.

    EDXCW/PR/PB/20808A


    All new aircraft design

    All-New Aircraft Design

    • Moving directly from the idea to the product has caused problems

      • e.g. aircraft designed for too narrow a market…

    AZ 8 L

    Vickers VC10

    Convair CV990

    • Only permanent questioning of concepts ensures that no better concept has been left aside

    EDXCW/PR/PB/20808A


    Carpet plots

    Carpet Plots

    EDXCW/PR/PB/20808A


    A bluffer s guide to drawing carpet plots 1 3

    A bluffer’s guide to drawing carpet plots (1/3)

    Variable

    B

    Variable

    A

    • Arbitrarily label each locus on the carpet plot (i.e. A to I)

    C

    F

    B

    G

    E

    I

    A

    N

    H

    R

    D

    C

    Variable

    B

    G

    Variable

    A

    - The highest and lowest corners (C & G) are the highest and lowest values,

    P

    L

    C

    - from which the their curves (R & N, P & L) can be determined

    F

    B

    G

    D

    A

    E

    I

    A

    N

    H

    E

    B

    H

    R

    D

    - The rest of the curves and loci should now be fairly easy to map

    M

    I

    F

    C

    Q

    G

    Variable

    B

    Variable

    A

    P

    L

    A couple of thoughts:- A 3×3 carpet plot is only six curves on the same axes

    - The X-axis of a carpet plot is an arbitrary scale

    • On a piece of paper, roughly sketch what you want your carpet plot to look like – it doesn’t have to be accurate

    • Map your sketch to your table of results:

    EDXCW/PR/PB/20808A


    A bluffer s guide to drawing carpet plots 2 3

    A bluffer’s guide to drawing carpet plots (2/3)

    C

    F

    B

    E

    I

    A

    N

    H

    R

    D

    M

    Q

    G

    Variable

    B

    Variable

    A

    L

    P

    • The second curve in this set will be “slipped” along the X-axis by a constant delta. Tabulate the co-ordinates for this curve and plot it as a new data series on the same chart

    • The third curve in the set is slipped again by a delta proportional to the spacing between the 1st variables (R, Q & P are assumed to be linearly spaced in this example).

    • In Excel, tabulate the co-ordinates of the first curve you wish to plot, with an arbitrary X-scale proportional to the spacing between the 2nd variables (L, M & N are assumed to be linearly spaced in this example).

    Plot these in an “XY Scatter” chart

    Tip: It’s simplest to start with a curve on the left-hand side of the carpet

    EDXCW/PR/PB/20808A


    A bluffer s guide to drawing carpet plots 3 3

    A bluffer’s guide to drawing carpet plots (3/3)

    C

    F

    B

    E

    I

    A

    N

    H

    R

    D

    M

    Q

    G

    Variable

    B

    Variable

    A

    L

    P

    • The remaining curves can be tabulated and plotted in the same way

    • Format the chart as required.

      - You will need to manually add labels to identify the curves

      - Remove X-axis values as these are meaningless

    • The first curve of the second set of data is plotted in a similar way, but you need to determine where each curve intersects with the first set of curves and use the same X-ordinates

    First co-ord. of curve “P”

    First co-ord. of curve “Q”

    First co-ord. of curve “R”

    EDXCW/PR/PB/20808A


    Process performance

    Process & Performance

    • Use shared & common assumptions – discuss & agree.

    •Set up spreadsheets to facilitate quick turnaround of data – get the

    process right, otherwise you’ll waste time later in the multi iterations.

    •OAD Integration – Component level sizing loops are key: Excellent wing concept on a poor overall aircraft won’t work !

    •Focus on generating data that assists decision making - sensitivities

    4Initial ‘guesstimates’ on design weights (MTOW/ OWE/ Fuel/ PL).

    4Performance evaluation at key points in flight envelope to meet required P-R;

    –TOFL & BFL

    –First segment & second segment ROC requirements

    –ICA – Top of climb thrust available to give 300 fpm ROC margin

    –Fuel volume calcs for ‘assumed’ aero efficiency & weights

    •Don’t complicate the solution unless absolutely certain its needed.

    EDXCW/PR/PB/20808A


    Sensitivity analysis fuel a c price study

    Sensitivity Analysis - Fuel & A/C Price Study

    DOC

    4.0

    2.5

    70

    Fuel Price ($/USgal)

    60

    Aircraft Price ($M)

    1.0

    50

    Example Carpet Plot showing Relative Seat-Mile COC & DOC sensitivity

    COC

    COC

    4.0

    4.0

    2.5

    2.5

    Fuel Price ($/USgal)

    Fuel Price ($/USgal)

    1.0

    1.0

    70

    70

    60

    60

    50

    50

    Aircraft Price ($M)

    Aircraft Price ($M)

    Notes:1) A constant aircraft configuration is used for fuel & price sensitivity studies

    2) A constant aircraft configuration has a constant cost.

    Reducing price to meet a DOC target directly affects profits

    EDXCW/PR/PB/20808A


    Sensitivity analysis wg area vs span trades

    Sensitivity Analysis - Wg Area vs Span Trades

    Note: Importance of using cost in technical trade studies, not fixed price

    Varying Cost

    Fixed Price

    Configuration changes can have significant DOC effects

    EDXCW/PR/PB/20808A


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