Over 100 years of aviation development, many unusual aircraft have been created. As a rule, these machines were distinguished by avant-garde design solutions and were not mass-produced. Their fates were bright, but short-lived. Some of them had a noticeable impact on the further development of aviation, others are forgotten. But they have always aroused increased interest both among specialists and among the public. Our magazine also decided to pay tribute to aviation exoticism.
History of creation
At the end of 1951, the first strategic bomber with the Boeing B-47 turbojet engine entered service with the US Air Force Strategic Aviation Command. As a medium bomber (maximum bomb load about 10 tons). it could not carry in its compartments the entire range of bombs from the US nuclear arsenal of that time. Thus, the jet B-47 was just an addition to the huge piston B-36. Therefore, the Air Force initiated the development of the B-52 heavy bomber. The first modifications of this aircraft in comparison with the B-47 had twice the take-off weight. range of about 5500 km and, most importantly, could carry a hydrogen bomb Mk 17 with a mass of 21 tons and a capacity of 20 Mt.
However, the prospect of the appearance in the near future of anti-aircraft guided missiles and supersonic interceptors has cast doubt on the very possibility of heavy subsonic bombers to reach their designated targets deep in the territory of the USSR. With this in mind, in 1954, the US Air Force issued an order to Convert for the construction of B-58 supersonic bombers. Operating from European bases, they were supposed to be the first to invade Soviet airspace and strike at key air defense facilities, opening the way for heavy B-52s. However, the Strategic Aviation Command never showed much enthusiasm for the B-58, mainly because this aircraft had a short flight range (without refueling only about 1,500 km) and carried an insignificant bomb load, and frequent accidents have thoroughly undermined its reputation. Back in late 1954, General Le Mae, Commander of the US Air Force Strategic Aviation. Having got acquainted with the calculated data of the B-58, he turned to the Ministry of Defense with a request to consider the issue of another bomber, which could in the future replace the B-52 - with a range without refueling of at least 11,000 km and "the maximum possible speed." This aircraft, for the operation of which existing airfields and ground equipment would be suitable, should have been in service with the Air Force from 1965 to 1975.
By order of Le May, the US Air Force issued GOR # 38, General Tactical Requirements for a Manned Intercontinental Bomber Weapon System Bomber. After a while, the following document appeared, in which the project was given the designation WS-110A - "Weapon System 110A". The scheme of the combat use of such an aircraft consisted in approaching the target at a very high altitude at a speed corresponding to the number M = 2, and with its increase to the corresponding number M = 3 over the enemy's territory. Having launched a guided air-to-ground missile with a nuclear warhead at the target, the bomber had to retire as fast as possible. At the suggestion of a group published at the Wright Research Center to study ways to implement these requirements, the chief of staff of the US Air Force ordered the development of the WS-110A project on a competitive basis. The main condition for victory was considered to be the achievement of the maximum possible altitude and flight speed. Serial aircraft deliveries were scheduled to begin in 1963.
Six firms submitted proposals to the Air Force in October 1955. The following month, two finalists, Boeing and North American, were awarded orders for detailed design studies of the bomber. It should be recalled that at that time the efficiency of turbojet engines left much to be desired, and long-range flight at supersonic cruising speed required an exorbitant supply of fuel. Both projects involved the creation of huge aircraft.
Thus, the project of the North American company provided for the development of a bomber with a take-off weight of 340 tons with a trapezoidal wing, to which were attached large forward-swept consoles with fuel tanks in the middle. The latter had the same dimensions as the B-47 fuselage, and contained 86 tons of fuel each, providing an intercontinental range at a high subsonic flight speed. After covering most of the path, the consoles with the tanks were dropped, and the aircraft accelerated to M = 2.3 for throwing to the target and leaving. Regarding this project, General Le Mae sarcastically remarked: "This is not an airplane, but a link of three airplanes." In addition, the operation of such an aircraft from existing airfields and the use of existing ground equipment was out of the question. Both projects presented were rejected, and soon the WS-110A program was limited only to studies of the very possibility of creating such a machine.
A year and a half later, Boeing and North American submitted new proposals for the WS-110A. Independently of each other, they came to the conclusion that using high-calorie synthetic fuel. it is possible to achieve supersonic cruising speed without resorting to exotic aerodynamic configurations. In addition, thanks to advances in aerodynamics, it became possible to significantly improve the aerodynamic quality of a heavy aircraft, which reduced the amount of fuel required to achieve intercontinental range. In aerodynamics, North American was particularly successful, deciding to use in its design the principle of increasing lift "from compression" developed by NASA. She carried out research in a wind tunnel to determine whether it is realistic to create an aircraft whose aerodynamic quality is improved by the additional lift generated by the shock waves. The results exceeded all expectations - it turned out that on the basis of this principle, very similar to the effect of planing a speedboat on the water surface, it is possible to create an aircraft that meets the requirements of the Air Force, even regardless of the type of fuel used.
In the late summer of 1957, the US Air Force, curious about these results, extended the design research program so that firms could submit designs describing the major systems. After their assessment by representatives of the Air Force in December 1957, preference was given to the project of the Valkyrie B-70 aircraft (Valkyrie the warlike maiden-goddess in Scandinavian mythology) by the North American company, with which they signed a contract for the construction of 62 aircraft - 12 experimental and pre-production and 50 serial. In parallel with General Electric, a contract was signed for the creation of the J93 engine. capable of operating on both conventional and synthetic fuels. The entire program was estimated at $ 3.3 billion.
When blowing the XB-70 model in the wind tunnel, the shock waves are clearly visible
Rescue capsule ground tests
Installing the YJ93-GE-3 engine
Part of the scientific research required for the project was planned to be carried out as part of the program to create a long-range interceptor "North American" F-108 "Rapier" with the same J93 engines, which could reach speeds of up to 3200 km / h and be armed with three guided missiles with nuclear warheads. The design range of the F-108 exceeded 1600 km, and the ferry range was 4000 km. "Rapiers" were supposed to accompany the B-70 and cover strategic objects from Soviet bombers, similar to the "Valkyrie", the appearance of which in the arsenal of the USSR would not be long in coming even if the B-70 was successful.
The US Air Force insisted on accelerating the development of the B-70 with that. so that its first flight took place in 1961, and the first wing of 12 aircraft took up combat duty by August 1964. The first stage of the program - the development, construction and approval of a model of the aircraft - was completed in April 1959. Based on the results of an inspection by Air Force specialists, it was proposed make 761 changes to the project and 35 changes to the layout. Since the B-70 development program was among the top priorities, all comments were quickly eliminated.
However, this did not last long. The first setback in the program was related to the high-calorific fuel for J93 engines, the so-called borohydride fuel. Its use, of course, provided greater combustion energy compared to kerosene, but at the same time, the exhaust gases of the engines contained a lot of toxic substances, which forced all ground personnel to work in a state of permanent chemical warfare. In addition, the cost of borohydrogen fuel turned out to be very high, and according to calculations, when it was burned in the afterburners of the J93 engines, the flight range of the Valkyrie increased by only 10%. This increase was considered insufficient to justify the costs of developing and producing new fuel. Even though the Olin Mathison firm had almost finished building the plant for its production, the program was terminated. The $ 45 million plant never started working.
A month later, the development program for the F-108 interceptor was also terminated, citing the fact that its engines had to run on borohydrogen fuel. However, the real reason for the termination of the development of the F-108 was the lack of funds - the large-scale development of intercontinental ballistic missiles required a lot of money, which led to the need to review funding for manned aircraft projects. But in parallel with the F-108, the development of the Lockheed A-12 (F-12A) fighter, similar in purpose, which later turned into the famous SR-71, was under way. Incidentally, Lockheed had abandoned boorhydrogen fuel even earlier and by the end of 1959 had almost completed the development of its interceptor. The funds freed up as a result of the closure of the F-108 program were transferred to the Kelly Johnson team to build prototypes of the A-12.
By October 1959, more than $ 315 million had already been spent on the creation of the B-70. Since part of the research related to the M-3 flight was to be carried out as part of the creation of the F-108, the cost of the necessary work on the B-70 program after the mentioned events increased by another $ 150 million. Despite this, in December 1959, the appropriation for the Valkyrie for the financial year 1961 was cut from $ 365 million to $ 75 million. The new plans provided for the construction of only one copy of the XB-70, and then without sighting, navigation and other combat systems. The first flight was scheduled for 1962, and the flight test program was extended until 1966.
However, in the summer of 1960 in Moscow, at the air parade in Tushino, the M-50 supersonic bomber developed by the design bureau of V. M. Myasishchev was demonstrated. The formidable combat appearance of the vehicle shocked the foreign military delegations present at the parade. Not knowing its true characteristics, the Americans immediately resumed funding for the development of the Valkyrie in the same amount. But already in April 1961, the new US Secretary of Defense, Robert McNamara. a big supporter of missiles, coolly reduced it to the construction of three experienced bombers. The first two, exclusively research, had a crew of 2 people and the designation XB-70A, the third aircraft, a prototype bomber with the designation XB-70B, had a crew of four (two pilots, an electronic warfare system operator and a navigator). This time, the Valkyrie was saved only by the fact that it could be used as a carrier of the GAM-87A (WS-138A) Skybolt missiles with a range of up to 1600 km, which were developed by the Douglas company. The B-70 could patrol beyond the borders of a potential enemy, and in the event of a conflict, release hypersonic missiles with powerful warheads. But all five experimental launches from the B-52 were unsuccessful. Seeing that the development of the rocket is costly, and that the fate of its carrier B-70 is very vague, the President of the United States stopped its development.
The first XB-70A in the assembly shop
A special lift was used to board the crew in the XB-70A cockpit.
In January 1962, in response to another threat of closure, the Valkyrie program was again subjected to changes, and the aircraft received the designation RS-70 - strategic reconnaissance bomber. this despite the fact that the US Air Force constantly sought all possible and impossible means to bring the B-70 back to life as a combat aircraft, claiming that it can be used as a supersonic vehicle. a preserved launch stage for combat spacecraft such as the Dinosaur; and platforms for launching ballistic missiles. It has even been suggested that he will be able to perform the functions of a space interceptor.
But all efforts to preserve the "Valkyrie" were in vain. The Secretary of Defense believed that better results could be achieved through other means. Even the importance of the experience gained during the creation of the B-70 for the development of a supersonic civilian aircraft, from McNamara's point of view, was not significant, although he personally headed a special committee on this issue. Note: In terms of configuration, weight and design, the B-70 fully corresponded to the views of that time on supersonic transport aircraft. Its cruising altitude was 21 km. and the speed reached M = 3. At the same time, its payload, equal to only 5% (12.5 t) of the take-off weight (250 t), was clearly insufficient for a commercial aircraft. At the same time, the Valkyrie's flight range was 11,000 km, while most of the transatlantic routes had a length of about 9,000 km. By optimizing the aircraft for these routes and reducing the fuel supply, the load could be increased to 20 tons, which would have made it possible to achieve the level of profitability required for a civil liner.
Of course, all these disruptions in funding and incessant debate in Congress did not promise anything good for the plane, but North American stubbornly continued to build the first prototype of the Valkyrie. As they say. Vaska listens and eats.
Technical features
One of the reasons for such a wary attitude to the B-70 was its too much unusualness for that time, one might say, revolutionary. Accordingly, the technical risk in the creation of the "Valkyrie" was extremely high. Among the main features of the aircraft, first of all, should be attributed to the aerodynamic configuration "duck", triangular wing and trapezoidal forward horizontal tail. In view of the large shoulder of the PGO, it was effectively used to balance the aircraft, especially at supersonic speeds, which made it possible to free the elevons for pitch and roll control. During the landing approach, the maximum deflection angle of the PGO was 6?, And its tail part could additionally deviate downward by 25 ° and served as landing flaps. By deflecting them, the pilot increased the pitch angle, while balancing the aircraft by pushing the control wheel forward, i.e. deflecting the elevons downward and further increasing the overall lift. At the same time, the PGO became a source of longitudinal and directional instability of the aircraft at high angles of attack, the canted flow from it had a harmful effect on the wing bearing properties and worsened the operation of the air intakes. However, North American said it had rigorously tested the B-70s in wind tunnels for 14,000 hours and solved all the problems.
The most important feature of the aerodynamic layout of the aircraft was the beneficial use of such, in principle, a harmful phenomenon as the shock waves formed during a supersonic flight. lifting force. This made it possible to cruise with a minimum angle of attack and, therefore, with low resistance. Tests in a wind tunnel and calculations have shown that in flight with a speed corresponding to M = 3, at an altitude of 21,000 m, due to shock waves, it is possible to increase the lift by 30% without increasing resistance. In addition, this made it possible to reduce the wing area and, therefore, to reduce the weight of the aircraft structure.
The source of this "useful" jump system was the Valkyrie's front air intake wedge. The air intake itself was divided into two channels with a rectangular section, having a height at the entrance of 2.1 m and a length of about 24 m. Behind the wedge there were three movable panels connected to each other. The position of the panels was adjusted depending on the required air flow. Holes were made in them to drain the boundary layer, which ensured a uniform flow at the inlet to each of the three engines. On the upper surface of the wing, the main and auxiliary air bypass flaps were located, allowing to some extent control the flow in the air intake. The calculations required to ensure the correct operation of the air intake in various flight conditions were performed using a complex system of sensors and analog computers.
Solemn roll-out of the first copy of the XB-70A
Refueling XB-70A with fuel
Takeoff of the first copy of the XB-70A
Jumps arising on the frontal glazing of the cockpit canopy with the usual configuration of the nose of the aircraft. inadmissibly increase the drag when flying at high speeds. To avoid them, the angles of inclination of all nose surfaces of the aircraft must be very small. At the same time, it is necessary to provide pilots with a good view during the landing approach. North American chose a relatively simple method to satisfy both requirements, made the windshields double, with the outer ones, as well as the upper surface of the fuselage nose in front of the windows, movable. In flight at low speed, they descended, providing the necessary visibility, and in supersonic flight, they rose, forming a smooth transition. The total area of the cockpit glazing is 9.3 m. All transparent panels, the largest of which is more than 1.8 m long, are made of heat-resistant tempered glass.
A completely unique feature of the Valkyrie is the wingtips, which are deflected downward during cruise flight to increase directional stability and reduce balancing drag. In addition, they made it possible to reduce the vertical tail area, thereby increasing the aerodynamic quality by about 5%. The firm stated that the aircraft's aerodynamic quality is 8-8.5 in supersonic cruise flight. and in subsonic - about 12-13.
All types of nuclear bombs could be placed in a large bomb bay with a length of almost 9 m, located between the air intake channels. The bomb bay was closed by a large flat sliding panel, which, when opened, slid back. True, the release of bombs from such a compartment at supersonic flight speeds is a problem. The North American asset, or rather the passive, already had the experience of developing such a design - the company did not bring the famous linear bomb bay on the Vigelent supersonic to a conditional one, which turned the deck bomber into a reconnaissance bomber.
The Valkyrie's chassis is also noteworthy. To reduce the space occupied in the retracted position, the four-wheeled carts on the main supports before harvesting were turned and pressed against the rack. At the same time, each carriage had a small fifth wheel of an automatic release mechanism, which prevents skidding and skidding of the aircraft on a slippery surface. The tires of wheels with a diameter of 1060 mm were made of special rubber and covered with silver paint to reflect infrared radiation. Before flying at high speeds, the pneumatics were tinted with fresh paint. During braking, when the tires were heated up to 230 ° C by pneumatics, the excess pressure in them was dumped by a special valve, which prevented their explosion.
The V-70 cockpit was located at a height of 6 m above the ground, which necessitated the use of special lifts for the crew and technical personnel. Thanks to the powerful air conditioning and sealing system, the Valkyrie crew members could dress in light flight suits and helmets with oxygen masks. This provided them with freedom of movement and relative comfort, unlike the pilots of other high-altitude and high-speed aircraft. For example, the pilots of the high-speed A-12 had to fly in spacesuits from the Gemini spacecraft, and the pilots of the high-altitude U-2 - in special suits and pressure helmets. The V-70 cockpit was divided into two compartments by a repetitive partition, in each of which, during high-altitude flights, a pressure corresponding to an altitude of up to 2440 m could be created. In the case of decompression, two doors opened in the fuselage, providing the cabin with an oncoming flow. Along the middle of it there was a passage leading to the compartment with electronic equipment in the rear of the cockpit. Fiberglass was used for thermal insulation. To cool the cockpit and the electronic equipment compartment, two refrigeration units operated on freon were used.
In the first flight, the landing gear could not be removed
The crew members of the B-70 were housed in individual capsules, which was supposed to radically increase the safety of ejection in all flight modes. Each capsule had an autonomous system of pressurization and oxygen supply, designed to ensure human life for 3 days, the seat inside it was regulated by the angle of inclination and height. Immediately before the ejection, the pilot's seat was tilted back by 20 °. and the capsule flaps closed. The upper fuselage panel was automatically dropped, and the capsule was fired to a height of about 1.5 m above the fuselage, after which its jet engine was turned on. Then two cylindrical rods with small parachutes at the ends were extended from the capsule, providing stabilization during free fall. The main parachute opened automatically. To cushion the impact on the ground, there was an inflatable rubber cushion at the bottom of the capsule. Estimated speeds of ejection - from 167 km / h to the corresponding number of M 3 at an altitude of about 21,000 m ejection of capsules of all crew members was carried out. With an interval of 0.5 s. At the same time, in some emergency situations, the pilot could close in the capsule without ejection. Inside it there were buttons with which it was possible to control the aircraft until it descended to a safe altitude, and the control of the engines from the capsule was limited only by a decrease in the number of revolutions. In the front part of the capsule there was a window that made it possible to monitor the readings of the instruments. After lowering the shutters, the capsules could be opened, and the pilot could resume control of the aircraft in normal mode.
Since the design of the B-70 was designed for a long flight at a speed of more than 3000 km / h. one of the most difficult problems in its development was kinetic heating. For the Valkyrie, this problem turned out to be even more difficult than for the experimental North American X-15 aircraft. designed for a short flight with a hypersonic speed corresponding to the number M 6. If on the surface of the latter the temperature peaks reached 650 ° C, but stayed at this level for only a few minutes, then for the B-70 the picture was different. A long, for several hours, flight at M 3 required that a significant part of the entire structure of the aircraft could operate effectively at a temperature of 330 ° C. This determined the choice of high-strength steel and titanium as the main structural materials. Temperatures in the engine compartments, reaching 870 ° C, led to the use of alloys based on nickel and cobalt. Silicon dioxide felt was used to protect drives and other mechanisms from the heat generated by the engines. The outer skin of the engine compartment was made of titanium. Operating temperatures of some of the cockpit glazing panels reached 260 C. The landing gear niches had to be cooled to 120 ° C using an ethylene glycol solution circulated through tubes soldered to the walls. When choosing construction materials, not only high temperatures were taken into account, but also possible weather conditions. For example. to study the effect of rain, the company accelerated structural elements using a rocket carriage to a speed of 1500 km / h. To reduce the weight of the structure, “layered” panels were used, consisting of two steel sheets with a thickness of 0.75 to 1.78 mm and a honeycomb filler between them. If all such panels were laid out next to each other, then they would cover an area of 1765 m. In addition to their low weight and high strength, such panels had low thermal conductivity. The aviation industry at that time did not have the technology to produce such panels, and the company started from scratch.
But perhaps more important in the creation of the Valkyrie than the use of new materials was the transition from riveting and manual assembly of aircraft structures to mechanical soldering and welding, which is comparable to the revolution in shipbuilding. In the factory building, where the XB-70A was being assembled, instead of the knocking of pneumatic hammers, only the hissing of dozens of welding units and grinders was heard, cleaning the seams. The method of assembling the aircraft structure by welding was so new that the welding equipment, methods of its application and the technology for controlling welds were finally developed only during the assembly of the first prototype aircraft. In some places of the structure, where it was impossible to do without riveting, to save weight, the rivets were replaced with tubes flared on both sides.
There were so many problems in the design of the XB-70 that the North American company could not cope with such a huge task alone and transferred part of the work to other companies, the number of which exceeded 2000. The main ones were: Air Research (air signal system). "Autonetic" (automatic control system). Avko (rear section of the upper fuselage), Chance Vout (horizontal and vertical tail). Newmo Dynamics (chassis). Curtiss Wright (wing tip deflection drive). Hamilton Standard (air conditioning system). "Pop" (wing elevons and toes), "Solar" (air intake). Sperry (inertial navigation system). "Sandstrand" (auxiliary power unit).
The Valkyrie, accompanied by the B-58A, returns after crossing the sound barrier for the first time. October 12, 1964
In this flight, paint fell off on many parts of the plane's surface.
The largest contractor, Boeing, was entrusted with the design and production of the Valkyrie wing, which became the largest delta wing of the time. worked in white gloves. Eleven fuel tanks, located in the wing and fuselage, held about 136 tons.fuel and had a welded structure. According to BBC statements. this was the main reason for the delay in the construction of the aircraft - the technologists could in no way ensure the tightness of the welded seams. Their porosity was, as a rule, microscopic, but it had to be eliminated, since in flight the tanks were pressurized with nitrogen, the leakage of which would lead to air entering the tanks and the formation of an explosive mixture. The first attempts to fix the leak by soldering were completely unsuccessful. In this regard, a rubber-like sealant "Viton" was developed to the place where the leak was found. one layer of Viton was applied. which cured for 6 hours at a temperature of 177 C. As a rule, to eliminate the leak, it was required to apply at least six coats of Viton. The coating was carried out by a person wearing sterile clothing, who was closed inside the tank. Then helium was pumped into the tank to check the sealing of the tank.
The helium leak was determined using special detectors. On the second prototype aircraft, the tanks were sealed using a new method. The areas of suspected leakage were covered with 0.75 mm thick nickel foil. which was soldered along the edges with silver solder. When the wing was finally manufactured and delivered to the assembly shop, it turned out that it did not fit into the fuselage! With great difficulty, manually, it was possible to install it in place and attach it by welding.
The first XB-70A was built by the beginning of May 1964, with a delay of a whole year and a half on May 11, a ceremonial rollout of the aircraft from the assembly shop took place, at which the director of the XB-70 production program, General Frode J. Scully, presented a prototype of the bomber to the media. The first flight was scheduled for August - the company wanted to test all the systems of the unique machine in three months. An extensive ground test program included testing the performance of the landing gear, landing gear flaps and braking parachute compartment under dynamic and static loads; vibration testing with a ground facility to evaluate flutter performance; Calibration of the air conditioning system, fuel system and power plant (with gas engines on the ground): checking and calibrating the instrumentation equipment. A container with control and recording equipment was placed in an empty bomb bay, which recorded several hundred parameters of robots of various aircraft systems. Of course, such an extensive work took the firm not three, but almost five months.
The second copy of the "Valkyrie" flies with wingtips deflected by 25 °
The Valkyrie is ready to fly at maximum speed. Wing tips deflected by 65 degrees
The last stage of ground tests, which began in September 1964, included taxiing and jogging along the runway, checking the performance of the release system for three braking parachutes with a diameter of 8 m. Without parachutes, the aircraft would need a runway at least 4100 m long. jogging reached 1070 ° С, pneumatics heated up to 120 ° С. During the last stages of ground tests, the refueling procedure was finally worked out. On average, refueling the Valkyrie lasted an hour and a half. First, the fuel was pumped from one tanker to the second, empty, which, meanwhile, was supplied with dry nitrogen under high pressure, nitrogen was blown through the fuel in the filler neck and displaced oxygen. Thus, the fuel entered the tanks as inert (explosion-proof) as can be achieved in the field. The fact. that the fuel was used as a coolant for some aircraft systems, and its normal temperature in flight exceeded 100 ° C. If the oxygen content in the fuel exceeded the permissible level, its vapors could flare up. Thus, if the "Valkyrie" was fueled in the traditional way, the plane could simply explode in the air.
At this time, the second prototype X8-70A was in the assembly stage. It was planned to lift it into the air at the end of 1964. The main difference between the second prototype was the presence of a small transverse "V" wing (only 5 °). The deflection angles of the wing consoles were also increased by 5 °.
Two crews were trained for flight tests of the XB-70A. Each was headed by an experienced "branded" test pilot, and the co-pilot was a representative of the Air Force. The main crew was led by Ell White (who had previously flown an F-107), with Colonel John Cotton as co-pilot. Their backup was Civil Test Pilot Van Shepard and Major Fitz Fulton. The flights were planned to be carried out over sparsely populated areas of the United States. stretching from Edwards Air Force Base towards Utah.
Flight tests
On September 21, 1964, at 08:38 in the morning, the XB-70A, driven by White and Cotton, taxied to the start, and White requested permission to take off. The plane was supposed to make a transfer from the factory airfield in Palmdel to the Air Force Flight Test Center at Edwards AFB. During the takeoff, the Valkyrie was accompanied by two helicopters of the rescue service, and in the air its behavior was monitored from the side of a two-seater T-38. Another T-38 was filming everything that was happening. The nose wheel lifted off the ground at a speed of 280 km / h. and in a moment the car began to climb. Failures began already when trying to remove the chassis: the front support retracted normally, and the main ones worked only half of the program. I had to return the chassis to its original position. After a while, the fuel automation of one of the six engines failed. But this “air adventure - XB-70A did not end there. The biggest trouble awaited the crew during the touchdown of the runway at Edwards AFB. The brake discs on the left strut got stuck, and the tire pneumatics caught fire from friction. For the entire length of the two-kilometer run, clouds of black smoke from burning rubber trailed behind the car. After stopping, the fire was extinguished, and the car was towed to the hangar. The first flight lasted 60 minutes.
XB-70A # 2 in the last flight. Nearby F-104, piloted by John Walker
Landing with faulty left landing gear. March 1966
The nose pad is jammed while cleaning. April 30, 1966
It took two weeks to eliminate the identified defects. On October 5, the KhV-70A made its second flight. The pilots intended to overcome the sound barrier, and the supersonic B-58 was included in the escort group. The chassis retracted without comment, but this time the surprise came from the hydraulic steering system. A small crack in the tube at an operating fluid pressure of 280 kgf / cm? (which is 35% more than in the hydraulic systems of conventional American aircraft) led to a decrease in pressure in the system and a switch to a backup channel. Nevertheless, the plane successfully landed on one of the airbase's landing strips.
On October 12, in the third flight, which lasted 105 minutes, the first prototype of the Valkyrie reached an altitude of 10,700 m and for the first time broke the sound barrier, accelerating to a speed corresponding to M 1.1. At the moment the barrier passed from vibrations, paint flew off some parts of the plane's surface, and after landing the XB-70A had a very shabby appearance.
On the fourth flight. On October 24, at an altitude of 13,000 m, the wingtips control system was switched on for the first time and all six engines were set to afterburner. The maximum deflection angle of the tips was 25 °. For 40 minutes the plane flew at a speed of M = 1.4. was easy to control and behaved steadily. True, fuel consumption turned out to be higher than expected, and the flight program had to be reduced. The aircraft returned to the plant for durability tests and refinishing. The test flights were scheduled to continue in February 1965.
In accordance with the plan, on February 16, the XB-70A returned to Edwards base. In flight, the wingtips deviated by 65 °. The maximum speed was M 1.6. On landing, the brake parachute release system failed, and the plane stopped only after 3383 m of run. In the sixth flight, the plane was first piloted by Fulton, with White as co-pilot. A small leak appeared in the air in the hydraulic system, which did not affect the safety of the flight.
In the seventh flight, the Valkyrie was accelerated to a speed of M = 1.85. and the plane flew with her for 60 minutes.
In the eighth flight, Shepard sat at the helm of the XB-70A. He first brought the plane to a speed of M = 2. Thus, all four pilots tested the Valkyrie.
In the ninth flight, the XB-70A again reached M-2. This time, the TACAN radio navigation system was a surprise. According to the readings of the instruments, the car was supposed to fly over the Mojave Desert, but in fact the Valkyrie was rushing over the sleeping Las Vegas in the early morning.
In the tenth flight, the bomber spent 74 minutes at supersonic, of which 50 - at a speed of over 2200 km / h.
On May 7, 1965, in the twelfth flight, at a speed of M 2.58, the pilots felt a sharp blow. Engines 3, 4, 5, 6 dropped their rpm, and the temperature began to rise. They had to be turned off, and the flight continued on the other two. The escort aircraft reported that the KhV-70A's front end of the wing collapsed (the top of the triangle). Probably, its debris fell into the air intake. When approaching the airfield, the pilots tried to start the fifth engine to create at least some thrust on the right side. Fortunately, they succeeded. The landing was successful. During the inspection, the worst fears were confirmed: parts of the skin damaged all six engines to varying degrees, which had to be replaced.
The F-104 exploded from the impact, and the XB-70A still flies by inertia
XB-70A went into a tailspin
In the fourteenth flight "Valkyrie" at an altitude of 20725 m reached a speed of M = 2.85 (3010 km / h)
On October 14, 1965, in the seventeenth flight, at an altitude of 21335 m, the XB-70A reached its design speed corresponding to the number of M-3. According to the assignment, the flight duration at this speed was supposed to be 5-6 minutes, but after 2 minutes the pilots heard a loud noise and turned off the afterburner. The reason for the noise was quickly found out: from the escort aircraft it was clearly visible that the section of the toe of the left wing console measuring 0.3x0.9 m, located next to the outer edge of the air intake, was torn off by the high-speed pressure. As luck would have it, this piece of skin did not hit the engines. Inspection of the aircraft showed that the curved skin panel had come off at the weld seam and fell off without damaging the honeycomb core. This time, the repair of the X8-70A took only one day.
After this incident, the maximum flight speed of the first prototype was limited to M 2.5. and all flights with the number M = 3 were decided to be carried out on the plane # 2. the flight of which took place on July 17, 1965. In that flight, the speed M = 1, 4 was immediately reached.
A typical flight of the Valkyrie proceeded as follows. After takeoff and landing gear retraction, the pilots began to climb. At a speed of 740 to 1100 km / h, the wingtips deflected by 25? in order to increase stability in the transonic zone. Upon reaching M-0.95, the outer windshields of the cockpit were raised, after which the visibility became almost zero, and the aircraft was controlled only by instruments. Then the sound barrier was broken. The speed M = 1, 5 was set at an altitude of 9753 m. The wing tips deviated to 60 °, and the XB-70A continued to climb to 15240 m. Then the plane passed M = 2 and at an altitude of more than 21000 m went to M 3 So, on December 11 1965 g the second copy of the bomber in its fifteenth flight flew at a speed of M = 2.8 for 20 minutes. No structural damage was found.
10 days later, on December 21, after seven minutes of flight at a speed of M = 2.9, the oil pump of the fourth engine on aircraft # 2 failed. The engine was immediately turned off, and the plane was deployed to the airfield. A few minutes after that, the temperature of the gases behind the turbine of the sixth engine exceeded the permissible limits, and it also had to be turned off. Landing proceeded without comment, but two engines had to be replaced. Frequent engine breakdowns caused concern among specialists. The fact is that only 38 YJ93-GE-3 turbojet engines were released, and they could simply not be enough until the test program was completed.
Some faults were already becoming traditional. So. in the 37th flight in March 1966on aircraft # 1, the hydraulic system failed again, and the left main landing gear was stuck in an intermediate position. Shepard managed to land the car with jewelry on the surface of the dried-up Rogers Lake, the mileage was more than 4.8 km. On April 30, 1966, White and Cotton were supposed to spend more than half an hour at a speed of M = 3, but after takeoff, the nose landing gear on aircraft # 2 did not retract. Attempts to return her to the released position have also been unsuccessful. This was the most serious accident since the start of flight tests. If the strut could not be released, the pilots would have to eject, because during a forced landing, the long "swan neck" of the XB-70A would inevitably be broken, fuel from the tanks would rush into the engines and then …
White came in twice and hit the main supports on the runway surface, but the front support was jammed thoroughly. While the Valkyrie was circling in the air, burning a huge supply of fuel, engineers puzzled over a solution to the problem In addition to two hydraulic landing gear systems, there was also a third - electrical, but it was disconnected from overloads in the electrical network. The only recourse was to try to short-circuit the fuses of the electrical system with a metal object. Cotton took an ordinary paper clip, which fastened the sheets of the flight mission, and crawled along the narrow manhole between the escape pods to the fuse box. Opening the flap, he found the necessary contacts on commands from the ground and closed them with an unbent paper clip. The nose pillar is in the extended position. But the next day, the newspapers were full of headlines like "A 39-cent paperclip saves a $ 750 million plane."
The planned long flight at M = 3 took place only on May 19. The plane flew at this speed for 33 minutes. In that flight, the highest speed and altitude for the entire time of the KhV-70A tests were achieved: M = 3.08 and 22555 m, respectively. This achievement marked the end of the first phase of flight tests.
The next phase was carried out mainly in the interests of NASA - for research on sonic booms. New pilots joined the program - NASA employees. Experienced North American test pilot John Walker was appointed as the first pilot. who has just finished flying the hypersonic X-15. In the bomb bay of aircraft # 2, new equipment worth $ 50 million was installed to fix the bends and vibration of the structure when crossing the sound barrier. The first flight of the second phase was scheduled for June 8, 1966. The flight pursued two goals: testing new equipment and filming an advertising film about the Valkyrie. For greater effect, the huge bomber was accompanied by F-4B, F-5, F-104 fighters and a T-38 trainer.
At 0827 hours in the morning, White and Major K. Cross took their places in the XB-70A cockpit. This was the 46th flight of aircraft # 2 and the first flight of Karl Cross. One of the escort aircraft, the F-104 Starfighter, was piloted by John Walker. When the planes, breaking through the clouds, lined up for shooting, the F-104, flying to the right of the Valkyrie, touched its wing to the lowered tip of the bomber's right wing, rolled over its fuselage, beating off both keels, hit the left console and exploded. The bomber pilots did not immediately understand what had happened. For 71 seconds, the Valkyrie continued its straight flight, then rolled over the wing, went into a spin and fell. Only Ella White managed to escape, who managed to eject his capsule in the last seconds before falling. His parachute lying on the ground was noticed from a rescue helicopter 20 kilometers from the KhV-70A wreckage. The landing of the capsule with a half-opened parachute was very rough, White received serious injuries and did not regain consciousness for three days. Little remained of the bomber itself. The nasal part, in which Cross was (it is believed that he lost consciousness from overloads), was torn into several parts. The car probably exploded while still in the air. White recovered but never flew again.
After this tragic test case of the remaining aircraft No. 1 continued for two more years. The first flight after the disaster took place on November 1, 1966, then 32 more flights were performed. In total, KhV-70A # 1 performed 83 flights, and # 2 - 46 flights. The total flight time of the two aircraft was 254.2 hours, of which No. 1 was 160 hours.
Dashboard in the cockpit
Nose landing gear
In 1968, work on the B-70 was discontinued. On February 4, 1969, the Valkyrie took off for the last time. The car was driven by Fitya Fulton from North America. and Ted Stenfold of the Air Force XB-70A landed at Wright-Patterson AFB and became an exhibit at the Air Force Museum. During the transfer of the plane to the museum representatives, one of the pilots said that he - … agrees to everything so that the Valkyrie continues to fly, but does not agree to pay for the flights -.
Indeed, the total cost of the XB-70A flight test program cost the US budget $ 1.5 billion. Only one bomber flight cost $ 11 million (according to other sources, only 1 hour of flight cost $ 5.9 million). Therefore, the "Valkyrie" is considered not only the fastest of the large aircraft (after all, it flew twice as fast as a bullet (1 *)), but also the most expensive of them.
