ae332 initial sizing
DESCRIPTION
it is intial sizing of aircraftTRANSCRIPT
![Page 1: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/1.jpg)
INITIAL SIZINGEstimation of Design Gross Weight
Prof. Rajkumar S. PantAerospace Engineering Department
IIT Bombay
![Page 2: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/2.jpg)
Estimation of its design take-off gross weight Wo
Weight at the start of the design mission profile
Mission Profile specified by the user
Additional Requirements by Regulatory Bodies
Objectives
Identify requirements that are likely to drive the design
First estimate of the size of the aircraft, through Wo
What is Initial Sizing ?
![Page 3: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/3.jpg)
AE-332M / 714 Aircraft Design Capsule-3
MISSION PROFILEVary with the purpose of the aircraft
![Page 4: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/4.jpg)
Mission ProfilesMission profile purpose of the aircraftGeneral Aviation Aircraft Simple Cruise + Hold
Commercial Transport Aircraft Main Profile + Missed Approach + Diversion + Hold
![Page 5: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/5.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Mission Profile: Simple Cruise
Warm up, Taxi-out, Take Off
Cruise
Loiter
1 2
3 4
5
5
6 7
Landing, Taxi-in
Approach
![Page 6: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/6.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Mission Profile: Air Superiority Aircraft
Warm up, Taxi-out, Take Off
Combat
Landing, Taxi-in
Loiter
1 2
3 4
5 5
67
Cruise 1
Cruise 2
LoiterWeapon Drop 8 9
Approach
![Page 7: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/7.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Mission Profile: Ground Attack Fighter
Warm up, Taxi-out,Take Off
Combat
Landing, Taxi-in
Loiter
1 2
3 4
5 5
6 7Cruise 1
Cruise 2
Loiter
Weapon Drop
8 9Approach
![Page 8: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/8.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Mission Profile: Strategic Bomber
Warm up, Taxi-out,Take Off
Combat
Landing,Taxi-in
Loiter
1 2
3 45 6
7 8
Cruise 1
Cruise 3
Weapon Drop
910
1211
* R: Re-Fuelling
Approach
![Page 9: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/9.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Mission Profile: UAV
Predator (Tier II) Mission Profile
![Page 10: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/10.jpg)
Very little known about a/c configuration
Most methods are deeply rooted in past Statistical inference of parameters
Similar aircraft designed earlier
Most procedures empirical / semi-empirical
Various methodologies / approaches, e.g., Loftin’s method
Raymer’s approach (explained here)
Issues in Initial Sizing
![Page 11: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/11.jpg)
50
25
205
25
Empty weight Payload Usable Fuel Trapped Fuel
Typical Take-off weight break-up
![Page 12: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/12.jpg)
Wo = Wcrew + Wpay + Wfuel + Wempty
Wempty
Weight of structure, engines, landing gear, fixed equipment, avionics, etc.
Wcrew and Wpay are both known User-specified requirements
Wfuel & Wempty are unknowns to be determined
Take-off weight build-up
![Page 13: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/13.jpg)
Equation for Initial Sizing
emptyfuelpaycrewo WWWWW +++=
+−
+=
o
fuel
o
empty
paycrewo
WW
WW
WWW
1
{ }fe
paycrewo ww
WWW
ˆˆ1 +−
+=
are the two unknowns to be determinedˆ ˆ&e fw w
![Page 14: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/14.jpg)
AE-332M / 714 Aircraft Design Capsule-3
ESTIMATION OF EMPTY WEIGHT FRACTION
Mostly using historical data !
![Page 15: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/15.jpg)
ώe = A WoC * Kvs
Where “A” and “C” are constants
Their values for various aircraft types are obtained from statistical curve-fits
Kvs is a factor depending on the a/c sweep
Kvs = 1.00 for conventional, fixed-wing
Kvs = 1.04 for wing with variable sweep
Estimation of empty weight fraction ώe
![Page 16: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/16.jpg)
A/C type A C Sailplane (unpowered) 0.83 -0.05 Sailplane (powered) 0.88 -0.05 Homebuilt-metal/wood 1.11 -0.09 Home-built composite 1.07 -0.09 General Aviation-1 Engine 2.05 -0.18 General Aviation-2 Engine 1.40 -0.10 Agricultural a/c 0.72 -0.03 Twin turboprop 0.92 -0.05 Flying Boat 1.05 -0.05 Jet trainer 1.47 -0.10 Jet fighter 2.11 -0.13 Military cargo 0.88 -0.07 Jet transport 0.97 -0.06
“A” and “C” for various a/c types
Note: Wo in kg
![Page 17: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/17.jpg)
AE-332M / 714 Aircraft Design Capsule-3
TYPE A CUAV- Recce and UCAV 1.53 -0.16UAV- High Altitude 2.48 -0.18UAV- Small 0.86 -0.06
ώe = A WoC * Kvs
UAV Weight Fractions
Source: Table 3.1, pg. 31, Raymer, 5th edition
![Page 18: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/18.jpg)
Empty Weight Fraction Trends
![Page 19: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/19.jpg)
Empty Weight Fraction Trends
![Page 20: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/20.jpg)
AE-332M / 714 Aircraft Design Capsule-3
y = 0.5598x
40000
50000
60000
70000
80000
90000
100000
110000
120000
130000
140000
80000 100000 120000 140000 160000 180000 200000 220000 240000
Wem
pty
-Em
pty
Wei
ght (
lbs)
WTO - Maximum Takeoff Weight (lbs)
Weight Trend Data - Single Aisle Jet TransportFrom The Elements of Airplane Design, Schaufele.
Bae 146-100
DC-9-10
BAC-111
BAE 146-200
F100
BAE 146-300
DC-9-30
737-200
DC-9-40
DC-9-50
717-200
737-300
737-400
MD-81
737-600
737-700
![Page 21: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/21.jpg)
Wfuel = Wmission fuel + W reserve fuel
Wmission fuel depends on Type of mission Aircraft aerodynamics Engine SFC
Wreserve is required for Missed Approach, Diversion & Hold Navigational errors and Route weather effects Trapped Fuel (nearly 0.5% to 1 % of total fuel)
Assumption Fuel used in each mission segment is proportional to a/c weight
during mission segment Hence ώf is independent of the aircraft weight
Estimation of mission fuel fraction ώf
![Page 22: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/22.jpg)
Estimation of Mission Segment Weights
Various segments or legs are numbered, with ‘0’ denoting the mission start
Mission segment weight fraction for ith segment = Wi/Wi-1
Total fuel weight fraction (W6/W0) obtained by multiplying the weight fractions of each mission segments
![Page 23: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/23.jpg)
Estimation of Mission Segment Weights
The warm-up, take-off, and landing weight fraction estimated by historical trends
Fuel consumed (and distance traveled) during all descent segments ignored
![Page 24: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/24.jpg)
Weight fractions in Climb and Acceleration
![Page 25: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/25.jpg)
Effect of using historical data
0
1
1
2
2
3
3
4
4
5
5
6
0
6
WW
WW
WW
WW
WW
WW
WW
⋅⋅⋅⋅⋅=
97.0985.00.1995.02
3
4
5
0
6 ⋅⋅⋅⋅⋅=WW
WW
WW
2
3
4
5
0
6 95067.0WW
WW
WW
⋅⋅=
Mission Profile
![Page 26: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/26.jpg)
AE-332M / 714 Aircraft Design Capsule-3
ESTIMATION OF FUEL WEIGHT FRACTION
Using mission profile and historical data for engines !
![Page 27: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/27.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Breguet Range Equation
dtTtsfcdW ××−=Fuel Consumption:
( )TtsfcdWVdtVds ∞
∞ −==Range for dW fuel
LWDT == ,During Cruise
Drag changes due to changing lift: assume L/D is constant,
WdW
DL
tsfcVds
−= ∞Hence:
Assuming L/D, tsfc and V∞ (= aM) are constant:
![Page 28: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/28.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Breguet Range Equation
Source: Jet Sense; The Philosophy and the Art of Aircraft Design, Zarir D. Pastakia
final
initial
WW
DLM
tsfcaR ln
=
a is sound speed
Engine efficiency (fuel consumption)
Aerodynamic efficiency
Structural efficiency
Winitial = MTOW (Maximum Takeoff Weight)Wfinal = OEW + Pax + reserve fuelOEW = Operational Empty Weight = Empty Weight + Crew + trapped fuel & Oil
![Page 29: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/29.jpg)
Fuel Fraction in Cruise segmentCruise segment mission weight fraction can be
estimated using the Breguet Range Equation
1lncruise i
cruisecruise i
V WLRc D W
− = ⋅ ⋅ R = Cruise Range (m)ccruise = Specific Fuel consumption in cruise (per sec) Vcruise = Cruise Velocity (m/s)[L/D]cruise = Optimum lift to drag ratio during cruise
= [L/D]max for Propeller driven a/c= 0.866*[L/D]max for Jet engined a/c
![Page 30: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/30.jpg)
Fuel Fraction in Loiter segmentLoiter segment mission weight fraction can be
estimated using the Breguet Endurance Equation
11 ln i
loiterloiter i
WLEc D W
− = ⋅ ⋅ E = Endurance (sec)cloiter = Specific Fuel consumption in Loiter (per sec) [L/D]loiter = Optimum lift to drag ratio during loiter
= 0.866 [L/D]max for Propeller driven a/c= [L/D]max for Jet engined a/c
![Page 31: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/31.jpg)
AE-332M / 714 Aircraft Design Capsule-3
WE WERE HERE ON 26 AUG
![Page 32: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/32.jpg)
AE-332M / 714 Aircraft Design Capsule-3
ESTIMATION OF MAX L/DMostly using historical data !
![Page 33: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/33.jpg)
Estimation of [L/D]max Accurate value is not available since the aircraft
configuration is not yet finalized !!
Thumb RuleFor 7 ≤ ARwing ≤ 11,
[L/D]max = 2 * ARwing
![Page 34: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/34.jpg)
Approx. values of Cruise L/D max
[L/D]max values for 4-6 seater Piston/Turboprop a/cCessna 310 13.0Beech Bonanza 13.8Cessna Cardinal 14.2
![Page 35: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/35.jpg)
Configuration dependent In level flight, L = W; L/D depends on D Two main components of subsonic D Parasite or “Zero Lift” f(wetted area) Induced or “lift dependent”: f(wing span)
Concept of wetted aspect ratio ARwet = b2/Swet
ARwet is a better indicator of max. L/D Proof: B-47 v/s Vulcan
Drivers of subsonic L/D
![Page 36: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/36.jpg)
Different shapes, same Max. L/D
Source: Raymer,D., Aircraft Design, A Conceptual Approach, 2nd ed., pp 20 , AIAA Education Series, 1989
![Page 37: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/37.jpg)
Wetted area ratios for some configurations
Source: Raymer,D., Aircraft Design, A Conceptual Approach, 2nd ed., pp 21, AIAA Education Series, 1989
![Page 38: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/38.jpg)
Max. L/D v/s ARwet
Source: Raymer,D., Aircraft Design, A Conceptual Approach, 2nd ed., pp 22, AIAA Education Series, 1989
![Page 39: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/39.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Historical Trends in Max L/D
From: The Historical Fuel Efficiency Characteristics of Regional Aircraft from Technological, Operational, and Cost Perspectives,R. Babikian, S. Lukachko and I. Waitz, http://web.mit.edu/aeroastro/people/waitz/publications/Babikian.pdf
20
![Page 40: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/40.jpg)
AE-332M / 714 Aircraft Design Capsule-3
ESTIMATION OF ENGINE PARAMETERS
Again using historical data !
![Page 41: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/41.jpg)
Jet Engine TSFC = fuel mass flow rate per unit thrust units = mg/N-s or lb/lb-hr
Propeller engine PSFC = fuel mass flow rate per unit power units = mg/W-s or lb/SHP-hr
SFC trends for various engine types
![Page 42: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/42.jpg)
Typical SFC values (SI system)
![Page 43: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/43.jpg)
AE-332M / 714 Aircraft Design Capsule-3
For a 2020 Airplane consider TSFC ~ 0.47-0.5
y = -0.00428x + 9.099R² = 0.835
0.5
0.52
0.54
0.56
0.58
0.6
0.62
0.64
0.66
1970 1975 1980 1985 1990 1995 2000
Cru
ise
TSFC
lb/
(lbf·h
)
Year
Historical TSFC Trend for Turbofan Engines
Series1Linear (Series1)
![Page 44: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/44.jpg)
AE-332M / 714 Aircraft Design Capsule-3
0
0.2
0.4
0.6
0.8
1
1.2
0 4 8 12 16
Inst
alle
d sf
c (lb
/hr/l
b)
Bypass Ratio
Trend Data for Cruise sfc: Jet Aircraft
HeavierBigger Landing Gear
![Page 45: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/45.jpg)
ηp and SFC for Propeller Driven a/c
Aircraft Type ηp c lb/(SHP-hr)
Personal / Utility 0.80 0.60
Commuter 0.82 0.55Regional Turboprop 0.85 0.50
![Page 46: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/46.jpg)
Concept of Equivalent Jet SFCBreguet Range & Endurance equations for
Turbo/Pistonprop a/c are very messy !!Equivalent jet SFC for Turbo/Pistonprop enginesCpower = Fuel Flow rate/Power = Fuel Flow rate/{TV/ηp } = [Fuel Flow rate/T] {ηp/V} = [Cjet]. ηp/V Thus, Cjet = CpowerV/ηp
Thus by using Cjet in Brequet Equations, we can use them also for Turbo/Pistonprop a/c also !
![Page 47: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/47.jpg)
Segment Weight fractions estimated using the Brequet equations for Cruise and Loiter segments, and historical values for others
Total fuel fraction estimated as
Wf/Wo= ώf = (1 + RFF)*(1 - Wx/Wo) o RFF = Reserve Fuel Fraction
o = 0.06 to 0.1 for commercial transport aircraft
Estimation of mission fuel fraction
![Page 48: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/48.jpg)
Design Gross Weight Estimation
( )
−++⋅−
+=
0
111WWRFFWA
WWW
xCo
paycrewo
{ }fe
paycrewo ww
WWW
ˆˆ1 +−
+=
![Page 49: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/49.jpg)
Steps in Wo estimation
Assume starting value of Wo (say, 4 times Wpay)
Estimate ώe = A WoC * Kvs
Estimate segment weight fractions, using
Historical Data
Breguet Range and Endurance formulae
Estimate ώf = (1 + RFF)*(1 - Wx/Wo)
Calculate Wo = {Wcrew + Wpay}/{1- ώe – ώf}
Iterate till convergence
![Page 50: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/50.jpg)
AE-332M / 714 Aircraft Design Capsule-3
EXAMPLE OF SIZINGMedium Range Jet Transport Aircraft
![Page 51: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/51.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Payload: 150 pax at 175 lb & 30 lb baggage each Crew: 2 pilots and 3 cabin attendants at 175 lb each
and 30 lb baggage each Range: 1500 nm, followed by 1 hour loiter, followed
by 100 nm flight to alternate and descent Altitude: 35,000 ft for design range Cruise speed: Mach number = 0.82 @ 35,000 ft Climb: direct climb to 35,000 ft at max WTO
Climb rate of 2500 ft/min at a speed at 275 kt Take-off & landing: FAR 25 field-length of 5,000 ft Assume ISA deg oC atmosphere
Requirements
![Page 52: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/52.jpg)
AE-332M / 714 Aircraft Design Capsule-3
Mission Profile
![Page 53: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/53.jpg)
AE-332M / 714 Aircraft Design Capsule-3
ώe = 0.97 Wo-0.06 (W0 in kg)
ώe = 1.02 Wo-0.06 (W0 in lb)
Max(L/D) = 16 Cruise: cj = 0.5 lb/hr/lb
Loiter cj = 0.55 lb/hr/lb
Diversion Cruise speed of 250 kts (FAR 25) L/D of 10 and cj = 0.9 lb/hr/lb
Reserve Fuel Fraction = 10%
Assumptions
![Page 54: AE332 Initial Sizing](https://reader036.vdocuments.us/reader036/viewer/2022081801/5695d24c1a28ab9b0299df74/html5/thumbnails/54.jpg)
AE-332M / 714 Aircraft Design Capsule-3
S O L V E !!