Digital aircraft
Write this article pushed me habratopik " Dedication Tu-154 ."
Argued that the old aircraft safer modern, because they contain fewer electronics. Using the example of the A-320, I will try to explain how the reliability and safety of modern “computer” aircraft is ensured.
What is “fly-by-wire”?
At the dawn of aviation, the aircraft was controlled mechanically - with the help of cables and rods connecting the controls (steering wheel and pedals) with ailerons and rudders and height.
As the size and speed of the aircraft grew, so did the physical effort spent by the pilot on the control. The booster mechanisms (boosters) came to help the person. Although they facilitated the work of the pilot, they were still controlled by cables and rods. The reliability of such control systems was ensured by the duplication of the ropes, cables and actuators.
Both control schemes, mechanical and booster, are still used today, both in light aircraft and on large aircraft, incl. on the SR-71 and on the An-225 "Mriya".
In the mid-50s, new ones were developed for military aircraft. statically unstable aerodynamic configurations, giving a significant increase in maneuverability, but not allowing to fly without constant correction. It was necessary to parry the emerging disturbances faster than they developed. Due to the low speed of the reaction, the person was not able to solve this problem and an electro-remote control system (EDSU or Fly-by-wire, FBW) was developed to control the statically unstable aircraft. Based on data from sensors and controls, the EDSU generated signals for servo drives of aerodynamic surfaces (ailerons and rudders). That is, the man flew EDSU, and EDSU flew the plane.
')
The first EDSU were analog, later digital ones appeared. Nowadays EDSUs are used on almost all combat aircraft and are being actively implemented in civil aviation. But in civil aviation they serve not for the purpose of super-maneuverability :)
Consider the implementation of the concept of Fly-by-Wire on the example of the A-320.
If you glance into the A320 cab, then instead of the steering wheels you will find joysticks (in Airbus-sidedics terminology) on the side consoles. Each side stick is equipped with strain gauges, the data from which are processed by computers and the current situation is transmitted to the actuators.
The A320 has 7 flight control computers - 2 ELAC computers (Elevator Aileron Computer), 3 SEC computers (Spoilers Elevator Computer) and 2 FAC computers (Flight Augmentation Computer).
anticipating questions about hardware - ELAC computers run on a Motorola 68000 processor, SEC - INTEL 80186. :)
Each of these computers has 2 modules - the Control Unit and the Monitoring Unit. In fact, these are 2 independent devices that receive and process the same data. But if the Monitoring Unit detects a mismatch of the results of its own calculations with the results of the calculations of the Control Unit, then this computer is considered faulty and its “partner” takes over its functions. To eliminate possible errors, the Control Unit and Monitoring Unit software was developed by different groups of programmers in different languages. *
Even in the case of complete failure of the pair, other couples will be able to perform its functions. For example, the ELAC2 computer is responsible for the stabilizer trimmer. If it fails, ELAC2 can take over ELAC1, then SEC1, then SEC2. That is, in addition to operating in parallel the same blocks, there is a duplication of functions between different blocks. This ensures multiple redundancy of the flight control system.
Each of the computers has a self-diagnostic function according to the following parameters - processor control (watchdog and checksums), power control, input and output control, feedback control. Diagnostics of inputs is provided by comparing the same signals received from different devices.
There are several levels - modes of operation of flight control computers, which in the terminology of Airbus are called “laws”.
The first mode is NORMAL LAW. This mode is the main and most used. The plane will obey the pilot, but will not allow the critical values ​​of the angle of attack, overload, heel and pitch to be exceeded, and will also control the speed, not allowing the maximum and minimum speed limits for the current flight mode to be passed. This mode keeps working in case of failure of any of 7 computers.
If several computers fail, the second mode is activated - ALTERNATE LAW. In this mode, protection against critical overloads is maintained, as well as against loss or overspeed.
With multiple failures of computers activated third mode - DIRECT LAW. In this mode, the signals from the side stick are not processed and are sent directly to the servos.
In the event of a total failure of all 7 flight control computers, the A-320 has a hydromechanical backup system for the course and pitch.
In conclusion. In the entire history of the A-320, the accident due to the fault of technology was only once - in 1988, after which all the aircraft were modified.
To date, about 5 thousand aircraft of this family have been produced.
_____________________________________________________
*
Engineers at Boeing are even more severe.
In each of the three computers of the Fly-by-Wire system of the Boeing-777 aircraft, in order to eliminate errors, three processors of different manufacturers are used - Intel 80486, Motorola 68040 and AMD 29050. All of them perform the same tasks. Software is written on ADA. However, each processor requires its own strapping and its own compiler, which also increases the reliability of the system as a whole. If there are differences in the results, the computer shuts down. Boeing calls this scheme "triple-triple redundant architecture".
Argued that the old aircraft safer modern, because they contain fewer electronics. Using the example of the A-320, I will try to explain how the reliability and safety of modern “computer” aircraft is ensured.
What is “fly-by-wire”?
At the dawn of aviation, the aircraft was controlled mechanically - with the help of cables and rods connecting the controls (steering wheel and pedals) with ailerons and rudders and height.
As the size and speed of the aircraft grew, so did the physical effort spent by the pilot on the control. The booster mechanisms (boosters) came to help the person. Although they facilitated the work of the pilot, they were still controlled by cables and rods. The reliability of such control systems was ensured by the duplication of the ropes, cables and actuators.
Both control schemes, mechanical and booster, are still used today, both in light aircraft and on large aircraft, incl. on the SR-71 and on the An-225 "Mriya".
In the mid-50s, new ones were developed for military aircraft. statically unstable aerodynamic configurations, giving a significant increase in maneuverability, but not allowing to fly without constant correction. It was necessary to parry the emerging disturbances faster than they developed. Due to the low speed of the reaction, the person was not able to solve this problem and an electro-remote control system (EDSU or Fly-by-wire, FBW) was developed to control the statically unstable aircraft. Based on data from sensors and controls, the EDSU generated signals for servo drives of aerodynamic surfaces (ailerons and rudders). That is, the man flew EDSU, and EDSU flew the plane.
')
The first EDSU were analog, later digital ones appeared. Nowadays EDSUs are used on almost all combat aircraft and are being actively implemented in civil aviation. But in civil aviation they serve not for the purpose of super-maneuverability :)
Consider the implementation of the concept of Fly-by-Wire on the example of the A-320.
If you glance into the A320 cab, then instead of the steering wheels you will find joysticks (in Airbus-sidedics terminology) on the side consoles. Each side stick is equipped with strain gauges, the data from which are processed by computers and the current situation is transmitted to the actuators.
The A320 has 7 flight control computers - 2 ELAC computers (Elevator Aileron Computer), 3 SEC computers (Spoilers Elevator Computer) and 2 FAC computers (Flight Augmentation Computer).
anticipating questions about hardware - ELAC computers run on a Motorola 68000 processor, SEC - INTEL 80186. :)
Each of these computers has 2 modules - the Control Unit and the Monitoring Unit. In fact, these are 2 independent devices that receive and process the same data. But if the Monitoring Unit detects a mismatch of the results of its own calculations with the results of the calculations of the Control Unit, then this computer is considered faulty and its “partner” takes over its functions. To eliminate possible errors, the Control Unit and Monitoring Unit software was developed by different groups of programmers in different languages. *
Even in the case of complete failure of the pair, other couples will be able to perform its functions. For example, the ELAC2 computer is responsible for the stabilizer trimmer. If it fails, ELAC2 can take over ELAC1, then SEC1, then SEC2. That is, in addition to operating in parallel the same blocks, there is a duplication of functions between different blocks. This ensures multiple redundancy of the flight control system.
Each of the computers has a self-diagnostic function according to the following parameters - processor control (watchdog and checksums), power control, input and output control, feedback control. Diagnostics of inputs is provided by comparing the same signals received from different devices.
There are several levels - modes of operation of flight control computers, which in the terminology of Airbus are called “laws”.
The first mode is NORMAL LAW. This mode is the main and most used. The plane will obey the pilot, but will not allow the critical values ​​of the angle of attack, overload, heel and pitch to be exceeded, and will also control the speed, not allowing the maximum and minimum speed limits for the current flight mode to be passed. This mode keeps working in case of failure of any of 7 computers.
If several computers fail, the second mode is activated - ALTERNATE LAW. In this mode, protection against critical overloads is maintained, as well as against loss or overspeed.
With multiple failures of computers activated third mode - DIRECT LAW. In this mode, the signals from the side stick are not processed and are sent directly to the servos.
In the event of a total failure of all 7 flight control computers, the A-320 has a hydromechanical backup system for the course and pitch.
In conclusion. In the entire history of the A-320, the accident due to the fault of technology was only once - in 1988, after which all the aircraft were modified.
To date, about 5 thousand aircraft of this family have been produced.
_____________________________________________________
*
Engineers at Boeing are even more severe.
In each of the three computers of the Fly-by-Wire system of the Boeing-777 aircraft, in order to eliminate errors, three processors of different manufacturers are used - Intel 80486, Motorola 68040 and AMD 29050. All of them perform the same tasks. Software is written on ADA. However, each processor requires its own strapping and its own compiler, which also increases the reliability of the system as a whole. If there are differences in the results, the computer shuts down. Boeing calls this scheme "triple-triple redundant architecture".
Source: https://habr.com/ru/post/83534/
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