History
Design and Development
The Convair Company of Fort Worth, Texas, began conceptual studies for a supersonic bomber in October 1946. Designated as Generalized Bomber (GEBO) by the US Air Force, the study explored a delta-winged aircraft weighing approximately 150,000 pounds. Convair’s experience with delta-wing aircraft, the experimental XF-92, made it a promising candidate to invent the supersonic bomber for the project. By 1948, Convair’s research on delta wings using the XF-92 provided critical data for the development of later aircraft like the F-102 Delta Dagger and F-106 Delta Dart.
Building on this foundation, the Air Force initiated GEBO-II in March 1949, seeking a supersonic bomber capable of cruising at 450 knots, flying at altitudes over 35,000 feet, carrying a 10,000-pound bomb load, and having a range of 1,200–2,500 miles. By January 1950, Convair shifted its focus from a parasite bomber concept (which envisioned a small supersonic bomber carried by a B-36) to a more conventional design after opposition from the Strategic Air Command (SAC). This led to the proposal of the MX-1626 long-range supersonic reconnaissance bomber on January 26, 1951.
Convair’s design evolved through extensive wind tunnel tests and competing studies. In 1952, Convair and Boeing were selected to proceed with prototype designs: the Convair XB-58 and the Boeing XB-59. Convair’s redesigned prototype incorporated four General Electric J79 engines optimized for supersonic flight, a powerplant later used in iconic aircraft like the F-104 Starfighter and F-4 Phantom II. In 1953, the Air Force selected Convair’s XB-58 for further development, leading to contracts for two prototypes: a bomber (XB-58) and a reconnaissance variant (XRB-58).
By August 1954, the final B-58 design was solidified. It incorporated a large delta wing with a leading-edge sweep of 60 degrees. It was to be powered by an arrangement of four General Electric J79-GE-1 turbojet engines on individual underwing pylons. All fuel was contained internally and in the podded lower component. The fuselage was aligned to the modified transonic area for supersonic speeds. The external wing tanks were eliminated, and the tail area was increased to 160 square feet. Finally, in December 1955, a definitive contract was issued to Convair for 13 aircraft. A second contract was issued on May 25, 1956, providing additional funds to maintain B-58 production at a minimum sustaining rate through October 1956. The USAF would have to see and decide if it should buy more aircraft by the fall of 1956.
Prototype and Production
The first prototype (55-660) was unveiled on August 31, 1956 under high security. Its maiden flight occurred on November 11, 1956, and exceeded Mach 1 on December 30, 1956. The second prototype was completed and designated XB-58, not XRB-58, and it first flew in February 1957. The flight-test program involving 30 aircraft continued until April 1959.
The first production B-58 bomber was delivered in February 1959, and flew at Mach 2 for over an hour in October 1959, achieving the first “supersonic cruise.” The Hustler name was given by the Convair engineering crew, and the Air Force expressed approval of the naming. A total of 116 B-58s were produced, including 30 trial aircraft and 86 production B-58A models. Most of the trial aircraft were later upgraded to operational standards.
The B-58 was built with aluminum honeycomb panels, which bonded outer and inner aluminum skins to a honeycomb of aluminum or fiberglass. The structure comprised 13.8% of the aircraft’s gross weight, a meager figure for the era, while the wing was extremely thin. The entire wing served as an integral fuel tank. The aircraft had a long tricycle landing gear for ground clearance for the engines and weapons pod.
The B-58 was operated by a crew of three: pilot, radar navigator/bombardier, and defense systems operator. They were seated in separated tandem cockpits, although the space was cramped and claustrophobic. Later versions of the B-58 provided each crew member with a protective, enclosed ejection capsule that could eject at 70,000 feet (21,000 meters) at speeds up to Mach 2.
The B-58 was equipped with a sophisticated Sperry AN/ASQ-42 bombing/navigation system that provided a heading reference. It also had the AN/APN-133 Doppler radar, which provides ground speed and wind speed data, along with a radar altimeter and search radar to provide range data for bomb release and trajectory.
The B-58 only had a single 20-mm T-171E-3 six-barrel 20-mm rotary cannon in a radar-aimed, tailed barbette. It was remotely controlled through the Emerson MD-7 automated radar fire-control system, only requiring the DSO to lock on a selected target blip on his scope and then fire the gun. It had a maximum firing rate of 4000 rounds per minute; however, its firing arc was minimal as the tailgun was faired to conform to the rest of the aircraft. The DSO also controlled the AN/ALQ-16 active jammer and AN/ALE-16 chaff dispensers to interfere with enemy radars.
The standard MB-1C weapons pod with tailfins was mounted on the centerline of B-58. It carried a W39Y1-1 multi-megaton nuclear weapon and fuel in a gigantic pod as its sole offensive armament. The pod was mounted slightly off-center from the aircraft’s centerline. It would spin-stabilize after jettison. Problems with fuel leaks led to the development of a new two-component pod system that used twin-stacked pods, with the upper nuclear bomb pod and the lower fuel pod. Once exhausted, the fuel pod would be independently jettisoned during an operational mission.
Operational Service
On August 1, 1960, the B-58 was declared operational nine months after delivering the first aircraft to the USAF. One month later, a single B-58 participated in the annual SAC Competition at Bergstrom. Unsurprisingly, the B-58 proved superior to competing Boeing B-47 Stratojets and B-52 Stratofortresses, securing first place in high-level and low-level radar bombing exercises.
The B-58 was difficult to fly, and its three-man crew was constantly busy, but its overall performance was exceptional in the era. Because of the 60-degree sweepback of delta wing platforms, the B-58 required a much higher angle of attack than a conventional aircraft, up to 9.4 degrees at Mach 0.5 at low altitudes. If the angle of attack exceeded 17 degrees, the bomber could pitch up and enter a spin. The aircraft must take off at a 14-degree angle of attack near 203.5 knots for a 150,000-pound combat weight. Combined with poor takeoff performance and unconventional stall characteristics, the B-58 was exceptionally challenging to fly. Only very experienced crews were selectively assigned to operate the B-58s.
After production ended in the fall of 1962, two SAC bomb wings only operated the B-58s. The 43rd Bombardment Wing operated the B-58s from 1960 to 1964 in Texas, and the 305th Bombardment Wing operated the aircraft from 1964 to 1960 in Arkansas. From 1961 to 1963, the B-58 was retrofitted with two tandem stub pylons under each wing root, adjacent to the centerline pod, for B43 or B61 nuclear weapons. These allowed the aircraft to carry a total of five nuclear weapons. However, Secretary of Defense McNamara declared the B-58 was not a viable weapon system. When the Soviet Union introduced and deployed SA-2 Guideline, a high-altitude surface-to-air platform, it arguably rendered B-58 useless, and the “solution” to this problem was to fly at low altitudes, minimizing the radar and reducing exposure time. Thus, the B-58 could not fly at supersonic speeds, and its moderate range was reduced further since the air was dense at low altitudes, negating the high-speed performance of the aircraft.
Despite efforts to keep the B-58 longer in service, McNamara ordered the retirement of the B-58 by 1970. The B-58 was more expensive to operate than other bombers, such as the Boeing B-52 Stratofortress, and required more frequent aerial refueling and constant specialized maintenance. The B-58 costs one-third more to operate than the B-52, which means with the cost of operating two B-58 wings, the SAC could operate six B-52 wings. Compounding these expensive costs, the B-58 also had a high accident rate; 26 of 116 B58 aircraft were lost in accidents, or 22.4% of total production, and more than half of the losses occurred during flight tests. Consequently, its service lifetime was shortened when the Department of Defense announced on October 29, 1969, that the B-58 would be withdrawn from service on January 31, 1970. At that time, the last B-58s were retired and placed into storage at Davis-Monthan Air Force Base, Arizona. They remained intact until 1977 when all aircraft were sold for scrap.
As a weapon system, the B-58 was effectively replaced by F-111 Advardarks. The F-111 was a cheaper and more flexible aircraft designed for low-altitude attack. It could carry conventional weapons and was less expensive to produce and maintain.
The B-58 set 19 speed records and the longest supersonic flight in history. In one instance, the B-58 flew from Tokyo to London (via Alaska) in 1963, with a distance of 8,028 miles (12,920 km), averaging 938 mph (1,510 km/h). It was the longest non-stop supersonic flight, with five air refuelings for 8 hours and 35 minutes. This record remains unbroken for the time being.
