The Chengdu Jian-20 - the AOE home page

The Chengdu Jian-20 - the AOE home page

The Chengdu Jian-20
Kris Douglas, Sam Kantor, Michael Palles and Grant Parrish
Image: defensetec.org
Configuration and Geometry
• Geometry estimated using
3-view drawing and graphics
application
• Relatively long, high-volume
fuselage compared to existing
5th generation fighters
J-20 AIRFRAME GEOMETRY
Length
(ft)
70.5
Height
(ft)
14.4
Span
(ft)
42.6
Swet
(ft2)
Vfuse
(ft3)
3025.7
2377.3
Configuration and Geometry
J-20 PLANFORM GEOMETRY
Swing
(ft2)
b
(ft)
Sref
(ft2)
493.2
42.6 829.9
Wing-Mounted
Control Surface
Aileron
Trailing Edge Flap
Leading Edge Slat
Non-Wing-Mounted
Control Surface
Canard
Tail
Aft Ventral Fin
Area
(ft2)
48.0
53.5
16.7
AR
Cr
(ft)
2.19
34.0
Area
(ft2)
Ct
(ft)
4.9
% Cave
20.8
30.8
17.9
6.6
6.6
4.9
λ
ΛLE
(°)
ΛTE
(°)
Γ
(°)
19.5
0.15
49.9
-8.4
-3.9
% b/2
13.0
23.2
9.7
Average
Chord (ft)
Cave
(ft)
38.7
32.0
44.6
Length
(ft)
7.3
8.2
3.4
Centroid Location
Relative to Nose (ft)
x
y
z
55.7
17.2
0.1
56.1
10.3
0.6
44.0
14.8
0.3
Dihedral
(°)
10.7
59.8
-60.3
Centroid Location
Relative to Nose (ft)
x
y
z
25.2
8.3
1.8
60.2
4.1
3.9
59.6
7.1
-2.2
Weight Estimation
Aircraft
Component
Multiplier and Reference
Reference
Value
Weights
(lb)
CG Location Aft of
Nose Apex (ft)
Main Wing
9.0×Wing Area (ft2)
493.2
4438.8
48.8
Horizontal Tail
4.0×Horizontal Tail Area (ft2)
125.3
501.2
40.0
Vertical Tails
5.3×Vertical Tail Area (ft2)
73.0
386.9
60.7
Fuselage
4.8×Fuselage Wetted Area (ft2)
1566.7
7520.3
33.0
Landing Gear
0.033× GTOW Guess (lb)
75000
2475.0
37.9
Installed Engine
1.3×Engine Weight (lb)
5000
6500.0
53.2
"All-Else Empty"
0.17×GTOW Guess (lb)
75000
12750.0
33.0
Empty Weight (lb)
34572.2
Wing Loading (lb/ft2)
90.5
Fuel and Payload (lb)
40427.8
Thrust-to-Weight
0.507
CG Location (%MAC)
20
Thrust-to-Weight
(Afterburners)
0.853
CG Estimate based on Gear
Placement (%MAC)
18.6
Gear Placement Guidelines
• Tipback angle between
12 and 15 degrees
• Overturn angle
between 54 and 63
degrees
• Results in CG location
of approximately
18.6% MAC
Stability Characteristics
AVL 3.27 Model (960 Panels)
• Varied Number of Panels
– Chordwise
– Spanwise
• Multiple Runs Varying
–
–
–
–
Mach Number
Angle of Attack
Sideslip Angle
CG Location
• Produced
– Stability Derivatives
– Lift Induced Drag
– Trim Drag
• Wing Airfoil: NACA 64206
• Tail Airfoils: 7% Thick Biconvex
Convergence History
CL Alpha vs. Number of Panels and Mach Number
3.2
3.15
5
3.1
Mach
0.0
0.1
0.2
0.3
0.4
0.5
0.6
4.5
4
3.5
300
400
500
600
700
800
Number of Panels
900
CLalfa
Neutral Point Location in %MAC
Neutral Point Location vs. Number of Panels and Mach Number
5.5
3
2.95
2.9
2.85
300
1000
400
500
600
700
800
Number of Panels
900
1000
Cn beta vs. Number of Panels and Mach Number
0.084
Cm Alpha vs. Number of Panels and Mach Number
Mach
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.445
0.44
0.435
0.43
0.425
0.083
0.082
Cnbeta
0.45
Cmalfa
3.05
0.081
0.08
0.42
0.079
0.415
0.41
300
400
500
600
700
800
Number of Panels
900
1000
0.078
200
400
600
800
Number of Panels
1000
Stability Derivatives
Mach
Mach
Mach
Mach
Drag Estimation: Viscous Drag
Chengdu J-20 Viscous Drag (35 kft)
0.014
CDF+CDForm
CDF
CDForm
Drag Coefficient, CD
0.012
0.010
0.008
0.006
0.004
0.002
0.000
0.0
0.5
1.0
1.5
2.0
Mach Number, M∞
2.5
3.0
• Viscous Drag calculated using friction2k6 code on course website, at
Mach 0.1 to 2.9 and altitudes of 15, 25, and 35 kft
• Combined skin friction and form drag coefficient did not vary with
altitude (identical to four decimal places)
Drag Estimation: Lift-Induced Drag
Lift Coefficient, CL
Chengdu J-20 Subsonic Drag Polar
Canard Schedule
1.2
1.2
1.0
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
CL
0.0
-0.2 0.00
0.03
0.06
0.09
0.12
0.15
0.18
0.2
0.0
-0.2 -30
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
Drag Coefficient, CD
-1.0
-10
10
30
Canard Deflection (DEG)
• Calculated using AVL and FRICTION.exe
− FRICTION.exe for profile drag
− AVL for induced drag
• Trim drag included
50
Drag Estimation: Trim Drag
12
Center of Gravity Effect on Trim Drag
11
Induced Drag Coefficient (CDi)
• Balanced 14% unstable
• Minimum trim drag
near 30% unstable
• Suggests other factors
drive static margin
• Varies little with Mach
number
-3
x 10
10
9
8
0.0
0.1
0.2
0.3
0.4
0.5
0.6
7
6
5
-40
-35
-30
-25
-20
-15
-10
Static Margin (%)
-5
0
5
10
Drag Estimation: Wave Drag
Chengdu J-20 Wave Drag Coefficient
Wave Drag Coefficient, CDw
0.06
0.05
0.04
0.03
0.02
0.01
0.00
1.0
1.5
2.0
Mach Number, M∞
2.5
• Wave drag estimated using AWAVE and awaveFileMake.m
updated to include arbitrary fuselage shapes
• Little variation with angle-of-attack for small α
Drag Estimation: Wave Drag
Chengdu J-20 Wave Drag
Wave Drag, Dw (klb)
80
ISA 35,000 ft
70
ISA 25,000 ft
60
ISA 15,000 ft
50
40
30
20
10
0
1.0
1.5
2.0
2.5
Mach Number, M∞
• Volumetric wave drag represents a high percentage of
the available thrust at high Mach
Drag Estimation: Total Drag
Chengdu J-20 Total Drag Buildup (35 kft)
60
Total Drag, D (klb)
50
40
30
20
10
0
0.0
0.5
1.0
1.5
Mach Number, M∞
2.0
2.5
• Note the jump in drag at the sonic speed due to onset of wave drag
• Maximum Mach clearly impacted by engine performance
Performance: Maximum Speed
• M = 2.13 (shock forms on nose cone)
• M = 2.81 (shock forms on probe)
• Enough thrust to achieve M ≈ 2.5
F-22
M = 2.25
F-35
M = 1.6+
J-20
M = 2.1-2.5
Performance: Range
• Max range calculated using Breguet Range equation and
weight fractions
• V/C assumed constant at each speed for these calculations
Performance:
Takeoff Distance & Climb Rate
• Ground roll required: 1398ft (black)
• Distance to achieve MIL 50’ clearance requirement: 144ft (red)
• Total take-off distance: 1542ft
• Climb angle for best rate of climb: 19.2°
Conclusions
• Configuration characteristics
– large internal volume (i.e. munitions capacity)
– long range
– supercruise capability
• Optimized for use as a long-range interceptor
and air-to-surface attack platform
• Actual performance dependent upon engine
development
References
•
Lake, J. “Out in the Open, Chengdu’s Jian-20.” Air International. February 2011.
•
Bharat Rakshak: Consortium of Indian Defence Websites. March 9, 2011.
http://forums.bharat-rakshak.com/viewtopic.php?f=3&t=3827&start=3800
•
Raymer, D. P. (2006). Aircraft Design: A Conceptual Approach. Reston, Virginia: American
Institute of Aeronautics and Astronautics, Inc.
•
Mason, W.H. “AOE 4124: Configuration Aerodynamics.” Department of Aerospace and
Ocean Engineering at Virginia Tech. March 20, 2011.
http://www.dept.aoe.vt.edu/~mason/Mason_f/ConfigAero.html
•
“Chengdu J-20: Stealthy Multi-Role Fighter.” MilitaryToday.com. March 1, 2011.
http://www.military-today.com/aircraft/j20.htm
•
Sweetman, B. “J-20 – Denial Is Not an Option.” Aviation Week. March 12, 2011.
http://www.aviationweek.com/aw/blogs/defense
Questions?
http://www.freerepublic.com/focus/f-news/2655343/posts