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LaviIsraels Lost Winged Lion
An Engineers
Perspect ive
by John Golan
Material derived from openly published sourcesNo technical data subject to the EAR or ITAR John Golan 2016
Reflections of an Aerospace Engineer
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John GolanA Brief Biography
Designer, structures analyst, and
engineering manager in the aerospaceindustry for over two decades
Participated in design, development and
field support for jet engines that power a
variety of civil and military aircraft: Bombardier C-Series to the Airbus A380
Boeing F-15 to the Lockheed-Martin F-35
As well as developmental programs
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Past publication credits include articles inAir Forces Monthly,
Combat Aircraft,Aviation History, and the Jerusalem PostMagazine
The opinions expressed are my own, and do not necessarily
reflect those of my employers, either past or present
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An Engineers Perspective
First studied the Lavi as a graduate engineering student
Teaching assistant for a senior-level airplane design class Explored the Lavi as an example of fighter design principals
As an aerospace engineertrained in airplane designyou
see aircraft differentlyAircraft features can be recognized as the product of different design
trades
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Evaluations made on the basis of
calculated metricsnot arbitrary
aesthetics
To such a perspective:the Lavi was the product of
specific and unique Israeli
requirements
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Comparison: Mission and Fuel
F-16 and Lavi provide a contemporary comparison in
contrasting aircraft design objectives and philosophies
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F-16 was designed as a
lightweight air-to-air fighter Immediate antecedent was
Northrops F-5E Tiger II
Thin, trapezoidal wing
Minimal fuel capacity in wing
Lavi was designed as a
lightweight strike jet Immediate antecedent was the
Douglas A-4 Skyhawk
Delta wing with thick root-section
Maximum wing fuel capacity
Also frees up fuselage volume
Wing Fuel Capacity: 3,250 lb
54% of Total Internal Fuel Volume
Wing Fuel Capacity: 1,290 lb
19% of Total Internal Fuel Volume
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Comparison: Structural Weight and Payload
Deeper wing root section of the Lavi also increased wing
stiffness: allowing the Lavi to carry more load at less weight
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t
b
d hx
=
12
Load-carrying wing spars are essentially
I-beams
Moment of inertia will increase with the
height cubed
Bending stress will decreasewith the height squared
Allowed Lavi to achieve a maximum take-off weight 13
percent greater than a Block 30 F-16C with an empty weight
that was 10 percent less
Allowed Lavi to achieve more than 50 percent greater
combat radius than a Block 40 F-16C with an empty weight
that was 20 percent less
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Vertical Tail Trade Studies
Both single and twin vertical tail concepts were examined
Tail-boom configuration was among the more unusual concepts Tail-boom improved control and stability at highest angles of attack
Single vertical tail eventually selected due to lower structural weight
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Early Lavi concept featuring
tail-boom configuration
Image Credit: Tsach and Peled, 16thICAS, p. 838
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Sizing the Airplane for the Mission
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Three engine models to select from: F404, PW1120, and F100 Represented three different thrust classes of engine
Image Credit: Tsach and Peled, 16thICAS, p. 837
Lavi program was initiatedwith the F404 engine in
February 1980
Requirements later out-grew
the initial engine selection
Engine selection changed to
larger PW1120 engine in May
1981
The Lavi as Sized to its Engine Candidates
F404-440 PW1120 F100-220
Maximum Thrust, Tmax 16,000 lb 20,620 lb 23,830 lb
71.2 kN 91.7 kN 106.0 kN
Weights
Max Take-Off Weight, WTO 32,980 lb 42,500 lb 49,120 lb
14,960 kg 19,280 kg 22,280 kg
Empty Weight, WE 11,720 lb 15,310 lb 17,830 lb
5,320 kg 6,940 kg 8,090 kg
Max Internal Fuel 4,590 lb 6,000 lb 6,990 lb
2,080 kg 2,720 kg 3,170 kg
Max External Fuel 7,120 lb 9,180 lb 10,610 lb
3,230 kg 4,160 kg 4,810 kg
Wing Area, S 276 sq ft 356 sq ft 411 sq ft
25.6 m2 33.0 m2 38.2 m2
Combat Radius (nm)
Hi-Lo-Hi 970 nm 1,150 nm 1,320 nm
1,800 km 2,130 km 2,440 km
Lo-Lo-Lo 580 nm 670 nm 790 nm
1,070 km 1,240 km 1,460 km
PW1120 offered 19% increase in
combat radius at same wing loading
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Lavi evolved from strike jet
experience with A-4 and Kfir F-16 influenced by F-5E
lightweight fighter experience
Design Trades: Thrust and Wing Loading
Lavi reflected compromises to meet range and payload F-16 emphasized advantages in thrust-to-weight ratio
In air-to-air role, Lavi emphasized advantages in wing loading
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F-16 continued to add weight as
payload demands grew over the years
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Design Trades: Energy-Maneuverability
Energy-Maneuverability or E-M Diagrams provide a more
comprehensive means for evaluating fighter performance E-M Diagrams plot iso-contours of specific excess power across a range of
speed and altitude or speed and turn rate conditions
Includes effects of thrust loading, wing loading andaerodynamic efficiency
Comparing E-M Diagrams of competing designs allows for a direct
comparison for the strengths and weaknesses of each
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Preparing an E-M
Diagram requires
extensive knowledge
of each airplane Aircraft weights
Engine performance Speed effects
Altitude effects
Drag polar External stores drag
Mach number effects
g-load effects
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Design Trades: Energy-Maneuverability
Lavi E-M
capability
extrapolated
from published
data Lightweight air
combat
configuration
illustrated
Drag polar
data-matched
to literature
sources Engine
performance
corresponds to
maximum
(afterburning)
thrust
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Design Trades: Energy-Maneuverability
Existing published data allows for an approximate comparison of
E-M characteristics between the F-16 and Lavi
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Lavi would have energyadvantage at higher turn
rates
F-16A would have
energy advantage atlower turn rates
Comparison in lightweight
air-to-air configuration
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Design Reflects Priorities and Compromises
No single airplane can be all things for all roles
Trades that go into an airplane will be reflected in its design Degree of air-to-air versus air-to-ground emphasis
Payload and range requirements
Budget or technology constraints
Requirements and priorities will be visible in the final product
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Lavi was aimed at
developing a light
weight, long-range
strike fighter with a
secondary air-to-air role Very different emphasis
from its contemporaries
Far exceeded capabilities
of its peers in this regard
Nati Harnik, Government Press Office
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Bibliography
Golan, John, Lavi: The United States,
Israel, and a Controversial Fighter Jet
(Sterling, VA: Potomac, 2016).Shmul, Menachem, Eli Erenthal, and
Moshe Attar, Lavi Flight Control
System, International Journal of Control,
No. 1, 1994: 159-182.
Tsach, S., and A. Peled, Evolution of the
Lavi Fighter Aircraft, in Proceedings ofthe 16th International Council of the
Aeronautical Sciences (ICAS)
(Jerusalem: Aug. 28 - Sept. 2, 1988):
827-841.
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