Airplanes that set new trends and leave a big mark on
aviation often have stormy and uncertain births, but few of them can match the
gestation record of the Northrop F-5.
The basic F-5 design (company designation N-156) survived
more than seven years of no sales before the first production order. Northrop
made its original presentations to the United States government in 1955. The
company has been selling hard ever since then, but the airplane did not start
getting official acceptance until the fall of 1962, and it is not clue to enter
wide service until 1966.
The bright spot in the design's early history was its
selection, in slightly modified form, as the USAF's supersonic trainer, the
T-38. This 1958 sale was a large one, and it kept the fighter design alive.
More than 460 T-38s have been delivered, another 174 have been funded, and
still another 126 have been programmed but are not yet covered by a contract,
bringing the total to more than 760 aircraft.
In spite of this success as a trainer, however, many
aviation people, as little as two years ago, considered the F-5 in its
fighter-bomber configuration a dead project. At that time it was argued
strongly that the F-5 would never he considered for first-line missions by
either the US or NATO air forces, primarily because of a relatively low top
speed and maximum altitude. The F-5 is a Mach 1.4, 50,000-foot-altitude air-
plane, and most of the USAF Century-series fighters are at least 300 mph faster
and can operate above 55,000 feet. Most important, the N-156 lost out in key
competitions during 1958 and 1959, which ended with the Lockheed F-104 being
selected as the new standard fighter for the Netherlands, Norway, Japan,
Canada, and West Germany.
Today, the picture has changed remarkably. Since the DoD's
1962 evaluation of the F-5 as a possible fighter-bomber to be supplied to
allied nations under the Military Assistance Program (MAP), more than 250 of
the aircraft have been ordered for Korea, the Philippines, Taiwan, Iran,
Turkey, Greece, and Norway. The F-5 even has begun to eat into the F-104
market. In response to a Norwegian request, the US is allowing that nation to
return one of the F-104G squadrons it was to have received and
"exchange" it as partial payment for sixty-four F-5s. Norway is
paying the balance of that purchase.
Prospects are good for further F-5 orders. Several nations
still are evaluating the aircraft, as is the USAF's Tactical Air Command, and
there is general enthusiasm over the airplane.
At first glance, the reasons for this latter-day enthusiasm
are not apparent. Certainly, the F-5 does not fit the classic description of a
pacesetting airplane with great portent for the future. In the past, its ten-year-old
design and far from record-contending speed and altitude performance would have
made it an also-ran in the eyes of most military officers for most types of
interceptor, air superiority, ground-support, or reconnaissance duty.
But selecting aircraft today is not as simple as it was in
the past. Speed, maneuverability, and load-carrying capacity are more important
for many missions than high performance at high altitude. The ability to get
combat tasks done depends on missile and ground environment as well as on
aircraft performance. Costs are being brought into the weapon selection
process as never before.
Every new aircraft from the counterinsurgency COIN through
the TFX to the new strategic bomber proposals has suffered from disagreements
over selection criteria.
The arguments are not going to be settled easily. But there
can be little doubt that the F-5 and some of its basic design ideas are going
to exert considerable influence on future combat aircraft—bomber as well as
fighter. There are sound reasons why the F-5 now is acceptable as a first-line
aircraft even though it was passed over a few years ago. There are equally good
reasons to expect that the F-5, despite its ten-year-old design, will have
unusually long life as a first-line aircraft. And there are also good reasons
for believing that the general F-5 design philosophy will become more
Basically, the F-5's appeal rests on the fact that it is the
most successful "small" airplane yet developed. It has taken the
"lightweight" philosophy to new limits. None of the designers who
have expounded the "lightweight" theory in recent years has done as
well as Northrop with the F-5. There are two prime "lightweight"
examples. The first is the Douglas A-413, which was designed by Ed Heinemann,
weighs about 16,000 pounds, and first flew in 1954; the other is Great
Britain's Folland Gnat, weighing in at less than 10,000 pounds.
The main objective with small aircraft has been to reduce
production costs, fuel consumption, and operating costs, all of which normally
take a big downturn as airframe weight and engine power are lowered. Some
sacrifice in maximum speed, altitude, and payload-range performance usually
has been necessary to get size and costs down to a minimum, but the cost/
effectiveness of "lightweight" aircraft generally has been rated high
for many fighter missions.
The F-5's superiority as a "lightweight" comes
mainly from its superior powerplants. From the beginning of the design in 1954
Northrop contended that only two engines in development, or even being
considered for development, would be light enough to give a small aircraft
truly outstanding performance. These were missile engines, the Fairchild J83
(scheduled for the long-canceled Goose) and the General Electric J85 (under
development for the Green Quail). Only the J85 reached production, and the
Northrop design activity was instrumental in expanding the program to include
development of a long-life, afterburner version suitable for supersonic manned
The resulting engine is impressive. Each J85—GE-13 in the
F-5 produces 4,080 pounds of thrust yet weighs only 585 pounds. Its
thrust-to-weight ratio of 7 to 1 is by far the highest of any operational gas
turbine today. By comparison, the Orpheus engine in the Gnat has a 4.8 to 1
thrust-to-weight ratio, and the US-built Sapphire in the A-4D is even lower,
at 3.5 to 1.
A substantial reduction in aircraft size has been achieved
by Northrop through use of the J85. It is difficult to be exact about this
reduction, but it is in the neighborhood of 5,000 to 6,000 pounds according to
an old rule of thumb. This is the rule that says that if the F-5 were powered
by engines with a thrust-to-weight ratio of 3.5, or half that of the J85, the
aircraft's engine weight would go up immediately by more than 1,000 pounds.
This added load would necessitate an increase in structural weight. Fuel weight
also would have to go up if the range were not to suffer. This added weight
would call for a heavier, more powerful, engine to keep top speed from
dropping. Experience has shown that the spiral of engine, structure, and fuel
weight increase results in a total aircraft weight of five to six pounds for
every pound of dead weight that must be added in any form.
By this rule, the F-5 should fly as fast, climb as rapidly,
and carry as big a load over as great a range as an aircraft that weighed 5,000
to 6,000 pounds more but was powered by engines only half as efficient from the
thrust-to-weight standpoint and about equal in the fuel-consumption department.
Applying this rule is tricky because excellence of aerodynamic and structural
design and the weight of electronic systems and accessories also can have a
large effect on aircraft weight.
The fact that Northrop has taken commendable advantage of
the J85's potential can be illustrated by comparing the F-5 with the F-100. The
first F-100 flew in 1953. Its C model has a powerplant thrust-to-weight ratio
of about 3.5. Takeoff weight is around 30.000 pounds for most missions, yet the
F-100C is directly comparable to the F-5, which takes off in the clean
configuration at 12,000 pounds and has a maximum flight weight of 20,000 pounds.
Maximum ordnance payload is 5,000 pounds for the F-100C and
6,200 pounds for the F-5A. For most attack missions their range-payload
performance is comparable. The F-5A is 0.03 Mach number faster in level
flight. It lands twenty knots slower and it has a 28,600 feet-per-minute (fpm)
unaccelerated rate of climb at sea level, compared with 19,000 fpm for the
The F-5's small size gives it an extremely powerful
cost/effectiveness advantage in lower fuel consumption. It uses about thirty
percent less fuel on any given mission than the F-100. Such a logistical
savings is difficult to ignore in modern operations. For instance, in a thirty-day
emergency operation an eighteen-airplane F-5 squadron would use 2,700,000
pounds of fuel, or 1,380,000 pounds of fuel less than a similar F-100C squadron.
This does not include the fuel consumed in delivering the squadron's supply.
Northrop pushed hard to expand the F-5's basic cost
advantage. Every effort was made to make maintenance simple and to keep the
required mechanics' skills relatively low. Maximum use was made of early
Century-series flight experience in developing a configuration which has
exceptionally docile handling characteristics at both subsonic and supersonic
speeds. Twin-engine design was planned from the first to improve the attrition
rate as well as to keep the engines small.
The accomplishments of this effort include a T-38 accident
rate that is the lowest of any USAF supersonic aircraft. Large-scale T-38
operations have demonstrated an operational readiness around seventy-four percent,
at a utilization rate of sixty hours per month and a maintenance man-hour
expenditure of about eleven hours per flight hour.
Maintenance materials costs for the F-5A are about $45 per
hour, or about the F-84 and F-86 level compared to more than $100 per hour for
the F-100 and nearly $250 for some Century-series fighters. Direct maintenance
man-hours per flight hour again is at the F-84, F-86 level and about half that
of the F-100.
Personnel strength (less pilots) of an F-5 squadron is forty-two
percent less than an F-100 unit—144 men to 210. On an equivalent manning basis
it would be possible to operate seven F-5 wings with the personnel of four
When all costs are considered—fuel, personnel, training, maintenance,
attrition, etc.—a unit of 400 F-5s could be operated for seven years for
forty-eight percent less than an equal number of F-100s.
Over-all the cost arguments for the F-5 are about as impressive
as those ever advanced for any airplane. Certainly, it has ushered in a new era
of low-cost supersonic operations and has set some standards that are going to
be difficult to top in the future.
Undoubtedly, the sales effort on the F-5 was slowed because
the savings claims were so large and because they were the key selling points.
Airplane performance data is relatively easy to come by with a prototype or two,
but it takes years to gather reliable, verifiable cost data that can stand up
under the type of checking and rechecking common today in military evaluations.
Without the good services of the T-38 trainer force it probably would not have
been possible to bring the F-5 costs down to their present level and to verify them
The continuous reappraisal of military requirements during
the last ten years also has had its effect on the pace of the F-5 program.
Today, it has become acceptable to divide military operations into at least three
basic types which overlap considerably. They range from Vietnam-type guerrilla
actions through large Korean-type operations to general or all-out war.
Each type places unique requirements on airpower. The COIN
fighter, recently contracted to North American for development, is the first
recent design aimed for guerrilla wars. The F-5A is among the aircraft now
being evaluated by the Tactical Air Command as a "super-COIN," which
could control the air effectively and inexpensively in Korean-type operations.
Broadening military requirements has broadened the attractiveness
of the F-5, which also would be useful in a general war. For instance, in the
words of the Norwegian government, the F-54s considered on the basis of
"an over-all evaluation of cost and operation more suitable for the tasks
of the Norwegian Air Force," which includes defending against a swiftly
striking, nuclear-armed attacker. Northrop reports that the Norwegian flight
tests showed that an F-5 was able to handle the faster F-104 consistently by
using its superior turning and climbing ability at most altitudes to stay in
position to launch its missile armament which compensated for the speed
Certainly there won't be universal agreement about the
validity of the Norwegian tests, but it does illustrate some truths about
airpower and point up some reasons why the F-5 probably will be around for many
years. Air warfare today, of the super-COIN and general war varieties, is much
faster than anything of the past. Missiles have not taken it over by any means.
Tactical doctrine, imaginative leadership, swift decisions, numbers of
aircraft, human skill, courage, and perseverance count more than ever. The true
criterion of performance is getting the job done. And it does not necessarily
follow that the fastest airplane at 40,000 feet will meet this standard.
High theoretical survivability during ground-support
operations is another advantage credited to the F-5. The F-5's small-size,
high-speed, twin engines appear to give it a significant and at least an
officially unrecognized advantage in this type of operation, which is critical
across the complete spectrum of hostile air operations from COIN to general
Two new F-5 models now are being offered—one the
"Improved F-5" and the other the "STOL F-5." The first one
features about five percent more engine power than the F-5A, a
"maneuvering" flap to cut down turn radius, more advanced fire
control, and other improvements. The STOL version has J85s uprated to provide
twenty-two percent more power than the F-5A's engines, increased wing area,
and the other features of the "Improved" model. Takeoff distance
drops from 2,410 feet to 1,190 feet on the clean STOL configuration. Ferry
range goes up from a maximum of 1,515 nautical miles for the F-5A to 2,400 for
the STOL F-5.
Other improvements undoubtedly will be made in the future to
increase the airplane's utility and service life. However, one fact over which
Northrop has no control probably will be the biggest factor in giving the F-5 a
long, useful life. This is the sad shape of the US gas-turbine development
program. The Air Force and Navy programs have both slowed down drastically
since the middle 1950s. The only really advanced work has been done in the Air
Force's lightweight gas-turbine technology program, which has resulted in the
construction of "demonstrator" engines by five manufacturers. These
engines feature advanced compressors, combustion chambers, and turbines. The
basic objective in each is to use a level of technology that is at least twice
that of any operational engine. While this program is a major step in building
technology the "demonstrator" engines are far from operational mode
Extensive and expensive development programs will be
required if we are to put any of these advanced ideas to use.
No plans for developing these engines have been approved. It
will be many years then before engines are ready which have thrust-to-weight
ratios significantly better than the J85. Until then it will not be possible
to build a "lightweight" fighter significantly better than the F-5.
F-5 Family Comparative Performance Summary
Gross Weight (Clean)
Rate of Climb
performance figures on the F-5A, the "Improved F-5," and STOL F.5
are listed at left. Performance gains are achieved with more powerful
engines and a larger, more efficient wing on the STOL F-5. Both new aircraft
also would have large "maneuvering" flap to make tighter turns.
Tactical Ordnance for the F-5
major F-5 requirement is to upgrade allied air forces receiving aircraft
under the Military Aid Program (MAP) by providing supersonic interceptor, air
superiority, and reconnaissance capability while performing all of the heavy
ground-support missions now accomplished by F-84 and F-86 fighters. More than
fifteen basic combat ordnance loads and two training loads are now provided
for the F-S. The maximum external load is 6,200 pounds, and it is exclusive
of the two M-39 20-mm. cannon and ammunition totaling 420 pounds. The major
loads that can be carried in various combinations include:
Two GAR-8 Sidewinders.
Two Shrike antiradar missiles.
Four GAM-83A Bullpups.
Three Walleye guided bombs.
Fourteen 30-gal. napalm containers.
Five 110-gal, napalm containers.
Sixteen 250-lb. bombs.
One 2,000-lb. bomb, two 1,000-1b. bombs, and two 750-lb. bombs.
Four rocket pods.
Bomblets-5,500 lb. total.
Four special stores.
Daily Report: Read the day's top news on the US Air Force, airpower, and national security issues.
Tweets by @AirForceMag