Case Study - very large transport airplane

Airplane Design: Past, Present and Future – An Early 21 st Century Perspective John H. McMasters Technical Fellow The Boeing Company [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

Notation and Symbols Used A Area (ft.

2 , m 2 ) a Speed of sound (ft./sec., m/s) AR Aspect ratio, b/ č = b 2 /S b č Wing span (ft., m) Average wing chord (ft.,m) C F Force coefficients (lift, drag, etc.) = F/qS C ℓ C M Section (2D) lift coefficient Moment coefficient = M/qSĉ C p Pressure coefficient = D Drag force (lb., N) Δp/q E Energy (Ft.-lbs., N-m) e “Oswald efficency factor” e w Wing span efficiency factor (= 1/k w ) F Force (lift, drag, etc.) (lbs., N) H Total head (reservoir pressure) I Moment of inertia k w Wing span efficiency factor (= 1/e w ) 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 ) = ½ρV 2 R Range (mi., km) Rn Reynolds number ( ρVℓ / μ) S Wing area (ft.

2 , m 2 ) T Thrust (lb., N) T Temperature ( o F) u Local x-direction velocity component V Velocity, Speed (ft./sec., m/s, mph, km/h) v Local y-direction velocity component w Downwash velocity (ft./sec., m/s) ż Sink rate (vertical velocity) (ft./sec., m/s) θ φ Λ μ ν γ γ ε Greek: α Angle of attack (deg.) Γ Circulation Climb or glide angle (deg., rad.) Ratio of specific heats in a fluid Wing twist angle (deg.) ρ Downwash angle (deg.) Velocity potential Wing sweep angle (deg.) Dynamic viscosity Kinematic viscosity ( μ/ρ) Fluid mass density (kg/m 3 )

Presentation Overview

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Case Studies II. “Very large” transport airplanes (A380s, flying wings and C-wings)

Case II. The “Big Airplane” Problem

Antonov An 225 “Mriya” Wing Span: 290 ft. (88.4 m) MTOW: 1,322,750 lb. (600,000 kg) Six 51,590 lb. ST (23,400 kgp) Lotarev D-18T turbofans

Boeing Product Development Opportunities

(circa 1990) In Production Development or Study

Typical Marketing “Range-Payload” Diagram

(Market Niches –Product Development Opportunities – circa 1985-90)

NLA 777 Seats 7J7 Range (nmi.)

Air Traffic Growth and Aircraft Arrival/Departure Data for Kennedy International Airport (to circa 1995) Passengers Per Year (millions) Aircraft Aircraft Per Year (thousands) Passengers 15 85 10 70 5 0 1960 Advent of Wide-Body Transports (B 747, DC-10, L 1011, etc.) 1970 1980 Year 1990 55 40 2000

Wake Vortex Separation Standards

Heavy (H) Airplanes over 300,00 lb. max. certified take-off weight (MCTOW) (e.g. B777, B767, B747, MD 11) Medium (M) Airplanes with MCTOW between 15,400 and 300,000 lbs.

Light (L) Airplanes with MCTOW less than 15,400 lbs.

Radar Separation: Time Separation: Heavy behind Heavy 4 n. mi. Medium behind Heavy 2 min.

Medium behind Heavy 5 n. mi. Light behind Heavy 3 min.

Light behind A380 Light behind Heavy Light behind Medium 10 n. mi.

6 n. mi.

5 n. mi.

“Square-Cube Law” Trends in Size & DOC (Conventional “Tube and Wing” Configurations) Passengers ~ 600 Passengers

Thanks to Ilan kroo

Classic Configuration Evolution

600+ passengers ~140 passengers Super 747 (NLA) 707-120 Too long to fit in terminal gates, so..

7?7 (NLA) 747-400 ~ 425 passengers

Outboard engines at wing tip stations of a 747

Airbus A380 Jumbo Jumbo-Jet

Goodyear

Jumbo 600 Passenger Subsonic Transport (circa 1992) Configuration Issues:

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Runway limits Taxiway limits Terminal gate limits Emergency evacuation Community noise Wake vortices Wing skin size limits Ditching/flotation Passenger comfort Must fit within a 80 m box

Airbus A380 in a Cross Wind

Northrop B-49 bomber (circa 1948-49) Northrop Grumman B-2

Early Attempts to Solve the “Large [600+ Passenger] Transport Airplane Problem” An Early Version of the Liebeck Blended Wing-Body Subsonic Transport McMasters/Boeing Conceptual “747 XXL” circa 1992 Wing Spans b ≈ 300 ft.

Griffith airfoil

From the desk of J. H. McMasters, 1992

C P -

The Griffith Airfoil

(circa 1944) Favorable gradient for laminar flow Pressure recovery (turbulent flow) ć 0 c t Conventional airfoil (chord ć ) + 1 Suction slot Griffith airfoil (chord c ) Transonic Griffith airfoil

A Suite of Drag Reducing Wing Tip Devices

A Flawed (and Clumsy) Attempt to Emulate Nature http://www.winggrid.ch/index.htm

A Family of Non-Planar Wing Configurations Constant wing span (b), area (S) and height-to-span ratio [ h/b=0.2 ] Total Drag (D) = Dviscous + Dinduced [+ Dcompressibility ] D viscous ~ S wet V 2 f(C L ) Induced Drag (drag due to lift) = Di ~ k w [Lift (L)/span (b)] 2 x speed (V) 2 ~ k w [W/b] 2 h k w = theoretical wing span efficiency factor b = 1/e w Biplane k w = 0.74

In steady, level flight, Lift (L) = Weight (W) Joined wing k w = 0.95

X-wing k w = 0.75

C-Wing k w = 0.69

Branched tips k w (“pfeathers”) = 0.76

Tip plated winglets k w = 0.83

Tip plates k w = 0.72

Winglets k w = 0.71

Dihedral k w = 0.97

Box biplane k w = 0.68

Note: For an optimally loaded planar wing of the same span and area k w = 1.0

Aspect ratio = b 2 Treffetz plane analyses due to Prof. Ilan Kroo, Stanford University (circa 1992).

S

Non-Planar Wing Span Loads

L/ 2 Planar Wing L/ 2 L/ 2 Winglets L/ 2 L 1 C-Wing L/ 2 L 2 L 1 b/ 2 h b/ 2 L/ 2 + L 2 L 1 L 1 L 2 h Winglet-let

A Possible [Slightly Grotesque] C-Wing Large Transport Airplane Configuration Baseline Baseline Configuration

From the desk of J.H. McMasters, 1994

600+ Passenger C-Wing Transport Configuration (Semi-Span Loader, Quasi-Three-Surface Airplanes)

Boeing configuration patent granted 1996 .

McMasters, J.H. and Kroo, I. M., “Advanced Configurations for Very Large Subsonic Transport Airplanes”, NASA CR 198351, Oct. 1996; also

Aircraft Design

, Vol. 1, No. 4, 1998, pp. 217-242.

Layout of Passenger Accommodations (LOPA) for a Single Deck, 3-Class, 600 Passenger C-Wing Transport

Size Comparison for a Conventional and C-Wing 600 Passenger Transport Airplane

Some Configuration Options For

Very

Large Commercial Transport Airplanes “Transonic Seagull” “Winged Watermelon” (“Flying Spud”) “Klingon Battle Cruiser” 2 or more “small” airplanes In formation ?

A “Smart” C-Wing BWB ?

Smart Wings

Analogies Pterosaur Airplane

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Brain Nerves Computer Fiber optic strain gages, pressure

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sensors Bone and tissue Composite materials Variable geometry Electro-mechanical control via large control of large and small muscles and small aerodynamic devices distributed over wing trailing edge Ultra light weight structure (strong but highly flexible) Potential Benefits Kroo MITEs (digitized, segmented Gurney flaps)

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Reduced wing weight for a given wing

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span

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Increased span (reduced drag) for wing of given weight May enable the use of highly non-planar wing configurations (e.g. C-wings) Inputs from nerves distributed throughout the living tissue of the wing membrane Brain highly modified to process sensory data and provide needed control output Control output to muscles throughout wing membrane