Selasa, 26 Agustus 2008

Convair XB-58 Hustler

Convair XB-58 Hustler by James Gordon.
Convair XB-58 Hustler during takeoff. Note the landing gear is just beginning to retract. Convair XB-58 Hustler in flight. The Convair B-58 Hustler was the first operational jet bomber capable of Mach 2 supersonic flight. The aircraft was developed for the United States Air Force Strategic Air Command during the late 1950s. Despite its sophisticated technology and Mach 2 performance, its operational flexibility was limited by high costs and changing mission requirements leading to a brief career between 1960 and 1969. Its specialized role would be succeeded by other American supersonic bombers, the FB-111A and the later B-1 Lancer.
It received a great deal of notoriety due to its sonic boom, which was often heard by the public as it passed overhead in supersonic flight.
The genesis of the B-58 program came in February 1949, when a Generalized Bomber Study (GEBO II) had been issued by the Wright-Patterson AFB Air Research and Development Command (ARDC). A number of contractors submitted bids including Boeing, Convair, Curtiss, Douglas, Martin and North American Aviation.
Building on Convair's experience of earlier delta-wing fighters, beginning with the XF-92A, a series of GEBO II designs were developed, initially studying swept and semi-delta configurations, but settling on the delta wing platform. The final Convair proposal, coded FZP-110, was a radical two-place, delta wing bomber design powered by General Electric J53s. The performance estimates included a 1,000 mph speed and a 3,000 mile range.
The USAF chose Boeing (MX-1712) and Convair to proceed to a Phase 1 study. The Convair MX-1626 evolved further into a more refined proposal redesignated the MX-1964 that was the winner of the design competition to meet the newly proposed SAB-51 (Supersonic Aircraft Bomber) and SAR-51 (Supersonic Aircraft Reconnaissance), the first General Operational Requirement (GOR) worldwide for supersonic bombers.
A Convair B-58 Hustler in the taxiway
The resulting B-58 design was the first "true" USAF supersonic bomber program. The Convair design was based on a delta wing with a leading-edge sweep of 60° with four General Electric J79-GE-1 turbojet engines, capable of flying at twice the speed of sound. Although its large wing made for relatively low wing loading, it proved to be surprisingly well suited for low-altitude, high-speed flight. It seated three (pilot, bombardier/navigator, and defensive systems operator) in separated tandem cockpits. Later versions gave each crew member a novel ejection capsule that made it possible to eject at an altitude of 70,000 ft (21,000 m) at speeds up to Mach 2 (1,320 mph/2,450 km/h). Unlike standard ejection seats of the period, a protective clamshell would enclose the seat and the control stick with an attached oxygen bottle. In an unusual test program, live bears were successfully used to test the ejection system. The XB-70 would use a similar system.
Because of heat generated at Mach 2 cruise, not only the crew compartment, but wheel wells and electronics bay were pressurized and air conditioned. The B-58 utilized one of the first extensive applications of aluminum honeycomb panels, which bonded outer and inner aluminum skins to a honeycomb of aluminum and fiberglass.
The B-58 typically carried a single nuclear weapon in a streamlined MB-1C pod under the fuselage. From 1961 to 1963 it was retrofitted with two tandem stub pylons under each wing, inboard of the engine pod, for B43 or B61 nuclear weapons for a total of five nuclear weapons per airplane. A single M61 Vulcan cannon was mounted in a radar-directed tail turret for defense, though some would note that at Mach 2, the exit speed of the shells would not be much faster than the speed of the aircraft. Although the USAF explored the possibility of using the B-58 for the conventional strike role, it was never equipped for carrying or dropping conventional bombs in service. A photo reconnaissance pod, the LA-331, was also fielded. Several other specialized pods for ECM or an early cruise missile were considered, but not adopted.
[edit]Operational history
The B-58 crews were elite, hand-picked from other strategic bomber squadrons. Due to some unique aspects of flying a delta-winged aircraft, the pilots used the F-102 Delta Dagger in their transition to the Hustler. The aircraft was difficult to fly and its three-man crews were constantly busy but the performance of the aircraft was exceptional. A lightly loaded Hustler would climb at nearly 4,600 ft/min (23.5 m/s), comparable to the best contemporary fighters, and it could cruise with a payload at 85,000 ft (26,000 m).
Nevertheless, it had a much smaller weapons load and more limited range than the B-52 Stratofortress. It had been extremely expensive to acquire (in 1959 it was reported that each of the production B-58As was worth more than its weight in gold). It was a complex aircraft that required considerable maintenance, much of which required specialized equipment, which made it three times as expensive to operate as the B-52. Also against it was an unfavorably high accident rate: 26 aircraft were lost in accidents, 22.4% of total production. An engine loss at supersonic cruise was very difficult to safely recover from due to differential thrust. SAC had been dubious about the type from the beginning, although its crews eventually became enthusiastic about the aircraft (its performance and design were appreciated, although it was never easy to fly).
This was the original XB-58. Accumulating 150 flights, it was the first B-58 to reach both Mach 1 and Mach 2. This particular craft was used for ALBM testing before being scrapped.
By the time the early problems had largely been resolved and SAC interest in the bomber had solidified, Secretary of Defense Robert McNamara decided that the B-58 was not going to be a viable weapon system. It was during its introduction that the surface-to-air missile became a viable and dangerous weapon system, one the Soviet Union extensively deployed. The "solution" to this problem was to fly at low altitudes, minimizing the radar line-of-sight and thus detection time.
While the Hustler was able to fly these sorts of missions, it could not do so at supersonic speeds, thereby giving up the high performance the design paid so dearly for. Its moderate range suffered further due to the thicker low-altitude air. Its early retirement, slated for 1970, was ordered in 1965, and despite efforts of the Air Force to earn a reprieve, proceeded on schedule. The last B-58s in operational service retired 16 January 1970, largely replaced by the FB-111A, a strategic bomber variant version of the two-seat swing wing fighter that was designed around the low-altitude attack profile, although it was slightly smaller and much less expensive.
A total of 116 B-58s were produced: 30 trial aircraft and 86 production B-58A models. Most of the trial aircraft were later brought up to operational standard. Eight were equipped as TB-58A training aircraft.
A number of B-58s were used for special trials of various kinds, including one (#665 called "Snoopy") used for testing the radar system intended for the Lockheed YF-12 interceptor. Several improved (and usually enlarged) variants, dubbed B-58B and B-58C by the manufacturer, were proposed, but never built.
XB-58: Prototype. Two built.
YB-58A: Pre-production aircraft. 11 built.
B-58A: Three-seat medium-range strategic bomber aircraft, 86 built.
TB-58A: Training aircraft, eight conversions from YB-58A.
NB-58A: This designation was given to a YB-58A, which was used for testing the J93 engine. The engine was originally intended for the XB-70 Valkyrie Mach 3 bomber.
RB-58A: Variant with ventral reconnaissance pod, 17 built.
B-58B: Unbuilt version. SAC planned to order 185 of these improved bombers; cancelled due to budgetary considerations.
B-58C: Unbuilt version. Enlarged version with more fuel and 32,500 lb of thrust J58, the same engine used on the Lockheed SR-71. Design studies were conducted with two and four engine designs, the C model had an estimated top speed approaching Mach 3, a supersonic cruise capability of approximately Mach 2, and a service ceiling of about 70,000 feet along with the capability of carrying conventional bombs. Convair estimated maximum range at 5,200 nautical miles. The B-58C was proposed as a lower cost alternative to the North American XB-70. As enemy defenses against high-speed, high-altitude penetration bombers improved, the value of the B-58C diminished and the program was cancelled in early 1961.
Specifications (B-58A)
Data from Quest for Performance[10]
General characteristics
Crew: 3: pilot; observer (navigator, radar operator, bombardier); defense system operator (DSO; electronic countermeasures operator and pilot assistant).
Length: 96 ft 9 in (29.5 m)
Wingspan: 56 ft 9 in (17.3 m)
Height: 29 ft 11 in (8.9 m)
Wing area: 1,542 ft² (143.3 m²)
Airfoil: NACA 0003.46-64.069 root, NACA 0004.08-63 tip
Empty weight: 55,560 lb (25,200 kg)
Loaded weight: 67,871 lb (30,786 kg)
Max takeoff weight: 176,890 lb (80,240 kg)
Powerplant: 4× General Electric J79-GE-5A turbojets, 15,600 lbf (69.3 kN) each
* Zero-lift drag coefficient: 0.0068
Drag area: 10.49 ft² (0.97 m²)
Aspect ratio: 2.09
Maximum speed: Mach 2.1 (1,400 mph, 2,240 km/h) at 40,000 ft (12,000 m)
Cruise speed: 610 mph (530 knots, 985 km/h)
Combat radius: 1,740 mi (1,510 nm, 3,220 km)
Ferry range: 4,720 mi (4,100 nm, 7,590 km)
Service ceiling 63,400 ft (19,300 m)
Rate of climb: 2,700 ft/min (13.7 m/s)
Wing loading: 44.01 lb/ft² (214.9 kg/m²)
Thrust/weight: 0.919
Lift-to-drag ratio: 11.3 (without weapons/fuel pod)
Guns: 1× 20 mm (0.787 in) T171 cannon
Bombs: 4× B-43 or B61 nuclear bombs; maximum weapons load was 19,450 lb (8,823 kg)

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