McDonnell Douglas AV-8B Harrier II

Origins In the late 1960s and early 1970s, the first-generation Harriers entered service with the Royal Air Force (RAF) and USMC but were limited in range and payload. In short takeoff and landing configuration, the AV-8A (American designation for the Harrier) carried less than half of the smaller A-4 Skyhawk's payload (), over a more limited radius. To address this, Hawker Siddeley and McDonnell Douglas began joint development of a more capable version of the Harrier in 1973. Early efforts concentrated on an improved Pegasus engine, designated the Pegasus 15, which was being tested by Bristol Siddeley. Although more powerful, the engine's diameter was too large by to fit into the Harrier easily. In December 1973, a joint American and British team completed a project document defining an advanced Harrier powered by the Pegasus 15 engine. The advanced Harrier was intended to replace the original RAF and USMC Harriers, as well as the USMC's A-4 Skyhawk. The aim of the advanced Harrier was to double the AV-8's payload and range and was therefore unofficially named AV-16. The British government pulled out of the project in March 1975 owing to decreased defense funding, rising costs, and the RAF's insufficient 60-aircraft requirement. With development costs estimated to be around £180–200 million (1974 British pounds), the United States was unwilling to fund development by itself and ended the project later that year. Despite the project's termination, the two companies continued to take different paths toward an enhanced Harrier. Hawker Siddeley focused on a new larger wing that could be retrofitted to existing operational aircraft, while McDonnell Douglas independently pursued a less ambitious, though still expensive, project catering to the needs of the U.S. military. Using knowledge gleaned from the AV-16 effort, though dropping some items—such as the larger Pegasus engine—McDonnell Douglas kept the basic structure and engine for an aircraft tailored for the USMC. Designing and testing As the USMC wanted a substantially improved Harrier without the development of a new engine, the plan for Harrier II development was authorized by the United States Department of Defense (DoD) in 1976. The United States Navy (USN), which had traditionally procured military aircraft for the USMC, insisted that the new design be verified with flight testing. McDonnell Douglas modified two AV-8As with new wings, revised intakes, redesigned thrust nozzles, and other aerodynamic changes; the modified forward fuselage and cockpit found on all subsequent aircraft were not incorporated on these prototypes. Designated YAV-8B, the first converted aircraft flew on 9 November 1978. The aircraft performed three vertical take-offs and hovered for seven minutes at Lambert–St. Louis International Airport. The second aircraft followed on 19 February 1979 but crashed that November because of an engine flameout; the pilot ejected safely. Flight testing of these modified AV-8s continued into 1979. Between 1978 and 1980, the DoD and USN repeatedly attempted to terminate the AV-8B program. There had previously been conflict between the USMC and USN over budgetary issues. At the time, the USN wanted to procure A-18s for its ground attack force and, to cut costs, pressured the USMC to adopt the similarly designed F-18 fighter instead of the AV-8B to fulfill the role of close air support (both designs were eventually amalgamated to create the multirole F/A-18 Hornet). Despite these bureaucratic obstacles, in 1981 the DoD included the Harrier II in its annual budget and five-year defense plan. The USN declined to participate in the procurement, citing the limited range and payload compared with conventional aircraft. In August 1981, the program received a boost when British Aerospace (BAe) and McDonnell Douglas signed a memorandum of understanding, marking the UK's re-entry into the program. Under the agreement, BAe was relegated to the position of a subcontractor, instead of the full partner status that would have been the case had the UK not left the program. Consequently, the company received, in man-hours, 40% of the airframe work-share. Meanwhile, 75% work-share for the engine went to Rolls-Royce, which had absorbed Bristol Siddeley, with the remaining 25% assigned to Pratt & Whitney. Four full-scale development (FSD) aircraft were constructed. The first of these, used mainly for testing performance and handling qualities, made its maiden flight on 5 November 1981. The second and third FSD aircraft, which introduced wing leading-edge root extensions and revised engine intakes, first flew in April the following year; the fourth followed in January 1984. and officially handed over one month later. The last of the initial batch of 12 was delivered in January 1985 to the front-line Marine Attack Squadron 331. These aircraft had F402-RR-404A engines, with 21,450 lb (95.4 kN) of thrust; aircraft from 1990 onwards received upgraded engines. In 1984, funding for eight AV-8Bs was diverted to the development of a two-seat TAV-8B trainer. The first of the 28 TAV-8Bs eventually procured had its maiden flight on 21 October 1986. With export interest from Brazil, Japan, and Italy serving as a source of encouragement to continue development of the Harrier II, McDonnell Douglas commenced work on a night-attack variant in 1985. With the addition of an infrared sensor and cockpit interface enhancements, the 87th production single-seat AV-8B became the first Harrier II to be modified for night attacks, leaving the McDonnell Douglas production line in June 1987. Flight tests proved successful and the night attack capability was validated. The first of 66 AV-8B(NA)s was delivered to the USMC in September 1989. An equivalent version of the AV-8B(NA) also served with the RAF under the designation GR7; earlier GR5 aircraft were subsequently upgraded to GR7 standards. In June 1987, as a private venture, BAe, McDonnell Douglas, and Smiths Industries agreed on the development of what was to become the AV-8B Plus with the addition of radar and increased missile compatibility. The agreement was endorsed by the USMC and, after much consideration, the Spanish and Italian navies developed a joint requirement for a fleet of air-defense Harriers. The United States, Spain, and Italy signed an MoU in September 1990 to define the responsibilities of the three countries and establish a Joint Program Office to manage the program. On 30 November 1990, the USN, acting as an agent for the three participating countries, awarded McDonnell Douglas the contract to develop the improved Harrier. The award was followed by an order from the USMC in December 1990 for 30 new aircraft, and 72 rebuilt from older aircraft. Italy ordered 16 Harrier II Plus and two twin-seat TAV-8B aircraft, while Spain signed a contract for eight aircraft. AV-8B Plus in-flight. The nose houses the Hughes APG-65 pulse-Doppler radar.|alt=Starboard view of gray jet aircraft in-flight against a blue sky Production was authorized on 3 June 1992. The maiden flight of the prototype took place on 22 September, marking the start of a successful flight-test program. Deliveries of new aircraft took place from April 1993 to 1995. At the same time, the plan to remanufacture existing AV-8Bs to the Plus standard proceeded. On 11 March 1994, the Defense Acquisition Board approved the program, which initially involved 70 aircraft, with four converted in fiscal year 1994. Conversion began in April 1994, and the first aircraft was delivered to the USMC in January 1996. End of production and further improvements In March 1996, the U.S. General Accounting Office (GAO) stated that it was less expensive to buy Harrier II Plus aircraft outright than to remanufacture existing AV-8Bs. The USN estimated the cost for remanufacture of each aircraft to be US$23–30 million, instead of $30 million for each new-built aircraft, while the GAO estimated the cost per new aircraft at $24 million. In 2001, Flight International reported that Taiwan might meet its requirement for a V/STOL aircraft by purchasing AV-8Bs outfitted with the F-16 Fighting Falcon's APG-66 radar. A Taiwanese purchase would have allowed the production line to stay open beyond 2005. Despite the possibility of leasing AV-8Bs, interest in the aircraft waned as the country switched its intentions to procuring the F-35 and upgrading its fleet of F-16s. Although there have been no new AV-8B variants, in 1990 McDonnell Douglas and British Aerospace began discussions on an interim aircraft between the AV-8B and the next generation of advanced V/STOL aircraft. The Harrier III would have presented an "evolutionary approach to get the most from the existing aircraft", as many of the structures employed on the Sea Harrier and AV-8B would be used. The wing and the torsion box were to be enlarged to accommodate extra fuel and hardpoints to improve the aircraft's endurance. Because of the increase in size, the wing would have had folding wingtips. To meet the heavier weight of the aircraft, Rolls-Royce was expected to design a Pegasus engine variant that would have produced more thrust than the latest production variant at the time. The Harrier III would have carried weapons such as AIM-120 AMRAAM and AIM-132 ASRAAM missiles. Boeing and BAE Systems continued studying the design until the early 2000s, when the project was abandoned. In 2013, the USMC was studying potential enhancements to keep the AV-8B Harrier IIs up to date until its planned retirement, such as a helmet-mounted cueing system. It was also predicted that additional work on the aircraft's radars and sensor systems might take place. The USMC's Harrier II fleet was planned to remain in service until 2030, owing to delays with the F-35B and the fact that the Harriers had more service life left than USMC F/A-18 Hornets. However, by 2014 the USMC had decided to retire the AV-8B sooner because changing the transition orders of Harrier II and Hornet fleets to the Lightning II would save US $1 billion (~$ in ). The F-35B began replacing the AV-8B in 2016, with the AV-8B then expected to continue service until 2025. Meanwhile, the AV-8B was to receive revamped defensive measures, updated data-link capability and targeting sensors, and improved missiles and rockets, among other enhancements. the last AV-8B is scheduled for retirement "by the second half of 2027." ==Design==