Aircraft Design StudiesBased on the

ATR 72

Mihaela Florentina NiţăSupervisor: Prof. Dr.-Ing. Dieter Scholz

HAW HamburgRRDPAE 2008

Recent Research and Design Progress in Aeronautical Engineering and its Influence on Education

Brno University of Technology, Czech Republic, 16-17 October 2008

– Preliminary sizing

(Paper on RRDPAE CD)

– Conceptual Design(Master Thesis on WWW)

Two Design Steps

Emphasis of this presentation

• Preliminary sizing

– Gives input parameters for the conceptual design:

» Maximum take-off mass,» Fuel mass,» Maximum operating empty mass,» Wing area, » Take-off thrust, or take-off power,

Overview

mMTOFm

mOESW

TTO TOP

• Conceptual design

Overview

• The Fuselage– Requirements:

» Passengers comfort

» Drag» Weight

– Cross section:

» Given: Number of passengers

» Yields: Number of seats abreast

and number of aisles

(CS 25.817)

Fuselage

70PAXn =

0.45 4SA PAXn n= ⋅ =

6 1SAn Aisle≤ ⇒

Fuselage

» Interior diameter of the fuselage

» Exterior diameter of the fuselage

, , , ,0.084 0.045 2.77F O F I F I F Od d d m d d m∆ = − = + ⋅ ⇔ =

, (2 ) 2 0.025 2.57F Id Bench width Aisle width m m m= × + + × =EmpiricalEquation

– Cabin and fuselage:» Seat pitch:

» Cabin Length

» Fuselage length

» Emergency exits: 2+2 type I and III

19.25PAXCABIN CABIN

SA

nl k mn

= ⋅ =

1.4 4 27.13F CABIN Fl l d m m= + ⋅ + =

Fuselage

31in 0,78 m;1 mCABINk

==

An average seat pitchincluding galleys,lavatories

Cockpit

length

Tail length

– Other parameters:» Slenderness parameter

Important parameter that determines drag and structural weight

9.79 10FF

F

ld

λ = = ≈

Fuselage

Wing

All interconnected

!!!

• The Wing– Design boundaries

Wing

– Design method

Wing

261.3WS m=

NACA 43018NACA 43013

– Results

0.41CRM =

12A =27.13b m=

025 3ϕ =

25( / ) cos 0.141t u v wt DD L Mt c k M C kϕ= ⋅ ⋅ ⋅ ⋅ =

Non linearregression

Chosenairfoil: NACA

430xx

( / ) 18%( / ) 13%

r

t

t ct c

==

, 00 0.4 4L CR

w tL

Ci

Cα

α ε= + − ⋅ =

Abbot, Pankhurst

03tε = −

00Wν =250.0360.45 opt e or statisticsϕλ − ⋅= ⋅

/ 0 .59t rc cλ = =

Wing

2 2.6[(1 ) ]r

k i

bc mA λ η λ λ

= =− + +

1.5t rc c mλ= =

21.5 3 3

tank tank,nec2

1 10.54 ( / ) 9.3 4.5(1 )W rV S t c m V m

Aλ τ λ τ

λ+ ⋅ + ⋅= ⋅ ⋅ ⋅ ⋅ = > =

+

From preliminarysizing

( / ) 0.72( / )

t

r

t ct c

τ = =where

High Lift System

• The high lift system– Design methodStart

Statistical reasearch

CL,max

Increase inLift calculation

Verifyequation

yesno

Stop

Iterativeprocess

,max ,max, 1.1 2.2L L INITIAL SIZINGC C= ⋅ =

,max, ,max, ,max ,max,0.95 L f L s L L cleanC C C C⋅ ∆ + ∆ ≥ −

: type of flap double slotted flap and slats

,max, 1 2 3 ,max( ) 1.089L f L basec k k k c∆ = ∆ =

,,max, ,max, 0.679W fL f L f

W

SC c K

S ϕ∆ = ∆ ⋅ ⋅ ='

,max, , ,max max 0.766L s l fcc ccδ δη η δ∆ = =

,,max, ,max, ,cos 0.613W sL s L s H L

W

SC c

Sϕ∆ = ∆ ⋅ ⋅ =

1.3 0.9≥

DATCOM

Empennage

• Estimating the empennage area from statistics

– Horizontal tail, vertical tail– Configuration: T-tail

(engine location on a high wing)

– Surface area from statistical approach

– Tail volume coefficient– Lever arm

1.05H HH

W MAC

S lCS c

⋅= =⋅

0.119V VV

W

S lCS b

⋅= =⋅

Tail volume

Tail volumecoefficient

50% 13.565V H Fl l l m= = ⋅ =

210.756H W MACH

H

C S cS ml

⋅ ⋅= =

214.904V WV

V

C S bS ml⋅ ⋅= =

Results

Empennage

– Other parameters

– Aspect ratio and taper ratio:

– Dihedral and sweep:

– Airfoil: for the vertical tailplane

for the horizontal tailplane

0.5 61.6

H w

V

A AA

= ==

0.60.6

H

V

λλ

==

0

0

80

0H

V

VV

=

=

025,

025,

8

25H

V

ϕ

ϕ

=

=

NACA 0012

NACA 0009

Mass and CG

• Mass estimation and CG location– Estimation per each component using a Class II method

(Torenbeek)

– Example calculation: wing mass

– The approximations are made by taking into account

variations with specific parameters, as it is shown in the next

table

0.303 0.75 0.55 /6.67 10 1 0.17

/refW s r

s ultMZF s MZF W

bm b tb nm b m S

−

= ⋅ ⋅ ⋅ + ⋅ ⋅ =

0.17 3045W MZFm m kg= ⋅ =

Mass and CG

Parameters used for the mass estimation

Results [kg]

Wing Bref/bs; mMZF/SW;nult 3045Fuselage Swet,F; lH; VD; dF 2323Horizontal Tailplane SH; VD 124Vertical Tailplane SV; VD 179Landing gear mMTO and coefficients 961Engine nacelle T, respectively P,η,V 242Installed engine nE; mE 1533Systems mMTO 3114Supplemental mass nSeat; nPax 1050Operating empty mass Sum of components 12834

– CG position and position of the wing towards the fuselage

Mass and CG

( ), , , 11WGLEMAC FG CG LEMAC WG LEMAC CG LEMAC

FG

mx x x x x mm

= − + − =

- CG position of the wing

-CG position of the fuselage

TORENBEEK, E.:"Synthesis of Subsonic Airplane Design“Delft University Press, 1988

Equilibriumof moments

25%CMAC

, 11.625i iWG LEMAC

i

m xx m

m⋅

= =��

11.392i iFG

i

m xx m

m⋅

= =��

Position of the wing:

• Sizing the empennage according to stability and control requirements– Horizontal Tail

• Sizing after control requirements

• Sizing after stability requirements

• Intersection of requirements

– Following the introduction of the stability margin, according to the next graph

/H W CG ACS S a x b−= ⋅ +

,

0.4887L

HL H H

MAC

Ca lCc

η= = −

⋅ ⋅, ,

,

0.20768M W M E

HL H H

MAC

C Cb lC

cη

+= =

⋅ ⋅

/H W CG ACS S a x −= ⋅, ,

, ,

0.3051

L W

HL H H

MAC

Ca

lCc

α

αεηα

= = ∂ ⋅ ⋅ − ⋅ ∂

20.156 9.701HH

W

S S mS

= ⇒ =

Stability and Control

Stability and Control

– Vertical Tail• Sizing after control requirements

• Sizing after stability requirements

– Evaluation of the results• If the area SH does not match Empennage results then:

• mH would need to be re-evaluated• and wing position adjusted

• For the vertical tail the larger area of the two was chosen

2

,2 ',

,

14.0851 ( )2 ( )

E DV

LMC F L theory V

L theory

N NS mc

V c K K lc

δδ

δ

ρ δ Λ

+= =

⋅ ⋅ ⋅ ⋅ ⋅

, , ,

, ,

2

0.1539

9.57

N N FV W

W Y V V

V

C CS bS C l

S m

β β

β

−= ⋅ =

−

⇒ =

Stability and Control

• Landing gear– Position: corelated with the CG aft position– Turn over angle in the x direction: min. 15°– Distance between wheels of the main LG– Tail clearence: 11°

– Lateral clearence:min. 7°required

, , 10.77LG N LG Mx m− =

4.10tracky m=

Landing GearTo preventtail tipping

To preventside tipping

• Drag estimation and polar– Three major components:

• Zero lift drag – it is being estimated for each component, according to the formula:

• Lift dependent drag• Mach drag – we neglect this from the beginning, as the aircraft flies

at lower speed

,0 /D f c c wett refC C FF Q S S= ⋅ ⋅ ⋅∑

Drag and Polar

Cf FFc Qc Swett/Sref CD,0

Fuselage 2.24·10-3 1.088 1 3.3 8.053·10-3

Wing 3.56·10-3 1.84 1 2.08 14·10-3

Horizontal Tailplane 3.392·10-3 1.368 1.04 0.17 0.8347·10-3

Vertical Tailplane 3.933·10-3 1.419 1.04 0.22 1.315·10-3

Nacelle 3.292·10-3 1.072 1.5 0.3 2·1.6·10-3

Total 27.4·10-3

– The polar is given by

» In the preliminary sizing calculation the value e = 0.85 was used

» The resulting L/D is E = 15.8

22

,0 0.027403 0.031LD D D L

CC C C CA eπ

= + ⇔ = + ⋅⋅ ⋅

Drag and Polar

• Design evaluation– AEA method (Association of European Airliners) for

estimating the direct operating costs (DOC)

DOC Estimation

Parameters used for the estimation

Results[mil$/year]

Depreciation Service life, residual value 0.99

Interest Average interest rate, total price of the aircraft

0.73

Insurance % of aircrafts price 0.07

Fuel Price and mass fuel, no. of flights per year

2.37

Maintenance Labor and material, inflation factor

1.44

Crew No. of crew members 2.07

Fees: – Landing Maximum take-off mass, no. of flights/year, inflation factor

0.39

– Navigation Maximum take-off mass,inflation factor

0.93

– Handling Maximum payload,inflation factor

1.45

– Total DOC = the sum of the costs of each of the following elements:

CDOC=10.5 mil US$/year

DOC Estimation

DOC DEP INT INS F M C FEEC C C C C C C C= + + + + + +

Components Redesign Original DeviationFuselageLengthDiameterCabin Length

27.13 m2.77 m19.25 m

27.17 m2.57 m19.21 m

0.1%-2.0%0.1%

Wing Wing SpanWing SurfaceWing LoadingHigh Lift Device

Power PlantPower Loading

27.13 m61.3 m2

373.7 kg/m2

Double sloted flaps and slats

179.8 W/kg

27.05 m61.0 m2

373.8 kg/m2

Double sloted flaps

179.9 W/kg

0.3 %0.5 %0.0 %

-0.1 %

Horizontal TailSurface 9.7 m2 11.7 m2 -17.1 %

Vertical TailSurface 14.1 m2 12.5 m2 12.8 %

MassMaximum Take-Off MassOperating Empty Mass

22925 kg12834 kg

22800 kg12950 kg

0.5%0.9%

Summary

For more information please visit the digital library:

http://bibliothek.ProfScholz.de

and check the RRDPAE CD