1998/1999 aiaa foundation graduate team aircraft design...
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Cardinal Design ProjectStanford University
1998/1999 AIAA Foundation Graduate Team Aircraft Design Competition:
Super STOL Carrier On-board Delivery Aircraft
Patrick A. LeGresley, Teal Bathke, Angel Carrion,Jose Daniel Cornejo, Jennifer Owens, Ryan Vartanian,
Juan J. Alonso, Ilan Kroo
Department of Aeronautics and AstronauticsStanford University
World Aviation CongressSan Diego, California
October 10, 2000
Cardinal Design ProjectStanford University
Outline• Design Requirements & Design Philosophy• Preliminary Weight & Performance Sizing• Configuration Selection & Component Design• Propulsion Selection & Installation• Structural Layout• Drag Estimation• Performance Analysis• Cost Estimation• Design Optimization• Conclusions
Cardinal Design ProjectStanford University
Design Requirements• Super Short Takeoff and Landing (SSTOL)
aircraft to provide center-city to center-city travel using river “barges”
• Also fulfill needs of US Navy to replace the C-2 Greyhound for Carrier On-Board Delivery (COD)
Cardinal Design ProjectStanford University
Design Requirements (cont.)• Takeoff ground roll of 300 ft, landing ground roll of
400 ft• 1500 nm cruise at 350 knots• Payload of 24 passengers and baggage for
commercial version• Payload of 10,000 lb, capable of carrying two GE
F110 engines for the F-14D, and a spot factor of 60 ft by 29 ft for military version
• Arresting hooks or catapult devices not allowed!• Technology availability date is 2005
Cardinal Design ProjectStanford University
Design Philosophy• Investigated two design approaches: tilt-wing and
fixed-wing with upper surface blowing (USB) flaps• Tilt-wing (as opposed to tilt-rotor) concept
demonstrated by Canadair CL-84 and XC-124• USB flaps utilized on NASA Quiet Short-haul
Research Aircraft (QSRA) and Boeing YC-14
Cardinal Design ProjectStanford University
Preliminary Weight & Performance• Used to estimate weight, wing area, and thrust or
power to meet performance constraints (cruise speed and range, takeoff and landing ground rolls)
• Fixed-wing with USB flaps:– 48,635 lb takeoff weight– 1000 sq ft wing area– 30,000 lb installed thrust
• Tilt-wing:– 59,922 lb– 700 sq ft wing area– 10,500 installed horsepower
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Fuselage• Fuselage laid out around engine containers:
x 4
Turbine orAfterburnerContainer Total of 4 containers for the 2 GE F110 Engines
Cardinal Design ProjectStanford University
Fuselage (cont.)
Military Version with two GE F110 engines for F-14D
Passenger version with accommodation for 24 passengers
Cardinal Design ProjectStanford University
Wing• Highly constrained by spot factor requirement
(60 ft x 29 ft, wing folding allowed)
• Final design incorporated wing pivoting and folding
Cardinal Design ProjectStanford University
Propulsion & High Lift• Two different concepts for high lift:
(I)Airflow over wing without BLC
(II)USB Concept
(III)BLC used to delay boundary layer build-up
Upper Surface Blowing (USB) Flaps
Tilt-wing
Cardinal Design ProjectStanford University
Propulsion & High Lift (cont.)• Analyzed using methodology in Aerodynamics of
V/STOL Flight by McCormick
• Flight test and wintunnel data for ‘sanity’ check
Sample Variation of Lift Coefficient
Engine Installation0 5 10 15 20 25 30 35 40 45
0
1
2
3
4
5
6
Momentum Coefficient, C µ
Lif
t Coe
ffic
ient
, CL
δf = 10 deg
α = 0 degCµ = Thrust/(q barS ref)
Cardinal Design ProjectStanford University
Structural Layout• Based on ‘typical’ configurations of cargo aircraft
and consists of frames, longerons, ribs, and spars
• Efforts to make use of advanced materials where useful and cost effective
Cardinal Design ProjectStanford University
Drag Estimation• Drag build-up approach: drag of each major
component computed, plus interference effects• Induced drag computed as function of wing/body lift
coefficient
0 0.1 0.2 0.3 0.4 0.5 0.6 0.70
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Lift Coefficient
Dra
g C
oeff
icie
nt
Drag Polar and L/D vs. CL for M = 0.61
Drag PolarL/D vs. CL
12
10
8
6
4
2
0
Lift-
to-D
rag
Rat
io
Start Cruise
End Cruise
Cruise Drag
Cardinal Design ProjectStanford University
Performance Analysis• Equations of motion numerically integrated to
compute takeoff and landing ground roll• Climb rate calculated from engine data & drag polar
30 35 40 45 50 55 100
150
200
250
300
350
400
450
SL, SA + 27 deg F
Landing
Takeoff
Weight, W (1000s lbs)
Gro
un
dro
ll, S
g (
ft)
0.2 0.3 0.4 0.5 0.6 0.7 0.8 -2000
0
2000
4000
6000
8000
10000
Mach Number, M
Ra
te o
f C
limb
, R
C (
ft/m
in) 0
10K
20K
30K
40K
Weight = 40,000 lbsMaximum Continuous Thrust
Takeoff and Landing Ground Rolls AEO Climb Rate
Cardinal Design ProjectStanford University
Performance (cont.)• Specific range computed from drag polar and
engine data for various weights• Range calculated by integrating specific range,
taking into account reserves requirements
150 200 250 300 350 400 450 0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
Speed, V (knots)
Sp
eci
fic
Ra
ng
e,
SR
(n
m/l
b)
30,000
35,000
40,000
45,000 Valid for h = 37,000 ft
0 500 1000 1500 2000 2500 3000 3500 0
5
10
15
20
25
Range, R (nm)
Pay
load
, W
PL
(100
0s lb
s)
Design Payload
Design Range Ferry Range
Specific Range Payload-Range
Cardinal Design ProjectStanford University
Cost Estimation• Cost estimation method based on statistical data gathered
for many existing aircraft
• Research, Development, Test, and Engineering (RDTE), Acquisition, Operating, and Disposal costs were computed, leading to the Life Cycle Cost (LCC)
27%
24%26%
< 1%
6%
17%
FlyingMaintenanceDepreciationLanding Fees,Nav.,TaxesFinancingIndirect
Military Version Operating Costs: 8.44US$/nm
Block Distance: 1500 nm
Commercial Version Operating Costs: 8.16US$/nm
< 1%8%
91%
1%
RDTE PhasesAcquisitionOperating CostsDisposal
Military Version Life Cycle Cost: $155B (750 military airplanes)
Commercial Version Life Cycle Cost: $149B (750 commercial airplanes)
Operating Cost BreakdownLife Cycle Cost
Cardinal Design ProjectStanford University
Design Optimization• Various subsystem analyses (high lift, weight,
propulsion, performance, cost, etc.) were combined into a collaborative optimization code
• The goal of the optimization was to produce the best design (in this case as measured by life cycle cost) which met all of the design requirements –takeoff and landing ground roll, cruise speed and range
• Constraints for FAR / MIL certification such as stability, climb gradients, tipover, etc. were also applied
Cardinal Design ProjectStanford University
Design Optimization (cont.)• A final design was selected based on the
relative costs of the various designs:
VerticalTakeoff Tiltwing
ShortTakeoff Tiltwing
Short Takeoff Fixed Wing
DOC $9.06/nm $7.82/nm $7.03/nm
IOC $1.81/nm $1.56/nm $1.41/nm
Fuel Price $1.20/gal $1.20/gal $1.20/gal
Engine Price (per engine)
$1.09 M $0.81 M $0.52 M
AEP $20.8 M $18.0 M $17.1 M
AMP $19.7 M $17.3 M $16.7 M
LCC $200.6 B $172.1 B $154.7 B
Cost Comparison
Final Three-View
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Trade Study on Performance Requirements
• Although performance requirements were specified, constraints were varied to analyze effect on LCC
• One of the more interesting is that for takeoff ground roll:
250 300 350 400 450 500 5501
1.1
1.2
1.3
1.4
1.5
1.6x 10
11
Takeoff Ground Roll(ft)
Lif
e C
ycle
Cos
t, L
CC
(US$
)
Cardinal Design
Variation of Life Cycle Cost with Takeoff Ground Roll Constraint
Cardinal Design ProjectStanford University
Conclusions• Upper Surface Blowing (USB) flaps and tilt-wing
considered as means to achieve Super Short Takeoff and Landing (SSTOL)
• Subsystem analyses methods developed for use in collaborative optimization
• A fixed-wing design with USB flaps was selected for its lower Life Cycle Cost
• Design studies showed that a relaxed takeoff constraint would have a significant effect on Life Cycle Cost