Posted on 12/01/2003 9:59:15 PM PST by BenLurkin
They may not be as sexy as their sleek brethren in the fighter corps, but the fast and heavy-duty bombers of the last 60 years have earned their own admirers.
Bombers such as the B-29, B-58, B-52 and XB-70 have carved their own niche in aviation history.
Four pilots of these aircraft shared their experiences recently at the Society of Experimental Test Pilots annual symposium.
Without their "mother ship" carrier aircraft - the B-29 and B-52 bombers - such groundbreaking aircraft as the X-1, X-15 and lifting bodies would never have gotten airborne.
Stan Butchart was a single-engine pilot when he first joined NASA's predecessor, the National Advisory Committee for Aeronautics, in 1951 and was checked out on the B-29, then the carrier for the X-1. He described the job as "hours and hours of boredom with moments of stark terror."
Without a radar or control room in those early days, the bomber served as "NACA 1," controlling the action from the pilot's seat, Butchart said.
The climb to altitude to drop the aircraft took as long as 90 minutes of "grinding, grinding," he said. "That poor B-29 took a beating."
In one harrowing flight, the X-1A exploded shortly before the launch point.
"We had an explosion, a terrific explosion," Butchart said. "I thought we'd hit another airplane at first."
X-1A pilot Joe Walker crawled into the B-29, where he shared an oxygen mask with Butchart until another could be found.
The fire didn't last long in the low-oxygen environment of that altitude, but the X-1A was hanging too low, beneath the B-29's landing gear, to land. Butchart was forced to "dump it on the desert" on the bombing range.
The B-29 eventually was replaced as carrier aircraft by the B-52.
Retired Air Force Brig. Gen. Guy Townsend piloted the B-52 on its maiden flight in April 1952. On that early flight, the forces on the control stick were strong enough to require two pilots to manipulate the airplane, he recalled.
A lethal member of the Air Force arsenal since 1955, the "BUFF" is in the service's war plans for another 40 years.
"I think we succeeded quite well," Townsend said.
While the B-52 was designed for subsonic missions, the B-58 Hustler was the Western world's first supersonic bomber.
Test pilot Fitz Fulton, who has logged 16,700 hours of flight time in 240 different types of aircraft, calls the B-58 his favorite.
Introduced 47 years ago, "it's still as pretty as anything in the air," he said.
However, with Mach 2 capabilities, the plane was also unforgiving.
"It required a lot of attention as far as piloting goes," Fulton said.
Fulton set two of the aircraft's 19 speed and altitude records. For one of these, carrying 11,023 pounds of payload to a record altitude of 85,360 feet, Fulton received the Harmon Trophy in 1962.
One drawback to the B-58 was weak tires that had a tendency to blow up.
On one of his flights, seven of eight tires on one side blew out on takeoff, Fulton said, cutting about 50 holes in the airplane and damaging one hydraulic system.
"I could see rubber going by," he remembered.
The crew jettisoned the canopies and dumped the load of fuel before landing on a runway covered with fire-retardant foam.
Eventually, wheels were developed that operated in pairs with a cast-aluminum flange between the two, so that the aircraft could run on it if the tires blew.
Fulton also piloted another supersonic bomber, the XB-70, as did Al White.
Only two of the Mach 3 aircraft were built, and were used as research aircraft, not bombers. The second "Valkyrie" was destroyed in a crash following a midair collision in 1966.
"Aerodynamically, it was a very effective airplane," White said. The windshield reduced drag, while canards allowed for low takeoff and landing speeds.
On one flight, White recalled, three of the bomber's six engines were shut down in flight.
"We flew back on three engines, which is a testimony to how good an airplane it is," he said.
Two supersonic transports, the Concorde and Russia's Tu-144, benefitted from the technologies developed by the B-58 and XB-70.
Robert Rivers had the chance to try his hand at the controls of a modified Tu-144 during a joint program among NASA, The Boeing Co. and the Russian aerospace industry to conduct high-speed research.
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Air Power |
The Convair B-58 Hustler was the first United States bomber to have a supersonic dash capability and required the development of much new technology. Although the B-58 was thought by many to be the harbinger of future generations of more advanced supersonic bombers, only about 115 of these unique aircraft were built, and they were quietly withdrawn from the SAC inventory after less than 10 years of service.
The general operating requirement, SAB-51, called for the replacement of the B-47 to be the first supersonic bomber. Research and development studies began in the late 1940's, and both Boeing and Convair developed conceptual designs. In 1952, the more revolutionary Convair design was chosen and designated the B-58, with the first flight occurring November 11, 1956. The program was not a competitive development, and Convair was given total development responsibility. As a result of money and schedule problems, the number of aircraft produced was reduced from 244 to 116, with its initial deployment in 1960.
The first B-58 was delivered in August 1960 and by 1964 deployment had reached about 90 aircraft. The B-58 had a Mach 2 dash capability and employed an external weapons pod. The last B-58 was retired in January 1970, about three months after the first FB-111 was accepted by SAC. Although the aircrews swore by the B-58, money and mission limitations led to it being phased out of the inventory after only 10 years of service.
The B-58 represented a drastic change from the B-47 in design, acquisition strategy, and deployment philosophy with SAB-51 being the first time that Air Force requirements called for radical, technological advances. The design specifications called for a Mach 2, high-altitude, medium-range nuclear bomber of minimum size to keep a low RCS. Convair was the prime contractor under the "Weapon System Management Concept" introduced with the B-58 and had responsibility for all subcontractor performance. This was in marked contrast to prior programs in which the Air Force was responsible for providing the prime contractor with "off-the-shelf" technology subsystems. The deployment concept was also different from the B-47 since the B-58 was designed to rely on quality rather than quantity.
These radical changes in the Air Force's approach to bomber development resulted in many problems. For example, meeting the technological requirements proved difficult and resulted in schedule slippages and cost overruns, while under-funding and lack of space on board affected development options. Subsequently, the B-58 was considered an interim bomber since the XB-70 was on the drawing boards.
The high altitude range of 3,500 nm for the B-58A and 4,000 nm for the B-58B included the use of a large centerline fuel pod. Although this range was better than the B-47, the lack of forward basing resulted in a requirement for more tanker support. While the B-58 was faster than Soviet fighters, the newly emerging threat was the development of SAMs in the late 1950's that forced the B-58 to adapt to low level penetration of enemy defenses. This change in mission profile caused a large increase in fuel consumption and compounded range problem.
The B-58, although the holder of numerous world speed records, was severely restricted in its usefulness and lifetime. Designed for supersonic, high-altitude penetration, the B-58 was limited in range, payload, and growth potential for the addition of advanced radar and other electronic equipment.
Thus, replacements were the main mode of modification. For example, analog electronic equipment with cooling problems was replaced by digital electronics. The B-58's planned production run was reduced because of the high cost per unit, a small payload, a mission profile different from its design concept, and, in the 1960's, a Secretary of Defense that downplayed the role of the bomber. In addition, it was very expensive to operate, and huge sums of money were needed for the Vietnam war.
Mission requirements for the Convair B-58 Hustler called for a subsonic cruise segment of several thousand miles followed by a supersonic dash (Mach 2.0) in the target zone of as much as 500 miles and, finally, a post-strike cruise segment. Diverse requirements such as these call for an aircraft of high aerodynamic efficiency at both subsonic and supersonic speeds, together with a versatile propulsion system capable of efficiently providing the required thrust in the different flight regimes. Today's response to the B-58 mission requirements would no doubt be a variable-sweep configuration employing afterburning turbofan engines. Unfortunately, the technology for a practical variable-sweep aircraft did not exist in the early 1950's when the B-58 was being designed - nor did afterburning turbofan engines. The only possible way in which the difficult mission objectives could be met in that time period was with the use of in-flight refueling.
With the increased effectiveness of enemy detection and antiaircraft capability discussed previously, the high-altitude Mach 2 method of weapons delivery became increasingly less viable, and an on-the deck method of attack became the preferred mode of operation. For this type of weapons delivery, however, the payload-range characteristics of the B-58 were much inferior to those of the B-52. For whatever reason, the last B-58 was withdrawn from service in January 1970 after about 10 years in the active inventory. First flight of the aircraft took place on November 11, 1956; approximately 115 units were built.
The B-58 represented a significant technical achievement in the 1950's time period, but the mission requirements called for innovations that far exceeded the technical state of the art then available.
Specifications:
Primary Function: Bomber
Contractor: Convair
Engines: Four General Electric J79-GE-1 turbojets of 15,000 lbs. thrust ea. with afterburner
Crew: Three - Pilot, Navigator/Bombardier, Defensive Systems Operator
Dimensions:
Span: 56 ft. 10 in.
Length: 96 ft. 10 in.
Height: 31 ft. 5 in.
Weights: Empty: 55,560 lb (25,201 kg) / Maximum Takeoff: 163,000 lb (73,935 kg)
Performance :
Maximum speed: 1,325 mph
Cruising speed: 610 mph.
Range: 4,400 miles max. ferry range
Service Ceiling: 64,800 ft.
Armaments:
one 20mm cannon in tail;
Up to 10,000-lb. bomb load of Nuclear or conventional weapons in pod or on under-wing pylons
For one pilot's life experiences with this airplane, please click here: Capt B.F. Brown's B-58 Page
All photos and information is Copyright of their owners
With research and development studies beginning in 1955, the XB-70 was a large, long-range strategic bomber was planned to be the replacement for the B-52. As in the B-58 program, the Air Force wanted new technology advances. To this end, the Air Force gave the prime contractor total weapon system responsibility. Competition between Boeing and North American for the contract occurred during the design phase. In 1958, the North American design was chosen and a development contract awarded. The Air Force requirement was for a Mach 3, high-altitude, long-range bomber capable of carrying nuclear and conventional weapons.
Although there was a technology breakthrough in 1957 that made Mach 3 possible, the XB-70 never went into production. The continuing emergence of new SAMs was the key factor in the demise of the XB-70, just as it affected the B-47 and B-58.
Designed by Rockwell International (North American Rockwell) the XB-70 had a long fuselage with a canard or horizontal stabilizer mounted just behind the crew compartment. The XB-70 had a length of 196 feet, a height at the tail of 31 feet, and an estimated maximum gross weight of 521,000 pounds. It had a crew of four: pilot, copilot, bombardier, and defensive systems operator. The delta wing had a span of 105 feet with six turbojet engines side by side in a large pod underneath the fuselage. The wing was swept at about 65 1/2o, and the wing tips were folded down hydraulically 25o in flight to 65o to improvelateral-directional stability at the aircraft's supersonic speeds of up to Mach 3. At this speed the Valkyrie was designed to ride its own shock wave. The large canard foreplane near the front of the fuselage with a span of 28 feet, 10 inches was used for stability. In addition to its sharply swept delta wings, the XB-70s had two large vertical tails. The airplane had two windshields: a moveable outer windshield was raised for high-speed flight to reduce drag and lowered for greater visibility during take off and landing.
The aircraft was fabricated using titanium and brazed stainless steel “honeycomb” materials to withstand the heating during the sustained high Mach number portions of the flights. The forward fuselage was constructed of riveted titanium frames and skin. The remainder of the airplane was constructed almost entirely of stainless steel. The skin was a brazed stainless-steel honeycomb material. The propulsion system consisted of six General Electric turbojet engines (J93-GE 3), each in the 30,000-lb thrust class, with two large rectangular inlet ducts providing two-dimensional airflow. Internal geometry of the inlets was controllable to maintain most efficient airflow to the engines.
The entire mission (including return) was to be flown at Mach 3, but even then the aircraft was vulnerable to SAMs of the 1960's vintage. A high altitude, Mach 3 penetrator cannot maneuver well; its straight and level trajectory would have been an easy course to plot and intercept. Further, the technology that made Mach 3 possible yielded an airframe with a large RCS that added to the effectiveness of SAMs against the XB-70. The airframe was not adaptable to low level penetration to avoid SAMs because the delta wings were very thin and did not lend themselves to the structural modifications necessary for sustained, low level flight.
The XB-70 design had payload flexibility but not mission flexibility. In 1959, the XB-70 concept was changed to a recon/strike RS-70, making it a reconnaissance aircraft with a bomber strike capability. However, its reconnaissance capability would not have been as good as the super high altitude aircraft designed to fill the reconnaissance role. The XB-70 was an aircraft which fulfilled the criteria it was designed to meet, but whose mission had been eliminated by defensive threat technology.
The high drag of the Mach 3 airframe required a fuel load comparable to the B-52 but limited the range to about 5,000 nm. It was capable of carrying both conventional and nuclear weapons internally, but due to its design and Mach 3 mission profile, it could not carry external ordnance.
In 1961, President Kennedy announced that the XB-70 program was to be reduced to research only, citing high cost (over $700 million per prototype) and vulnerability. The Kennedy administration felt ICBMs were more cost effective because they were less vulnerable and were cheaper operationally. The XB-70 had speed, range, and adequate payload, but it was expensive, not suited to low level penetration, and thus did not compete with ICBMs for strategic funds.
Originally conceived as an advanced bomber for the United States Air Force, production of the XB-70 was limited to two aircraft when it was decided to limit the aircraft's mission to flight research. First flight of the XB-70 was made on Sept. 21, 1964. The number two XB-70 was destroyed in a mid-air collision on June 8, 1966. Program management of the NASA-USAF research effort was assigned to NASA in March 1967.
During the early 1960s, the NASA Flight Research Center was involved in support of the national Supersonic Transport Program (SST). Two prototype Mach 3+ high altitude bombers, built by North American Aviation for the Air Force, became available for SST research with the cancellation of their intended military program. The major objectives of the XB-70 flight research program were to study the airplane's stability and handling characteristics, to evaluate its response to atmospheric turbulence, and to determine the aerodynamic and propulsion performance. In addition there were secondary objectives to measure the noise and friction associated with air flow over the airplane and to determine the levels and extent of the engine noise during take off, landing, and ground operations.
The fastest mph flight was on Jan. 12, 1966, speed was 2,020 mph with White and Cotton as crew. The fastest Mach flight was on Apr. 12, 1966, achieved Mach 3.08 with White and Cotton as crew. And the highest flight was on Mar. 19, 1966, attained 74,000 ft with White and Shepard as crew.
Aircraft No. 2 (serial # 62-0207) with its improved wing design, was capable of sustained Mach 3 flight at altitudes around 70,000 ft. This highly instrumented vehicle was destroyed in a mid-air collision with NASA F-104N (N813NA) on 8 June 1966.
An attempt to substitute the slower No. 1 aircraft (serial # 62-0001) into the research program met with limited success. Ship #1 was flown by the NASA Flight Research Center (now NASA Dryden), Edwards, Calif. from March 1967 through early 1969. The final flight was flown on Feb. 4, 1969. The XB-70A program produced a significant quantity of information about supersonic flight up to Mach 3 speeds. In many areas, such as noise (including sonic boom runs), clear air turbulence, flight controls, aerodynamics and propulsion system performance and operation problems, it related to SSTs.
Specifications:
Type: high-altitude, long-range bomber
Crew: four (pilot, copilot, bombardier, and defensive systems operator)
Engines: Six General Electric YJ-93s of 30,000 lbs. thrust each with afterburner.
Dimensions:
Span: 105 ft.
Length: 185 ft. 10 in. without boom; 192 ft. 2 in. with boom
Height: 30 ft. 9 in.
Weight: 534,700 lbs. loaded
Performance :
Maximum speed: 2,056 mph. (Mach 3.1) at 73,000 ft.
Cruising speed: 2,000 mph. (Mach 3.0) at 72,000 ft.
Range: 4,288 miles
Service Ceiling: 77,350 ft.
Armaments:
Internal stores for Nuclear and convention weapons
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