The General Dynamics F-16 Fighting Falcon
is one of most significant fighters of the latter part of the 20th century. It was
originally developed from a concept for an experimental lightweight fighter and has
evolved into an all-weather fighter and precision attack aircraft. The F-16 has been
manufactured on as many as five separate production lines, making it the largest fighter
program in the Western world. Over 4000 F-16s have been built, with production still
continuing.
As early as 1965, the USAF had begun
concept formulation studies of new high-performance fighters. These included the F-X, a
heavy interceptor/air-superiority fighter, and the lightweight Advanced Day Fighter (ADF).
The F-X was to be in the 40,000-pound class and was to be equipped with advanced,
sophisticated radars and armed with long-range, radar-guided air-to-air missiles. The ADF
was to be in the 25,000-pound class and was to have a thrust-to-weight ratio and a wing
loading that would better the performance of the MiG-21 by at least 25 percent. The
general concept behind the ADF was much the same as the reasoning which had led after the
Korean War to the Lockheed F-104A Starfighter.
The appearance of the Mach 2.8-capable
MiG-25 Foxbat in 1967 frightened Defense Department analysts and prompted a redirection in
USAF fighter plans, with high performance once again becoming the primary concern. The F-X
concept was eventually to emerge as the McDonnell Douglas F-15 Eagle, a twin-engined
fighter with advanced avionics and long-range missiles. The ADF was temporarily shelved.
The ADF concept was kept alive by former
fighter instructor Major John Boyd and Pierre Sprey, a civilian working in the office of
the Assistant Secretary of Defense for Systems Analysis. They both disliked the F-X
concept as it then existed, and preferred a much simpler design. In the late 1960s, they
came up with a 25,000 pound design designated F-XX, which was to be a dedicated air
superiority fighter with a high endurance, minimal electronics, and no long-range
missiles. Later studies brought this weight down to 17,000 pounds. The concept met with
much opposition within the Air Force hierarchy, since some considered it a threat to the
existing F-X project. However, the Pentagon decided to continue the project at a low level
just in case the F-X (i.e. F-15) program got delayed or encountered serious developmental
difficulties.
In 1969, a Pentagon memorandum suggested
that both the Air Force and the Navy adopt the F-XX as a substitute for the F-15 and F-14
respectively, since both these planes were becoming increasingly expensive. Both services
vigorously resisted these moves, and both the F-14 and F-15 surged ahead.
Deputy Defense Secretary David A. Packard
(who came in with the new Nixon Administration in 1969) was a strong advocate of returning
to the concept of competitive prototyping as a way of containing the ever-increasing costs
of new weapons systems. During the 1960s, under Secretary of Defense Robert MacNamara, the
Total Procurement Package philosophy had been adopted, in which an aircraft was committed
to production even before the first example had flown and without any competitive flyoff
against rival designs. This had led to such controversial aircraft as the Lockheed C-5A
Galaxy and General Dynamics F-111, which had both encountered expensive and time-consuming
developmental problems and extensive cost overruns. Under the new competitive prototyping
philosophy, Air Force Secretary Robert C. Seamans drew up a set of ground rules in which
the initial funding of a new weapons project would be relatively limited, with the initial
performance goals and military specifications being kept to a minimum. By 1971, Boyd was
working for the Air Force Prototype Study Group. He was able to push the concept at a time
when the idea of competitive flyoffs was coming back into fashion.
A Light Weight Fighter (LWF) program came
into being under Packard's watch. A Request For Proposals (RFP) was issued to the industry
on January 16, 1971. The RFP called for a high thrust-to-weight ratio, a gross weight of
less than 20,000 pounds, and high maneuverability. No attempt would be made to equal the
performance of the MiG-25 Foxbat, the emphasis being placed instead on the most-likely
conditions of future air combat--altitudes of 30,000-40,000 feet and speeds of Mach 0.6 to
Mach 1.6. Emphasis was to be on turn rate, acceleration, and range rather than on high
speed. A small size was stressed, since the small size of MiG-17 and MiG-21 had made them
difficult to detect visually during combat over North Vietnam. The RFP specified three
main objectives. The aircraft should fully explore the advantages of emerging
technologies, reduce the risk and uncertainties involved in full-scale development and
production, and provide a variety of technological options to meet future military
hardware needs.
In the meantime, with the selection of
the McDonnell Douglas F-15 Eagle as winner of the F-X contract, General Dynamics engineers
had been concentrating on studies of a LWF for daytime dogfighting, with only minimal
air-to-air electronics being provided. These studies had all been performed under the
company designation of Model 401.
Five manufacturers submitted proposals in
response to the RFP--Boeing, Northrop, General Dynamics, Ling-Temco-Vought, and Lockheed.
In March of 1972, the Air Staff concluded that the competing Boeing Model 908-909 was the
first choice, with the General Dynamics Model 401 and the Northrop Model P-600 being rated
as close seconds. The Vought V-1100 and Lockheed CL-1200 Lancer had been eliminated.
The Source Selection Authority, after
further work, rated the General Dynamics and Northrop proposals ahead of the Boeing
submission. The General Dynamics Model 401-16B and the Northrop P-600 were chosen for
further development on April 13, 1972. Contracts for the two designs were awarded under
the designation YF-16 and YF-17 respectively. Rather than the "X" (experimental)
prefix being used, the "Y" (development) prefix was used in order to indicate
that a mixture of off-the-shelf and experimental technologies were being used.
Two examples of each design were ordered
by the USAF, and a flyoff of the two designs would be carried out against each other,
although there was no assurance that any production of the winning candidate would
actually be carried out. At the time, the Air Force was still very much committed to the
F-15 fighter, and visualized the LWF program as more of a technology-demonstration project
rather than a serious effort for a production aircraft. The "cost plus fixed
fee" contracts covered the design, construction, and testing of two prototypes, plus
a year of flight testing.
The YF-16 was designed and built at Fort
Worth under the direction of William C. Dietz and Lyman C. Josephs, with Harry Hillaker as
chief designer. The General Dynamics Model 401 had studied in models, mockups, and wind
tunnel testing dozens of different configurations before the final configuration was
chosen. No attempt was made to push individual technological advances to their limits,
with proven systems and components being used in those areas where the development of new
technology was not required. Components and detail assemblies were designed for ease of
manufacture, using low-cost conventional materials where possible. In order to keep costs
down, many of the components were designed to have commonality with existing or projected
aircraft. However, new technology was to be used in those situations where it would have
the greatest effect in meeting performance goals.
General Dynamics decided to use a single
Pratt & Whitney F100 turbofan for their proposal rather than a pair of low-bypass GE
YJ101s, which were used by the competing Northrop design. The F100 was also the powerplant
of the F-X (F-15) design, but Pratt & Whitney had to do some special design work to
adapt it to a single-engined aircraft A single F100 was estimated to provide a
substantially lower fuel demand than a pair of YJ101s, and studies revealed no significant
attrition advantage for a twin-engine arrangement. The single-engined format made it
possible to achieve a mission weight of 17,050 pounds, whereas a format powered by twin
General Electric YJ101 engines would have had a mission weight of 21,470 pounds.
During the early design development of
the F-16, General Dynamics had considered both single and twin vertical tails. Wind tunnel
tests had showed that vortices produced by the forebody strake generally improved
directional stability, but that certain strake shapes actually reduced stability at high
angles of attack when twin tails were used. It was concluded that a twin-tail format would
result in significantly greater development risks and that a single vertical tail would
give satisfactory results provided that it was sufficiently tall.
The General Dynamics team also studied
several different air intake configurations before settling on the final air intake
located underneath the nose. The ventral location for the intake was chosen to minimize
the sensitivity of airflow into the engine to high angles of attack. At a 20-degree AoA,
the local flow direction to a ventral intake was only ten degrees below datum, as compared
to 35 degrees in the case of side-mounted inlets. The design team had actually started
with a chin-mounted Crusader-type intake, but it was gradually pushed further and further
back to save weight until the process finally had to be halted to keep the intake ahead of
the nosewheel. There are some disadvantages to such an air intake location--the mounting
of the inlet underneath the fuselage is potentially dangerous to ground personnel and
appears at first sight to invite foreign object damage (FOD) to the engine by the
ingestion of stones and other runway debris into the intake. However, it avoids the gun
gas ingestion problem, and since the nosewheel is further back, it avoids
nosewheel-induced FOD. In order to save weight and complexity, the geometry of the intake
was fixed, which limits the maximum speed of the F-16 to below Mach 2.
Four different wing planforms--straight,
swept, variable, and delta--were reviewed. The variable-geometry wing was rejected because
of its high weight and complexity. The delta wing had the advantage of low weight per unit
of area and low wave drag, but was ultimately rejected because of its high drag-at-lift
and trim drag penalties. A low-sweep, straight wing was finally chosen because it was
thought to offer the best combination of good maneuverability, high acceleration, and
maximum lift to ensure good altitude performance. The team chose a computer-controlled
variable camber wing with leading-edge maneuvering flaps and trailing-edge flaperons which
could match the camber of the wing to flight conditions, thus maximizing wing efficiency.
The wing and main fuselage body were smoothly blended into each other in three dimensions,
making it impossible to define where the wing ends and the fuselage begins. The blended
wing-body, or lifting body effect is achieved by having a smooth fairing of the wing and
fuselage rather than the conventional sharp intersection, providing improved lift at high
angles of attack. The wing was fitted with smoothly-blended leading edge strakes. These
strakes create vortices at high angles of attack which maintain the energy of the boundary
layer air flowing over the inner section of the wing, delaying the stalling of the wing
root and maintaining the directional stability. Since the wing was far too thin to
accommodate landing gear members, the main undercarriage was fuselage-mounted, with the
wheels retracting into under-fuselage wells. The wing is made predominantly of aluminum,
with small amounts of steel, titanium and composite materials.
A "relaxed" static
stability/fly-by-wire (RSS/FBW) control system was provided. A number of elements were
added to aid the pilot in up to 9g combat. These included a side-stick console layout, an
ejector seat tilted backwards by 30 degrees, and an all-round vision bubble canopy.
Although the LWF requirement specified
only minimal electronics, the design team recognized that an operational aircraft would
probably require a heavier and more bulky avionics package. The decision was made to size
the aircraft to carry heat-seeking Sidewinder missiles plus an M61 cannon, but to make
provisions to allow Sparrow radar-homing missiles to be carried at a later date should
this be required.
The original specification had called for
a load factor of 7.33 g while carrying 80 percent internal fuel. General Dynamics
engineers decided to increase this figure to 9g at full internal fuel and to increase the
service life of the airframe from 4000 hours to 8000 hours.
Recognizing that the YF-16 pilot would
use externally-carried fuel on the outbound trip to the combat zone and then return on the
internal fuel, the design team allocated internal fuel volume accordingly, reducing the
airframe size and shaving 1470 pounds off the empty weight and reducing the loaded weight
by 3300 pounds. By doing this, the turning rate could be increased by ten percent and
acceleration by 30 percent.
Costs were reduced by using
interchangeable left- and right-handed tailplanes and flaperons. Most of the undercarriage
structure was also common to either side. Avionics were simple and armament consisted of
one 20-mm M61A1 rotary cannon and two AIM-9 Sidewinder missiles on the wingtips, plus
stores on two external hardpoints underneath each wing.
Sources:
- Combat Aircraft F-16, Doug Richardson,
Crescent, 1992.
- General Dynamics Aircraft and their
Predecessors, John Wegg, Naval Institute Press, 1990.
- The American Fighter, Enzo Angelucci and
Peter Bowers, Orion, 1987.
- United States Military Aircraft Since
1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.
- F-16 Fighting Falcon--A Major Review of
the West's Universal Warplane, Robert F. Dorr, World Airpower Journal, Spring 1991.
- The World's Great Interceptor Aircraft,
Gallery, 1989.
- Modern Military Aircraft--F-16 Viper, Lou
Drendel, Squadron/Signal Publications, 1992.
