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Description
The North American A-5 Vigilante was an American carrier-based supersonic bomber designed and built by North American Aviation (NAA) for the United States Navy. Prior to 1962 unification of Navy and Air Force designations, it was designated the A3J Vigilante. Development of the A-5 had started in 1954 as a private venture by NAA, who sought to produce a capable supersonic long distance bomber as a successor to the abortive North American XA2J Super Savage. It was a large and complex aircraft that incorporated several innovative features, such as being the first bomber to feature a digital computer, while its ability to attain speeds of up to Mach 2 while carrying a nuclear strike payload was also relatively ambitious for the era. The US Navy saw the value of such a bomber, leading to a contract for its full development and production being issued to the firm on 29 August 1956. The type performed its first flight just over two years later, on 31 August 1958. The Vigilante was introduced by the US Navy during June 1961; it succeeded the Douglas A-3 Skywarrior as the Navy's primary nuclear strike aircraft, but its service in this capacity was relatively brief due to the deemphasising of manned bombers in the US' nuclear strategy. A far larger quantity of the RA-5C tactical strike reconnaissance variant were also procured by the service, which saw extensive service during the Vietnam War. It also established several world records in both long-distance speed and altitude categories. During the mid-1970s, the withdrawal of the type commenced after a relatively short service life, largely due to the aircraft being expensive and complex to operate, as well being a victim of post-Vietnam military cutbacks. Development Origins The late 1940s and early 1950s were marked by a series of high-paced advancements in the field of aviation. The aircraft manufacturer North American Aviation (NAA) was one of a large number of companies that sought to harness these recent innovations in developing a new generation of aircraft. During early 1954, the company embarked on a private study into a conceptual carrier-based, long-range, all-weather strike bomber, that would be capable of supersonic speeds while carrying a sizable payload. This aircraft was envisioned as a successor to the abortive North American XA2J Super Savage. Much of this early work was undertaken by NAA's recently acquired Columbus division, overseen by chief of preliminary design Frank G Compton. During the mid-1950s, the notion of a nuclear-armed aircraft capable of speeds of up to Mach 2 was considered to be quite ambitious, and only more so for that same aircraft to be operable under the unavoidable constraints imposed by aircraft carrier operations. In terms of its basic configuration, the conceptual aircraft featured twin-engines and high-mounted wing, as did the XA2J, but differed substantially by being highly swept and adopting jet propulsion. According to aviation authors Bill Gunston and Peter Gilchrist, NAA's design incorporated numerous advanced technology features, such as being the first supersonic bomber to be designed with a slim forward fuselage, as well as being the first with fully-variable wedge-type side air intakes.The company's preliminary design studies had been typically centred around a twin vertical fin/rudder arrangement, but this was substituted for a single large all-moving vertical fin as design definition proceeded. This proposal, which was referred to the North American General Purpose Attack Weapon (NAGPAW) concept, was promptly evaluated by the United States Navy. The service produced numerous challenging demands, including the somewhat contradictory necessity of both a high speed of Mach 2 and the ability to take off from an aircraft carrier at maximum weight with no head-wind, also known as wind-over-the-deck, to assist the take-off. Compton's team were able to reconcile these performance requirements into the design. Following these changes, US Navy officials voiced their approval of the design and advocated for its procurement. During July 1955, an initial design contract, which included the production of a mockup, was issued to NAA. During September 1956, a follow-on contract for the production of a pair of flight-worthy prototypes, was awarded to the firm. On 31 August 1958, one of these prototypes performed the type's maiden flight from Columbus, Ohio. By this point, the role envisioned for the aircraft within the US Navy had shifted somewhat. According to Gunston and Gilchrist, officials had viewed the aircraft through the lens of the Korean War and placed a high value on performing low-level conventionally-armed attack missions, but had subsequently shifted towards viewing the in-development bomber as a successor to the Douglas A-3 Skywarrior in the strategic nuclear attack role instead. Thus, the design team implemented a somewhat unorthodox bomb bay as to accommodate the stowage of a nuclear weapon, which was also designed to accommodate both fuel tanks and reconnaissance payloads. Further development An RA-5C Vigilante During the late 1950s and early 1960s, NAA worked on an improved bomber model, designated A-5B. The took advantage of the zero-wind requirement's elimination to considerably increase the aircraft's maximum weight, the fuselage being redesigned with a hump back to accommodate additional fuel. The wings were also redesigned with enlarged trailing-edge flaps and fully-blown flaps; these changes, when carrying four external drop tanks, roughly doubled the bomber's range. Development was halted after only six A-5Bs had been completed due to a shift in the US Navy's strategic focus that placed less value on manned bombers.[ The majority of Vigilantes were of a reconnaissance configuration, designated RA-5C. It had a slightly greater wing area and added a long canoe-shaped fairing under the fuselage for a multi-sensor reconnaissance pack, which housed an APD-7 side-looking airborne radar (SLAR), AAS-21 infrared line scanner, and camera packs, as well as improved electronic countermeasures. An AN/ALQ-61 electronic intelligence system could also be carried. The RA-5C retained the AN/ASB-12 bombing system, and could, in theory, carry weapons, although it never did in service. Later-build RA-5Cs had more powerful J79-10 engines with afterburning thrust of 17,900 lbf (80 kN). The reconnaissance Vigilante weighed almost five tons more than the strike version with almost the same thrust and an only modestly enlarged wing, resulting in reduced acceleration and climb rate, though it remained fast in level flight. The Royal Australian Air Force (RAAF) considered acquiring the RA-5C as its principal bomber to succeed its fleet of English Electric Canberras. Various other aircraft, such as the McDonnell F-4C/RF-4C, Dassault Mirage IVA, and the BAC TSR-2 were also considered for the role. However, the General Dynamics F-111C, a variant of the TFX (F-111) tailored to fulfil the requirements of the RAAF, was procured to meet the service's needs instead.[9][10] Due to the F-111C's protracted development, a team of RAAF officers advocated for an interim fleet of 36 Vigilantes to be acquired by the RAAF, having determined that the aircraft satisfied the service's requirements and could be delivered within a shorter time frame. The Australian Government rejected this advice and no such procurement occurred. Design The North American A-5 Vigilante was a supersonic carrier-based bomber. At the time of its introduction, the Vigilante was one of the largest and by far the most complex aircraft to operate from an aircraft carrier. It was furnished with a high-mounted swept wing with a boundary-layer control system (blown flaps) to improve low-speed lift. It lacked ailerons; instead, roll control was provided by spoilers in conjunction with differential deflection of the all-moving tail surfaces, which were paired with a relatively large all-moving single vertical stabilizer. The use of aluminum-lithium alloy for wing skins and titanium for critical structures was also unusual for the era; other exotic materials included the use of a gold coating to reflect heat in key areas such as the bomb bay. The wings, vertical stabilizer and the nose radome all folded to enable easier stowage onboard aircraft carriers. Two widely-spaced General Electric J79 turbojet engines were supplied with air through inlets with variable intake ramps.While the same engine was used by several other US military aircraft, such as the Convair B-58 Hustler and the McDonnell Douglas F-4 Phantom II, the powerplants used on the A-5 differed in some ways, such as the use of a somewhat uncommon air-impingement starter along with a single igniter. Both engines were equipped with constant-speed drives for alternators to generate a steady 30kVA for the onboard electrical systems, a hydraulically-driven emergency supply generated by a ram air turbine was also installed.The electronics of the Vigilante were relatively advanced and complex at the time of its entry to service. It incorporated one of the first "fly-by-wire" systems on an operational aircraft, along with mechanical/hydraulic backup. Other elements of its avionics include a computerized AN/ASB-12 nav/attack system incorporating a head-up display ("Pilot's Projected Display Indicator" (PPDI), one of the first), multi-mode radar, radar-equipped inertial navigation system (REINS, based on technologies developed for North American's Navaho missile), closed-circuit television camera under the nose, and an early digital computer known as "Versatile Digital Analyzer" (VERDAN) to operate it all. According to Gunston and Gilchrist, the Vigilante was the first bomber to feature a digital computer. It was operated by a crew of two, a pilot and a bombardier-navigator (BN), that were seated in tandem; both were provided with North American HS-1A ejection seats. On the reconnaissance-orientated aircraft; the bombardier-navigator was replaced by a reconnaissance/attack navigator (RAN) instead. The A3J "stores train" within the bomb bay Given its original design as a carrier-based, supersonic, nuclear heavy attack aircraft, the Vigilante's main armament was carried in an unusual "linear bomb bay" between the engines in the rear fuselage, which allowed the bomb to be dropped at supersonic speeds. The single nuclear weapon, commonly the Mk 28 bomb, was attached to two disposable fuel tanks in the cylindrical bay in an assembly known as the "stores train". A set of extendable fins was attached to the aft end of the most rearward fuel tank. These fuel tanks were to be emptied during the flight to the target and then jettisoned with the bomb by an explosive drogue gun. The stores train was propelled rearward at about 50 feet (15 m) per second (30 knots) relative to the aircraft. It then followed a ballistic path. In practice, the system was not reliable and no live weapons were ever carried in the linear bomb bay. In the RA-5C configuration, the bay was used solely to accommodate fuel. On three occasions, the shock of the catapult launch caused the fuel cans to eject onto the deck; this phenomenon reportedly resulted in one aircraft loss. Early production Vigilante were outfitted with a pair of wing pylons, which were intended primarily for drop tanks. The second Vigilante variant, the A3J-2 (A-5B), featured two additional wing hardpoints, for a total of four, and also incorporated internal tanks for an additional 460 gallons of fuel (which added a pronounced dorsal "hump"). In practice, these hardpoints were rarely used. Other improvements to the type included blown flaps on the leading edge of the wing and stronger landing gear. While designated by the US Navy as a "heavy" aircraft, the A-5 was surprisingly agile; without the drag of bombs or missiles, even escorting fighters found that the clean airframe and powerful engines made the Vigilante very fast at high and low altitudes. However, its high approach speed and high angle of attack contributed to a high workload during carrier landings.

Description
The North American A-5 Vigilante was an American carrier-based supersonic bomber designed and built by North American Aviation (NAA) for the United States Navy. Prior to 1962 unification of Navy and Air Force designations, it was designated the A3J Vigilante. Development of the A-5 had started in 1954 as a private venture by NAA, who sought to produce a capable supersonic long distance bomber as a successor to the abortive North American XA2J Super Savage. It was a large and complex aircraft that incorporated several innovative features, such as being the first bomber to feature a digital computer, while its ability to attain speeds of up to Mach 2 while carrying a nuclear strike payload was also relatively ambitious for the era. The US Navy saw the value of such a bomber, leading to a contract for its full development and production being issued to the firm on 29 August 1956. The type performed its first flight just over two years later, on 31 August 1958. The Vigilante was introduced by the US Navy during June 1961; it succeeded the Douglas A-3 Skywarrior as the Navy's primary nuclear strike aircraft, but its service in this capacity was relatively brief due to the deemphasising of manned bombers in the US' nuclear strategy. A far larger quantity of the RA-5C tactical strike reconnaissance variant were also procured by the service, which saw extensive service during the Vietnam War. It also established several world records in both long-distance speed and altitude categories. During the mid-1970s, the withdrawal of the type commenced after a relatively short service life, largely due to the aircraft being expensive and complex to operate, as well being a victim of post-Vietnam military cutbacks. Development Origins The late 1940s and early 1950s were marked by a series of high-paced advancements in the field of aviation. The aircraft manufacturer North American Aviation (NAA) was one of a large number of companies that sought to harness these recent innovations in developing a new generation of aircraft. During early 1954, the company embarked on a private study into a conceptual carrier-based, long-range, all-weather strike bomber, that would be capable of supersonic speeds while carrying a sizable payload. This aircraft was envisioned as a successor to the abortive North American XA2J Super Savage. Much of this early work was undertaken by NAA's recently acquired Columbus division, overseen by chief of preliminary design Frank G Compton. During the mid-1950s, the notion of a nuclear-armed aircraft capable of speeds of up to Mach 2 was considered to be quite ambitious, and only more so for that same aircraft to be operable under the unavoidable constraints imposed by aircraft carrier operations. In terms of its basic configuration, the conceptual aircraft featured twin-engines and high-mounted wing, as did the XA2J, but differed substantially by being highly swept and adopting jet propulsion. According to aviation authors Bill Gunston and Peter Gilchrist, NAA's design incorporated numerous advanced technology features, such as being the first supersonic bomber to be designed with a slim forward fuselage, as well as being the first with fully-variable wedge-type side air intakes.The company's preliminary design studies had been typically centred around a twin vertical fin/rudder arrangement, but this was substituted for a single large all-moving vertical fin as design definition proceeded. This proposal, which was referred to the North American General Purpose Attack Weapon (NAGPAW) concept, was promptly evaluated by the United States Navy. The service produced numerous challenging demands, including the somewhat contradictory necessity of both a high speed of Mach 2 and the ability to take off from an aircraft carrier at maximum weight with no head-wind, also known as wind-over-the-deck, to assist the take-off. Compton's team were able to reconcile these performance requirements into the design. Following these changes, US Navy officials voiced their approval of the design and advocated for its procurement. During July 1955, an initial design contract, which included the production of a mockup, was issued to NAA. During September 1956, a follow-on contract for the production of a pair of flight-worthy prototypes, was awarded to the firm. On 31 August 1958, one of these prototypes performed the type's maiden flight from Columbus, Ohio. By this point, the role envisioned for the aircraft within the US Navy had shifted somewhat. According to Gunston and Gilchrist, officials had viewed the aircraft through the lens of the Korean War and placed a high value on performing low-level conventionally-armed attack missions, but had subsequently shifted towards viewing the in-development bomber as a successor to the Douglas A-3 Skywarrior in the strategic nuclear attack role instead. Thus, the design team implemented a somewhat unorthodox bomb bay as to accommodate the stowage of a nuclear weapon, which was also designed to accommodate both fuel tanks and reconnaissance payloads. Further development An RA-5C Vigilante During the late 1950s and early 1960s, NAA worked on an improved bomber model, designated A-5B. The took advantage of the zero-wind requirement's elimination to considerably increase the aircraft's maximum weight, the fuselage being redesigned with a hump back to accommodate additional fuel. The wings were also redesigned with enlarged trailing-edge flaps and fully-blown flaps; these changes, when carrying four external drop tanks, roughly doubled the bomber's range. Development was halted after only six A-5Bs had been completed due to a shift in the US Navy's strategic focus that placed less value on manned bombers.[ The majority of Vigilantes were of a reconnaissance configuration, designated RA-5C. It had a slightly greater wing area and added a long canoe-shaped fairing under the fuselage for a multi-sensor reconnaissance pack, which housed an APD-7 side-looking airborne radar (SLAR), AAS-21 infrared line scanner, and camera packs, as well as improved electronic countermeasures. An AN/ALQ-61 electronic intelligence system could also be carried. The RA-5C retained the AN/ASB-12 bombing system, and could, in theory, carry weapons, although it never did in service. Later-build RA-5Cs had more powerful J79-10 engines with afterburning thrust of 17,900 lbf (80 kN). The reconnaissance Vigilante weighed almost five tons more than the strike version with almost the same thrust and an only modestly enlarged wing, resulting in reduced acceleration and climb rate, though it remained fast in level flight. The Royal Australian Air Force (RAAF) considered acquiring the RA-5C as its principal bomber to succeed its fleet of English Electric Canberras. Various other aircraft, such as the McDonnell F-4C/RF-4C, Dassault Mirage IVA, and the BAC TSR-2 were also considered for the role. However, the General Dynamics F-111C, a variant of the TFX (F-111) tailored to fulfil the requirements of the RAAF, was procured to meet the service's needs instead.[9][10] Due to the F-111C's protracted development, a team of RAAF officers advocated for an interim fleet of 36 Vigilantes to be acquired by the RAAF, having determined that the aircraft satisfied the service's requirements and could be delivered within a shorter time frame. The Australian Government rejected this advice and no such procurement occurred. Design The North American A-5 Vigilante was a supersonic carrier-based bomber. At the time of its introduction, the Vigilante was one of the largest and by far the most complex aircraft to operate from an aircraft carrier. It was furnished with a high-mounted swept wing with a boundary-layer control system (blown flaps) to improve low-speed lift. It lacked ailerons; instead, roll control was provided by spoilers in conjunction with differential deflection of the all-moving tail surfaces, which were paired with a relatively large all-moving single vertical stabilizer. The use of aluminum-lithium alloy for wing skins and titanium for critical structures was also unusual for the era; other exotic materials included the use of a gold coating to reflect heat in key areas such as the bomb bay. The wings, vertical stabilizer and the nose radome all folded to enable easier stowage onboard aircraft carriers. Two widely-spaced General Electric J79 turbojet engines were supplied with air through inlets with variable intake ramps.While the same engine was used by several other US military aircraft, such as the Convair B-58 Hustler and the McDonnell Douglas F-4 Phantom II, the powerplants used on the A-5 differed in some ways, such as the use of a somewhat uncommon air-impingement starter along with a single igniter. Both engines were equipped with constant-speed drives for alternators to generate a steady 30kVA for the onboard electrical systems, a hydraulically-driven emergency supply generated by a ram air turbine was also installed.The electronics of the Vigilante were relatively advanced and complex at the time of its entry to service. It incorporated one of the first "fly-by-wire" systems on an operational aircraft, along with mechanical/hydraulic backup. Other elements of its avionics include a computerized AN/ASB-12 nav/attack system incorporating a head-up display ("Pilot's Projected Display Indicator" (PPDI), one of the first), multi-mode radar, radar-equipped inertial navigation system (REINS, based on technologies developed for North American's Navaho missile), closed-circuit television camera under the nose, and an early digital computer known as "Versatile Digital Analyzer" (VERDAN) to operate it all. According to Gunston and Gilchrist, the Vigilante was the first bomber to feature a digital computer. It was operated by a crew of two, a pilot and a bombardier-navigator (BN), that were seated in tandem; both were provided with North American HS-1A ejection seats. On the reconnaissance-orientated aircraft; the bombardier-navigator was replaced by a reconnaissance/attack navigator (RAN) instead. The A3J "stores train" within the bomb bay Given its original design as a carrier-based, supersonic, nuclear heavy attack aircraft, the Vigilante's main armament was carried in an unusual "linear bomb bay" between the engines in the rear fuselage, which allowed the bomb to be dropped at supersonic speeds. The single nuclear weapon, commonly the Mk 28 bomb, was attached to two disposable fuel tanks in the cylindrical bay in an assembly known as the "stores train". A set of extendable fins was attached to the aft end of the most rearward fuel tank. These fuel tanks were to be emptied during the flight to the target and then jettisoned with the bomb by an explosive drogue gun. The stores train was propelled rearward at about 50 feet (15 m) per second (30 knots) relative to the aircraft. It then followed a ballistic path. In practice, the system was not reliable and no live weapons were ever carried in the linear bomb bay. In the RA-5C configuration, the bay was used solely to accommodate fuel. On three occasions, the shock of the catapult launch caused the fuel cans to eject onto the deck; this phenomenon reportedly resulted in one aircraft loss. Early production Vigilante were outfitted with a pair of wing pylons, which were intended primarily for drop tanks. The second Vigilante variant, the A3J-2 (A-5B), featured two additional wing hardpoints, for a total of four, and also incorporated internal tanks for an additional 460 gallons of fuel (which added a pronounced dorsal "hump"). In practice, these hardpoints were rarely used. Other improvements to the type included blown flaps on the leading edge of the wing and stronger landing gear. While designated by the US Navy as a "heavy" aircraft, the A-5 was surprisingly agile; without the drag of bombs or missiles, even escorting fighters found that the clean airframe and powerful engines made the Vigilante very fast at high and low altitudes. However, its high approach speed and high angle of attack contributed to a high workload during carrier landings.