Conceptual Design and Configuring Airplanes

Thoughts on the design process and innovation

John H. McMastersTechnical Fellow

The Boeing Companyjohn.h.mcmasters@boeing.com

and

Affiliate Professor

Department of Aeronautics and Astronautics

University of Washington

Seattle, WA

April 2007

Ed Wells Partnership Short Course

Based on: American Institute of Aeronautics and Astronautics (AIAA) & Sigma Xi Distinguished Lectures &

Von Kármán Institute for Fluid Dynamics Lecture Series: “Innovative Configurations for Future Civil Transports”, Brussels, Belgium June 6-10, 2005

Airplane Design: Past, Present and Future – An Early 21st Century Perspective

John McMastersTechnical Fellow

Ed Wells Partnership

The central of several purposes of this course is to examine the co-evolution of our industry, aeronautical technology, and airplane design practice in a broad historical context. Attention then focuses on speculations on possible future trends and development opportunities within an unconventionally broad and multi-disciplinary context. It may then be shown that while aeronautics may be a “maturing industry”, there are numerous opportunities for further advance in our ever-changing enterprise. The emphasis throughout will be concepts and ways of thinking about airplane design in a systems sense rather than on the details of the methodologies one might use in design. The material for this course is a continuing work in progress and represents the instructor’s personal, sometimes idiosyncratic perspective which is in no way intended to reflect an official position of The Boeing Company or its current product development strategy.

Course Objectives:• Provide familiarization to non-specialists on the topics to be discussed

• airplane design,• systems thinking, • the value of very broad multidisciplinary inquiry)

• Present airplane design and its evolution in a very broad historical context• Present one perspective on a general approach to airplane configuration synthesis at the conceptual level• Provide a basic aeronautics and airplane design “vocabulary”• Stimulate thought and imagination about the future of aeronautics

Target Audience: Anyone interested in airplanes and aeronautical technology in a very broad, multi-disciplinary system sense.

WARNING

ITAR and EAR ComplianceImportant Security Information:

Registration for this course (the following notes for which contain no ITAR/EAR-sensitive information) does not enforce the International Traffic in Arms Regulations (ITAR) and Export Administration Regulations (EAR) in any discussions that may result from it. Each attendee is responsible for complying with these regulations and all Boeing policies.

EAR/Compliance Home Site: http://policyplus.boeing.com/PS/PDF/DDD/PRO-2805.pdf

ITAR/Compliance Site: http://policyplus.boeing.com/PS/PDF/DDD/PRO-174.pdf

Notation and Symbols Used

A Area (ft.2, m2)a Speed of sound (ft./sec., m/s)AR Aspect ratio, b/č = b2/Sb Wing span (ft., m)č Average wing chord (ft.,m)CF Force coefficients (lift, drag, etc.) = F/qSCℓ Section (2D) lift coefficientCM Moment coefficient = M/qSĉCp Pressure coefficient = Δp/qD Drag force (lb., N)E Energy (Ft.-lbs., N-m)e “Oswald efficency factor”ew Wing span efficiency factor (= 1/kw )F Force (lift, drag, etc.) (lbs., N)H Total head (reservoir pressure)I Moment of inertiakw Wing span efficiency factor (= 1/ew)L Lift force (lb., N)ℓ Length (ft., m)M Mach number (V/a)M Mass (kg)M Moment (ft. lbs., N m)P Power (ft.-lbs./sec., N-m/sec.)p Static pressure (lbs./ft.2)

q Dynamic pressure (lbs./ft.2) = ½ρV2

R Range (mi., km)Rn Reynolds number (ρVℓ / μ)S Wing area (ft.2, m2)T Thrust (lb., N)T Temperature (oF)u Local x-direction velocity componentV Velocity, Speed (ft./sec., m/s, mph, km/h)v Local y-direction velocity componentw Downwash velocity (ft./sec., m/s)ż Sink rate (vertical velocity) (ft./sec., m/s)

Greek:α Angle of attack (deg.)Γ Circulationγ Climb or glide angle (deg., rad.)γ Ratio of specific heats in a fluidε Wing twist angle (deg.)θ Downwash angle (deg.)φ Velocity potentialΛ Wing sweep angle (deg.)μ Dynamic viscosityν Kinematic viscosity (μ/ρ)ρ Fluid mass density (kg/m3)

•Conceptual Design and Configuring Airplanes•Thoughts on the design process and innovation

Presentation Overview

Some VERY Basic Principles in Designing Airplanes

• Flying is ultimately about “defying gravity”, thus Weight is generally the dominant force in designing a good airplane (most of the time).

• Historically, the dominant factor in advancing airplane performance has been engine/propulsion technology [with structures/materials (and thus weight) and aerodynamics contributing the rest].

Newton quoth: F = d(mV)/dt To create a given aerodynamic or propulsive force, it’s much better to move a lot of air through

a small ΔV than a lesser amount through a bigger ΔV.

AerodynamicEfficiency(L/D)

Wing span 2/Total exposed area - ( b2 / Swet )

Wing Weight

Wing Span

But

A Classic Configuration Comparison(Modified from Torenbeek and Roskam who both got it serious wrong)

Evolution of the Boeing B-47

Boeing B-47 B

Avro “Vulcan” B.2

Max. Take-off Wt. MTOW (lbs.) 202,000 204,000Ref. Wing area S (ft.2 ) 1,428 3,965

Wetted Surface Area S wet (ft.2 ) 7,070 ~ 9,600Wing Span b (ft.) 116 111Aspect Ratio AR (= b2/S) 9.42 3.1 Max. Wing Loading W/S @TO (lb./ft.2 ) 141.5 51.5Max. Span Loading W/b @TO (lbs./ft.) 1741 1834

Boeing B-47 Avro Vulcan

Max. Lift/Drag Ratio L/D max ~ 18.1 ~ 16.8

Velocity-Load Factor [V-n] Diagrams

Load Factorn = L / W

Load Factor (n) = Lift (L) / Weight (W)

0

+

-

Velocity - V

Vmin ≈ Vstall

Vdive maxVcruise max

Vertical Gust Loads

Max. Maneuver Load [ L = ½ρ V2CLmax S]

Design and Gust Load conditions per appropriate Regulations (e.g. FARs)

Wing Weight Estimation(based on simple beam theory)

W = U + Wwing

U = weight of everything but the wing

Wing span (b)

Lift (L) 2L 2

Load factor = n = L W

Total Weight = W ~ U + C[ n U b AR (c/t) ] Є

Modes of Failure (static or dynamic):• Bending strength• Bending deflection • Torsional strength• Torsional deflection • Buckling• Flutter (either in bending or torsion)

Chord ( c )

Thickness (t)

AR = b2/S = b / c avg

Trying for the “Ideal” Swept Wingfor a Long-Range Cruising Airplane

Perspectives in Cruise Wing Design

Aerodynamics:• Provide lift required with minimum surface area• Minimum drag at design condition(s)• Acceptable stability and control characteristics (no “Mach tuck”, pitch-up, etc.)• Compatible with high-lift (take-off and landing) requirements

Structures & Manufacturing• Adequate thickness (everywhere)• Increasing span is going to cost you• Mostly straight lines and no compound curves (except maybe parts that can be made of plastic)

Other Folks (Propulsion, Systems, etc.)• Good “rack” for hanging engines from, etc.• Adequate fuel volume• Room for all the actuators and other systems (e.g. the landing gear)

Management• Minimum cost• Marketable (looks good, etc.)• NOT a subject of endless trade-studies Wing span (b)

(compatible with terminal gate limits)

Λc/4

Constant shock sweep

“Yehudi”

Straightisobars

Tip raked to avoid local “unsweep” effects

Leading edge glove to minimize “root effects” or allow greater local thickness

• Actual wing “length” is different than the wing span (b). [Length (L) = b sec Λc/4 ]

• Defining the “aerodynamically effective” area of this wing is problematical

Area Ruling the Convair F-102

F-102 Before Area Ruling F-102 After Area Ruling

Convair F-106

Junkers patent drawing March 1944

Junkers Ju 287 circa 1944

Heinkel P. 1068 circa 1944

Heinkel P. 1073 circa 1944

Heinrich Hertel1902-1982

Subsonic Area Ruling

Otto Frenzl + Heinrich Hertel

Transonic Area Ruling

Boeing “7X7” circa 1972Mcruise ≈ 0.96

Boeing studycirca 1995

Mcruise = 0.95

Martin XB-51

Blackburn “Buccaneer”

Transonic Tailoring and Kϋchemann “Carrots”

Shockwaves

Convair CV 990

Horizontal tail staggered relative to vertical tail

Kϋchemann “carrots” orWhitcomb“speed bumps”

Oblique Wing (“ideal” area ruling )

Tupolev Tu 20 “Bear”

Sonic Booms and Their Amelioration(Toward a viable supersonic business jet –SSBJ ?)

Ground footprint of sonic boom

ΔP - Classic N-wave sonic boom signature

NASA modified F-5E for sonic boom reduction

SSBJ concepts

ModifiedN-wave

Bow shock wave

Tail wave

A Summary of Early Progress in Airplane Technology

1900 1910 1920 1930 1940 1950 1960

Supersonic flight

Swept wing

Jet engines

Coanda “ducted fan”

Aluminum airplane (Junkers)

DeHaviland “Comet”

Pressurization

Modern air transportation

• Streamlining• Retractable landing gear• High-lift devices

Aerodynamics

Propulsion

Materials &Structures

Systems

Wood, Steel,Fabric

Biplanes tomonoplanes

DigitalMicro-process

Airplanes prove their utility in WW 1

Boeing B-47

Communications & Navigation AidsParachutes & Safety Systems

Internal combustionEngines

Radar

Future Large “Airplane” Development Opportunities

Civil• Future design must be increasingly efficient, quite, safe, and cost effective.

Military• The B-52 has been operational for 50 years. • Will the B-1 & B-2 remain viable for similar time periods? UCAV replacements??• Global range logistics will remain a key element in future US foreign policy and peace-keeping.

Aerospace• All “airplanes” must take off and land. Even hypersonic vehicles must be designed for “low-speed” operations.

Non-Traditional• To meet future transportation system needs, new technologies my be exploitable in the 21st century. 1960 1980 2000 2020 2040

707

727

DC-8 737 757

767747

DC-9DC-10

777

737-NG

B-52

B-2

B-1

C-141 C-5

C-17

NASPX-20DynaSoar

SpaceShuttle

X-34/X-43 Aerospace Planes ?

Future Logistics Requirements [ Military and Civil ]

Future Strategic Strike/Recon. Requirements?

Ground Transport (Trains, Maglevs, etc.)

Surface Effect Vehicles

Lighter-Than-Air ?

SST ?

737/A320 Replacements

Airbus A 380

BlendedWing-Body

787

Year

[Airplane] Design Technology Progress

1900 1950 2000

ActualAchievement

Possible Achievement

Historical Time

“Cut & Try”• Heavy on experimentation• Very limited theory• Heavy on rules of thumb• Limited material choice

“Analysis & Testing”• Heavy reliance on testing• Handbooks methods important• Early computational capability• Widening gap between engineering & manufacturing

“Computation & Validation”• Massive simulation capability• Testing shifts to validation•“Integrated Product Teams”• “Lean” concepts

?

Progress

WW 2 Berlin Wall

Faster, Farther, Higher Quicker, Better, Cheaper

Issues & Constraints• Cost/profit uber alles• Geopolitical uncertainties• Environmental concerns• Critical resources availability• Lawyers (regulations, litigation, etc.)

• All the “-ilities” (old and new) (reliability, maintainability, etc., etc.)

• Customer needs and wants

Evolution of Airplane Development Process

In the beginning (to ~1950)

Identify aneed or

opportunity

“Small” groupof engineers

develop adesign

Skilledcraftsmen

build itDrawingsReqmts.

Test Customer

Prototype(Production )

Ordersyes

Oblivion

no

Potential customer(s)

Evolution of Airplane Development Process

Maturing phase (~1950 - 1985)

Need orOpportunity

EngineersDesign

Build

Drawings

Reqmts.

Test Customer

Prototype(Production )

Orders yes

Oblivion

no

• Strong link between customer, marketing and requirements• Regulations, standards., etc.

• Large organization• Functional separation

Engineering Manufacturing• Large organization• Functional separation

Drawings• Exhaustive testing• Limited prototyping

Lots of paper and bureaucracy

Launchorders

Yes

No

Evolution of Airplane Development Process

In the beginning (to ~1950)

Need orOpportunity

Engineers

DesignBuild

DrawingsReqmts.

Test Customer

Orders ?yes

Oblivion

no

Modern era (post 1990)

• “Customer In”• Lots and lots of lawyers

Engineering & Manufacturing• Large organizations• Integrated Product Teams (IPTs)

• Up the “value chain”• No more paper drawings• No more shims• “Flat(er) organizations”

Acquire “Defineproduce” Support

Customer

Outsourcing

What Happens When You Let Electrical Engineers Design Airplanes

Lockheed Martin F-117

Evolution of the Airplane Development Process

One Possible Option for Our [Immediate] Future

Modern era (post 20XX) ?

AcquireOrders “Defineassemble” Support

Customer

Outsourcing/Risk Sharing

Requirements

Manufacturing Engineering

TestDeliver

Quicker, Better, Cheaper ?

Large-Scale System Integration Supplier management

Changing Times in Aerospace

Original Mantra (1903-1990):

Faster, farther, higher (and safer).

Post Cold War Mantra (1990-2000):

Quicker (to market), better, cheaper (and safer).

Emerging New Mantra (2001 - ?)

Safer, better, faster, higher, farther, cheaper, quicker, quieter, cleaner, etc..

Or: “Leaner, meaner, greener (and safer)” ?