In the1970s, McDonnell Douglas and Lockheed introduced DC-8-60 and L-1kloc-0/1Samsung respectively. Boeing, on the other hand, mainly makes special modifications to Boeing 747, which is at a disadvantage for competing products. Several western European countries have joined forces to set up Airbus, and the launch of the first A300 is also threatening. In particular, the four engines of Boeing 747 were at a disadvantage in the oil crisis. Boeing began to launch a brand-new 7X7 plan, and its first product was Boeing 767.
Boeing found that some routes have fewer cabins than 767, which also laid the groundwork for the birth of 757. At the same time, the three-engine Boeing 727 gradually failed to keep up with the market rhythm and entered the end of the market life. So Boeing developed 757 on the basis of learning from 767. In design, Boeing 757 retains the fuselage diameter of 707/727 and the arrangement of 3+3. Its cockpit design, control mode and maintenance procedures are similar to those of the 767. After the launch of Boeing 757, it received a positive response from the market. 1982 In February, Boeing 757-200 received the order for 105.
Boeing 757 is the longest flight of narrow-body passenger aircraft, which can carry 200 people and has a range of 7200 kilometers. The most commendable thing is the climbing performance of Boeing 757, which can climb to 65438+100000 meters in the shortest time compared with other passenger planes, and is called "rocket plane" by American pilots. However, Boeing 757 needs to carry 75% passengers to make ends meet, which also causes the market positioning to fluctuate. In 1990s, orders for 65438+757 began to drop sharply, which forced Boeing to stop the whole production line in 2005.
June, 5438+October, 2003 10, with Continental Airlines (now merged into United Airlines) announcing that its remaining 757-300 orders were converted to 737-800, Boeing officially announced that it would end the 757 project one year later. Yes, this script is very familiar, much like A380. On June 24th, 2004, 10, with the last 757 rolled off the assembly line, the production line that lasted for 2 1 year was declared closed, and the output of 757 stayed at 1050 forever.
9 1 1 Needless to say, it is the eternal pain of the aviation industry, especially the aviation industry in North America. At the time node of 200 1-2003, the unstable situation in the Middle East led to the increase in oil prices, accompanied by the decrease in passenger flow, which directly led to the tightening and dieting of airlines.
What's more, because the main application scenario of 757 at that time was the east-west coast route of the United States, there are still a few small passenger transoceanic point-to-point routes that 757 is proud of now. Compared with 757, the new generation of medium-sized aircraft 737NG and A32 1 have the ability to operate the east-west coast routes at that time, and the route arrangement is more flexible, and they have more advantages in fuel consumption and stand-alone cost than 757, which is more than ten years behind. In this way, 9 1 1 and oil price are the last two straws to crush 757. In addition, the 757 project has achieved the goal of profitability financially, and Boeing's choice is of course understandable.
We also know the story after that. With the recovery of the global economy and the easing of oil prices, the aviation industry is booming. The 757, whose range and passenger capacity are just between wide-body and traditional narrow-body medium-sized aircraft, has become a unique existence. It can be used for domestic flight and can be installed. Compared with wide-body aircraft, it has lower cost and is not afraid of losing money.
757 was developed as a sister machine of 767. The cockpit they exchanged was also talked about by the airlines in the fleet of 757 and 767 of the three major airlines in North America. With little overtraining, pilots can switch between these two kinds of passenger planes with completely different appearances and uses at will. But the difference between 737 and 757 is big. The control interfaces of most subsystems, such as hydraulic, electric, supercharging and air bleed, are located on the top plate. We can roughly understand the difference between the two planes through the top panel of each model.
From the original 737-200 prototype to the latest 737 Max, the positions and operations of fuel, electrical, flight control, hydraulic, air conditioning components, cabin pressurization, engine ignition switch and other subsystems are basically the same, which greatly facilitates pilots to switch between different generations of 737s.
And the roof of 757, although it looks a lot modern, is 108 thousand miles worse than that of 737 in previous dynasties. From the difference of switch form to the change of subsystem panel position, the gap between the two modes is everywhere.
The difference between the 757 and the 737 born out of the wide body 767 goes far beyond the cockpit design:
The control surface of 757 is driven by pure hydraulic pressure, while 737 retains cable drive.
The 757 adopts lever stabilizer for balance, while the 737 still retains the handwheel of mechanical transmission.
The 757 has three sets of inertial navigation, air data computer and autopilot, while the 737 has only two sets.
The 757 has a spare ram turbo RAT to ensure the hydraulic and power supply in case of emergency, while the 737 only relies on battery and cable transmission to ensure the most basic control of the aircraft.
In-depth knowledge and familiarity of pilots and service personnel is the first line of defense to ensure flight safety. For this reason, the cost of pilot model training and the interoperability between models in the fleet are factors that every airline has to ignore.
The design of interoperability between 737 models allows pilots to switch freely between various models in the fleet, which also greatly facilitates the deployment of airline crew. Especially in the current passenger aircraft replacement cycle, when the new aircraft enters service, the old aircraft is still in its prime. Even after the service of the 737 Max, Southwest Airlines retired the last 737 Classic. Pilots often fly between NG and Max, which highlights the importance of aircraft interoperability. The highly similar design also means that a lot of aviation materials and ground crew training can be used between different generations of aircraft. For Boeing, various modifications of the 737 can be mixed, which increases the flexibility and reduces the initial investment. It can be said that there is no harm in it.
In contrast, the introduction of 757 as the replacement model of 737 means that a large number of pilots need to undergo a lot of system training and testing to control the new model, and at the same time, these pilots have temporarily lost the ability to drive the old model, which is definitely a great reduction for airlines. Coupled with the loss of advantages brought by other aircraft mentioned above, it can be said that the attraction of a passenger plane is greatly unfavorable.
Since it is a shortened version of the 757, the wings of the 757 will naturally remain under normal circumstances. However, this kind of wing can carry 757-300 124 tons of takeoff weight. The wing area of 185 square meters is nearly half that of 737 series 125 square meters, while the wingspan of 38 meters is two meters longer than that of 737 series. Compared with this, the maximum takeoff weight of the largest model 737-900ER of NG generation is only 85.2 tons. Don't underestimate this extra two-meter wingspan: the maximum allowable wingspan of ICAO Class C aircraft is 36 meters. The 737 is within this range, but the 757 can only be attributed to a D-class aircraft with a wingspan of 36-52 meters. This means that the 757 can't use many airports designed with Class C aircraft as the standard, and can't stop at some parking spaces set up by airlines for A320 and 737.
The large wing area of the 757 is too redundant for the heavyweight of the 737, which has many disadvantages compared with the wing of the 737 series itself:
Larger wing area will bring higher structural weight and impermeability.
Lower aspect ratio leads to more induced drag.
Shortening the fuselage means that the horizontal tail needs to generate higher negative lift to offset the effect of shorter arms. This means that the deflection angle of the horizontal tail needs to be increased, and the wing also needs to generate higher lift to offset the increased negative lift. Both will increase resistance.
As airlines become more and more picky about fuel consumption, A3/KOOC-0/9neo and 737 Max 7, two shortened models, cannot compete with Bombardier C series with small wings (now Airbus A220) in the/KOOC-0/00-/KOOC-0/50 seat market even if they rely on interoperability with other models. This can only be blamed on the wing being too heavy for the load.
To sum up, at the beginning of the 737 Max project, there were many disadvantages in replacing the 737 with a shortened model based on the 757, which will be taken into account by Boeing.
The market positioning failed, and now Boeing 737MAX and Boeing 787 can replace it.
Boeing 757 is a medium and long-range narrow-body passenger aircraft launched by Boeing series in 1970s. At that time, the West had just experienced the skyrocketing oil price, so the original intention of the Boeing 757 design was to take fuel saving as the main goal, and two engines (RB2 1 1 was the engine of Boeing 747 at that time) were arranged, plus a narrow single channel, and the maximum range reached more than 7,200 kilometers.
At the beginning, Boeing planned that Boeing 737 was responsible for 100 market and Boeing 757 was responsible for 200 markets. The work of Airbus, the old rival, is the A320 with a seat of 150. You can enter the water without violating the back river.
But we don't want Airbus to launch A3 18 with A3 120 seats to compete with Boeing 737, lengthen the fuselage of A320 by 40%, increase the passenger capacity by 40%, and launch A32 1 to compete with Boeing 757.
Airbus A320 family, just hit the junction of 757 and 737, and then spread.
The chubby Airbus A32 1 is not as powerful as Boeing 757, with a range of 5,600 kilometers, but its operating cost is less than that of Boeing 757 1/4 or more, and the market share of 200 seats within 5,000 kilometers is robbed.
So Boeing will either launch a scaled-down version of Boeing 757, but the basic model of Boeing 757 is there, and the tail turbulence is the same as that of large and medium-sized passenger planes, which is not conducive to airport arrangements and must be replaced to reduce operating costs. Another option is to lengthen the Boeing 737, which is Boeing's choice. After three cosmetic operations, the 737 finally reached the highest level of 190 seats, which can cover the market of Boeing 757 short-haul routes.
From the seat distribution of Boeing 757 and Boeing 787, the wide-body double-channel cabin comfort is far more popular than the narrow-body single channel.
In terms of extending the seat of Boeing 757, the customer's demand has changed. The cabin of narrow-body single-aisle passenger aircraft is too narrow and cramped, and people with more than 200 seats are beginning to like wide-body passenger aircraft. So Boeing launched the 787 series, covering 240 to 330 markets with different fuselage lengths, and the range was further increased to 1. 1 10,000-1.3,000 kilometers, which can fly intercontinental routes, such as the most profitable Atlantic route.
This problem is actually the result of the increasing competition caused by the constant change and growth of the global civil aviation transportation market.
In the mid-1970s, Boeing had two four-engine aircraft products, Boeing 707 and Boeing 747, in the field of medium and long-distance trunk passenger aircraft. The former has a commercial passenger capacity of 150 seats and a voyage of 6700km. The latter has a commercial passenger capacity of 360 seats and a voyage of 1000 km. In the field of short-haul trunk passenger aircraft, there are Boeing 737 and Boeing 727. The former adopts double-engine configuration, with commercial load 100- 130 seats and a voyage of 4000km. The latter is equipped with three engines, with a commercial load of 130- 180 seats and a range of 4500km (compared with commercial positioning, the 727 is a bit nondescript).
Among these four kinds of products, Boeing 747 is a unique product, regardless of McDonnell Douglas and Lockheed in the United States at that time, Airbus in Europe, Dassault in France, British Aerospace, Ilyushin in the Soviet Union, tupolev, Ya kolev and so on. At present, similar competitive products have not been launched; In this long-distance air transportation field between 6000- 10000km, more competitors have begun to appear.
More importantly, in the 1970s, a serious oil crisis broke out around the world, and oil prices rose many times, which greatly increased the operating pressure of airlines and put forward higher requirements for the fuel economy of civil aviation aircraft.
To this end, Boeing plans to eliminate Boeing 707 and Boeing 727 and 737, and thus launch two new passenger aircraft products, namely Boeing 757 and 767. According to Boeing's strategic concept, both 757 and 767 adopt dual-engine power mode, and the fuselage structure adopts "quasi-wide-body structure" (slightly wider than narrow-body passenger aircraft, but not as wide as today's wide-body passenger aircraft); In terms of commercial positioning, 767 focuses on high-density long-haul routes, with a commercial capacity of 250-350 seats and a voyage of 7500- 1 1000km, and 757 focuses on low-density long-haul routes, taking into account short-haul routes, with a commercial capacity of 200-240 seats and a voyage of 6400-7200km.
In other words, Boeing's vision is to connect the 757 and 767 twin-engine passenger aircraft products up and down, and strive to seize the long-distance transportation market in the global civil aviation passenger transport.
However, Boeing has neglected a trend in the development of civil aviation passenger planes, and the market segments of civil aviation passenger transport have gradually changed from the previous three to two:
1. In the medium and long-distance trunk line market, the performance of passenger planes should be maintained between 250 and 350 seats, and the range should be between 12000- 14000km, so as to meet the demand of global intercontinental long-distance routes;
2. In the short-haul trunk line market, the performance of passenger planes should be kept between 120-220, and the range should be between 5,000 and 6,000 km, which can meet the needs of domestic routes and short-haul international routes all over the world;
Under this background, the newly established Airbus Company introduced the A300 wide-body medium and long-range passenger plane to the civil aviation industry at 1974, with a commercial capacity of 260-300 seats and a voyage of 7300km, which is worthy of flying across the North Atlantic, from the United States to Europe. Because of the dual-engine power configuration, the fuel economy was better than that of four-engine aircraft and three-engine aircraft, which made it very popular in the civil aviation market at that time and became a best-selling model.
In the case of A300' s big sales, Airbus also launched a smaller version of A3 10, still adopting the wide-body fuselage+double-engine mode, with a commercial passenger capacity of 220 seats and a range of 7000km.
Airbus successfully defeated Boeing 757 and 767 with A300 and A3 10 wide-body twin-engine medium-range passenger aircraft, resulting in extremely low production of these two models in Boeing history.
However, Airbus became confused and obsessed with the four-engine large passenger aircraft products, and successively launched two four-engine passenger aircraft products, A340 and A380, with poor market performance.
In order to regain a game, Boeing started its own large-scale long-range wide-body passenger aircraft plan in the 1980s, namely Boeing 777 and Boeing 787. With the commercial carrying capacity of 200-400 seats and the voyage of 12000- 14000km, these two passenger aircraft products have helped Boeing regain the lost medium and long-range passenger aircraft market and completely turn over A340 and A380.
And the Boeing 737 has been improved again and again, and the third generation Boeing 737 and the fourth generation Boeing 737 have been launched successively. The commercial passenger capacity has covered 100-220 seats, and the voyage is 6000-8000km, which basically covers the business scope of the original 757.
Therefore, the disappearance of any kind of passenger aircraft products is because its own performance does not meet the current market demand. Aircraft manufacturers can only continue to make profits by continuously developing passenger planes that meet the actual needs of the market.
Presumably speaking of this, I basically answered the question clearly.
Friends who are interested in aviation may wish to pay attention to Eagle Airlines.
Improving the 737 depends largely on cost savings and pressure from competitor Airbus. Time does not allow Boeing to redesign and manufacture new aircraft. In order to be competitive, we have to upgrade again and again, and everything has its limits. The plane crash was also because the final transformation was for the sake of change, and there was no scruple about safety hazards.
757 and 737 are in two different markets, and 837 is in the mass market. At present, the market demand is the largest, while the original 757 is mainly for long-distance flights on plateau and narrow body, and Boeing with long-distance flights on narrow body also has 737-900er and 737max 10. Therefore, 737 is Boeing's star bestseller, and it will definitely be upgraded continuously.
Before you say this, please think about what the old airport used to be like, and finish. .
A Boeing 757 cargo plane crashed in Costa Rica. Why is the accident rate of Boeing aircraft so high? A Boeing 757 cargo plane crashed in Costa Rica. The main reasons for the high accident rate of Boeing aircraft include: firstly, the widespread use of Boeing aircraft in the world; secondly, there are some problems in Boeing aircraft itself; thirdly, Boeing aircraft mainly produces large aircraft, so there are many buyers; finally, Boeing pilots are careless in flying. It needs to be elaborated and analyzed from the following three aspects.
First of all, Boeing aircraft are widely used in the world.
First, a Boeing 757 cargo plane crashed in Costa Rica. The reasons for the high accident rate of Boeing aircraft mainly include that Boeing aircraft is widely used in the world. For many areas, the aircraft brands used are all Boeing aircraft brands, so the accident rate of Boeing aircraft in all aircraft is very high under such a large background. After all, other aircraft brands are not so widely distributed around the world.
Second, there are some problems with the Boeing aircraft itself.
Secondly, a Boeing 757 cargo plane crashed in Costa Rica. The reasons for the high accident rate of Boeing aircraft mainly include some problems of Boeing aircraft itself. Many Boeing aircraft have hidden dangers in the production process. Because there are some technical problems to be solved, the accident rate of Boeing aircraft is so high in the world.
Third, Boeing aircraft mainly produces large aircraft, so there are many buyers.
In addition, a Boeing 757 cargo plane crashed in Costa Rica. The reasons for the high accident rate of Boeing aircraft include that Boeing aircraft mainly produces large aircraft. There are many buyers all over the world, and many buyers like Boeing planes. After all, Boeing aircraft can save a lot of flight costs for airlines, so the accident rate of Boeing aircraft is very high all over the world.
Fourth, Boeing pilots are too careless in their flight operations.
Finally, a Boeing 757 cargo plane crashed in Costa Rica. The reasons for the high accident rate of Boeing aircraft include that the pilots of Boeing aircraft are too careless in flight operation, and it is easy to cause accidents if the aircraft is not operated according to the prescribed procedures.
A Boeing 757 cargo plane crashed in Costa Rica, and other objective reasons for the high accident rate of Boeing aircraft:
The Boeing plane that had an accident was generally in bad weather under flight conditions, or the mechanical part of the Boeing plane was not inspected.
B757 aircraft with the maximum allowable takeoff gross weight greater than 7000 kg and less than 136000 kg, the wake type identifier is m ..., where B757 aircraft (including B757-200, B757-300, etc.). ) belongs to medium-sized aircraft;
RECAT-CN classification and interval standard
As mentioned in the previous article, the classification standard of aircraft wake has begun to change. In ICAO4444 document, wake levels are divided into four categories according to the certified maximum takeoff weight:
1, super heavy/super (j): the model approved by ICAO DOC 8643;
2. Weight/weight (h): mtow ≥ 136t, except for the overload;
3. Medium/medium (m): 7t ≤ mtow <136t;
4. Light/light (l): mtow < 7t.
Last year, the trial operation was carried out in Guangzhou and Shenzhen airports in China, but few domestic super-class aircraft were operated. RECAT-CN classifies aircraft wake levels into five categories according to the traffic flow characteristics of busy airports in China. Among them, the existing heavy aircraft (H) are re-classified into two categories: heavy aircraft (B) and general heavy aircraft (C) according to the maximum takeoff weight and wingspan size of the aircraft, and others are consistent with the current ICAO standards. The simulation data show that the expected effect of RECAT-CN is basically the same as that of RECAT-I in the United States and RECAT-EU in Europe.
Open the application to view high-definition images.
Compared with the wake classification and separation standard of ICAO Doc 4444, RECAT-CN subdivides heavy aircraft (see 3. For the classification method of RECAT-CN),
1 The standard of wake interval depends on the model. In RECAT-CN, aircraft types are divided into five categories according to the maximum allowable takeoff weight and span.
② Ultra-heavy aircraft: the aircraft with the maximum allowable takeoff gross weight equal to or greater than 136000kg, the wingspan equal to or greater than 75m and the wake type identification of J;
3. Heavy aircraft: aircraft with the maximum allowable takeoff gross weight equal to or greater than136,000 kg, wingspan equal to or greater than 54m and less than 75m, and wake type identification B;
4. General heavy aircraft: aircraft with the maximum allowable takeoff gross weight equal to or greater than 136000kg, wingspan less than 54m and wake type identification C;
Medium-sized aircraft: the aircraft with the maximum allowable takeoff gross weight of more than 7000kg and less than 136000kg and the wake type identification of M, among which, B757 aircraft (including B757-200, B757-300, etc.). ) belongs to medium-sized aircraft;
6. Light aircraft: the aircraft with the maximum allowable takeoff weight equal to or less than 7000kg and the wake type identification L.
Therefore, the wake interval can be reduced to a certain extent, and the operation efficiency of the airport and the approach (terminal) control area can be improved. For example, in ICAO Doc 4444, B767 and B747 are both heavy aircraft, and the minimum wake interval required for two aircraft to follow the approach is 7.4km；; In RECAT-CN, B767 belongs to Class C aircraft and B747 belongs to Class B aircraft, and the wake interval does not need to be considered when approaching B747 and B767.
1 When the current engine is an ultra-heavy aircraft (J) and the rear engine is a heavy aircraft (B), it shall not be less than 9.3km；;
2. When the front aircraft is a super heavy aircraft (J) and the rear aircraft is a general heavy aircraft (C), it shall not be less than11.1km;
3. When the current aircraft is a super-heavy aircraft (J) and the rear aircraft is a medium-sized aircraft (M), it shall not be less than13.0km; ;
4 When the front aircraft is a super heavy aircraft (J) and the rear aircraft is a light aircraft (L), it shall not be less than14.8km; ;
5 When the current engine is a heavy aircraft (B) and the rear engine is a heavy aircraft (B), it shall not be less than 5.6km；;
6 When the current engine is a heavy aircraft (B) and the rear engine is a general heavy aircraft (C), it shall not be less than 7.4km；;
7 When the front aircraft is a heavy aircraft (B) and the rear aircraft is a medium-sized aircraft (M), it is not less than 9.3km；;
8 When the current engine is a heavy aircraft (B) and the rear engine is a light aircraft (L), it shall not be less than13.0km; ;
9 When the front aircraft is a general heavy aircraft (C) and the rear aircraft is a medium-sized aircraft (M), it is not less than 6.5km；;
10 When the current engine is a general heavy aircraft (C) and the rear engine is a light aircraft (L), it shall not be less than11.1km;
1 1 When the current aircraft is a medium-sized aircraft (M) and the rear aircraft is a light aircraft (L), it should be no less than 9.3km.
What is a Boeing 757 medium-range airliner? Boeing 757 is a medium-range passenger aircraft developed by Boeing Aircraft Company of the United States. /kloc-0 started development in March, 1979, and 1 Boeing 757 made its first flight in February, 1982. In February of the same year, KLOC-0/2 obtained the airworthiness certificate of the United States Federal Aviation Administration and began to deliver. In order to reduce the development and production costs, reduce the aircraft price, shorten the development cycle and put it into use as soon as possible, Boeing Company developed Boeing 757 on the basis of the most successful Boeing 727 in the past, using a lengthened Boeing 727 fuselage and new wings and engines. The wing sweepback angle of 757 is less than 727, and a low-drag supercritical airfoil is adopted. Install two Gao Han turbofan engines to reduce fuel consumption and noise, and the engines adopt wing crane layout; Structurally, Boeing 757 adopts three kinds of high-quality aluminum alloys (7 150-T65 1, 2324-T395 1) and high-quality titanium alloys and composites. High-quality aluminum alloy can reduce the structural weight by 227kg；; Composite materials can reduce the structural weight by 360 kg. The cockpit layout, auxiliary power unit, air conditioning system, engine compartment, wing technology and structural materials of Boeing 757 are basically the same as those of Boeing 767 medium and long-range passenger aircraft developed in the same period. The main design goal of Boeing 757 is to reduce the operating cost of aircraft by reducing fuel consumption and weight. However, since the 1980s, the oil crisis that broke out in the 1970s began to ease, oil prices gradually decreased, and many old models with higher fuel consumption but lower prices were still in use. Therefore, the sales of Boeing 757 were not large in the early period of the rib era, and it was not until the late 1980s that the sales gradually increased. By March 1990, 632 Boeing 757*** aircraft had been ordered. Its development cost is 800 million dollars (1978 dollars). The main models are: -200, basic type; -200PF, freight type, 1987 delivered in September; -200M passenger and cargo are mixed, and the main cargo hold can carry 123- 148 passengers after carrying three standard containers. The following contents apply to type -200.
Power plant: two Rolls-Royce RB2 1 1-535 turbofan engines with thrust of 2×165.9KN; Or two CF6-32 turbofan engines of General Electric Company with thrust of 2×161.6kn..
Cockpit, the cockpit has driver's seat and passenger seat, and the cabin can carry passengers 178-239.
The main airborne equipment includes Collins FCS-700 autopilot flight director, EFIS-700 electronic flight instrument, engine indication and crew alarm system, RMI-743 radio ranging magnetic indicator, Honeywell inertial coordinate system, flight control computer, digital air data computer and color weather radar.
The size data show that the wingspan is 38.05m, the captain is 47.32m, the aircraft height 13.56m, the wing area 185.25m2, the chord length sweepback angle 1/4, the aspect ratio is 7.77, and the cabin length × width× height is 36.09m× 3.57.
For the weight data, the empty weight is 57440kg, the maximum load is 25200kg, the maximum oil load is 42,600 liters, the maximum takeoff weight is 1 13400kg, and the maximum landing weight is 898 10kg.
Performance data The cruising speed is 9 17km/h, the economical cruising speed is 850 km/h, the take-off field length is 1750m, the landing field length is 1400m, the maximum fuel range is 6320km, and the maximum load range is 3560km.