conceptual design and configuring airplanes thoughts on the design process and innovation john h....
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Conceptual Design and Configuring Airplanes
Thoughts on the design process and innovation
John H. McMastersTechnical Fellow
The Boeing [email protected]
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
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
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)” ?