Flying Low and Slow - HAW Hamburg · Flying Low and Slow ... from A320* Requirements m MPL 19256 kg...

AIRCRAFT DESIGN AND SYSTEMS GROUP (AERO)

Flying Low and Slow

(and the Tools for its Calculation)

12th European Workshop on Aircraft Design Education (EWADE) 2015

Delft, 10. September 2015

Dieter Scholz Hamburg University of Applied Sciences

Dieter ScholzFlying Low and Slow

10.09.2015, Slide 2Aircraft Design and Systems Group (AERO)

12th EWADE 2015Delft, 10. September 2015

Content

Flying Low and Slow with New Aircraft Designs

Flight Mechanics Fundamentals

Drag Polar

Specific Fuel Consumption and the SFC-Paradox

Flying Low and Slow with a Given Aircraft

Summary and Conclusions

Flying Low and Slow (and the Tools for its Calculation)





• Standard Jet Configuration"The Rebel"

Optimization for minimum fuel

• Standard Prop Configuration"Smart Turboprop"

Optimization for minimum DOC

Genetic algorithm (Differential Evolution) proposesparameters. Aircraft „designed“ automatically in EXCEL.About 2000 feasible designs tested in one optimization run.




Parameter Value Deviationfrom A320*

Requirements

mMPL 19256 kg 0 %

RMPL 1510 NM 0 %

MCR 0.55 - 28 %

max(sTOFL , sLFL) 2700 m + 53 %

nPAX (1-cl HD) 180 0 %

mPAX 93 kg 0 %

SP 28 in - 3 %


Requirements

mMPL 19256 kg 0 %

RMPL 1510 NM 0 %

MCR 0.55 - 28 %

max(sTOFL , sLFL) 2700 m + 53 %

nPAX (1-cl HD) 180 0 %

mPAX 93 kg 0 %

SP 28 in - 3 %

Standard Jet Configuration: "The Rebel"Parameter Value Deviation

from A320*

Main aircraft parameters

mMTO 66000 kg - 10 %

mOE 39200 kg - 5 %

mF 7500 kg - 42 %

SW 68 m² - 45 %

bW,geo 48.5 m + 42 %

AW,eff 34.8 + 266 %

Emax 26.1 + 48 %

TTO 89100 N - 20 %

BPR 15.5 + 158 %

SFC 1.03E-5 kg/N/s - 37 %

hICA 30000 ft - 23 %

sTOFL 2490 m + 41 %

sLFL 2110 m + 45 %

tTA 32 min 0 %



mMTO 66000 kg - 10 %

mOE 39200 kg - 5 %

mF 7500 kg - 42 %

SW 68 m² - 45 %

bW,geo 48.5 m + 42 %

AW,eff 34.8 + 266 %

Emax 26.1 + 48 %

TTO 89100 N - 20 %

BPR 15.5 + 158 %

SFC 1.03E-5 kg/N/s - 37 %

hICA 30000 ft - 23 %

sTOFL 2490 m + 41 %

sLFL 2110 m + 45 %

tTA 32 min 0 %



mMTO 66000 kg - 10 %

mOE 39200 kg - 5 %

mF 7500 kg - 42 %

SW 68 m² - 45 %

bW,geo 48.5 m + 42 %

AW,eff 34.8 + 266 %

Emax 26.1 + 48 %

TTO 89100 N - 20 %

BPR 15.5 + 158 %

SFC 1.03E-5 kg/N/s - 37 %

hICA 30000 ft - 23 %

sTOFL 2490 m + 41 %

sLFL 2110 m + 45 %

tTA 32 min 0 %

Early conceptual design

0

5

10

15

20

25

0 2000 4000 6000

Payload mass [t]

Range [NM]

Contingency: 10 % Alternate: 200 NM Loiter time: 30 min Add. tank: 4 m³ Ref. aircraft: A320

Payl

oad

Mas

s [t

]

0

5

10

15

20

25

0 2000 4000 6000

Payload mass [t]

Range [NM]

Contingency: 10 % Alternate: 200 NM Loiter time: 30 min Add. tank: 4 m³ Ref. aircraft: A320

Payl

oad

Mas

s [t

]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 200 400 600 800 1000 1200Thrust-to-weight ratio [-]

Wing loading in kg/m²

Thru

st to

Wei

ght R

atio

[-]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 200 400 600 800 1000 1200Thrust-to-weight ratio [-]


Thru

st to

Wei

ght R

atio

[-]






DOC mission requirements

RDOC 750 NM 0 %

mPL,DOC 19256 kg 0 %

EIS 2030 -----

cfuel 1.44 USD/kg 0 %

Results

mF,trip 3700 - 36 %

Ua,f 3070 + 6 %

DOC (AEA) 93 % - 7 %



RDOC 750 NM 0 %


EIS 2030 -----


Results

mF,trip 3700 - 36 %

Ua,f 3070 + 6 %

DOC (AEA) 93 % - 7 %

Standard Jet Configuration: "The Rebel"

25%

13%

0.3%1.0%

25%

7%

24%

5%

Operating empty mass breakdown

Wing

Fuselage

Horizontal tail

Vertical tail

Engines

Landing gear

Systems

Operator's items

32%

38%

4%

8%

17%

Component drag breakdown

Wing

Fuselage

Horizontal tail

Vertical tail

Engines

17%

14%

1%

24%6%

15%

23%

Direct operating cost breakdown

Depreciation

Interest

Insurance

Fuel

Maintenance

Crew

Fees







mMTO 56000 kg - 24 %

mOE 28400 kg - 31 %

mF 8400 kg - 36 %

SW 95 m² - 23 %

bW,geo 36.0 m + 6 %

AW,eff 14.9 + 57 %

Emax 18.8 ≈ + 7 %

Peq,ssl 5000 kW ------

dprop 7.0 m ------

ηprop 89 % ------

PSFC 5.86E-8 kg/W/s ------

hICA 23000 ft - 40 %

sTOFL 1770 m 0 %

sLFL 1300 m - 10 %

tTA 32 min 0 %



mMTO 56000 kg - 24 %

mOE 28400 kg - 31 %

mF 8400 kg - 36 %

SW 95 m² - 23 %

bW,geo 36.0 m + 6 %

AW,eff 14.9 + 57 %

Emax 18.8 ≈ + 7 %

Peq,ssl 5000 kW ------

dprop 7.0 m ------

ηprop 89 % ------

PSFC 5.86E-8 kg/W/s ------

hICA 23000 ft - 40 %

sTOFL 1770 m 0 %

sLFL 1300 m - 10 %

tTA 32 min 0 %


Requirements

mMPL 19256 kg 0 %

RMPL 1510 NM 0 %

MCR 0.51 - 33 %

max(sTOFL , sLFL) 1770 m 0 %

nPAX (1-cl HD) 180 0 %

mPAX 93 kg 0 %

SP 29 in 0 %


Requirements

mMPL 19256 kg 0 %

RMPL 1510 NM 0 %

MCR 0.51 - 33 %

max(sTOFL , sLFL) 1770 m 0 %

nPAX (1-cl HD) 180 0 %

mPAX 93 kg 0 %

SP 29 in 0 %

Natural Laminar Flow (NLF)

Standard Prop Configuration: "Smart Turboprop"

0

5

10

15

20

25

0 2000 4000 6000

Payload mass [t]

Range [NM]

Contingency: 10 % Alternate: 200 NM Loiter time: 30 min Ref. aircraft: A320

Payl

oad

Mas

s [t

]

0

5

10

15

20

25

0 2000 4000 6000

Payload mass [t]

Range [NM]


Payl

oad

Mas

s [t

]

0

5

10

15

20

25

0 2000 4000 6000

Payload mass [t]

Range [NM]


Payl

oad

Mas

s [t

]

0

100

200

300

400

0 200 400 600 800Power-to-mass ratio [-]


Pow

er to

Mas

s R

atio

kW

/t

0

100

200

300

400

0 200 400 600 800Power-to-mass ratio [-]


Pow

er to

Mas

s R

atio

kW

/t





Standard Prop Configuration: "Smart Turboprop"

13%

1.4%

25%

1.0%1.7%

18%

6%

26%

7% 1.4%


Wing

Struts

Fuselage

Horizontal tail

Vertical tail

Engines

Landing gear

Systems

Operator's items

Soundproofed material

23%

9%

48%

6%

8%5%


Wing

Struts

Fuselage

Horizontal tail

Vertical tail

Engines

14%

11%

1%

27%6%

16%

24%


Depreciation

Interest

Insurance

Fuel

Maintenance

Crew

Fees

13%

1.4%

25%

1.0%1.7%

18%

6%

26%

7% 1.4%


Wing

Struts

Fuselage

Horizontal tail

Vertical tail

Engines

Landing gear

Systems

Operator's items

Soundproofed material

23%

9%

48%

6%

8%5%


Wing

Struts

Fuselage

Horizontal tail

Vertical tail

Engines

14%

11%

1%

27%6%

16%

24%


Depreciation

Interest

Insurance

Fuel

Maintenance

Crew

Fees



RDOC 755 NM 0 %


EIS 2030 -----


Results

mF,trip 3700 kg - 36 %

Ua,f 3600 h + 5 %

DOC (AEA) 83 % - 17 %



RDOC 755 NM 0 %


EIS 2030 -----


Results

mF,trip 3700 kg - 36 %

Ua,f 3600 h + 5 %

DOC (AEA) 83 % - 17 %






Often claimed:"There is one speed for minimum drag!" Really only one?

WmdL SCVLmg ,2

21 flying lower:

A/C Performance





The Pilot's View of Flying Low and hence Fast

Lower altitude => Higher Speed of Sound => Higher True Airspeed(cruise Mach number remains constant

High Speed & high density => very low lift coefficient => very low L/D

=> Extremely high fuel consumption !




Drag Polar

Drag Polar (Airbus A320, approximated, based on the following equations)

Mach dependent induced drag

wave drag

CD0 = 0.0179

Mach number

eACCCC L

WDDD

2

,0,




Induced Drag Prediction Method (Nita 2012)

Drag Polar

APQk

e Me

,

Fetheo keQ

,

1

K = 0,380,DKCP

from one of many handbook methods2

, 21

bdk F

Fe

1;0

1,

ee

e

b

compeMe

ca

cMMak

e

3.0182.1000152.0

comp

e

e

e

Mcba

(f

Hörner 1965

Fuselage:

Mach:

Generic parameters:

eACC L

iD

2

,

Afetheo

)(1

1

for unswept wings:




Drag Polar

NACA Report 921

opt

25

250375.045.0 eopt

250375.045.0357.0 e

Afetheo

)(1

1

0119.0)(0706.0)(1659.0)(15.0)(0524.0)( 234 f

for all sweep angles 25:

25 in deg




Drag Polar

Mach Dependent Induced Drag (A320)

y = -8431,955x6 + 31050,614x5 - 47355,820x4 + 38277,125x3 - 17289,215x2 + 4136,125x - 408,255

R2 = 0,998

0,5000

0,6000

0,7000

0,8000

0,9000

1,0000

1,1000

0,50 0,55 0,60 0,65 0,70 0,75 0,80 0,85

M

e_A3

20

k

_e,M

,A32

0

e_A320k_e,Mk_e,M,A320Poly: k_e,MCalc: e_A320Calc: e_A320Polynomisch (k_e,M,A320)

a_e = ‐0,0027016b_e = 8,6017

Parameters for A320:

Parameters for A320: y = -8431,955x + 31050,614x - 47355,820x + 38277,125x3

- 17289,215x2 + 4136,125x - 408,255R2 = 0,998

6 5 4




Drag Polar

Wave Drag Prediction Method

0,015

0,017

0,019

0,021

0,023

0,025

0,027

0,029

0,60 0,65 0,70 0,75 0,80 0,85

M

C_D

0 +

CD

,wav

e

C_D0 A320C_D0 Calc

A320:CD0 = 0.0179

Shevell 1980: A = 0.00057, B = 3.348

Own proposalof generic parameters (from 5 A/C): A = 0.00127, B = 3.4766

with a = A, b = B

In case Mcrit is not given:




Specific Fuel Consumption

The SFC Paradox

Heating value. Kerosene: H = 42.5 MJ/kg

HmF

: overall efficiency of the flight

cT = c : Thrust-Specific Fuel ConsumptioncT = mF / TcT = 16.10-6 kg/N/s (typical for jet)

Efficiency increasesto any value if only speed is increased.=> Paradox ! = 1:

V = 680 m/s, M = 2 (MSL)




Deriving a Basic SFC as a Function of Speed or Mach Number


cP = c' : Power-Specific Fuel ConsumptioncP = mF / P / tcP = 0.075 .10-6 kg/W/s (typical for turboprop)

a* is slope …

c' is slope …

VccTVcPcTcmF





Élodie Roux 2002

The Basic SFC Function

… a* is slope




Preparation


relative fuel consumption

if the aircraft is unchangedand CL is kept constantE only depends onke,M and CD0,W

E = L/D

WDD

refWDD

refMe

Me

ref CCCC

kk

EE

,00

,,00

,,

,

WDDxma CC

eAE,00




The Reference


The New Flight Condition




More Basics






Numbers (A320)




-4,00%

-3,50%

-3,00%

-2,50%

-2,00%

-1,50%

-1,00%

-0,50%

0,00%

0,60 0,62 0,64 0,66 0,68 0,70 0,72 0,74 0,76 0,78

M

Del

ta m

_F /

m_F

,ref

Results


Reference:long range cruise




Results


V m/s 224 220 215 210 205 200 190rho kg/m³ 0,364 0,378 0,396 0,415 0,435 0,458 0,507h m 10999 10698 10333 9955 9563 9158 8300T K 217 219 221 223 226 229 234a m/s 295 296 298 300 301 303 307M 0,76 0,74 0,72 0,70 0,68 0,66 0,62k_e_M 0,8450 0,8988 0,9399 0,9651 0,9802 0,9891 0,9970CD0W 0,0011 0,0009 0,0007 0,0005 0,0004 0,0003 0,0001E 17,9 18,6 19,1 19,4 19,7 19,8 20,0c kg/N/s 1,66E-05 1,65E-05 1,64E-05 1,63E-05 1,61E-05 1,60E-05 1,58E-05Bs m 2,47E+07 2,53E+07 2,56E+07 2,56E+07 2,55E+07 2,52E+07 2,45E+07Mff 0,893 0,895 0,896 0,897 0,896 0,895 0,892m_F/m_TO 0,1072 0,1048 0,1036 0,1034 0,1040 0,1049 0,1077fuel saving 0,00% -2,26% -3,39% -3,51% -3,01% -2,11% 0,48%

• E = L/D increases continuously with flying slower (down to M = 0.3).• Thrust-specific fuel consumption c = SFC decreases with flying slower.• The Breguet factor Bs is proportion to speed and decreases once E stops

increasing with substancial rate.• Fuel consumption decreases as long as the Breguet factor Bs increases.




Flying Low and Slow

Summary and Conclusions

• Flying slower gets you on a better drag polar (this is true also below the critical Mach number)

• The best lift coefficient has to be maintained• This can be done by letting the design find its optimum condition with respect to

altitude and wing area and …

• Given aircraft have to accept the given wing area and can fly lower when slower

• An example calculation showed fuel burn reduction of 3.5 % at 0.05 Mach less than reference Mach number (0.76)

• This could be done today(!) with all aircraft(!) and would also reduce contrails

• But: Productivity goes down and DOC go (most probably) up! This is "only" a financial question, however decisive!

Flying Low and Slow - HAW Hamburg · Flying Low and Slow ... from A320* Requirements m MPL 19256 kg...

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