D8.x Aircraft Development — Update

Mark Drela

Aero & Astro Presentation

20 Oct 10

NASA’s N+3 Program

Chosen Current-Technology Baseline:

B737-800 mission: 3000 nmi, 180 PAX

N+3 Objective:

Identify concepts and technologies needed for

70% (!) reduction in Fuel / PAX-mile by 2025

Good bet: Tweaking current designs won’t do it

Presentation Outline

• Transport Aircraft System OPTimization (TASOPT)

• D8.x “Double Bubble” transport aircraft concept

TASOPT Objective

Find global optimum in Aircraft + Engine + Ops design space

fuel economy isocontours

existing engines

existing airplanes

common apparent (false) optimum

W/S , M . . .

true optimum

FPR, T

.

.

.

t 4

Pratt’s, GE’s design domain

Boeing’s, Airbus’s design domain

TASOPT Summary

Collection of coupled low-order physical models

• Primary structure

• Aero

• Engine

• Balance, trim, stability

• Flight trajectory

TASOPT Operation

• Inner sizing loop (design closure)

– Specify design inputs

– Size airframe via L=W, stresses, stability&trim

– Size engines via T=D

– Size fuel burn for design range

– Iterate on initial weight guesses

• Middle optimization loop

– Evaluate fuel volume, takeoff performance

– Tweak chosen subset of inputs (design variables) to minimize fuel

burn, with chosen constraints on fuel volume, takeoff, span

– Back to inner loop

• Outer parameter-sampling loop

– Explicitly change chosen subset of inputs (design parameters)

– Back to inner loop

TASOPT Operation

Initial weight guesses

Structural gauges

Volumes and Weights

Y

N

Surface spans, areas

Loads, Shears, Moments

DesignVariables

Optimize Design Variables

Y

N

DesignParameters

Fuel burn minimized?

Drag, Engine size+weight

Trajectory, Fuel Weight

Total Weight converged?

i, j

i, j

for i = 1 : Ni for j = 1 : Nj

Sweep, Altitude, FPR, BPR, Tt4 ... Configuration, Weight, Fuel burn, T/O perf, ...

( j )

( i )

( Sweep, Altitude, FPR, BPR, Tt4 ... )

( Range, Payload, Mach Nmax, fstress OPR, Tmetal, lBFmax ... )

Calibration/Verification

B737-800 Sizing, Airframe+Ops Optimization (fixed engine)

WMTO Wfuel S Λ◦ λt AR CLCRhCR

Actual 171000 39000 1250 25.00 0.250 10.20 0.550 33500Sized only 166001 38474 1229 25.00 0.250 10.20 0.550 33500Optimized 163862 36923 1289 24.33 0.144 10.61 0.530 34070

OptimizedSized only

Final N+3 Designs

D8.1 (Aluminum) D8.5 (Composite)

B737−8000.80 Mach15.2 L/D166k MTOW8000 ft field

0.72 Mach22.0 L/D130k MTOW5000 ft field

0.74 Mach24.9 L/D100k MTOW5000 ft field

−70% Fuel Burn−49% Fuel Burn

−45% Fuel Burn

D8.1b19.5 L/D120k MTOW

Fuselage Comparison

700 10 20 30 40 50 60 80 90 100 110 120 ft

9

700 10 20 30 40 50 60 80 90 100 110 120 ft

D8.x

B737−800

8

D8.1 Details

70

010

20

30

40

50

60

80

90

100

110

120 ft

22,23 rows180 seats19"x33"

70

010

20

30

40

50

60

80

90

100

110

120 ft

10 20 30 40 50 60

optionalthrustreverser

N+3 D8.1

Dfan = 49 inFPR = 1.58BPR = 7.1OPR = 35.8

8

Mach = 0.72Area = 1298 ft^2Span = 150 ftMAC = 10.6 ftAR = 17.3L/D = 22.0MTOW = 129965 lbWfuel= 20233 lbRange= 3000 nmiField= 5000 ft

Sh=252 ft^2Sv=144 ft^2

Breguet Parameter Comparison

Wfuel = WZF

exp

TSFC′

M

D′

L

R

a

− 1

≃ WZF

TSFC′

M

D′

L

R

a

737-800 D8.1 D8.1b D8.5

WMTO 166001 129965 120366 99756

Wfuel 38474 20233 21174 11296

WZF 127528 109732 99192 88460

TSFC′/M 0.694 0.628 0.633 0.500

L/D′ 15.18 22.00 19.53 24.85

W WZF fuelM LW WZF fuelM L W WZF fuelM L

1

0

D8.1 D8.5B737−800

TSFC’ TSFC’ TSFC’D’ D’ D’

D8.1b

D8.x Configuration (vs B737)

Wide double-bubble fuselage

• partial span loading via 216” wide fuselage (vs 154”)

• reduced floor-beam weight via center floor support

• shorter landing gear and load path

M(y) M(y)

D8.x Configuration (vs B737)

Lifting nose, rear flat fuselage

• increased fuselage carryover lift → smaller wing

• built-in nose-up moment from nose lift → smaller tail

D8.x

B737−800

D8.x Configuration (vs B737)

Reduced M = 0.72 with unswept wing (vs M = 0.80)

• reduced CDi, via larger AR allowed by unsweep

• LE slat can be eliminated, via increased CLmax from unsweep

• NLF on wing bottom possible, via unsweep and no slat

• faster load/unload of two aisles compensates for slower cruise

737−800

D8.x

30 x 6 per aisle

per aisle23 x 4

(30 minutes load,unload)

(15 minutes load,unload)

D8.x Engine/Tail Configuration

• Rear fuselage and tails double as flow-aligning nacelles– only minimal nacelles needed

– shield fan faces from ground observers

• Provides Boundary Layer Ingestion (BLI)– local potential flow M ≃ 0.6 matches fan requirement

– no additional BL diffusion – no streamwise vorticity into fan

• Fin strakes synergystically exploited:– function as pylons carrying engine loads and tail surface loads

– shield fan faces from ground observers

D8.1 BL Profiles at Cruise

• local potential flow M ≃ 0.6 matches fan requirement

• little nacelle diffusion – no streamwise vorticity into fan

• only fan does BLI — core intake sees clean flow- avoids core surge risk

- ideal situation for best overall SFC

1 ft

θ

e

k

M = 0.784H = 1.217 = 0.074 ft

θ

e

k

M = 0.724H = 1.265 = 0.108 ft

θ

e

k

M = 0.623H = 1.372 = 0.185 ft

Tail Size and Loads Comparison

D8.1 horizontal tail is 28% smaller and 27% lighter.Two-point support reduces bending moment and weight.

Sh = 350 ft Sh = 252 ft2 2

B737 D8.1

Wh = 2320 lb Sh = 1690 lb

Tail Size and Loads Comparison

D8.1 vertical tail total is 50% smaller and 70% lighter.5x smaller engine-out yaw moment no longer sizes the VT.

Sv = 144 ft 2

Sv = 284 ft 2

B737 D8.1

Wv = 1570 lbWv = 470 lb

Optimum-Engine “Surprises”

• Optimized takeoff turbine inlet temperature is modest→ Excessive takeoff Tt 4 carries cooling-flow penalty in cruise

• Optimized Bypass Ratio and Fan Pressure Ratio are modest→ BLI favors smaller engine and higher fan loading

D8.1 GE90Tt 4TO 1543◦K 1770◦K

BPR 7.1 9.0FPR 1.58 1.50

u u2

Fnet

jetE

( ) Fnet( )=

( ) ( )jetE<

A

B

B

B A

A

. .m u.

m u. 21

2

=

=

+

−

+−

+

++

+

Fuel Weight Sensitivity to Span Constraint

0.9

0.95

1

1.05

1.1

1.15

90 100 110 120 130 140 150 160

span [ft]

D/L / D/L_opt

WZF / WZF_opt

Wfuel / Wfuel_opt

737 Wfuel737 D / L 737 W_ZFD8.1 WfuelD8.1 D / L D8.1 W_ZF

Summary

• Examination of entire Airframe+Engine+Ops design space(TASOPT)

• Global optimization for minimum fuel burn

• N+3 D8.x configuration, reduction in Mach, give up to49% fuel burn decrease with conventional technology(45% decrease with 118 ft span constraint)

N+3 Phase II

• Detailed design of rear fuselage/engine installation

• Test 1:4 powered model of fuselage + stub wings

• Investigate performance of small-core engines (Pratt)

22x14 ft

D8.1 Low Speed1/4 scalePowered model

D8.5 Details

70

010

20

30

40

50

60

80

90

100

110

120 ft

10 20 30 40 50 60

22,23 rows180 seats19"x33"

70

010

20

30

40

50

60

80

90

100

110

120 ft

optionalthrustreverser

N+3 D8.5Mach = 0.74Area = 1162 ft^2Span = 170 ftMAC = 8.12 ftAR = 24.85L/D = 25.3MTOW = 101590 lbWfuel= 11485 lbRange= 3000 nmiField= 5000 ft

Dfan = 52 inFPR = 1.42BPR = 20OPR = 50

D13.1 (777 size, M=0.72, 1-class, Aluminum)

Dfan = 93 inFPR = 1.55BPR = 8.0

Sh=744 ft^2Sv=590 ft^2

Range= 7600 nmiMach = 0.83Area = 4780 ft^2Span = 213 ftMAC = 26.7 ftAR = 9.5L/D = 21.1MTOW = 640100 lbWfuel= 212500 lb

42,43 rows500 seats19"x33"

70

10

20

30

40

50

60

80

90

100

110

120

130

140

150

160

170

180

190 ft

70

10

20

30

40

50

60

80

90

100

110

120

130

140

150

160

170

180

190 ft

10 20 30 40 50 60 70 80 90 100 11010 20 30 40

thrustreverser

D13.1

D15.1 (777 size, M=0.83, 1-class, 3-aisle, Aluminum)

Dfan = 93 inFPR = 1.55BPR = 8.0 Sh=709 ft^2

Sv=710 ft^2

22,23 rows500 seats19"x33"

70

10

20

30

40

50

60

80

90

100

110

120

130

140

150

160

170

180

190 ft

70

10

20

30

40

50

60

80

90

100

110

120

130

140

150

160

170

180

190 ft

10 20 30 40 50 60 70 80 90 100 110

LDz

Range= 7600 nmiMach = 0.83Area = 3650 ft^2Span = 226 ftMAC = 15.8 ftAR = 14.0L/D = 24.0MTOW = 440000 lbWfuel= 98000 lb

D15.1

D17.1 (787 size, M=0.85, 3-class, Aluminum)

70

10

20

30

40

50

60

80

90

100

110

120

130

140

150

160

170

180

190 ft

70

10

20

30

40

50

60

80

90

100

110

120

130

140

150

160

170

180

190 ft

10 20 30 40 50 60 70 80 90 100 11010 20 30 40

thrustreverser

12 x 14 rows = 168 seats 33"x19"

D17.18 x 6 rows = 48 seats 39"x26"

4,6 x 2 rows = 10 seats 60"x30"

Dfan = 60 inFPR = 1.79BPR = 6.70

Range= 8000 nmiMach = 0.85Area = 2410 ft^2Span = 163 ftMAC = 17.8 ftAR = 11.0L/D = 19.0MTOW = 274000 lbWpay = 50000 lbWfuel= 102500 lb

Sh=344 ft^2Sv=340 ft^2

D17.4 (787 size, M=0.85, 3-class, Composite)

thrustreverser

12 x 14 rows = 168 seats 33"x19"

8 x 6 rows = 48 seats 39"x26"

4,6 x 2 rows = 10 seats 60"x30"

D17.4Range= 8000 nmiMach = 0.85Area = 2240 ft^2Span = 192 ftMAC = 14.0 ftAR = 16.4L/D = 20.8MTOW = 200000 lbWpay = 50000 lbWfuel= 60600 lb

Dfan = 72 inFPR = 1.54BPR = 22.0

Sh=338 ft^2Sv=349 ft^2

70

10

20

30

40

50

60

80

90

100

110

120

130

140

150

160

170

180

190 ft

70

10

20

30

40

50

60

80

90

100

110

120

130

140

150

160

170

180

190 ft

10 20 30 40 50 60 70 80 90 100 11010 20 30 40

TASOPT Fuselage Loading Model

p∆

(x)

x

W

Wtail

h

+ Wpay padd + W +shell

+ hLrMh

(x)v

Lr vMv

N

N ( W )+ W + floorWwindow insul + Wseat

added bending stringers

xwbox

TASOPT Fuselage Section Model

R fuse

dbw

Lv

v

tτtσ

tσ db

added bending material

t skin

Askin

skincone cone

skin

skin

stringers

fuse

max

A

floor

floor beams

TASOPT Wing Geometry and Loading Model

η = 2 y/b

10 o

structural box

ηs

(projected)

Λ

Engine weight alternativeto strut force

∆Lt

∆Lo p(η)

(η)w

NWNWinn out

η

structural cross section

TASOPT Wingbox Section Model

t cap

twebh

fuelA

wc

box

box

hboxhr

TASOPT Engine Model

.m

8

6

0

4

m.

.mα

πdπf

πb3

5

74a

πhcπlc ht lt

4.5πc

2.5

αc

4.1

πfnK inl

2

1.9

2.11.8

1.8

N NN G/

∆ ∆h h

4.9

πtn

l hl

core

core

TASOPT Fuselage Drag Model

x

A(x)∆∗ ∗ΘΘ, , (x)

y

z ∗ ∗, , (x)δ θ θ

b (x)0

Θwake

(x)Λ

(x)λ