The Northrop F-5A and F-5B Freedom Fighter and the F-5E and F-5F Tiger II are part of a supersonic light fighter family, initially designed in the late 1950s by Northrop Corporation. Being smaller and simpler than contemporaries such as the McDonnell Douglas F-4 Phantom II, the F-5 cost less to both procure and operate, making it a popular export aircraft. The F-5 started life as a privately funded light fighter program by Northrop in the 1950s. The design team wrapped a small, highly aerodynamic fighter around two compact and high-thrust General Electric J85 engines, focusing on performance and low cost of maintenance. Though primarily designed for the day air superiority role, the aircraft is also a capable ground-attack platform. The F-5A entered service in the early 1960s. During the Cold War, over 800 were produced through 1972 for U.S. allies. Though the USAF had no acknowledged need for a light fighter, it did procure roughly 1,200 Northrop T-38 Talon trainer aircraft, which were directly based on the F-5A.
After winning the International Fighter Aircraft competition in 1970, a program aimed at providing effective low-cost fighters to American allies, Northrop introduced the second-generation F-5E Tiger II in 1972. This upgrade included more powerful engines, higher fuel capacity, greater wing area and improved leading edge extensions for a better turn rate, optional air-to-air refueling, and improved avionics including air-to-air radar. Primarily used by American allies, it remains in US service to support training exercises. It has served in a wide array of roles, being able to perform both air and ground attack duties; the type was used extensively in Vietnam. A total of 1,400 Tiger IIs were built before production ended in 1987. More than 3,800 F-5 and the closely related T-38 advanced trainer aircraft were produced in Hawthorne, California. The F-5N/F variants are in service with the United States Navy and United States Marine Corps as an adversary trainer. Approximately 500 aircraft are in service as of 2014.
The F-5 was also developed into a dedicated reconnaissance version, the RF-5 Tigereye. The F-5 also served as a starting point for a series of design studies which resulted in the Northrop YF-17 and the F/A-18 navalized fighter aircraft. The Northrop F-20 Tigershark was an advanced variant to succeed the F-5E which was ultimately canceled when export customers did not emerge.
The design effort was led by Northrop vice president of engineering and aircraft designer Edgar Schmued, who previously at North American Aviation had been the chief designer of the successful North American P-51 Mustang and F-86 Sabre fighters. Schmued recruited a strong engineering team to Northrop and assigned them the goal of reversing the trend in fighter development towards greater size and weight in order to deliver an aircraft with high performance, enhanced maneuverability, and high reliability, while still delivering a cost advantage over contemporary fighters. Recognizing that expensive jet aircraft could not viably be replaced every few years, he also demanded "engineered growth potential" allowing service longevity in excess of 10 years. Schmued recognized that new jet engine and aerodynamic technology were crucial to these goals, such as the compact but high thrust-to-weight ratio General Electric J85 turbojet engine, and the recently discovered transonic area rule to reduce drag. The J85 engine had been developed to power McDonnell's ADM-20 Quail decoy employed upon the Boeing B-52 Stratofortress. This engine with thrust-to-weight ratios of 6.25 to 7.5 over various versions had a notable thrust per pound advantage over contemporaries, such as the 4.7 thrust-to-weight ratio of the J79 engine used in the F-4 Phantom.
Another highly influential figure was chief engineer Welko Gasich, who convinced Schmued that the engines must be located within the fuselage for maximum performance. Gasich also for the first time introduced the concept of "life cycle cost" into fighter design, which provided the foundation for the F-5's low operating cost and long service life. The low costs involved has been recognized as an important element of the aircraft's effectiveness; defense analyst and combat aircraft architect Pierre Sprey stated in a 1982 U.S. Department of Defense report that, "Increases in cost and complexity that were unnecessary to enhance air-to-air effectiveness have decreased today's effective force size per constant dollar by factors of 25 to 75, relative to the F-86's 2000 sorties/day per billion dollars. The only exception to this strikingly adverse trend is the F-5E, which manages to produce 500 sorties/day per billion dollars." The total cost of an F-5 sortie is approximately 20% that of an F-16 sortie. even though the F-16 is a cost effective modern fighter. This low cost was also a very deliberate strategy of Northrop in following a focused light fighter plan. A Northrop design study stated "The application of advanced technology was used to provide maximum force effectiveness at minimum cost. This became the Northrop philosophy in the development of the T-38 and F-5 lightweight trainer and fighter aircraft."
The flying qualities of the F-5 are often highly rated, comparable to the North American F-86 Sabre and the General Dynamics F-16 Fighting Falcon. The safe and predictable flying qualities of the F-5, while still maintaining high agility, was a deliberate goal of the design team. The company stated "Northrop took a new approach that the initial design layout shall stress excellent flying qualities such that utilization of the complete performance envelope is available to the pilot."
According to defense analyst and prominent Pentagon fighter mafia (of F-16 fame) member Pierre Sprey, the F-5 was perhaps the most effective U.S. air-to-air fighter in the 1960s and early 1970s based on his published fighter effectiveness criteria. Sprey defines the key factors of fighter effectiveness in order of importance as 1. Ability to surprise the enemy without being surprised, 2. On a per budget basis, ability to outnumber the enemy via lower unit cost and higher sortie rates and reliability, 3. Ability to outmaneuver the enemy, and 4. Once in position to fire by either surprise or maneuver, ability to attain reliable kills (weapon system effectiveness). As a prominent example of a well implemented light fighter, the F-5 is a close match to these criteria in the time frame before Beyond Visual Range missiles became reliable. A small visual and radar cross section size and consequent detection difficulty often conferred the F-5 the advantage of surprise. The F-5 has the smallest planform area of any fighter in common usage. This is a critical practical combat advantage since historically about 80% of air to air kills do occur by surprise. The aircraft is highly cost effective and reliable, allowing superior numbers in the air on a per budget basis. The aircraft also has a high sortie rate, low accident rate, high maneuverability, and is armed with an effective combination of 20mm cannon and heat seeking missiles.
The F-5 development effort was formally started in the mid-1950s by Northrop Corporation for a low-cost, low-maintenance fighter. The company designation for the first design as the N-156, intended partly to meet a U.S. Navy requirement for a jet fighter to operate from its escort carriers, which were too small to operate the Navy's existing jet fighters. That requirement disappeared when the Navy decided to withdraw the escort carriers; however Northrop continued development of the N-156, both as a two-seat advanced trainer, designated as N-156T, and a single-seat fighter, designated as N-156F.
The N-156T was quickly selected by the United States Air Force as a replacement for the T-33 in July 1956. On 12 June 1959, the first prototype aircraft, which was subsequently designated as YT-38 Talon, performed its first flight. By the time production had ended in January 1972, a total of 1,158 Talons were produced. Development of the N-156F continued at a lower priority as a private venture by Northrop; on 25 February 1958, an order for three prototypes was issued for a prospective low-cost fighter that could be supplied under the Military Assistance Program for distribution to less-developed nations. The first N-156F flew at Edwards Air Force Base on 30 July 1959, exceeding the speed of sound on its first flight.
Although testing of the N-156F was successful, demonstrating unprecedented reliability and proving superior in the ground-attack role to the USAF's existing North American F-100 Super Sabres, official interest in the Northrop type waned, and by 1960 it looked as if the program was a failure. Interest revived in 1961 when the United States Army tested it, (along with the Douglas A-4 Skyhawk and Fiat G.91) for reconnaissance and close-support. Although all three types proved capable during Army testing, operating fixed-wing combat aircraft was legally the responsibility of the Air Force, which would not agree to operate the N-156 or allow the Army to operate fixed-wing combat aircraft, a situation repeated with the C-7 Caribou.
In 1962, however, the Kennedy Administration revived the requirement for a low-cost export fighter, selecting the N-156F as winner of the F-X competition on 23 April 1962 subsequently becoming the "F-5A", being ordered into production in October that year. It was named under the 1962 United States Tri-Service aircraft designation system, which included a re-set of the fighter number series. Northrop manufactured a total of 624 F-5As, including three YF-5A prototypes, before production ended in 1972. A further 200 F-5B two-seat trainer aircraft, lacking a nose-mounted cannon but otherwise combat-capable, and 86 RF-5A reconnaissance aircraft, fitted with a four-camera nose, were also built. In addition, Canadair built 240 first generation F-5s under license, CASA in Spain built 70 more aircraft.
In 1970, Northrop won the International Fighter Aircraft (IFA) competition to replace the F-5A, with better air-to-air performance against aircraft like the Soviet MiG-21. The resultant aircraft, initially known as F-5A-21, subsequently became the F-5E. It had more powerful (5,000 lbf) General Electric J85-21 engines, and had a lengthened and enlarged fuselage, accommodating more fuel. Its wings were fitted with enlarged leading edge extensions, giving an increased wing area and improved maneuverability. The aircraft's avionics were more sophisticated, crucially including a radar (initially the Emerson Electric AN/APQ-153) (the F-5A and B had no radar). It retained the gun armament of two M39 cannon, one on either side of the nose of the F-5A. Various specific avionics fits could be accommodated at customer request, including an inertial navigation system, TACAN and ECM equipment.
The first F-5E flew on 11 August 1972. A two-seat combat-capable trainer, the F-5F, was offered, first flying on 25 September 1974, at Edwards Air Force Base, with a new nose, that was 3 feet longer, which, unlike the F-5B that did not mount a gun, allowed it to retain a single M39 cannon, albeit with a reduced ammunition capacity. The two-seater was equipped with the Emerson AN/APQ-157 radar, which is a derivative of the AN/APQ-153 radar, with dual control and display systems to accommodate the two-men crew, and the radar has the same range of AN/APQ-153, around 10 nmi. On 6 April 1973, the 425th TFS at Williams Air Force Base, Ariz. received the first F-5E Tiger II.
A reconnaissance version, the RF-5E Tigereye, with a sensor package in the nose displacing the radar and one cannon, was also offered.
The F-5E eventually received the official name Tiger II; 792 F-5Es, 146 F-5Fs and 12 RF-5Es were eventually built by Northrop. More were built under license overseas: 91 F-5Es and -Fs in Switzerland, 68 by Korean Air in South Korea, and 308 in Taiwan.
The F-5E proved to be a successful combat aircraft for U.S. allies, but had no combat service with the U.S. Air Force (though the F-5A with modifications referred to as F-5C was flown by the U.S. in Vietnam). The F-5E evolved into the single-engine F-5G, which was rebranded the F-20 Tigershark. It lost out on export sales to the F-16 in the 1980s.
The F-5E experienced numerous upgrades in its service life, with the most significant one being adopting a new planar array radar, Emerson AN/APQ-159 with a range of 20 nmi to replace the original AN/APQ-153. Similar radar upgrades were also proposed for F-5F, with the derivative of AN/APQ-159, the AN/APQ-167, to replace the AN/APQ-157, but that was cancelled. The latest radar upgrade included the Emerson AN/APG-69, which was the successor of AN/APQ-159, incorporating mapping capability. However, most nations chose not to upgrade for financial reasons, and the radar saw very little service in USAF aggressor squadrons and Swiss air force.
Various F-5 versions remain in service with many nations. Singapore has approximately 49 modernized and re-designated F-5S (single-seat) and F-5T (two-seat) aircraft. Upgrades include new FIAR Grifo-F X-band radar from Galileo Avionica (similar in performance to the AN/APG-69), updated cockpits with multi-function displays, and compatibility with the AIM-120 AMRAAM and Rafael Python air-to-air missiles.
One NASA F-5E was given a modified fuselage shape for its employment in the Shaped Sonic Boom Demonstration program carried out by DARPA. It is preserved in the Valiant Air Command Warbird Museum at Titusville, Florida.
The Royal Thai Air Force (RTAF) had their F-5s undergo an entensive upgrade program, resulting in the aircraft re-designated as F-5T Tigris. They are armed with Python III and IV missiles; and equipped with the Dash helmet-mounted cueing system.
Similar programs have been carried out in Chile and Brazil with the help of Elbit. The Chilean upgrade, called the F-5 Tiger III Plus, incorporated a new Elta EL/M-2032 radar and other improvements. The Brazilian program, re-designated as F-5M, adds a new Grifo-F radar along with several avionics and cockpit refurbishments, including the Dash helmet. The F-5M has been equipped with new weapon systems such as the Beyond Visual Range Derby missile, Python IV short-range air-to-air missile, SMKBs smart bomb, and several other weapons.
The first contract for the production F-5A was issued in 1962, the first overseas order coming from the Royal Norwegian Air Force on 28 February 1964. It entered service with the 4441st Combat Crew Training School of the USAF, which had the role of training pilots and ground crew for customer nations, on 30 April that year. At that point, it was still not intended that the aircraft be used in significant numbers by the USAF itself.
This changed with testing and limited deployment in 1965. Preliminary combat evaluation of the F-5A began at the Air Proving Ground Center, Eglin AFB, Florida, during the summer of 1965 under project Sparrow Hawk, with one airframe lost through pilot error on 24 June. In October 1965, the USAF began a five-month combat evaluation of the F-5A titled Skoshi Tiger. A total of 12 aircraft were delivered for trials to the 4503rd Tactical Fighter Squadron, and after modification with probe and drogue aerial refueling equipment, armor and improved instruments, were redesignated as the F-5C. Over the next six months, they performed combat duty in Vietnam, flying more than 2,600 sorties, both from the 3rd Tactical Fighter Wing at Bien Hoa over South Vietnam and from Da Nang Air Base where operations were flown over Laos. Nine aircraft were lost in Vietnam, seven to enemy ground fire and two to operational causes. Although declared a success, with the aircraft generally rated as capable a ground-attack aircraft as the F-100, but suffering from a shorter range, the program was considered a political gesture intended to aid the export of more F-5s than a serious consideration of the type for U.S. service. From April 1966, the aircraft continued operations as 10th Fighter Commando Squadron with their number boosted to 17 aircraft. (Following Skoshi Tiger the Philippine Air Force acquired 23 F-5A and B models in 1965. These aircraft, along with remanufactured Vought F-8 Crusaders, eventually replaced the Philippine Air Force's F-86 Sabre in the air defense and ground attack roles.)
In June 1967, the 10th FCS's surviving aircraft were supplied to the air force of South Vietnam, which previously had only Cessna A-37 Dragonfly and Douglas A-1 Skyraider attack aircraft. This new VNAF squadron was titled the 522nd. The president of Vietnam had originally asked for F-4 Phantoms used by the USA, but the VNAF flew primarily ground support as North Vietnamese forces employed no opposing aircraft over South Vietnam. When Bien Hoa was later overrun by North Vietnamese forces, several aircraft were captured and used operationally by the NVAF, in particular against Khmer Rouge. In view of the performance, agility and size of the F-5, it might have appeared to be a good match against the similar MiG-21 in air combat; however, U.S. doctrine was to use heavy, faster and longer-range aircraft like the Republic F-105 Thunderchief and McDonnell Douglas F-4 Phantom II over North Vietnam. 41 F-5s were captured by the NVA when they defeated South Vietnam on 30 April 1975 and the USSR received a complete F-5E, along with various spare parts and support equipment; aircraft would arrive in Poland and Russia for study of U.S. aviation technology, while others were decommissioned and put on display at museums in Vietnam.
The F-5 was also adopted as an opposing forces (OPFOR) "aggressor" for dissimilar training role because of its small size and performance similarities to the Soviet MiG-21. In realistic trials at Nellis AFB in 1977, the F-14 reportedly scored slightly better than a 2:1 kill ratio against the simpler F-5, while the F-15 scored slightly less. There is some contradiction of these reports, another source reports that "For the first three weeks of the test, the F-14's and F-15's were hopelessly outclassed and demoralized"; after adapting to qualities of the F-5 and implementing rule changes to artificially favor long range radar-guided missiles, "the F-14's did slightly better than breaking even with the F-5's in non-1 v 1 engagements; the F-15's got almost 2:1". A 2012 Discovery Channel documentary Great Planes reported that in USAF exercises, F-5 aggressor aircraft were competitive enough with more modern and expensive fighters to only be at small disadvantage in Within Visual Range (WVR) combat.
The F-5E served with the U.S. Air Force from 1975 until 1990, in the 64th Aggressor Squadron and 65th Aggressor Squadron at Nellis Air Force Base in Nevada, and with the 527th Aggressor Squadron at RAF Alconbury in the UK and the 26th Aggressor Squadron at Clark Air Force Base in the Philippines. The U.S. Marines purchased used F-5s from the Air Force in 1989 to replace their F-21s, which served with VMFT-401 at Marine Corps Air Station Yuma. The U.S. Navy used the F-5E extensively at the Naval Fighter Weapons School (TOPGUN) when it was located at NAS Miramar, California. When TOPGUN relocated to become part of the Naval Strike and Air Warfare Center at NAS Fallon, Nevada, the command divested itself of the F-5, choosing to rely on VC-13 (redesignated VFC-13 and which already used F-5s) to employ their F-5s as adversary aircraft. Former adversary squadrons such as VF-43 at NAS Oceana, VF-45 at NAS Key West, VF-126 at NAS Miramar, and VFA-127 at NAS Lemoore have also operated the F-5 along with other aircraft types in support of Dissimilar Air Combat Training (DACT).
The U.S. Navy F-5 fleet continues to be modernized with 36 low-hour F-5E/Fs purchased from Switzerland in 2006. These were updated as F-5N/Fs with modernized avionics and other improved systems. Currently, the only U.S. Navy and U.S. Marine Corps units flying the F-5 are VFC-13 at NAS Fallon, Nevada, VFC-111 at NAS Key West, Florida, and VMFT-401 at MCAS Yuma, Arizona. Currently, VFC-111 operates 18 Northrop F-5N/F Tiger IIs. 17 of these are single-seater F-5Ns and the last is a twin-seater F-5F "FrankenTiger", the product of grafting the older front-half fuselage of an F-5F into the back-half fuselage of a newer low-hours F-5E acquired from the Swiss Air Force. A total of three "FrankenTigers" were made.
According to the FAA, there are 18 privately owned F-5s in the U.S., including Canadair CF-5Ds.