Northrop F-5G/F-20A Tigershark

Last revised January 7, 2000




F-5G was the designation given to a vastly improved version of the F-5E Tiger II that would be offered to the export market. It was to have been a reasonably-priced aircraft that would have a performance equal to that of the best first-line fighter aircraft available anywhere in the world.

The project was approved by Northrop management in January of 1980, and they decided to proceed with the development of several pre-production aircraft at their own expense. Northrop received approval for the development of the F-5G from the State Department, which issued a specification for an Intermediate Export Fighter known as FX. This was basically a US government call for the private venture development of a tactical fighter for export in those circumstances where the supply of a front-line USAF fighter might be considered as being inappropriate. President Jimmy Carter had revoked an earlier ruling that military aircraft could no longer be built specifically or modified for export. The FX was thought to meet the President's arms transfer policy, which still maintained that countries would best be served by aircraft specifically tailored to their requirements, with front-line USAF fighters never being supplied regardless of the circumstances. However, the State Department also made it clear that there would be no financial help from the government for aircraft such as the F-5G. The Northrop company nevertheless decided to push ahead, assuming that the firm success of the F-5E would assure a lucrative market for a follow-on aircraft.

The F-5G design drew heavily on an aircraft designed to meet a DoD requirement for a Sparrow-carrying version of the F-5 intended for sale to Taiwan. This new aircraft was to have the twin J85 turbojets replaced by a single F404 turbofan. In the event, improved relations with the Mainland led to an American veto of any sale of a Sparrow-capable F-5 to Taiwan. Nevertheless, the aircraft became a basis for Northrop's FX study, although the Sparrow became only an option rather than a baseline weapon. It was hoped that the FX would be economical to operate but would be as combat effective as an F-16.

The twin J85 turbojets of the F-5E were replaced by a single General Electric F404 low-bypass turbofan, offering an afterburning thrust of 16,000 pounds. The F404 was designed as the successor to the J79 turbojet. It had about the same amount of thrust as the J79, but weighted about half as much and had 7700 fewer moving parts. The F404 turbofan was extremely reliable and was easy to maintain.

An effort was made to keep the weight down, and although the F404 turbofan was heavier than the pair of J85s that it replaced, the empty weight of the F-5G was only 17 percent greater than that of the F-5E. With an additional 60 percent of engine thrust the F-5G offered significant performance improvements. Maximum speed was expected to be in excess of Mach 2. Climb rate was to be improved by 567 percent in comparison to the F-5E, with an initial climb rate of 54,000 feet per minute. Ceiling was above 53,000 feet. Supersonic turn rates were 47 percent higher than those of the F-5E. Sustained turn rate at Mach 0.8 and 15,000 feet rose to 11.5 degrees per second, which compared well with the F-16's 12.8 degrees per second.

The wing of the F-5G was much the same as that of the earlier F-5E. However, it was provided with tapered inboard leading edge extensions that were lengthened and modified as a result of the redesign of the engine inlet ducts. These new inboard leading edge extensions increased the maximum lift coefficient of the wing by about 12 percent with an increase in wing area of only 1.6 percent. By destabilizing the aircraft in pitch, the LERXes improved the instantaneous turn rate by 7 percent, to 20 degrees per second. The skin on the inboard sections of the wing was increased in order to take account of the F-5G's higher empty weight.

The nose was flattened slightly and rounded in planform to enhance stability at high angles of attack. This made the aircraft nose look somewhat like that of a shark, and prompted the Tigershark name. The new nose contour improved directional stability at angles of attack of up to 40 degrees and reduced the tendency of the aircraft to depart when inverted at low airspeeds.

The rear fuselage was quite a bit narrower than that of the F-5E as a result of the powerplant change, but the longitudinal stability characteristics of the earlier F-5s were retained by the addition of a flat shelf on either side of the lower rear fuselage which gave it much the same shape as that of the twin-engined F-5. A single variable-geometry exhaust nozzle replaced the twin nozzles. Graphite composite skins were used in the rear fuselage and fin for increased strength and reduced weight. Internal fuel capacity was unchanged, but the F404's lower specific fuel consumption gave the newer aircraft a ten percent increase in combat radius.

In order to address the F-5E's sluggish pitch characteristics, the horizontal tail was increased in area by 30 percent and was controlled by a dual-channel fly-by-wire control system with mechanical reversion and override. The center of gravity was moved further aft.

Improved airflow around the rear fuselage permitted a reduction in fin size, with the new fin being mounted on a long fairing, with the brake chute compartment at the rear and a ram air intake at the front.

The engine intakes were extended forward and enlarged slightly. They were mounted further from the fuselage in order to clear the thicker boundary layer encountered at the higher speeds. They were equipped with two-shock inlet ramps to ensure more efficient operation at Mach 2+ speeds.

The cockpit canopy was 44 percent larger in area and offered an improved all-round view as compared to the F-5E. The fighter cockpit was the most advanced of its day, having been designed by a close-knit team of engineers, human factors engineers, and fighter pilots. It featured a wide-angle HUD having an up-front controller and a pair of high-set monochrome multi-function displays. Pilot workload was minimized by the use of input buttons on the control column and throttle for the control of sensors, weapons delivery, and avionics. Switch selections were minimized by clever use of automation. For example, the three-position air-to-air weapons selector was pushed forward for BVR weapons, pulled back toward the pilot for IR-homing missiles, and pulled all the way back for guns.

The initial avionics suite of the F-5G was to be essentially the same as that of the late F-5E, including the Emerson radar and the General Electric gyro gunsight, which helped to reduce the cost. It was planned to offer numerous different avionics options so that the customer could tailor the Tigershark to his own individual requirements and budget. The Tigershark was equipped with Multimode Coherent Radar (MCR) which can fulfill three different functions and can pinpoint objects that are either moving or stationary. Other electronics include a Digital Display and Control Set, a Mission Computer, a Laser Inertial Navigation System, and a Heads-up Display. The throttle was mounted on the control stick, which meant that the the pilot could operate the aircraft in combat without having to take his hands off the control stick.

The Air Force was sufficiently interested that it ordered four examples of the F-5G for evaluation. Serials were 82-0062/0065. The first F-5G (82-0062) took off on its maiden flight from Edwards AFB on August 30, 1982, Russ Scott at the controls. It also carried the civil registration of N4416T. It achieved Mach 1.04 on its first flight.

Although the Tigershark was quite different from the F-5E Tiger II which preceded it, the aircraft had been designated F-5G, which implied that it was simply a modified version of the earlier F-5. This designation for the Tigershark was chosen partly because of political reasons--the designation implied that the aircraft was simply an extension of an already proven design, one which had already been cleared for export. There should be no resemblance to new fighters such as the F-15 or F-16 which were to be kept off the foreign market in the interest of avoiding the evils of arms proliferation. However, under the new administration of President Ronald Reagan, which came into office on January 20, 1981, there was much less reluctance to export advanced weapons overseas. In particular, it soon became clear that the F-16 would now be made available for export, and would be a serious competitor to the F-5G on the world arms market. The designation of F-5G was now thought to be a disadvantage--having perhaps an unwelcome connotation of obsolescence, over-simplification, and compromise. At the request of Northrop, the Air Force assigned the Tigershark a brand new series number, which would be a much truer representation of what the Tigershark really was--a brand-new technologically-advanced fighter, one that was superior to the F-16 in several key respects. In November of 1982, the F-5G was redesignated F-20A. Some references indicate that the reason for the mysterious gap at F-19 was that this designation had been deliberately skipped at Northrop's request so that the Tigershark could be given the F-20 slot, the number 20 presumably making for better advertising copy--"Northrop F-20: first of a new series of fighters....".

The first order for four Tigershark aircraft was placed by Bahrain. However, having experienced government resistance in sales support, the decision to initiate production was delayed since the Bahrain order was too small.

The F-20A was shown at the Paris Air Show in 1983 and at Farnborough in England in 1984. Following Paris, the more powerful 17,000 lb.s.t. F404-GE-100 turbofan was fitted. With the new engine, the thrust-to-weight ratio was improved to 1.13 to 1, and climb performance to 40,000 feet was decreased from 2.2 minutes to 1.1 minutes.

The Tigershark aircraft had an excellent performance, and was in most respects actually superior to the General Dynamics F-16, its most likely competitor. Northrop had high hopes that the F-20A would be the natural successor to the F-5E Tiger II on the world arms export market. It even hired the famous test pilot Chuck Yeager as a "consultant" to tout the virtues of the F-20A in the hope that on the strength of Chuck's recommendation foreign customers would beat a path to Northrop's door, checkbooks in hand.

By April 1983, work was well under way on the second Tigershark (82-0063, N3986B). It was powered by the F404-GE-100 and was fitted with GE G-200 radar (later redesignated APG-67), a GE heads-up display, Honeywell laser inertial navigation, a Bendix head-down display, and a Teledyne mission computer. It also featured a lengthened and bulged canopy. The General Electric APG-67 radar fitted to the F-20A had the same basic modes ad the F-16A's APG-66.

The third F-20 (82-0064/N44671) flew on May 12, 1984 and conducted numerous weapons trials including Sparrow missile launches and Harpoon antishipping missile compatibility tests. Also tested was the GPU-5/A gun pod. The F-20A was also evaluated with various combinations of "iron" and "smart" bombs.

Although the F-20's performance appeared to make it very attractive to foreign air forces, it soon became obvious that a sale large enough to justify starting production would have to wait until there was a substantial buy for US forces first.

On October 10, 1984, test pilot Darrel Cornell was killed when his F-20 (82-062/N4416T) crashed while flying a demonstration for the ROKAF at Suwon in Korea. Cornell had put his F-20 into a climbing roll with flaps and landing gear extended, when his plane stalled and crashed. The cause of the mishap was the result of several factors, pilot factors being the primary cause. Suwon airfield was a strange airfield for Darrel Cornell, and no practice had been allowed before his demonstration flight took place. Five months later, on May 14, 1985, Tigershark No. 2 (82-063/N3986B) crashed while performing a similar maneuver at Goose Bay, Labrador. The pilot, David Barnes, was killed. The Canadian F-20 accident report ascribed G-force induced pilot loss of consciousness as the cause.

The fourth F-20 was to have been much closer to the proposed production configuration with increased internal fuel capacity, and newly-designed 330-US gallon external tanks. Changes in the nose would allow an increase in radar antenna size. The leading edge and trailing-edge flaps were redesigned to incorporate three-point drives instead of being driven at a single point. Actuation speed was increased and the number of automatic settings was increased. The aircraft was to be powered by a more powerful version of the F404, rated at 18,000 lb.s.t.. The flap and thrust changes were expected to improve turn performance by two degrees per second.

Although the F-20A Tigershark had many attractive features, its fate was sealed by a change in defense priorities introduced by the administration of President Ronald Reagan which came into office on January 20, 1981. The Reagan administration was much less reluctant to export advanced American weapons overseas, and the F-16 Fighting Falcon was now to be made available to overseas customers which had previously been denied access to this warplane. The need for a special FX export fighter suddenly evaporated, and it soon became obvious that American allies would no longer accept an aircraft developed exclusively for export when the USAF-operated F-16 was now available. The only way that the F-20A was ever going to attract any customers would be if the USAF or Air National Guard were to acquire the aircraft for themselves.

A USAF order for the F-20 was considered quite unlikely, since the F-16 now had a virtual lock on all Air Force fighter contracts. However, by 1985, there were beginning to be Congressional worries about the rising defense budget, and it was obvious that the F-15s and F-16s already funded would not meet the USAF's planned force requirements and could not be delivered within the originally-planned schedules. Perceiving an opportunity, on April 3, 1985, Northrop offered the USAF 396 F-20s at a cost of $15 million apiece. These planes would be cheaper than the F-16Cs that were then on order. Northrop claimed that the F-20 would be an excellent complement to the F-16--the General Dynamics aircraft had superior long-range interdiction capabilities but the F-20 offered faster reaction and turnaround times and would probably be better against close-in targets and in the air-to-air role. The Northrop bid came too late for FY86 funding, but was seriously considered for FY87.

Although the Air Force was firmly committed to the F-16 and was unlikely to want to buy an additional new fighter, there was a possibility that the F-20A might meet an Air National Guard requirement for an air defense interceptor to replace the F-106 and the F-4. The F-20A had already proven that it could carry and launch the AIM-7 Sparrow, and the aircraft was especially well-suited to the air defense role because its Honeywell Laser INS required no spinup, which gave the F-20 the fastest scramble time of any interceptor in the world. However, the USAF decided to purchase modified F-16As for the continental air defense role, effectively dooming the F-20A.

The lack of a USAF order had made the F-20A virtually unmarketable overseas. In view of the protracted development of the F-20 and its uncertain future, in 1985 Bahrain substituted its 1982 order for four Tigersharks with an order for the F-5E Tiger II. After having spent over a billion dollars on the project, the Northrop Corporation officially terminated the program on November 17, 1986. All work on the fourth prototype was abandoned.

Northrop still tried to keep the door open on the F-20 and made attempts to sell the entire program as a package for license production overseas. The State Department refused permission for Northrop to sell the tooling to the most likely customer -- Taiwan --for fear of offending the Mainland Chinesee government, but several other nations were also approached. However, no customers were found and the F-20 Tigershark program quietly died. The sole surviving F-20 now hangs in the California Science Center in Los Angeles

Serials of F-20A:

82-0062/0065		Northrop F-5G Tigershark 
				redesignated F-20A in 11/82.
				0062 carried civilian registration N4416T
					w/o 10/10/84, Suwon AB, Korea.
				0063 carried civilian registration N3986B
					w/o 5/14/85, Goose Bay, Labrador
				0064 carried civilian registration N44671.
					now in California Science Center, Los Angeles
				0065 cancelled before completion

Specification of Northrop F-5G (F-20A) Tigershark:

Engine: One General Electric F404-GE-100 low-bypass turbofan, 17,000 lb.s.t. with afterburning. Performance: Maximum speed: Mach 2.1 at 36,000 feet. Service ceiling: 55,000 feet. Initial climb rate: 50,300 feet per minute. Climb to 40,000 feet in 2 min 18 sec. Takeoff run: 1450 feet. Range with maximum fuel was 1543 miles. Combat radius with maximum internal fuel and three 275 US gallon external tanks and two Sidewinder missiles: 345 miles. Ferry range with maximum internal and external fuel: 1715 miles. Total internal fuel capacity was 677 US gallons. With maximum external fuel, a total of 1502 US gallons could be carried. Dimensions: Wingspan 27 feet 12 inches, wing area: 186 square feet Length: 46 feet 6 inches, height: 13 feet 10 inches. height 13 feet 4 inches, wing area 186 square feet. Weights: 11,220 pounds empty, 15,060 pounds combat, 26,290 pounds maximum takeoff. Armament: Armed with two 20-mm cannon in the fuselage nose. Two AIM-9 Sidewinder missiles could be carried at the wingtips. A total of 8000 pounds of ordnance or fuel tanks could be carried on external pylons.

Sources:


  1. The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.

  2. Jane's American Fighting Aircraft of the 20th Centry, Michael J.H. Taylor, Mallard Press

  3. Modern Air Combat, Bill Gunston and Mike Spick, Crescent, 1983.

  4. United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.

  5. Fighters of the United States Air Force, Robert F. Dorr and David Donald, Temple Press/Aerospace, 1990

  6. The World's Great Attack Aircraft, Gallery, 1988.

  7. Northrop F-5, Jon Lake and Robert Hewson, World Airpower Journal, Vol 25, 1996.

  8. E-mail from Gene Megas, formerly Northrop System safety engineer.

  9. E-mail from Johan Visschedijk on