Low Fare Airline – Design Project 2006-2007

EDXCW/PR/PB/20808A

Low Fare Airline – Design Project 2006-2007

University of Southampton

3rd November 2006

P Bradshaw

Skill Group Leader

Airbus Future Projects

EDXCW/PR/PB/20808A© A

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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.


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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 HD1800nm and 3000nm versions


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Based on current and emerging technology and materials

Novel configurations are not excluded

Realistic approach to technology and risk

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.


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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 ?


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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


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What are Customers’ Needs ?

• Future concept selection will be chosen to fulfill the requirements to be met…………

Range

Payload

Noise

Safety

Operating cost – (Profit for airlines !)

Manufacturing Cost (Profit for us !)

•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 ??

Reliable etc etc etc (OI, MMEL)

Cheap to maintain (DMC)


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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:1. 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.2. 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

3. Communicate• Share information early – decide what’s improtant/ what isn’t• Single failure=Collective failure


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General Tips – Some Do’s and Don’ts

• Understand the question:Differentiate between the “hard” and “soft” requirements Identify key driversAssess the ‘cost’ of each requirementChallenge 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.


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• 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....).


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Always reference your design against a known solutionSanity checkCalibration

• 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 !


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• Ensure you draw, maintain and use a GA of the aircraftGives design change traceabilityAssists in understanding of scale & ‘fit’ Unique definition of the configuration and geometry


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• 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 appropriateAlways ‘sanity check’ results – does it look/ feel right ?

"Tools don't design aircraft, engineers do”


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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 workingGood project management Good control of the project design

• Make your points as clearly as you can – peer review your chapters before submission.


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The Question

• Requirements drive the solution

• Payload and Range define some major aircraft parameterse.g. 150 pax / 3000nm

• These will form a significant part of the design drivers

Payload

Range

Max Payload Limit

MTOW Limit

Fuel Volume Limit

Fuel Volume Margin

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


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Design Process

• Design is iterativeYou can’t unpick the ends to untie the knotYou can’t work out a solution from the question in a straight

line

• ‘Cut the Gordian Knot’Choose a conceptAnalyse itAssess itChange itStart again…


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Performance & CostPerformance & Cost

Refine Config

Configuration: Size, Position ...

OK?

Design Weights,Engine Size, CLmax,

YesNo

Space Allocation(Fuel Volume, LG, Hi-Lift...)

Component Weights Aerodynamics

‘Actual’ V ‘Targets’(Wing area, MTOW, ..)

Initial Cardinal Geometry

Minimise Cost

The Iterative Design Process

Component Weights Aerodynamics


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Example of Simplified Calculation

• Take-Off Field Performance

Weight

T/O

ff D

ist.

Wing Area or Thrust

Parametric No (P)

T/O

ff D

ist.

Take-Off Dist = aP + b


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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


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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)


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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)


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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)


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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)


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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 etcDoors (based on highest density layout)

• Layout cabin to determine length (and iterate)

• Add nose and tail (length based on scaling of existing aircraft)


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ent. 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

Door distribution requirements

chart 25


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due to certification requirements emergency slide function

min. door spacing= 4.5m

spacing to engines

spacing to flaps

EDXCW/PR/PB/20808A

Door distribution requirements


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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


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LG continued

• Ensure wing & LG integration with rest of aircraft;NLG impact on high speed landing (A/C attitude too nose down

on touchdown?) – resolve through body setting angle or more

powerful high lift devices ? Tail tip on loading – MLG too far forward.

Wing (& MLG) too far aft – rotation @ T/O may be difficult.Longitudinal constraints: Tail-scrape on rotation (LG length

or longitudinal position/ rear fuselage shape/ ‘Power’ of High

Lift Devices) Lateral constraints: x-wind landing, turnover angle theta < 30

degrees typically

Position NLG & MLG to retain at least 5% MTOW over NLG in static

balance about CG, to ensure steering feasibility.


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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?


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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 = 50mmBelly fairing thickness = 100mmNose bay skin thickness = 100mm


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Results in an Envelope for LG Fairing Sizing

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

Tyre clearance illustration for stowed

Main Gear.


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Section through stowed leg in wing

Wing surfaces


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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;


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Landing gear layout

“equivalent single wheel load”to estimate impact on ground surfaceby scaling of pavement test results(number, size , pressure & spacing)

load per wheel under nominal and special conditionsto be less than tire’s allowables(number, size & ply rating)

retraction into compact landing gear bayincluding free-fall capability(number, size & spacing)

attachment to wing & fuselageto guide static and braking loads(available space between spars & flaps)

volume for brake discsinside wheel(number & size)


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maximum “ground pressure”

20-3

0t p

er w

heel

Landing gear characteristics

Number and size of wheels driven by max gross weight and ground impact requirement

0

4

8

12

16

20

0 100 200 300 400 500 600

number of wheels

MTOW [t]

0

10

20

30

40

50

0 100 200 300 400 500 600

load / wheel / diameter / width

MTOW [t]


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Powerplant Positioning & Integration

Powerplant position:

–+/ - 5 degree disc burst cones for fuel tank boundaries and feeds to

Engine.

–MLG longitudinal position on NLG collapse to ensure engine clearance.

– Gulled wing ? (local increase in dihedral at root)


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Engine installation constraints

Safety requirements bound optimisation window

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

Toe-in1.7°

Door 7 slide2.0 m

17.5°Door 7

position

5°3°

110mm margin


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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


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Wing Sizing

• Develop understanding of component level sizing & links

to OAD;

•Wing planform versus drag & economics;

TR, Span, t/c, S – which gives the best multidisciplinary balance ?

Span versus Area

Sweep versus t/c

TR versus CoP

Check fuel volume requirement is met in wing.

Value of Weight versus Drag for Economics terms – Which most influences ?

Is aero benefit of elliptical lift distribution more powerful than BM relief due to

more inboard position of CoP ?


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Wing Area Selection

constant AR

Minimum Area for capability and growth potential

• 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


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Aspect Ratio (AR) Definition

Balance between aerodynamic performance and wing weight depends on aircraft requirements (range etc.)

• More fuel volume• Better engine & gear installation• Lower wing weight:

Wwing = fn(span3)

• Possibly tip stall problems• Quieter aircraft • Improved aerodynamic performance:

Induced drag = fn(span –2)

constant wing area


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Sweep Angle Selection

Balance between high speed and low speed performance

• Improved low speed performance• Lower wing weight

• Improved high speed performance• Easier engine segregation• Easier gear installation

constant wing area and AR


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Spanwise Lift Distribution

Optimum depends on the requirements –Range in particular

Elliptical

• Minimum induced drag

Triangular

• Higher induced drag• Lower wing weight


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Span vs Area vs Block Fuel

Span and Area TradesMission Efficiency

-6

-4

-2

0

2

4

6

DO

CM

Blo

ck F

uel

Ch

ang

e[%

]

-15

-10

-5

0

5

10

15

AreaSpan

Baseline33.4m

38.7m125m

2

145m2

Fuel limit boundary 3500nm

Design Mission (500 nm)

Vapp limit

const. AR

TTC limit


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Weight and Drag Balance

Minimising Operating Cost means balancing weight and drag benefits

0.98

0.99

1.00

1.01

1.02

D.O

.C.

[Ra

ng

e =

60

00

nm

]

0.98

0.99

1.00

1.01

1.02

drag

MWE

datum

+5dc

-5dc

datum

-1t

-2t

+2t

+1t


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Span vs Area vs DOC/ Weight

Span and Area TradesWeight

-10

-5

0

5

10

15

Win

g W

eig

ht

Ch

ang

e

[%]

Span

Area

Baseline

33.4m

38.7m

125m2

145m2

wing weight for iso Vapp

Span and Area TradesOperator Cost

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

ED

P C

han

ge

[%]

-4

-2

0

2

4

6

Area

Span

Baseline

33.4m

38.7m

125m2

145m2

CoC

Design Mission (500 nm)

Fuel Price assumened at 0.7 $/Gal

Other key trades include:

•DOC vs A/C price vs Fuel price

•Fuel margin vs Area vs Span

•Aircraft Price vs Area vs Span


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Requirements for High Lift Devices

Vapproach = 1.23 x Vs1g + 5 kts

CLapproach = f(CLmax)

Clmax limit

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

CL

Alpha

CL0

Overspeed cases –

Alpha min

Max Alpha case - Tailscarape

TailstrikeNLG First Impact


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Useable Rotation Angle – Take-off & Landing

• For landing, the compressed main gear is a usefulde-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


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Trailing Edge:

Leading Edge:

Split Flap Plain Flap Single Slotted double Slotted Triple Slotted

Plain Slat Krueger Hinged

Improved Aerodynamics

Increased Weight, Cost, Maintenance

Different Ways to Meet LS Targets


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Trailing Edge - Three principle mechanism types:

4-Bar Link

Medium weightMedium costGood deploymentGood lap & gap control

Selection is a balance of all characteristics at the aircraft level

Drop-hinge (pure rotation)

Low weightLow costLimited deploymentPoor lap & gap

Track & Lever

Heavier weightHigher costExcellent deployment Excellent lap & gap control

Actuation Mechanism


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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 weightRibs & Spars approx 25% wing weightFLE & Movables approx 5% - 10%FTE & Movables approx 15% - 20%

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

Turbine blades: +/- 15ºCompressor blades:

– 1/3rd of a disk; +/ - 3 º

– Intermediate fragment; +/ - 5 º


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• Fuel Volume AvailabilityGross volume - Outside skin lineNett Volume – What is available to useRemember: 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.

Some Sanity Checks - 2


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Economics


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Why we’re Producing Aircraft ?

Consider economics throughout, not just as a result

Making moneyis the reason why mostcompanies are in the aerospace industry

Operating Costsare an important criterion

used by airlines when choosing new aircraft

Operating Costmethods give engineersa useful multi-disciplinary

assessment tool in thesizing process


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Low Cost Operator TAT (Hub vs. Destination)

Data for many different airports and airlines available for analysis

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


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

Total Operating Cost (TOC)

Indirect Operating Cost (IOC)•Ground Property & Equipment

Depreciation & Maintenance

•Administration & Sales Servicing administrationReservations & salesAdvertising & publicityGeneral

•ServicingPassenger servicesAircraft servicesTraffic services

Direct Operating Cost (DOC)• Financial Costs

DepreciationInterestInsurance

Cash Operating Cost (COC)• Flying Costs

FuelLanding feesCockpit crewCabin crewNavigation charges

• Maintenance CostsAirframeEngines

Dependent on aircraft design Dependent on airline operations


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• Indirect Operating Costs (IOC):Airline infrastructure costs

Highly airline dependent – No reliable quantitative method

• Calculate COC for “airline” a/c comparisons

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

• Calculate DOC for technical trade studies• Assess IOC issues qualitatively


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AEA Method - Inputs, Assumptions & Results

Inputs• Mission data:

Stage Length (nm) Block Fuel [BF] (lb) Block Time [BT] (hr) Passengers [Pax]

• Weight data: MTOW (t) MWE (t) Engine Weight (t)

• Engine parameters: Number of Engines [NE] SLST [T] (t) Bypass Ratio [BPR] Overall Pressure Ratio [OPR] No. of compressor stages [NC]

• Price data: Engine Price [ENP] ($) Manufacturers Study Price [MSP] ($) Airframe Cost [AFC] ($) Fuel Price ($/USgal)

Fuel Density = 6.7 lb/USgal Labour Rate [R] = 66 $/hr

Assumptions Results

COC

DOC

• Financial Costs: Depreciation [DEP] Interest [INT] Insurance [INS]

• Maintenance Costs: Airframe Maintenance

[AMC] Engine Maintenance

[EMC]

• Flight Costs: Cockpit Crew [CPC] Cabin Crew [CAC] Navigation Charges [NAV] Landing Fees [LAF] Fuel [FUE]

(All costs calculated as $/trip)

AEA DOC Method


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The Study mission is not the same as the Design mission

AEA Method - Study Mission (COC & DOC)

For DOC, use Study Mission with Standard Payload

Design Mission (nm) Aircraft Category Study Mission (nm)

Range <= 3000 Short Range 500

3000 < Range <= 5000 Medium Range 1000

5000 < Range <= 7000 Long Range 3000

Range > 7000 Very Long Range 4000

Use the values from the following table:

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

• 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.


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AEA Method - Utilisation (DOC)

Increased utilisation = More trips = More fares =

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

Study Mission (nm)

Available Hours per Year (hours)

Turn Around Time (hours)

Range < 1000 4000 0.5 1000 <= Range <= 2000 5100 1.4

Range > 2000 6500 3.0

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)


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= 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])

AEA Method - Total Investment (DOC)

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


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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


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AEA Method - Crew Costs (COC & DOC)

= 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 memberFor 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

Total Crew Costs = Cost of current and reserve crews


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AEA Method - AF Maintenance Costs (COC & DOC)

Airframe Maintenance Costs [AMC]

= Airframe Labour

= R250t6808075AFW

35076AFW090

.....

+ 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)


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AEA Method - Eng Maintenance Costs (COC & DOC)

Engine Maintenance Costs [EMC]The method depends on the engine type:

Turbojet or Turbofan Contra-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 BPR0.2 A = 8.5 × (N / 3 × P + 28)0.5 + 0.9C2 = 0.4 × (OPR / 20)1.3 + 0.4 B = (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 Ratio N= Take Off SHP×10-3

NC = No. of Compressor Stages OPR = Overall Pressure Ratio D= Prop Diameter (m)tƒ = Flight time = Block time - 0.25 (hrs) P = No. of Propeller Blades


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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)

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

• 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)

Historic price~1 $/USgal

Current price>2 $/USgal


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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)

Price is not the same as Cost

• The Price is what the airline is willing to pay for the aircraftMarket 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.


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Cost Estimation - Price Prediction

• The Price is what airlines are willing to pay for the aircraftPrice 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 be estimated by statistical assessment of a/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


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Price - List vs. Discounted

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

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

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

... 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.

In addition, the deal retroactively applies the newest, biggest discounts

to 89 previously ordered jets that Boeing hasn't yet delivered

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

Discounts are unpredictable – Always use list price

... already discounted between 17 and 27 percent from the public list price of

$61.5 million to $69.5 million...

Boeing jet prices glimpsed in dealHow 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.


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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:

Aircraft cost is determined by the aircraft design

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 = (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


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• 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 yearsTests: Wind tunnel test program, Materials & structures testsJig and tooling costsStatic & fatigue test airframesFlight 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

Cost Estimation - NRC Prediction


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Results - Example COC & DOC Input Data

Example Design Project

Airframe Price $M 48.0 ?Engine Price (per engine) $M 6.0 ?Fuel Price $/USGal variable variableLabour rate $/hr 66 66

SPP Passengers 150 ?Stage Length (Study Mission) nm 500 ?Block Fuel lbs 7189 ?Block Time hrs 1.602 ?

MTOW T 75.5 ?MWE T 38.0 ?Engine Weight T 3.5 ?

Number of Engines 2 ?Sea Level Static Thrust klb 26500 ?Take-Off Shaft horsepower SHP×10-3 n/a ?BPR 4.75 ?Propeller Diameter m n/a ?Propeller blades n/a ?Compressor Stages 14 ?OPR 27.4 ?


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Results - Example COC & DOC Results

Fuel Price $/USgal 1.0 2.5 4.0

Financial CostsDepreciation $/trip 2567.44 2567.44 2567.44Interest $/trip 1797.21 1797.21 1797.21Insurance $/trip 189.18 189.18 189.18

Maintenance CostsAirframe Maintenance $/trip 1046.58 1046.58 1046.58Engine Maintenance $/trip 421.36 421.36 421.36

Flight CostsCockpit Crew $/trip 608.76 608.76 608.76Cabin Crew $/trip 480.60 480.60 480.60Navigation Charges $/trip 568.94 568.94 568.94Landing Fees $/trip 453.00 453.00 453.00Fuel $/trip 1072.99 2686.46 4291.94

Total COC Sector Cost $/trip 4652.23 6261.71 7871.19Total COC Seat-Mile Costs cent/seat-nm 6.20 8.35 10.49

Total DOC Sector Cost $/trip 9206.07 10815.54 12425.02Total DOC Seat-Mile Cost cent/seat-nm 12.27 14.42 16.57

Use these results to validate your method


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Blue = Financial Costs Green = Maintenance Costs Red = Flight Costs

Results - Example COC & DOC Pie charts

HistoricFuel = 1.00 $/USgal

Airframe maintenance22%

Engine maintenance9%

Cockpit crew13%

Cabin crew10%

Navigation charges12%

Landing fees10%

Fuel24%

Depreciation27%

Interest20%

Insurance2%



Cockpit crew7%

Cabin crew5%


Landing fees5%

Fuel12%

CurrentFuel = 2.50 $/USgal



Cockpit crew10%

Cabin crew8%


Landing fees7%

Fuel42%

Depreciation24%

Interest17%

Insurance2%

Airframe maintenance10%Engine maintenance

4%

Cockpit crew6%

Cabin crew4%


Landing fees4%

Fuel24%

The Future?Fuel = 4.00 $/USgal



Cockpit crew8%

Cabin crew6%


Landing fees6%

Fuel55%

Depreciation21%

Interest14%

Insurance2%



Cockpit crew5%

Cabin crew4%


Landing fees4%

Fuel34%

COC

DOC

Airline analysis: Use COC Design studies: Use DOC


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Sensitivity Analysis - Trade Studies

• Price Variability StudiesBoth fuel price and MSP are fixed by market forces, not the

manufacturer, so investigate their effect on COC

• Technical Trade StudiesAs 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. MetallicFor technical trade studies it is important to use a Cost + Profit

method (i.e. price variant), rather than assumed aircraft price.


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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.


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All-New Aircraft Design

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

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

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

AZ 8 L

Convair CV990

Vickers VC10


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Carpet Plots


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

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

A

VariableB

Variable A

P Q R

Variable

B

L 0.9 1.7 2.5

M 1.9 2.7 3.5

N 2.9 3.7 4.5

Variable A

P Q R

Variable

B

L 0.9 1.7 2.5

M 1.9 2.7 3.5

N 2.9 3.7 4.5

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

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

VariableA

VariableB

A

B

D

E

F

G

H

I

C

G

C

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

G

CI

H

D

E

F

A

B

VariableA

VariableB

A

B

C

D

E

F

G

H

I

P

R

L

N

QM- The rest of the curves

and loci should now be fairly easy to map

P

R

L

N

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

3) Map your sketch to your table of results:

Variable A

P Q R

VariableB

L 0.9 1.7 2.5

M 1.9 2.7 3.5

N 2.9 3.7 4.5


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Plot these in an “XY Scatter” chart

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4

Variable A = R

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4 5

Variable A = R

Variable A = Q

5) 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

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4 5 6

Variable A = R

Variable A = Q

Variable A = P

6) 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).

4) 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).

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

VariableA

VariableB

A

B

C

D

E

F

G

H

I

P

R

L

N

Q M

Variable A

P Q R

VariableB

L 0.9 1.7 2.5

M 1.9 2.7 3.5

N 2.9 3.7 4.5


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7) 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

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4 5 6

Variable A = R

Variable A = Q

Variable A = P

Variable B = L

First co-ord. of curve “P”

First co-ord. of curve “Q”

First co-ord. of curve “R”

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

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4 5 6

Variable A = R

Variable A = Q

Variable A = P

Variable B = L

Variable B = M

Variable B = N

Trade Study showing the effect of varying "A" and "B"

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4

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Variable "B"

R

Q

P L

M

N

Variable "A"

9) Format the chart as required.

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

- Remove X-axis values as these are meaningless

Variable A

P Q R

VariableB

L 0.9 1.7 2.5

M 1.9 2.7 3.5

N 2.9 3.7 4.5VariableA

VariableB

A

B

C

D

E

F

G

H

I

P

R

L

N

Q M


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Process & Performance

• Use shared & common assumptions – discuss & agree.

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

•Set up spreadsheets to facilitate quick turnaround of data – get the process right, otherwise you’ll waste time later in the multi iterations.

•Focus on generating data that assists decision making - sensitivities

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

Performance 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.


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Co

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(%)

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Co

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(%)

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4.0

1.0

70

Aircraft Price ($M)

Fuel Price ($/USgal)

2.5

DOC

Sensitivity Analysis - Fuel & A/C Price Study

Reducing price to meet a DOC target directly affects profits

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

6050

4.0

1.0 70

Aircraft Price ($M)


Notes: 1) A constant aircraft configuration is used for fuel & price sensitivity studies2) A constant aircraft configuration has a constant cost.

2.5

COC

6050

4.0

1.0 70

Aircraft Price ($M)


2.5

COC


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Sensitivity Analysis - Wg Area vs Span Trades

Fixed Price

Varying Cost

Configuration changes can have significant DOC effects

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

Low Fare Airline – Design Project 2006-2007

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Transcript of Low Fare Airline – Design Project 2006-2007