Boeing 2707

The Boeing 2707 is a supersonic airliner project developed by Boeing in the 1960s. Being the most advanced of all the supersonic airliners created at that time (Concorde, Tu-144), the Boeing 2707 was too complicated to implement and was not created. The project was closed. Airplanes never flew.

History

The history of post-war civil aviation around the world, especially the 1950-1960s, was full of events. In the first years after the war, it became clear that piston planes had reached their limits and there was practically nowhere to develop them. But, at this time, the rise of new technology began, which was destined to conquer the sky. Jet military aircraft appeared in the fleets of airpower and very quickly proved their almost absolute superiority over old machines. Following the military jet aircraft, the time has come for civil. In 1949 he made the first flight of De Havilland Comet. The first-ever commercial jet airliner was a real revolution. Despite many problems and accidents, he proved that the future lies with jet aircraft and, of course, its most important advantage was speed: at cruising speeds of up to 840 km / h it was a third faster than piston counterparts (Lockheed Constellation cruising speed is about 550 km / h).

Over the next few years, their jet airliners appeared in other countries: Tu-104, Boeing 707, DC-8, Sud Caravelle, and so on. New liners replaced the old ones, becoming more reliable, more comfortable, and faster. Speed ​​remained the main trend: aircraft manufacturers tried to maximize these characteristics and, if the first airliners flew at speeds of about 800 km / h, then the next generation went for 900 km / h, and some planes even approached indicators under 1000 km / h (cruising speed Convair 880 reached 990 km / h). But that was the limit of what classic jet aircraft could afford. To overcome this milestone it was necessary to make a revolution.

On October 14, 1947, the experimental Bell X-1 aircraft, during a test flight at maximum speed, crossed the sound barrier for the first time in history. The supersonic era has begun. In the early 1950s, the first production supersonic F-100 Super Saber and MiG-19 fighters took to the sky, and soon, Dassaul Super Mystère, the first European in the class, joined them. Technology and the entire industry developed at a frantic pace and supersonic became an option not only for light fighters but also for bombers. In the late 1950s, the world saw the first representatives of this breed – the B-58 Hustler and Tu-22 bombers.

By this time, a new topic had become obvious: since technologies allow the creation of supersonic bombers, it means that perhaps they can already open the doors of supersonic commercial aircraft. Having speeds close to the speeds of military aircraft, these airliners will be able to deliver passengers significantly (potentially – multiple) faster than their subsonic versions. This was enough to interest all industry leaders.

Work begins

The first research work on the topic of supersonic passenger aircraft began in the early 1950s with various tests in wind tunnels and small prototypes. In 1958, a commission was formed at Boeing to deal directly with these issues.

Over several years, the commission worked on many different variations of designs and concepts within the framework of the program, which received the Model 733 code. Most versions of aircraft designs had a deltoid wing or its variations with an influx (animate wing). Such a wing was considered promising and was adopted as the main one when developing both the European Concorde and the Soviet Tu-144. However, in 1959, engineers drew attention to another promising version of the wing with variable-sweep.

The main problem of the wing of a supersonic aircraft was that its small span, large sweep, and the small area made it quite suitable for high flight speeds, but at low speeds, it significantly worsened the flight characteristics of aircraft. The concept of the revitalizing deltoid wing, developed by BAC and Sud Aviation, in principle, solved this problem, although an aircraft with such a wing still had a fairly high minimum speed with a relatively small size and was forced to take off and land while maintaining a large angle of attack.

American engineers drew attention to another promising version of the wing variable-sweep (swing-wing). Such a wing had a very important advantage, having the ability to change the central shape, such a wing adapted to flight speed. At high speeds, it had a maximum sweep, allowing the aircraft to overcome the sound barrier, and at low speeds, its sweep approached the performance of conventional subsonic aircraft, giving the machine their advantages. This concept in the early 1960s had many supporters and was implemented, first of all, in the TFX program (the program for creating a universal bomber – the future General Dynamics F-111). After conducting research and competitions inside Boeing, they concluded that the wing of the variable-sweep is more promising than the deltoid.

In 1961, the administration of the recently elected President of the United States, John F. Kennedy, became concerned about the development of civil aviation. Its exponential growth was starting to cause problems and authorities were considering issues of solution. Within a few months, the FAA developed two large-scale programs that were supposed to optimize the industry: Project Beacon was to create new methods and systems for optimizing air traffic control, and Project Horizon was to work on the creation of new airliners. generations.

In the framework of the Horizon project, FAA management actively promoted the idea of ​​creating supersonic airliners, since it was believed that such aircraft, over time, would dominate commercial passenger traffic. However, this concept in the United States was confronted by opposition from proponents of the concept of increasing the dimensions of aircraft, rather than their speed. The plane was moving hard, and some representatives of the Presidential Administration, for example, Secretary of Defense Robert McNamara, did not hide his skepticism on this issue, insisting on the unavailability of the industry for such aircraft to continue basic research.

The debate continued for a long time. Supporters of supersonic airliners insisted that flying at multiple speeds would increase the number of flights, reducing the number of aircraft themselves. Opponents also drew attention to potential environmental risks, as well as to the prohibitively high fuel consumption of such aircraft – in case of rising fuel prices, supersonic aircraft will become uncompetitive.

Concord

In 1962, the European corporations – BAC and Sud Aviation formed a consortium and officially announced the program for creating the first supersonic airliner. The project enjoyed very great support from both London and Paris, and by that time the concept of the prospects for supersonic flights was becoming prevailing. Everyone believed that such aircraft would conquer the sky, and Europeans, having created such an aircraft first, would conquer the aircraft manufacturing market. This is extremely worried for Americans who are lagging. There was little news from Western Europe, so it soon became clear that its supersonic airliner was being created in the Soviet Union.

Just a few days after the announcement of the Concorde project, FAA management sent letters to President Kennedy, stating that if the United States does not overcome its supersonic shipping competition, then America will lose tens of thousands of jobs, billions of dollars and many important future competencies.

It was necessary to create their airliner, moreover, superior to analogs from overseas. Moreover, it was initially proposed to create an aircraft with a speed of up to 3 Machs – more than its counterparts, but having a flight range of about 4 thousand kilometers – the aircraft had to carry out domestic flights, and, due to lagging behind Europeans, it was assumed that transatlantic routes were inevitable take over Concord.

Despite the strong opposition and skepticism from many industry experts, Concorde and Tu-144, as well as the pressure of the public and the FAA, they became a powerful impetus for the creation of the aircraft. Also, outrage at the lag behind competitors grew even stronger when the main US airline, Pan American, announced a contract for the purchase of Concordes. Pan Am President Juan Trip, being a very influential person in the industry, was a low-key supporter of supersonic traffic and stated that Pan Am could not ignore this trend, even if the American aviation industry would not do such aircraft. In the end, the National Supersonic Transport project was announced by President Kennedy in 1963.

Program deployment

All major US aircraft manufacturers attended the competition for the creation of future aircraft. Lockheed and North Americans were engaged in gliders, and the power plants were developed by Curtis-Wright, General Electric, and Pratt & Whitney. Studies have shown potential demand for 500 airliners before 1990. The excitement was huge, even though until 1964 it was not entirely clear which aircraft would be created, many airlines had already signed memorandums of future purchases.

Lockheed and North American offered delta-wing aircraft, more reminiscent of Concords. But, having soon connected to the Boeing tender, he came up with his well-developed Model 733 project with a variable-sweep wing. By 1966, the project was renamed and received the official name Boeing Model 2707 (although in internal documents it remained model 733).

Unlike its counterparts, the Boeing 2707 had a tail, a rather large fixed part of the wing, elongated along almost the entire fuselage and a wing of the variable-sweep. Also, Boeing developed a very breakthrough supercritical wing design for an airplane – previously, such technologies were not used in large commercial aircraft. The design is quite similar to the later Rockwell B-1 Lancer strategic bomber, created 10 years later. The liner suggested the possibility of changing the length of the fuselage, which allows, in the future, to vary the capacity from 150 to 227 passengers.

Lockheed led its project CL-823, which in design seemed to be an enlarged version of Concord – a tailless with a deltoid wing and a narrow fuselage. Unlike the European airliner, the engines of Boeing and Lockheed aircraft should have been located in individual nacelles, and not in pairs. At the same time, the CL-823 was the largest of the projected options, its capacity was 218 seats.

The third NAC-60 project, led by North American, was created with a clear eye on the XB-70 Valkyrie heavy bomber that they were developing. The plane received a deltoid wing and front horizontal tail. Thanks to the plumage, the aircraft could maintain a minimum flight speed with a small angle of attack, and therefore there was no need for a lowered nose section. In this case, the nose of the aircraft was not made in the form of a sharp cone, which gave it a more classical shape. However, this decision limited the flight speed to a maximum of Mach 2.65.

However, the North American option was considered insufficiently promising. Also, it was assumed that the company would be occupied by a bomber. As a result, the NAC-60 did not reach the final of the race, as did the engine developer Curtiss-Wright for it. Model 2707 was increased to a capacity of 250 seats, and the engines were located under the significantly increased tail unit. The plumage was designed so that when the wing was switched to the maximum sweep mode, it “merged” with the tail, forming a single deltoid surface.

After the publication of the final package of detailed requirements, the liners were again adjusted and enlarged. As a result, in 1966, the 300-seater Boeing 2707 (Model 733-390) and Lockheed L-2000 participated in the tender. Both aircraft received full-size mock-ups for demonstration. As a result, in early 1967, the Boeing was declared the winner: the variable-sweep wing and advanced mechanization allowed their liner to maintain lower take-off and landing speeds, which made it more flexible in operation and quieter at these modes, which was important for settlements near airports.

The Boeing 2707 was an incredible breakthrough project. Even if he were not supersonic, he would still be considered one of the most advanced. Firstly, it was huge, the length of the aircraft reached 93 meters versus 64 for the Tu-144 and 61 for the Concord, and the maximum take-off weight exceeded the analog indicator by a third (306 tons versus 207 tons for the Tu-144 and 187 tons for Concord).

Oddly enough, despite the aerodynamic requirements of supersonic flights (even though the aircraft was supposed to fly at speeds of up to 2900 km / h and altitudes of about 22 km), it was the Boeing 2707 that was one of the first wide-body aircraft with a maximum fuselage width of almost 5 meters (width changed along the length), the interior of which was to receive a configuration of 7 seats in a row with two aisles (2 + 3 + 2). The salon was planned to be equipped with entertainment systems onboard with pull-out televisions between the rows, in the first class a television was put on each pair of seats adjacent to it.

Given that the angle of attack of the aircraft during takeoffs and landings was still quite large, Boeing engineers went the same way as their European and Soviet colleagues, making the nose of the liner lower. However, the nose cone was divided into two sections, and if the main part descended similarly to Concord and Tu-144, then the front edge deviated upwards, compensating for this and remaining constantly in a horizontal position. This made it possible to increase the nose lowering angle (without touching the surface of the earth) and improve the operation of the weather radar located there.

Also, the liner was supposed to get the most advanced avionics at the time of creation. The cockpit, designed for three crew members, was equipped with the first elements of a “glass” cockpit, which later became the base for all commercial airliners.

As the power plant was supposed to use the latest engines General Electric GE4. They were created specifically for the liner, although the design was based on the General Electric YJ93 military engines, which were equipped with prototypes of North American XB-70 bombers. With traction at 220 kN without afterburner and 281 kN at afterburner, the GE4 was the most powerful in the class.

It was assumed that the assembly of the prototypes will begin in 1967, and test flights can be carried out already from the 1970s. By 1974, the liners were to receive type certificates.

However, in the process of creating the design, the company encountered serious difficulties. The main problems stemmed from the main advantages: the long and wide fuselage under the influence of loads of supersonic flight was severely deformed, which reduced the life of the airframe. An even bigger problem was the variable-sweep wing. All its advantages were compensated by the complexity and large mass of the mechanism – even if it was made of titanium, the similar mechanism of each console weighed more than 2 tons and had rather significant dimensions. It turned out that with such a design, the aircraft will not be able to achieve the specified speed and range.

As a result, the engineers had to take a step back by developing a new glider with a deltoid wing and without a horizontal tail. The fuselage is also slightly reduced to 234 seats. The new aircraft received the Boeing index 2707-300. The creation of its functional layout and two prototypes began in 1969 with a delay of 2 years from the schedule.

Despite all the difficulties, Boeing was very optimistic about the project. Over the next years, it was assumed that the 2707 model would conquer the trunk transportation market with a range of about 7,000 kilometers, while the Boeing 747 was positioned as a liner for long-distance travel up to 10,000 kilometers. The company has formed a portfolio of orders for 122 airliners from 26 airlines.

However, despite all the efforts of the engineers, neither Boeing nor its overseas competitors were able to solve the fundamental problem of supersonic flights: the sonic boom.

In 1964, a series of tests were conducted in the city of Oklahoma to test the impact of a sonic boom from flying aircraft on populated areas. For some time, not far from the city, the XB-70 prototype flew over-the-air. Despite all the measures taken and the fact that the plane flew at a maximum altitude of about 23 km, the local authorities received thousands of complaints from the population, and the impact of a sonic boom broke the glass and destroyed structures. Also, high-altitude flights and exhaust emissions raised concerns about the risk of ozone depletion.

All these factors were permissible in the case of only periodic flights of special or military aircraft. But, in the case of the development of mass commercial aviation with the operation of hundreds of such aircraft, these risks became very serious.

By 1971, the project cost has grown so much that, despite the support of the Richard Nixon administration, the US Congress decided to stop funding, considering the project unpromising and too expensive.

This caused outrage among many enthusiasts, and aerospace industry experts and unions warned that the simultaneous phasing out of the Apollo lunar program and the supersonic airliner project would lead to a sharp increase in unemployment in the industry. But politically, the Americans ’race for supersonic sound was lost: the Tu-144 took off in 1968, the Concord in 1969, and the Boeing 2707 in 1971 did not even begin ground tests. It was stated that the creation of the first-generation aircraft no longer makes sense and the United States should return to basic research to create a second-generation aircraft in the 1980s and 1990s.

As a result, the project was closed. The two prototypes assembled at that time were never completed, and Boeing faced serious financial problems due to the collapse of the project and difficulties in launching the Boeing 747 – the company almost went bankrupt. As a result, they had to reduce staff by 60,000, dramatically increasing unemployment in Seattle and causing a massive outflow of the population. Since then, the Boeing 2707 has come to be often referred to as “the plane that Seattle nearly ate.”

Nevertheless, curtailing the project, despite all the dire consequences, was the right decision. As shown by the example of the exploitation of competitors, they did not achieve commercial success. Of the 150 Concord planned for delivery, only 14 aircraft were delivered, and that, with huge state support. Concordes continued to fly until the beginning of the XXI century but did not bring profit to operators and were, rather, an instrument for ensuring the image.

The Soviet Tu-144, even with even greater support from the Government of the USSR, turned out to be even less successful and was operated for only a few months.

Given the complexity and cost of the Boeing 2707, under such conditions, it would probably be the most expensive and the loudest failure of the American aircraft industry. And the consequences of this failure that almost happened for a long time discouraged aircraft manufacturers from wanting to deal with this topic. In fact, over the next several decades, work on supersonic airliners returned to the stage of basic research and was carried out mainly within the framework of NASA research programs.

However, despite all the progress, at the moment, the main problems of supersonic airliners, primarily, high fuel consumption and sonic boom, are still not resolved. The economic efficiency of such aircraft will continue to be significantly inferior to the efficiency of subsonic airliners. Even Boeing’s attempt to create a transonic Sonic Cruiser airliner was unsuccessful – the airliners were too expensive, and the advantages of high-speed flights were not obvious.

Boeing 2707 remained the project. Its prototypes were not assembled, and the models were handed over to the aviation museums.

Specifications

  • Type: Supersonic Main Passenger Aircraft
  • Powerplant: General Electric GE4 / J5P
  • Engine thrust: 4 X 220 kN (22.4 ts) without afterburner
  • 2 X 281 kN (28.65 ts) afterburner
  • Maximum number seats: 277 (economy class 1)
  • Practical ceiling: 22,000 m
  • Flight range: 7,871 km (full payload)
  • Maximum take-off weight: 306 t
  • Cruising speed: 2 900 km / h
  • Wingspan: 54.97 m (minimum sweep)
  • 32.23 m (maximum sweep)
  • Length: 93.27 m
  • Height: 14.10 m
Graduated from Embry-Riddle Aviation University with a master's degree in aviation science. He began his career as an aviation researcher in local periodicals. Has a pilot license. Now are the author and developer of the Plane Worlds.