development / production / upgrade / life extension

                          Last update 21-11-2020

Northrop N-156 family program

The US Air Force was engaged in a run to obtain higher and higher performances and armament load from its new fighters up to the sixties, with the consequences of increasing complexity, increase in airframe weight, spiralling maintenance costs and necessity for long runways.
Northrop studies on lightweight fighters begun in the mid fifties with the N-102 "Fang" project, which was not built. This had no resemblance to the future N-156/F-5.

  Photo: Northrop
        Northrop N-102 Fang mock-up with fictitious serial 22777

Small, lightweight engines with enough power were a problem, solved wth the availability of General Electric's J-85 beginning 1955. A new project was started with the designation N-156 and implied a family of aircrafts, consisting in a ground based fighter (N-156F), a carrier-borne fighter (N-156N) and a trainer (N-156T, later TZ-156).
Since small escort aircraft carriers, for which the N-156N was foreseen, were used only as aircraft transport carriers the development of this version was stopped by the end of the 50's.

The US Air Force needed at the time a new supersonic trainer to replace the Lockheed T-33A; it issued in May 1955 an operational requirement for what was to be selected and designated Northrop T-38A.

Northrop went on with development of the fighter version as a private venture, although the US Air Force was not interested in the proposal for its own use, but the aircraft might have been of interest to allied nations. Official presentation to the USAF of both the single- and double-seater was in January 1956.

Construction go-ahead (with company funding) was given early 1958. On 27-05-58 (rather unusually) an research and development contract with the US Department of Defense was formalized in July 1959, allocating almost USD 50m (32m to Northrop and 18m to General Electric) for 3 aircrafts and 1 static test airframe to Norair, the division of the new Northrop Corporation now responsible for building aircrafts and missiles.

                Mock-up with fictitious 56 (Fiscal Year) 156 (project number) serial.     Photo: Northrop

Official first prototype roll-out followed at Hawthorne on 31-05-59. Representatives of forty allied nations attended to the ceremony.
Licence production discussions were held with European aircraft builders: Fokker of the Netherlands, SABCA of Belgium and FIAT of Italy but their governments selected the Lockheed F-104G as their new fighter. Discussions were also held with Australia and the United Kingdom without results.

                                                            Drawing: Northrop
                                               Publicity Northrop drawing, rocket assisted take-off!!!!!!!!!!!!!!!!!!

Northrop - USAF trials
First flight of the first prototype, serial 59-4987, took place on 30-07-59 (without any Air Force insignia and markings) at Edwards AFB, where the aircraft had been transferred, going supersonic on the first flight despite the low thrust of the installed General Electric YJ-85-1 engine.

   Photo: Northrop
Overflight of Edwards AFB still in company colours (Norair on tail, no nationality markings)Freedom Fighter F-5 inscription)

                                                Photo: Northrop
                                         Nose inscription before selection by USA

        The second protoype at an Edwards AFB open-day with Sidewinders and a full load of tanks
. No nationality
        or US Air Force markings were painted as the type had not been accepted by

  Photo: Northrop
Flight tests proceeded smoothly, a USAF project test pilot flying the aircraft from th
e third flight for preliminary evaluation. No cannon armament was originally fitted, but tests with 20mm underwing podded cannons took place.

                    First prototype with GAM-83 Bullpup missile underwing.
            Photo: Northrop

Non US (French) air-to-air and air-to-ground missiles (quite unusual!) were taken in consideration as
armament in 1960:
Nord AA.20 (a-a) AS.20 (a-g), Nord AA.25, AS.25 and AS.30, without follow on.

The first prototype with
nose probe, Nord AS.30 underfuselage, AS.20 underwing
and AIM-9B Sidewinder missiles at wingstip
in 1962.                  Photo: unknown

More powerful General Electric YJ-85-5, with afterburner, replaced the early version after 32 test flights; the second prototype was foreseen to fly in January 1960.

Intensive armament trials took place: live 250/500/750 pounds bombs and napalm canisters were dropped, 2.75 inch rockets were fired,  AIM-9B Sidewinder air-to-air missiles were carried on the wingtips, a "special missions" (nuclear) bomb mock-up under the fuselage.

Photo: unknown
                                          The third prototype on a test flight, note long nose pitot tube.

US Air Force tests at Edwards AFB were concluded with great satisfaction in August 1960, but this did not lead to an Air Force change of mind. No order for its own use was placed and it seemed the the programm was going to be stopped, so the construction of the third prototype remained incompleted.

Official interest in the aircraft was renewed when the Kennedy administration beginning 60's decided to suppy it allies with a low-cost fighter under the Military Assistance Program FX; a competition was held involving the Freedom Fighter, the Douglas A-4 Skyhawk and the Lockheed F-104H, a simplified version of the Lockheed F-104G, this last being preferred by the Air Force.

The Northrop F-5A was anyhow selected as the winner, officially announced on 23-04-62, receiving the USAF designation Northrop F-5A Freedom Fighter in August 1962. The third prototype, designated Northrop YF-5A, was completed and flew on 31-07-63, being fully representative of production aircrafts. Both earlier prototypes were later brought up to YF-5A standard

Northrop - US Army trials
The US Army's wish to operate its own supportforce led in January 1961 till July 1961 to trials for the possible selection of a jet aircraft. This would have operated in the Forward Air Control and the Close Air Support role operating from uniproved airfields near front lines. Initial factory tests were held on a grass runway at Hughes airfield, Culver City, not far from the Hawthorne factory, followed at NAS Jacksonville and NAS Pensacola.

Two Fiat G-91R-3s, two G-91R-4s, one G-91T-1, two Douglas A-4D-2 (A-4B) Skyhawks and the two Freedom Fighters prototypes (59-04987/988) participated at Fort Rucker Army Base to the trials.

    Photo: unknown
Bombs armed Northrop YF-5A 94987 (without guns) in company with its competitors, 
Fiat G-91R-3 and Douglas A-4B.

    Photo: Northrop Grumman Corp.
        First Northrop YF-5A 94987 on an US Army test carrying two underwing tanks.

The Northrop aircraft was preferred by the Army, but the project was cancelled due to US Air Force fierce opposition.

Soft ground trials
at Pensacola in June 1961: the second Freedom Fighter prototype with
larger tires on the main and two-wheels on the front landing gear, later removed. Trials
included landing in 1300 ft/396m on grass and taking off with a maximum load in less
than 2'500 ft/762m.
USAF inscription was replaced by "Army" in September 1961 for
additional tests at Pensacola NAS.

Northrop - US Navy
A certain interest was shown after World War II by the US Navy, their piston engined aircrafts could be hardly handled by small escort carriers; its interest died when the Navy retierd these.

   Northrop F-5A / RF-5A / F-5B - Freedom Fighter

Northrop F-5A
The break through came on 22-10-62 when the USAF placed an order for 71 MAP funded aircrafts, followed by a second one placed on 27-08-63 for 99 Freedom Fighters, to be supplied to friendly nations. It was planned to build 12 aircrafts per month, initial delivery  planned during the first quarter of 1965.

Costruction of the third prototype could be completed, works already starting on 26-04-62, followed by the first flight on 31-07-63. This was the first airframe to feature all seven external stores pylons, designated Northrop YF-5A.

Production started immediately at the Hawthorne, a combined production line shared with the F-5B and Northrop T-38 trainer was capable of producing 22 aircrafts per months. The first production/fourth prototype aircraft (63-08367) flew for the first time in October 1963 (less then a month from the order); it joined the test program at the end of 1963, together with the second production/fifth prototype (63-08368).

Northrop delivered the first three protypes, designated F-5A Freedom Fighter, to the Air Force by the third quarter (July-September) of Fiscal Year 1963.
On 30-06-1963 there were two active F-5A and one non-operational. First military test flight was on 14-08-63.

Category I testing took place between October 1962 and May 1965. First aircraft accepted for Category II tests by the Air Force Flight Test Center, Edwards AFB, was serial number 63-08367 on 01-02-64, performance, stability and control testing began on 30-04-64 with s/n 63-08368. Both Category II and III lasted between February and October 1964. Tests continued till 1966; 16'000 flight hours were simulated.

                                Photo: USAF
                   Armament tested on the 5th prototype
at Edwards AFB was the Bullpup air-to-ground missile (an
                   highly unpropable load due to the thin wings), together with bombs.

An operational requirement to incorporate two 20 mm Pontiac M-39A to increase Freedom Fighter's firing power was issued in 1964 by the USAF. Only a ranging set mounted in the nose and an optical sight were at pilot's disposal for air-to-air and air-to-ground operations.

Approximately 140 USAF personnell from Tactical Air Command, Air Training Command, Edwards AFB Flight Test Centre, together with Northrop personnell, were involved in 1030 trials flight hours during FY 1964. Acceptance of the first Freedom Fighter by Tactical Air Command was on 30-04-64. Future Williams AFB instructor pilots were also contemporanously trained.

               Photo: USAF
  The first production examples undergoing in 1965 tests with wing and underfuselage tanks.                                                                                    

            Photo: M. Hooks
rthrp F-5A was used for armament testing; here it is equipped with 3 napalm bombs.

Fatigue tests were carried out between 1964 and 1966 for a total of 16'000 simulated fight hours.

                                     View on Northrop's Freedom Fighte assembly line at Palmdale during the 1960s'

Northrop showed two of its Freedom Fighters (serials 69175/176) at the le Bourget air show while transting

Europe on delivery to Iran.

    Serial 69176 (with code 203 on the nose) at le Bourget on 03-06-67.   Photo: unknown

See under the respective Air Forces pages for information regarding delivery/use of the Northrop F-5A.

The USAF had accepted
from Northrop for the USA Military Assistance Program to allied countries by 01-07-68.:
                               405 Northrop F-5A;  during FY 69 an additional  27, Total 432
                                  1 Northrop RF-5A; during FY 69 an additional 15, Total   16
                                 58 Northrop  F-5B; during FY 69 an additional   7, Total   65
Fiscal Year goes from October till the following September.
Produced as Foreign Military Sales during FY69:  10 Northrop F-5A, 5 Northrop F-5B

Northrop F-5B
Operational conversion on the new fighter dictated the construction of a two-seater, designated . This had no cannon armament but could carry any all other armament under the wings. One two-seater per nine single-seaters was foreseen in the two initial contracts.

First flight of this new version was on 24-02-64 by serial 63-8438; it was declared operational already on 30-04-64, earlier than the single-seater which was in August 1964. Deliveries started on April 30th, 1964 to the 4441st Combat Crew Training Squadron at Williams AFB, a new USAF unit taking care of pilots belonging to the countries selected to receive the aircraft training.

              Photo: Northrop
Prototype Northrop F-5B 38438 with long nose pitot tube and underwing stores in 1964.

Sales demonstration was undertaken by the first company demonstrator between June and September 1964 in Europe and the Middle East: Italy, Belgium, Germany and Saudi Arabia. Unfortunately it was lost during one of the last demonstration flights.
The second Northrop F-5B (serial 38445) replaced immediately the lost one.

              Photo: unknown
             The first company demonstrator shown at Brussels-Zavestem in unusual colours on 28-06-64.

   Unscheduled engine change was demostrated by the first Northrop F-5B in Saudi Arabia

The fourth production Northrop F-5B (serial 63-08421) with several design improvements and a more powerful GE J-85-15 was used for 7 hours/8 missions tests at Edwards AFB between the 9th and 15-06-65; some of these improvements were later incorporated in the development of F-5As supplied to various Air Forces as well a being offered, without success, to Belgium.

Further engine trials took place at a later stage again on the Northrop F-5B company demonstrator with the much more powerful General Electric J-85-21, first flown as such on 28-03-69; they lasted five months for a total of approximately 130 flight hours. This engine was to power the next generation Northrop F-5E Tiger.

  Photo: Northrop
     Northrop F-5B 38445 with
General Electric J-85-21 on a test flight.

By mid-73 eighty-four of eighty-eight F-5B foreseen for MAP countries had been handed over to the USAF for onward transfer, together with 13 sold under Foreign Military Sales program (2 to Lybia, 6 to Norway, 5 to Iran); additional 2 FMS to Jordan were to be delivered to Jordan begignning 1974.

The static tests airframe (serialled C-8123) was withdrawn from use and transferred to the Lackland AFB for preservation where it was seen on 18-11-87.

See under the respective
Air Forces pages for information regarding delivey/use of the Northrop F-5B.

An USA official document states tha by September 1975 that the a Northrop reprsentative was appointed to sell Northrop F-5s: Belgium, Denmark, France, Germany, Italy, Luxembourg, Netherlands, Norway, Portugal and the United Kingdom.

Northrop RF-5A
Necessity of a reconnaissance version for countries receiving Military Assistance Program help, was recognized by the mid 60s. An order for 13 aircrafts for Iran was placed in October 1967, followed by the first flight in May 1968. Tests were held the same year at Edwards AFB during the period July 1st and August 28th with the first production aircraft (for Iran, s/n 67-21219) flying 58.8 hours in 47 test missions.

              Photo: Northrop
  Northrop's own Northrop F-5A-15 serial 38372 was modified as RF-5A prototype in 1968,
  later being modified again as F-5A-15 and used for tests.

Main difference to the fighter version was the modification of the nose to mount four KS-92 cameras, otherwise retaining its combat capabilities.

The second aircraft
built (serial 89102) was demonstrated at Le Bourget air show in June 1969 before onward delivery to the Norwegian Air Force.

  Photo: R.A. Scholefield
Northrop RF-5A for the Norwegian AF seen at le Bourget air show on 07-06-69.

This version was only built for US allied Air Forces; USAF never adopted it, not even for training.

See under the corresponding Air Forces pages for information regarding delivey/use of this version.

Freedom Fighter production
Monthly production rate at the Hawthorne plant was at the beginning of 1965 of ten mixed, single- and two seaters; 150 Freedom Fighters had been handed-over to the USAF for onward delivery to the Military Assistance Program (MAP) countries in October 1965.
By the end of Fiscal Year 1967 Northrop had produced 527 aircrafts.

Production of the F-5A came to an end in March 1972, unfortunately there are several versions regarding the exact number built.
One version states that 3 prototypes, 617 F-5A 624 production airframes have been completed (2 modified as F-5B).
Production of the F-5B ended in the mid-seventies,
134 200 airframes having been completed.
Production of the RF-5A ended in June 1972 having completed 89 airframes, for an total of 3 prototypes and 844 production airframes.

A second version mentions the construction of 3 prototypes, 1 static airframe and 617 production Northrop F-5A, 89 RF-5A, 134 F-5B, total 844 aircrafts
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
   Northrop F-5E / F-5F / RF-5E - Tiger

Flight testing of an uprated General Electric J-85-GE-21 engine in a highly modified Northrop F-5B started in March 1969 and lasted till August of that year for a total of approximately 130 flying hours; this demonstrated the availability of an engine which could power an higher performance fighter of the family to be used mainly air-superiority missions by nations with little technological knowledge.

Northrop made an unsolicited offer to the US Secretary of Defence/Air Force but these wanted confirmation of the higher performance by flight tests. The US Congress required a competition between several manufactures, before funds would be granted covering the 1973 Fiscal Year for the so-called Advanced International Fighter programm. Four companies answered in March 1970 to the request for proposal placed on 26-02-70: Northrop with its F-5E; a stripped down version of its the F-4E Phantom was offered by McDonnel-Douglas, Lockheed of its F-104 Starfighter, Ling-Temco-Vought of its F-8 Crusader.
All these underwent a seven months USAF evaluation at the end of which the Northrop F-5E was officially declared winner on 20-11-70.
A fixed price contract for 325 aircrafts was placed on 08-12-70, all funded bs Military Assistance Grant Aid; deliveries were foreseen: 26 in Fiscal Year 1972, 71 during FY 1973, 120 in FY 1974 and 108 in FY 1975. On November 1970 the first flight date was set to December 1972.

The new fighter was officially named Northrop F-5E Tiger on 28-12-70.
The first production F-5E was initially planned to be produced in February 1973; the aircrafts during February to October 1973 were to be used by the USAF for tests and evaluation, for training and a few to be delivered to Vietnam.

First four F-5Es were built on F-5 subassembly line at Hawthorne, fifth and following aircrafts were assembled at Palmdale; these five were foreseen to run the test program, but various modifications delayed the completion (and increased the costs) of the programm, necessitating the addition of a sixth aircraft to flight testing. All these aircrafts were to be refurbished and transferred to the Air Force for operational use upon completion of the development phase, as they actually were.

The most important difference to the Freedom Fighter was the installation of an Emerson Electric radar, AN/APQ-153 in the early examples, replaced by an improved search range Emerson Electric AN/APQ-159 in later examples; the double-seaters were equipped with Emerson Electric AN/APQ-157, a dual-control variant of the first radar.

Static engine tests were completed by May 1972, roll-out of the first prototype took place at Hawthorne plant on 23-06-72, first flight on 11-08-72 at Edwards AFB. An altitude of 20'000 feet was reached during this flight.
Engine malfunctions happend the same month, 1972 forcing suspension of flight tests between 21-09-72 and 16-12-72. Finally, the first Tiger was accepted by the Air Force on 03-08-73 for flight tests at Edwards AFB. Definitive engine approval had been given on 25-04-73 after modifications by General Electric. 

   Photo: unknown
The third prototype seen at an open-day at Edwards AFB in 1973 with early Sidewinder AIM-9B
on wing tip. No tiger painted on tail.

Prototype number two with Tiger painted on tail landing on 11-04-79 at Edwards AFB.
Of note 30mm underfuselage gun pod
                                               Photo: USAF/J. Porter

                      Photo: unknown
                            Northrop F-5E 11418 testing GPU-5 30mm underbelly cannon.

      Photo: MBB
MBB Modular Dispenser System demonstration and test prototype under the fuselage of the
second Northrop F-5E prototype.

Thirty tousand simulated flight hours airframe fatigue tests were completed on 22-11-75, consisting of 85% air-to-air combat and 15% air-to-ground combat. Tests continued till 1955; 24'000 flight hours were simulated. This brought to a redesign of the vertical stabilizer due to failure.

Delivery of the first Tiger to the 425th Tactical Fighter Training Squadron at Williams AFB was on 06-04-73, four months ahead of schedule; Squadron's role was to train pilots of countries that had ordered Tigers.

In May 1975 there were 6 Northrop F-5E undergoing tests by the Joint Test Force (Northrop /USAF) at Edwards AFB; they participated from this Air Base to the development of special features for non-US customers.
Northrop showed its new product at the le Bourget air show in June 1975 with the presence of one Northrop F-5E, serial 01467 code 51.
All prototypes were transferred between 1976 and 1981 to the US Air Force and used at Williams AFB for training.

                                                Photo: Northrop
                                                     Wingtip Sidewinder and LGBs underwing plus tests noseboom

    A little known configuration/test of second prototype Northrop F-5E 11418 with 4 Huges
    AGM-59 Mavericks, configuration available only to SaudI Arabia.

See under the respective Air Forces pages for information regarding delivey/use of the Northrop F-5E.

Northrop F-5F Tiger
No second generation conversion trainer was initially deemed to be necessary in view of the modest number of single-seater thought to be sold; the Northrop F-5B would take care of training new pilots. Increasing number of Tigers sold dictated the development and production of the next generation trainer.

Two Fiscal Year 1973 (00889/00891) were completed as two-seaters, both aircrafts first flew from Edwards AFB on 25-09-74 where they remained, undergoing several tests.

        Photo: USAF
                                     First prototype testing an underwing target pod.

      Photos: collection The Northrop F-5 Enthusiast
The first prototype F-5F 00889 at Kefkavik on the way to demostration at
Le Bourget air-salon on 16-06-75 in a typical Groenland day.

  Demostration flights, eg. Le Bourget Air Show in June 1975, were performed as well
  as armament and target tug tests from Edwards AFB for foreign customersat least until
  November 1976. These tests were taken care by the 6512nd Test Squadron, 6510th
  Test Wing/Air Force Flight Test Center-Edwards AFB in conjunction with Northrop

Badge 6512 Test Squadron.

       The second prototype being prepared for spin tests on 10-11-76 at Edwards AFB;
       of note the extra long nose pitot tube.                                        Photo: unknown

See under the respective Air Forces pages for information regarding delivey/use of the Northrop F-5F

Northrop RF-5E Tiger Eye

Original Northrop plan was to provide the Tiger with limited reconnaissance capability installing a similar nose as the RF-5A had. This solution had already applied earlier to some Saudi Northrop F-5E but was unsatisfying as the nose was too small to accept latest reconnaissance equipment; the company decided therefore to go (using company funds) for a new design carrying sensors as cameras or infrared systems on quick-change pallets inside the lengthened, strengthened, wider nose. It would have similar capacity as the McDonnell RF-4E for countries already operating the Tiger, a market for between 100 and 150 aircrafts was forecasted.

An alternative possibility to convert Northrop F-5E Tigers fighter into reconnaissance aircrafts was not considered by Northrop as not effective due to the high costs.

One of the Northrop F-5E Tiger prototypes (74-01420) was leased back from USAF to be converted as prototype and first flown as RF-5E on 29-01-79 from Edwards AFB's Air Force Flight Test Center.

Flight evaluation took place at the same base; the aircraft was converted again to fighter configuration by December 1979/April 1980, at the end of the evaluation. Demonstration flights were hold during this period to possibe non US customers: Jordan, Thailand, Korea, China/Taiwan, Saudi Arabia, Malaysia, Norway, Switzerland, Morocco and Portugal.

    Photo: DoD/USAF
Northrop RF-5E 11420 seen on 14-03-79 in its original metallic colours; clearly visible the
undernose camera windows.

            Camouflaged Northrop RF-5E 11420 on a test flight.        Photo: Northrop

It was shown also at the Le Bourget (France) show in June 1979 but the sales were disappointing mainly due to the high cost (50% more than the fighter). Only 12 aircrafts were sold: two bought by Malaysia and ten by Saudi Arabia.

Necessity for a reconnaissance version of the Tiger was still felt in Asia beginning of the 1990s; Singapore initiated a programm to locally convert eight Northrop F-5E to reconnaissance aircrafts by STAerospace in 1991, delivered in 1994. The same company converted seven Republic of China (Taiwan) Northrop F-5E to the reconnainsance version with initial delivery in August 1997.

See under the respective Air Forces pages for information regarding delivey/use of the Northrop RF-5E.

   Northrop F-5G / F-20 Tigershark

A third generation of the Northrop product with the latest airframe, engines, radar and avionic features was studied beginning mid-70s, keeping in mind the same requirements as the previous versions: low cost, ruggedness and ease of operation.
The study ended with the construction of the Northrop F-5G, later redesignated F-20, first flown on 30-08-82; it had little connonality with the earlier version, though initially designated in the F-5 range.
    Three prototypes were built
(here the first prototype), received initially USAF serials, were
    painted in the markings of several possible customers; later they wore civilian registration
    for demonstration purposes to various countries.Two were lost during these demonstrations.

Politics first blocked the sale of this fighter; authorisation
in 1983 to sell the more advanced, expensive and complicated General Dynamics F-16 abroad gave the death blow to the project.
Three airframes had been built, two of which were lost in crashes, an additional airframe was only partially completed. Presence of the fighter at Edwards AFB with the 6512 Test Wing was from 10-04-84 till April 1985.

By 1986 Northrop had incurred in a loss of USD 1,2 billion, when further development/sales efforts were cancelled in December.

No further details of this third F-5 generation fighter are included as this is outside the scope of this study.

End of Northrop production

Production of F-5E, F-5F Tiger variants was completed on 16-01-87 with the hand-over at Northrop's Palmdale plant of two single-seater Tiger to the Bahrain. These were not the last as five additional Northrop F-5E and 3 F-5E were assembled from spare parts for Singapore by the beginning of July 1989, almost to underline the vitality of the design.

               Photo: Northrop
Final variants seen in flight: Northrop F-5F N3139Y, F-20A N4416T (both Northrop demonstrators)
and Malaysian AF RF-5E M29-20.

The exact number of Tiger built is 953 divided in 4 prototypes built at Hawthorne, 941 at Palmdale and 8 at Mojave (from spare parts); exactly how many of each type is not known.There are several versions: F-5E 792/793 RF-5E 12, F-5F 146
786, 793, F-5F  140,147 Who can help?).

A total of around 2'160 aircrafts of all variants were built by Northrop or built under licence abroad, an enormous success in consideration that the aircraft was not originally taken in consideration by the US Air Force.

Northrop's Tiger upgrades/life extension

Northrop, and other US companies, had no luck in selling F-5 upgrade programs, mainly due to missing government support (F-5G/F-20) and late entry into the hard fought update market for Freedom Fighters and Tigers.

        Northrop F-5E publicity

The second Northrop F-5E prototype was used at Edwards AFB, starting from November 1982, for trials of the Northrop AN/ALQ-171(V) pod-mounted Conformal Countermeasures System, partially paid by the Swiss government. This pod fitted around the underfuselage pylon, allowing the pylon to carry external fuel or ordnance. The prototype completed a nine flights demonstration program at Edwards AFB that included aircraft handling and jamming capabilities; additional tests were held beginning 1983 at the USAF Electronic Warfare Environment Simulator at Fort Worth, completed in June 1983.

Another upgrade trial took place in 1985, when an Emerson APG-69 was installed in a Swiss double-seater (J-3209); the aircraft was demonstrated at the Le Bourget Air Show in June 1985 without any sales success. Another radar set was installed on a USAF 425th Squadron Northrop F-5F and completed 200 test missions at Williams AFB.

One Tiger was tested in 1991 at Fallon NAS with an Westinghouse APG-66 radar, but the radar was again not adopted by any Air Force.

(Northrop had purchased Grumman in 1994) tried to enter the upgrade market at the end of 1993 with an avionics upgrade in order to establish the Northrop F-5s as a lead-in trainer to the General Dynamics F-16.

Later one aircraft of the US Navy 127 Sqns, serial 741568 code 46, was modified to represent between 20-04-95 and the end of 1997 an improved version named Tiger IV.
The initial 12 flights concentrated on evaluating air-to-air modes of the Westinghous APG-66 pulse-Doppler radar, doubling the detection range, after which the aircraft was grounded for a software upgrade. A furter seven flights tested air-to-ground radar modes of the integrated weapon-system and delivery.
This version was offered in several possible packages; costs were lowered using components already in use in various other aircrafts. Main packages included 1 or 2 Bendix Multifunction Displays as used by the Taiwanese IDF, a GEC Head Up Display as used by the F-16, an Westinghouse APG-66 radar, an INS, HOTAS control and many other features; one cannon had to be removed to allow space for the new avionics.

The aircraft was reconfigurated to a normal Northrop F-5E end of 1997, and re-delivred to the US Navy, as no interest was shown by the various Air Forces. Cost of the modifications had been sustained by the various firms supplying the avionics.

                                   Photo: Northrop        Tiger IV on tail
                                                                         Northrop F-5E 741568 modified as Tiger IV

The project was realised in partnership with the Air Force San Antonio Air Ligistics Center; stored Northrop F-5E (serial 741568) was obtained as a free loan in 1994 from the US Navy, avionics companies supplied their products, NorthropGrumman made a structural upgrade. The first flight of the modified aircraft took place on 20-04-95 from Los Angeles International Airport, transferring directly to Edwards AFB were it underwent on a six months test program.
The project had no luck, though partial modifications, according to the client's wishes were offered; the aircraft was modified back to the original version in 1998.

Grumman X-29

        Grumman built two aircrafts, designated X-29A, using two hightly modified Northrop F-5A airframes (63-8372
        becoming 82-0003 
and 65-10573 becoming 82-0049),
utilising the forward fuselage and landing gear of the
        Freedom Fighters. The first flight of the new (old) aircraft was on 14-12-84 from Edwards AFB.

        NASA used the the test aircrafts (in collaboration with Grumman, DARPA and the USAF) between 1984 and 1991
        demonstrating a 
number of new technologies and techniques plus new use of existing technologies.
        This photo shows clearly shows the Northrop F-5A origin.

        Photo: NASA

US Navy airframe/avionics modifications
Worn-out US Navy Tiger airframes needed to be replaced by the beginning of the 2000 years. Several options were taken into consideration; a modification/upgrade program by Norair, involving initially 32, later 44 former low-time (an average of 2'500 flight/hours) Swiss Northrop F-5E, was selected.

The program started in 2003 (with the delivery of airframes from Emmen, Switzerland): 41 were modified at St Augustine's Manufacturing and Flight Test Center as upgraded single-seaters with the designation Northrop F-5N, three were converted as double-seaters, keeping the designation F-5F, the forward fuselage being replaced by an original, refurbished US Navy one. The programm ended on 29-04-09 with the handing over to the US Navy of the last aircraft.

Fatigue critical components were replaced. areas of the aft fuselage were refurbished, newly designed upper cockpit longerons were installed, avionics were brought up to present standard, aircrafts were completely rewired, the liquid oxygen system was replaced by a gaseous one, anti-skid brakes were added. The conversion lasting approximately five months with the cost of around USD 1m each.

            "Franken Tiger" Northrop F-5F 761586 roll-out on 23-04-08 at the St Augustine plant,
            the aircraft was delivered to the US Marines, colours were changed to standard camouflage.
                                                                                                  Photo: Northrop Grumman

Last modified ex Swiss F-5E (serial 761550) seen at the handing over ceremony at the St Augustine plant.
                                                                                                                   Photo: Northrop Grumman
Life extension
A first increase in service life
to 8'000 hours (the Northrop F-5E anf F-5F were originally cleared for a service life of 4'000 flying hours) was granted in 1977 following thorough tests on a complete Northrop F-5E airframe. The new clearance was given in the assumption of 85 percent of flights in air-combat and 15 percent for ground-attack missions.

A great number of Freedom Fighters and Tigers built between 1968 and 1989 are still in use with many Air Forces. This dictated the necessity to maintain and enhance the structural integrity of the airframes.

Northrop Grumman was selected in 1995 to manufacture 14 new wings, upper and lower cockpit/dorsal longerons, fuselage bulkheads  and other parts for foreign Northrop RF-5A, F-5A, F-5B, F-5E, F-5Fs; the company contemporanously expanded its spare parts business providing a "one-stop" team for total support of the fighters. Upgrade retrofit kits, including INS/GPS navigation system, antiskid brakes, an onboard oxygen-generating system to reduce costs compared to the early liquid oxygen system were also offered.

The role of the Tiger switched in the world more and more to that of a lead-in trainer; the company offered (without success) in mid 90's a conversion kit to convert single-seaters F-5E to double-seaters F-5F with new manufactured forward fuselages.

Beginning of 2005 Northrop developed a new system support plan in order to enable the users to obtain part of the necessary structure and other spare parts from another company. A teaming agreement was signed on 04-05-10 with the Swiss company RUAG Aviation to provide worldwide sustainment and life cycle logistics, as well as modifications and upgrade programs, to countries flying the F-5 Tiger. RUAG is the prime support provider for the Swiss Air Force and other F-5 operators.