Are you looking for question bank for the subject "AE 1401 AVIONICS" ? Here is the collection of 2 mark questions with answers. This will be very useful for the B.E Aeronautical Engineering students under Anna University as well as other university students. Read below to find the collection of question bank.
1. What is avionics?
Avionics means "aviation electronics". It comprises electronic systems for use on aircraft, artificial satellites and spacecraft, comprising communications, navigation and the display and management of multiple systems.
2. Explain the advantage of using avionics in civil aircraft.
• Reducing the crew workload by automating tasks.
• The reduction in weight can be translated to increased passengers or long range.
• To enable the flight crew to carry out the aircraft mission safely and efficiently.
• All weather operation and reduction in maintenance costs.
3. Explain the advantage of using avionics in military aircraft.
• A single seat fighter or strike aircraft is lighter and Costs less than an equivalent two seat version.
• Elimination of the second crew member (navigator/observer/crew member) results in reduction in training costs.
• Improved aircraft performance and control and handling and reduction in maintenance costs
• Secure communication.
4. Give the general advantage of Avionics over the conventional aircraft system.
• Increased safety
• Air traffic control requirements
• All weather operation
• Reduction in fuel consumption
• Improved aircraft performance and control and handling and reduction in maintenance costs
5. Define the usage of avionics in space systems.
• Fly-by-wire control systems were used for vehicle attitude and translation control.
• Sensors used around the aircraft for data acquisition.
• Redundancy system and autopilot.
• On board computers used in satellites for processing.
6. Explain “illities” of Avionics system.
• Capability
• Reliability
• Maintainability
• Certificability
• Survivability(military)
• Availability
• Susceptibility
• vulnerability
• Life cycle cost(military) or cost of ownership(civil)
• Technical risk
• Weight & power
7. Give various systems where the avionics used in aircrafts.
• Aircraft intercoms
• Wide Area Augmentation System
• Terrain awareness and warning system
• Ground proximity warning system
• Aircraft collision avoidance systems
• Display systems
• Traffic Collision Avoidance System
8. Explain the steps involved in design of avionics system.
• The three stages are:
i. Conceptual design - What will it do?
ii. Preliminary design - How much will it weigh?
iii. Detailed design - How many parts will it have?
9. What are digital computers?
A device that processes numerical information; more generally / any device that manipulates symbolic information according to specified computational
procedures is called as digital computers. The term digital computer or simply, computer embraces calculators, computer workstations, control computers (controllers) for applications such as domestic appliances and industrial processes.
10. What is a volatile memory and give examples?
Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply. It has been less popularly known as temporary memory. Most forms of modern random access memory (RAM) are volatile storage.
11. What is aliasing?
In computing, aliasing describes a situation in which a data location in memory can be accessed through different symbolic names in the program. Thus, modifying the data through one name implicitly modifies the values associated to all aliased names, which may not be expected by the programmer. As a result, aliasing makes it particularly difficult to understand, analyze and optimize programs. Aliasing analyses intend to make and compute useful information for understanding aliasing in programs.
12. Differentiate between volatile and non volatile memories.
Volatile memory: The data is lost on reboot, you will lost all of your data when your electricity go out.. This is the ram memory. Random-access-memory.
Non-volatile memory: The data is saved to a hard drive or flash drive, or it could be a hard coded chip. This is rom memory. Read-only-memory. All data that stored in this type of memory will retain when you shutdown your computer.
13. What is microprocessor?
A complex microcircuit (integrated circuit) or set of such chips that carries out the functions of the processor of an information technology system; that is, it contains a control unit (and clock), an arithmetic and logic unit, and the necessary registers and links to main store and to peripherals.
14. Explain the registers of microprocessor?
In computer architecture, a processor register (or general purpose register) is a small amount of storage available on the CPU whose contents can be accessed more quickly than storage available elsewhere. Typically, this specialized storage is not considered part of the normal memory range for the machine. Processor registers are at the top of the memory hierarchy, and provide the fastest way for a CPU to access data.
15. What is Accumulator?
In a computer's central processing unit (CPU), an accumulator is a register in which intermediate arithmetic and logic results are stored. Without a register like an accumulator, it would be necessary to write the result of each calculation (addition, multiplication, shift, etc.) to main memory, perhaps only to be read right back again for use in the next operation. Access to main memory is slower
than access to a register like the accumulator because the technology used for the large main memory is slower (but cheaper) than that used for a register.
16. Explain the types of memories?
Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply. It has been less popularly known as temporary memory. Most forms of modern random access memory (RAM) are volatile storage, including dynamic random access memory (DRAM) and static random access memory (SRAM)Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory,
most types of magnetic computer storage devices (e.g. hard disks, floppy disks, and magnetic tape), optical discs, and early computer storage methods such as paper tape and punch cards.
17. Give few avionics architecture.
• First Generation Architecture ( 1940’s –1950’s)
i. Disjoint or Independent Architecture ( MiG-21)
ii. Centralized Architecture (F-111)
• Second Generation Architecture ( 1960’s –1970’s)
i. Federated Architecture (F-16 A/B)
ii. Distributed Architecture (DAIS)
iii. Hierarchical Architecture (F-16 C/D, EAP)
• Third Generation Architecture ( 1980’s –1990’s)
i. Pave Pillar Architecture ( F-22)
• Fourth Generation Architecture (Post 2005)
i. Pave Pace Architecture- JSF
ii. Open System Architecture
18. Explain Federated architecture.
In FEDERATED ARCHITECTURE Data conversion occurs at the system level and the datas are send as digital form – called Digital Avionics Information Systems(DAIS). Several standard data processors are often used to perform a variety of Low – Bandwidth functions such as navigation, weapon delivery , stores management and flight control Systems are connected in a Time – Shared
Multiplex Highway. Resource sharing occurs at the last link in the information chain – via controls and displays.
19. Explain centralized architecture.
As the digital technology evolved, a central computer was added to integrate the information from the sensors and subsystems. The central computing complex is connected to other subsystems and sensors through analog, digital, synchro and other interfaces. When interfacing with computer a variety of different transmission methods, some of which required signal conversion (A/D) when
interfacing with computer. Signal conditioning and computation take place in one or more computers in a LRU located in an avionics bay ,with signals transmitted over one way data bus. Data are transmitted from the systems to the central computer and the DATA CONVERSION TAKES PLACE AT THE CENTRAL COMPUTER.
20. How is federated architecture different from centralized architecture?
In FEDERATED ARCHITECTURE Data conversion occurs at the system level and the data are send as digital form – called Digital Avionics Information Systems (DAIS). It is fully digital.
In centralized architecture Data conversion takes place at the central computer. Analog wires are used.
21. Explain MIL-STD 1553B components?
• BUS CONTROLLER
• BUS MONITOR
• REMOTE TERMINAL
• TRANSMISSION MEDIA
22. Explain the status word of MIL-STD 1553B.
Status words are transmitted by the RT in response to command messages from the BC and consist of:
• 3 bit-time sync pattern (same as for a command word)
• 5 bit address of the responding RT
• 11 bit status field
• 1 parity check bit.
The 11 bits in the status field are used to notify the BC of the operating condition of the RT and subsystem.
23. Explain the bus controller and Remote terminal of MIL-STD 1553B.
There is only one Bus Controller at a time on any MIL-STD-1553 bus. It initiates all message communication over the bus. A Remote Terminal can be used to provide:
• An interface between the MIL-STD-1553B data bus and an attached subsystem
• A bridge between a MIL-STD-1553B bus and another MIL-STD-1553B bus.
24. Explain ARINC 429 standard.
ARINC 429 is the technical standard for the predominant avionics data bus used on most higher-end commercial and transport aircraft. It defines the physical and electrical interfaces of a two-wire data bus and a data protocol to support an aircraft's avionics local area network.
25. Explain ARINC 629 standard.
ARINC 629 is a multi-transmitter protocol where many units share the same bus. It was a further development of ARINC 429 especially designed for the Boeing 777
26. What is an auto pilot?
An autopilot is a mechanical, electrical, or hydraulic system used to guide a vehicle without assistance from a human being. Most people understand an autopilot to refer specifically to aircraft, but self-steering gear for ships, boats, space craft and missiles are sometimes also called by this term.
27. What is brick walling or partitioning in avionics architecture?
The purpose of partitioning is fault containment: a failure in one partition must not propagate to cause failure in another partition. The function in a partition depends on the correct operation of its processor and associated peripherals, and partitioning is not intended to protect against their failure - this can be achieved only by replicating functions across multiple processors in a fault-tolerant
manner.
28. Define Glass cockpit.
A glass cockpit is an aircraft cockpit that features electronic instrument displays. Where a traditional cockpit relies on numerous mechanical gauges to display information, a glass cockpit uses several displays driven by flight management systems, that can be adjusted to display flight information as needed. This simplifies aircraft operation and navigation and allows pilots to focus only on the
most pertinent information. They are also popular with airline companies as they usually eliminate the need for a flight engineer. In recent years the technology has become widely available in small aircraft.
29. Define plasma panel.
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32" inches or larger). Many tiny cells between two panels of glass hold a mixture of noble gases. The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light.
30. Differentiate LED & LCD.
LEDs are based on the semiconductor diode. When the diode is forward biased (switched on), electrons are able to recombine with holes and energy is released in the form of light. This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching. However, they are relatively expensive and require more precise current and heat management than traditional light sources.
A liquid crystal display (LCD) is a thin, flat panel used for electronically displaying information such as text, images, and moving pictures Among its major features are its lightweight construction, its portability, and its ability to be produced in much larger screen sizes than are practical for the construction of cathode ray tube (CRT) display technology. Its low electrical power consumption
enables it to be used in battery-powered electronic equipment. It is an electronically-modulated optical device made up of any number of pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome.
31. Explain CRT and its usage in aircraft displays.
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen.
32. What is meant by DVI?
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors. It was developed by an industry consortium, the Digital Display Working Group (DDWG). It is designed for carrying uncompressed digital video data to a display.
33. What are MFD and its significance in Aircraft?
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a Primary Flight Display. MFDs are part of the digital era of modern planes or helicopter. The first MFD were introduced by airforces. The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit.
Many MFDs allow the pilot to display their navigation route, moving map, weather radar, NEXRAD, GPWS, TCAS and airport information all on the same screen.
34. What is HOTAS?
HOTAS, an abbreviation for Hands On Throttle-And-Stick, is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircraft's cockpit, allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls. Having all switches on the stick and throttle allows the pilot to keep his "hands on throttle-and-stick", thus allowing him to remain focused on more
important duties than looking for controls in the cockpit.
35. Explain HUD?
A head-up display, or abbreviated as HUD, is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint. The origin of the name stems from the user being able to view information with his head "up" and looking forward, instead of angled down looking at lower instruments. Although they were initially developed for military aviation, HUDs are now used in commercial aircraft, automobiles, and other applications.
36. Explain Navigation.
Navigation is the process of reading, and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks. The word navigate is derived from the Latin "navigare", meaning "to sail".All navigational techniques involve locating the navigator's position compared to known locations or patterns.
37. Explain the types of Navigation.
• Dead reckoning
• Navigation by Piloting
• Celestial navigation
• Electronic navigation
38. Explain Dead reckoning type of navigation.
Dead reckoning (DR) is the process of estimating one's current position based upon a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time, and course. While traditional methods of dead reckoning are no longer considered primary means of navigation, modern inertial navigation systems, which also depend upon dead reckoning, are very widely used.
39. What is INS?
An Inertial Navigation System (INS) is a navigation aid that uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external references. It is used on vehicles such as ships, aircraft, submarines, guided missiles, and spacecraft.
40. What are different types of INS?
It is of two different configurations based on the inertial sensor placement. They are
a. Stable or Gimballed platform.
b. Strap down platform
41. What is GPS?
The Global Positioning System (GPS) is a U.S. space-based global navigation satellite system. It provides reliable positioning, navigation, and timing services to worldwide users on a continuous basis in all weather, day and night, anywhere on or near the Earth. GPS is made up of three parts: between 24 and 32 satellites orbiting the Earth, four control and monitoring stations on Earth, and the GPS receivers owned by users. GPS satellites broadcast signals from space that are used by GPS receivers to provide three-dimensional location (latitude, longitude, and altitude) plus the time.
42. Explain about P and C/A codes.
Binary data that is modulated or "superimposed" on the carrier signal is referred to as Code. Two main forms of code are used with NAVSTAR GPS: C/A or Coarse/Acquisition Code (also known as the civilian code), is modulated and repeated on the L1 wave every millisecond; the P-Code, or Precise Code, is modulated on both the L1 and L2 waves and is repeated every seven days. The
(Y) code is a special form of P code used to protect against false transmissions; special hardware, available only to the U.S.government, must be used to decrypt the P(Y) code.
43. What is Flight control system?
An aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered as flight controls as they change speed.
44. What is Actuator?
An actuator is a mechanical device for moving or controlling a mechanism or system. An actuator typically is a mechanical device that takes energy, usually created by air, electricity, or liquid, and converts that into some kind of motion.
45. Explain different types of actuator.
• plasma actuators
• pneumatic actuators
• electric actuators
• hydraulic cylinders,
• linear actuators
•
46. What is FBW?
A fly-by-wire system actually replaces manual control of the aircraft with an electronic interface. The movements of flight controls are converted to electronic signals, and flight control computers determine how to move the actuators at each control surface to provide the expected response. The actuators are usually hydraulic, but electric actuators have also been used.
47. Explain the advantage of FBW over conventional FCS.
• Care free maneuvering characteristics
• Continuous automatic stabilization of the aircraft by computer control of the control surfaces
• Auto pilot integration
• Good consistent handling which is sensibly constant over a wide flight envelope and range of load conditions
• Enables a lighter, higher performance aircraft designed with relaxed stability
48. What is strap down Navigation?
Strapdown systems have all their sensors mounted on a platform that changes orientation like the plane. Instead of mechanical gyros to hold it level, it has three more accurate gyros that sense the orientation of the system. Additionally, it has the same three acceleration sensors. Whereas the gimballed system just senses the orientation of the platform to get the aircraft's attitude, the strapdown systems have three gyroscopes that sense the rate of roll, pitch, and yaw. It integrates them to get the orientation, then calculates the acceleration in each of the same axes as the gimballed system. Due to the sensing of the rate of rotation, rather than just holding a platform level, very accurate and sensitive gyroscopes are needed.
49. What is FMS?
A Flight Management System is a fundamental part of a modern aircraft in that it controls the navigation. The flight management system (FMS) is the avionics that holds the flight plan, and allows the pilot to modify as required in flight. The FMS uses various sensors to determine the aircraft's position. Given the position and the flight plan, the FMS guides the aircraft along the flight plan. The FMS is normally controlled through a small screen and a keyboard.
50. What is meant by jammers in electronic warfare?
Electronic jamming is a form of Electronic Warfare where jammers radiate interfering signals toward an enemy's radar, blocking the receiver with highly concentrated energy signals. The two main technique styles are noise techniques and repeater techniques.
51. Give the difference between ECCM and ECM.
Electronic countermeasures (ECM) are a subsection of electronic warfare which includes any sort of electrical or electronic device designed to trick or deceive radar, sonar, or other detection systems like IR (infrared) and Laser. It may be used both offensively or defensively in any method to deny targeting information to an enemy. The system may make many separate targets appear to the enemy, or make the real target appear to disappear or move about randomly. It is used
effectively to protect aircraft from guided missiles. Most air forces use ECM to protect their aircraft from attack.
Electronic counter-countermeasures (ECCM) is a part of electronic warfare which includes a variety of practices which attempt to reduce or eliminate the effect of electronic countermeasures (ECM) on electronic sensors aboard vehicles, ships and aircraft and weapons such as missiles. ECCM is also known as electronic protective measures (EPM), chiefly in Europe. In practice, EPM often means resistance to jamming.
52. Explain RADAR.
Radar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And Ranging. A radar system has a transmitter that emits microwaves or radio waves. These waves are in phase when emitted, and when they come into contact with an object are scattered in all directions. The signal is thus partly reflected back and it has a slight change of wavelength (and thus frequency) if the target is moving. Although the signal returned is usually very weak, the signal can be amplified through use of electronic techniques in the receiver and in the antenna configuration. This enables radar to detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect.
53. Explain Certification.
Certification refers to the confirmation of certain characteristics of an object, person, or organization. This confirmation is often, but not always, provided by some form of external review, education, or assessment.
54. Explain V & V
Verification and validation is the process of checking that a product, service, or system meets specifications and that it fulfills its intended purpose. These are critical components of a quality management system such as ISO 9000. Sometimes preceded with "Independent" (or IV&V) to ensure the validation is performed by a disinterested third party.
55. Explain Reliability.
• The idea that something is fit for purpose with respect to time;
• The capacity of a device or system to perform as designed;
• The resistance to failure of a device or system;
• The ability of a device or system to perform a required function under stated conditions for a specified period of time;
• The probability that a functional unit will perform its required function for a specified interval under stated conditions.
• The ability of something to "fail well" (fail without catastrophic consequences)
56. Explain maintainability.
The probability that a failed system can be made operable in a specified interval or downtime is called as maintainability.
57. Explain Electronic warfare.
Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy. The purpose of electronic warfare is to deny the opponent the advantage of, and ensure friendly unimpeded access to, the EM spectrum. EW can be applied from air, sea, land, and space by manned and unmanned systems, and can target communication, radar, or other services. EW includes three major subdivisions: Electronic Attack (EA), Electronic Protection (EP), and Electronic warfare Support (ES).
58. Explain the specific advantages of INS.
• It is the self contained, autonomous and unjammable.
• It is faster than the data given by the GPS.
• INS is very accurate over the short distance.
59. Explain Gimbaled INS.
Gimbaled systems have a platform in the device that is mounted in gimbals. This device has 2 or more mechanical gyroscopes (not likely there are more than 3) that keep this platform level. On the platform, in addition to the gyroscopes, are usually three accelerometers, one in each direction. This was the earlier type of INS. It does not need accurate gyroscope orientation sensing, they only need mechanical gyroscopes to keep a platform level -- a much less demanding task for the gyroscopes. Additionally, since the accelerometers are already oriented (usually north/south, east/west, and up/down) the actual integration to obtain velocity and then position can be done by simpler, analog electronics.
60. Give few examples of integrated avionics system used in weapon system.
• Hemet Mounted Display (HMT)
• Head Level Display (HLD)
• Night Vision Goggles (NGV)
• Forward Looking Infra Red Displays (FLIR)
61. Give few examples of Standards used in design of avionics system.
1. What is avionics?
Avionics means "aviation electronics". It comprises electronic systems for use on aircraft, artificial satellites and spacecraft, comprising communications, navigation and the display and management of multiple systems.
2. Explain the advantage of using avionics in civil aircraft.
• Reducing the crew workload by automating tasks.
• The reduction in weight can be translated to increased passengers or long range.
• To enable the flight crew to carry out the aircraft mission safely and efficiently.
• All weather operation and reduction in maintenance costs.
3. Explain the advantage of using avionics in military aircraft.
• A single seat fighter or strike aircraft is lighter and Costs less than an equivalent two seat version.
• Elimination of the second crew member (navigator/observer/crew member) results in reduction in training costs.
• Improved aircraft performance and control and handling and reduction in maintenance costs
• Secure communication.
4. Give the general advantage of Avionics over the conventional aircraft system.
• Increased safety
• Air traffic control requirements
• All weather operation
• Reduction in fuel consumption
• Improved aircraft performance and control and handling and reduction in maintenance costs
5. Define the usage of avionics in space systems.
• Fly-by-wire control systems were used for vehicle attitude and translation control.
• Sensors used around the aircraft for data acquisition.
• Redundancy system and autopilot.
• On board computers used in satellites for processing.
6. Explain “illities” of Avionics system.
• Capability
• Reliability
• Maintainability
• Certificability
• Survivability(military)
• Availability
• Susceptibility
• vulnerability
• Life cycle cost(military) or cost of ownership(civil)
• Technical risk
• Weight & power
7. Give various systems where the avionics used in aircrafts.
• Aircraft intercoms
• Wide Area Augmentation System
• Terrain awareness and warning system
• Ground proximity warning system
• Aircraft collision avoidance systems
• Display systems
• Traffic Collision Avoidance System
8. Explain the steps involved in design of avionics system.
• The three stages are:
i. Conceptual design - What will it do?
ii. Preliminary design - How much will it weigh?
iii. Detailed design - How many parts will it have?
9. What are digital computers?
A device that processes numerical information; more generally / any device that manipulates symbolic information according to specified computational
procedures is called as digital computers. The term digital computer or simply, computer embraces calculators, computer workstations, control computers (controllers) for applications such as domestic appliances and industrial processes.
10. What is a volatile memory and give examples?
Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply. It has been less popularly known as temporary memory. Most forms of modern random access memory (RAM) are volatile storage.
11. What is aliasing?
In computing, aliasing describes a situation in which a data location in memory can be accessed through different symbolic names in the program. Thus, modifying the data through one name implicitly modifies the values associated to all aliased names, which may not be expected by the programmer. As a result, aliasing makes it particularly difficult to understand, analyze and optimize programs. Aliasing analyses intend to make and compute useful information for understanding aliasing in programs.
12. Differentiate between volatile and non volatile memories.
Volatile memory: The data is lost on reboot, you will lost all of your data when your electricity go out.. This is the ram memory. Random-access-memory.
Non-volatile memory: The data is saved to a hard drive or flash drive, or it could be a hard coded chip. This is rom memory. Read-only-memory. All data that stored in this type of memory will retain when you shutdown your computer.
13. What is microprocessor?
A complex microcircuit (integrated circuit) or set of such chips that carries out the functions of the processor of an information technology system; that is, it contains a control unit (and clock), an arithmetic and logic unit, and the necessary registers and links to main store and to peripherals.
14. Explain the registers of microprocessor?
In computer architecture, a processor register (or general purpose register) is a small amount of storage available on the CPU whose contents can be accessed more quickly than storage available elsewhere. Typically, this specialized storage is not considered part of the normal memory range for the machine. Processor registers are at the top of the memory hierarchy, and provide the fastest way for a CPU to access data.
15. What is Accumulator?
In a computer's central processing unit (CPU), an accumulator is a register in which intermediate arithmetic and logic results are stored. Without a register like an accumulator, it would be necessary to write the result of each calculation (addition, multiplication, shift, etc.) to main memory, perhaps only to be read right back again for use in the next operation. Access to main memory is slower
than access to a register like the accumulator because the technology used for the large main memory is slower (but cheaper) than that used for a register.
16. Explain the types of memories?
Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply. It has been less popularly known as temporary memory. Most forms of modern random access memory (RAM) are volatile storage, including dynamic random access memory (DRAM) and static random access memory (SRAM)Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory,
most types of magnetic computer storage devices (e.g. hard disks, floppy disks, and magnetic tape), optical discs, and early computer storage methods such as paper tape and punch cards.
17. Give few avionics architecture.
• First Generation Architecture ( 1940’s –1950’s)
i. Disjoint or Independent Architecture ( MiG-21)
ii. Centralized Architecture (F-111)
• Second Generation Architecture ( 1960’s –1970’s)
i. Federated Architecture (F-16 A/B)
ii. Distributed Architecture (DAIS)
iii. Hierarchical Architecture (F-16 C/D, EAP)
• Third Generation Architecture ( 1980’s –1990’s)
i. Pave Pillar Architecture ( F-22)
• Fourth Generation Architecture (Post 2005)
i. Pave Pace Architecture- JSF
ii. Open System Architecture
18. Explain Federated architecture.
In FEDERATED ARCHITECTURE Data conversion occurs at the system level and the datas are send as digital form – called Digital Avionics Information Systems(DAIS). Several standard data processors are often used to perform a variety of Low – Bandwidth functions such as navigation, weapon delivery , stores management and flight control Systems are connected in a Time – Shared
Multiplex Highway. Resource sharing occurs at the last link in the information chain – via controls and displays.
19. Explain centralized architecture.
As the digital technology evolved, a central computer was added to integrate the information from the sensors and subsystems. The central computing complex is connected to other subsystems and sensors through analog, digital, synchro and other interfaces. When interfacing with computer a variety of different transmission methods, some of which required signal conversion (A/D) when
interfacing with computer. Signal conditioning and computation take place in one or more computers in a LRU located in an avionics bay ,with signals transmitted over one way data bus. Data are transmitted from the systems to the central computer and the DATA CONVERSION TAKES PLACE AT THE CENTRAL COMPUTER.
20. How is federated architecture different from centralized architecture?
In FEDERATED ARCHITECTURE Data conversion occurs at the system level and the data are send as digital form – called Digital Avionics Information Systems (DAIS). It is fully digital.
In centralized architecture Data conversion takes place at the central computer. Analog wires are used.
21. Explain MIL-STD 1553B components?
• BUS CONTROLLER
• BUS MONITOR
• REMOTE TERMINAL
• TRANSMISSION MEDIA
22. Explain the status word of MIL-STD 1553B.
Status words are transmitted by the RT in response to command messages from the BC and consist of:
• 3 bit-time sync pattern (same as for a command word)
• 5 bit address of the responding RT
• 11 bit status field
• 1 parity check bit.
The 11 bits in the status field are used to notify the BC of the operating condition of the RT and subsystem.
23. Explain the bus controller and Remote terminal of MIL-STD 1553B.
There is only one Bus Controller at a time on any MIL-STD-1553 bus. It initiates all message communication over the bus. A Remote Terminal can be used to provide:
• An interface between the MIL-STD-1553B data bus and an attached subsystem
• A bridge between a MIL-STD-1553B bus and another MIL-STD-1553B bus.
24. Explain ARINC 429 standard.
ARINC 429 is the technical standard for the predominant avionics data bus used on most higher-end commercial and transport aircraft. It defines the physical and electrical interfaces of a two-wire data bus and a data protocol to support an aircraft's avionics local area network.
25. Explain ARINC 629 standard.
ARINC 629 is a multi-transmitter protocol where many units share the same bus. It was a further development of ARINC 429 especially designed for the Boeing 777
26. What is an auto pilot?
An autopilot is a mechanical, electrical, or hydraulic system used to guide a vehicle without assistance from a human being. Most people understand an autopilot to refer specifically to aircraft, but self-steering gear for ships, boats, space craft and missiles are sometimes also called by this term.
27. What is brick walling or partitioning in avionics architecture?
The purpose of partitioning is fault containment: a failure in one partition must not propagate to cause failure in another partition. The function in a partition depends on the correct operation of its processor and associated peripherals, and partitioning is not intended to protect against their failure - this can be achieved only by replicating functions across multiple processors in a fault-tolerant
manner.
28. Define Glass cockpit.
A glass cockpit is an aircraft cockpit that features electronic instrument displays. Where a traditional cockpit relies on numerous mechanical gauges to display information, a glass cockpit uses several displays driven by flight management systems, that can be adjusted to display flight information as needed. This simplifies aircraft operation and navigation and allows pilots to focus only on the
most pertinent information. They are also popular with airline companies as they usually eliminate the need for a flight engineer. In recent years the technology has become widely available in small aircraft.
29. Define plasma panel.
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32" inches or larger). Many tiny cells between two panels of glass hold a mixture of noble gases. The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light.
30. Differentiate LED & LCD.
LEDs are based on the semiconductor diode. When the diode is forward biased (switched on), electrons are able to recombine with holes and energy is released in the form of light. This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching. However, they are relatively expensive and require more precise current and heat management than traditional light sources.
A liquid crystal display (LCD) is a thin, flat panel used for electronically displaying information such as text, images, and moving pictures Among its major features are its lightweight construction, its portability, and its ability to be produced in much larger screen sizes than are practical for the construction of cathode ray tube (CRT) display technology. Its low electrical power consumption
enables it to be used in battery-powered electronic equipment. It is an electronically-modulated optical device made up of any number of pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome.
31. Explain CRT and its usage in aircraft displays.
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen.
32. What is meant by DVI?
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors. It was developed by an industry consortium, the Digital Display Working Group (DDWG). It is designed for carrying uncompressed digital video data to a display.
33. What are MFD and its significance in Aircraft?
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a Primary Flight Display. MFDs are part of the digital era of modern planes or helicopter. The first MFD were introduced by airforces. The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit.
Many MFDs allow the pilot to display their navigation route, moving map, weather radar, NEXRAD, GPWS, TCAS and airport information all on the same screen.
34. What is HOTAS?
HOTAS, an abbreviation for Hands On Throttle-And-Stick, is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircraft's cockpit, allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls. Having all switches on the stick and throttle allows the pilot to keep his "hands on throttle-and-stick", thus allowing him to remain focused on more
important duties than looking for controls in the cockpit.
35. Explain HUD?
A head-up display, or abbreviated as HUD, is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint. The origin of the name stems from the user being able to view information with his head "up" and looking forward, instead of angled down looking at lower instruments. Although they were initially developed for military aviation, HUDs are now used in commercial aircraft, automobiles, and other applications.
36. Explain Navigation.
Navigation is the process of reading, and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks. The word navigate is derived from the Latin "navigare", meaning "to sail".All navigational techniques involve locating the navigator's position compared to known locations or patterns.
37. Explain the types of Navigation.
• Dead reckoning
• Navigation by Piloting
• Celestial navigation
• Electronic navigation
38. Explain Dead reckoning type of navigation.
Dead reckoning (DR) is the process of estimating one's current position based upon a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time, and course. While traditional methods of dead reckoning are no longer considered primary means of navigation, modern inertial navigation systems, which also depend upon dead reckoning, are very widely used.
39. What is INS?
An Inertial Navigation System (INS) is a navigation aid that uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external references. It is used on vehicles such as ships, aircraft, submarines, guided missiles, and spacecraft.
40. What are different types of INS?
It is of two different configurations based on the inertial sensor placement. They are
a. Stable or Gimballed platform.
b. Strap down platform
41. What is GPS?
The Global Positioning System (GPS) is a U.S. space-based global navigation satellite system. It provides reliable positioning, navigation, and timing services to worldwide users on a continuous basis in all weather, day and night, anywhere on or near the Earth. GPS is made up of three parts: between 24 and 32 satellites orbiting the Earth, four control and monitoring stations on Earth, and the GPS receivers owned by users. GPS satellites broadcast signals from space that are used by GPS receivers to provide three-dimensional location (latitude, longitude, and altitude) plus the time.
42. Explain about P and C/A codes.
Binary data that is modulated or "superimposed" on the carrier signal is referred to as Code. Two main forms of code are used with NAVSTAR GPS: C/A or Coarse/Acquisition Code (also known as the civilian code), is modulated and repeated on the L1 wave every millisecond; the P-Code, or Precise Code, is modulated on both the L1 and L2 waves and is repeated every seven days. The
(Y) code is a special form of P code used to protect against false transmissions; special hardware, available only to the U.S.government, must be used to decrypt the P(Y) code.
43. What is Flight control system?
An aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered as flight controls as they change speed.
44. What is Actuator?
An actuator is a mechanical device for moving or controlling a mechanism or system. An actuator typically is a mechanical device that takes energy, usually created by air, electricity, or liquid, and converts that into some kind of motion.
45. Explain different types of actuator.
• plasma actuators
• pneumatic actuators
• electric actuators
• hydraulic cylinders,
• linear actuators
•
46. What is FBW?
A fly-by-wire system actually replaces manual control of the aircraft with an electronic interface. The movements of flight controls are converted to electronic signals, and flight control computers determine how to move the actuators at each control surface to provide the expected response. The actuators are usually hydraulic, but electric actuators have also been used.
47. Explain the advantage of FBW over conventional FCS.
• Care free maneuvering characteristics
• Continuous automatic stabilization of the aircraft by computer control of the control surfaces
• Auto pilot integration
• Good consistent handling which is sensibly constant over a wide flight envelope and range of load conditions
• Enables a lighter, higher performance aircraft designed with relaxed stability
48. What is strap down Navigation?
Strapdown systems have all their sensors mounted on a platform that changes orientation like the plane. Instead of mechanical gyros to hold it level, it has three more accurate gyros that sense the orientation of the system. Additionally, it has the same three acceleration sensors. Whereas the gimballed system just senses the orientation of the platform to get the aircraft's attitude, the strapdown systems have three gyroscopes that sense the rate of roll, pitch, and yaw. It integrates them to get the orientation, then calculates the acceleration in each of the same axes as the gimballed system. Due to the sensing of the rate of rotation, rather than just holding a platform level, very accurate and sensitive gyroscopes are needed.
49. What is FMS?
A Flight Management System is a fundamental part of a modern aircraft in that it controls the navigation. The flight management system (FMS) is the avionics that holds the flight plan, and allows the pilot to modify as required in flight. The FMS uses various sensors to determine the aircraft's position. Given the position and the flight plan, the FMS guides the aircraft along the flight plan. The FMS is normally controlled through a small screen and a keyboard.
50. What is meant by jammers in electronic warfare?
Electronic jamming is a form of Electronic Warfare where jammers radiate interfering signals toward an enemy's radar, blocking the receiver with highly concentrated energy signals. The two main technique styles are noise techniques and repeater techniques.
51. Give the difference between ECCM and ECM.
Electronic countermeasures (ECM) are a subsection of electronic warfare which includes any sort of electrical or electronic device designed to trick or deceive radar, sonar, or other detection systems like IR (infrared) and Laser. It may be used both offensively or defensively in any method to deny targeting information to an enemy. The system may make many separate targets appear to the enemy, or make the real target appear to disappear or move about randomly. It is used
effectively to protect aircraft from guided missiles. Most air forces use ECM to protect their aircraft from attack.
Electronic counter-countermeasures (ECCM) is a part of electronic warfare which includes a variety of practices which attempt to reduce or eliminate the effect of electronic countermeasures (ECM) on electronic sensors aboard vehicles, ships and aircraft and weapons such as missiles. ECCM is also known as electronic protective measures (EPM), chiefly in Europe. In practice, EPM often means resistance to jamming.
52. Explain RADAR.
Radar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And Ranging. A radar system has a transmitter that emits microwaves or radio waves. These waves are in phase when emitted, and when they come into contact with an object are scattered in all directions. The signal is thus partly reflected back and it has a slight change of wavelength (and thus frequency) if the target is moving. Although the signal returned is usually very weak, the signal can be amplified through use of electronic techniques in the receiver and in the antenna configuration. This enables radar to detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect.
53. Explain Certification.
Certification refers to the confirmation of certain characteristics of an object, person, or organization. This confirmation is often, but not always, provided by some form of external review, education, or assessment.
54. Explain V & V
Verification and validation is the process of checking that a product, service, or system meets specifications and that it fulfills its intended purpose. These are critical components of a quality management system such as ISO 9000. Sometimes preceded with "Independent" (or IV&V) to ensure the validation is performed by a disinterested third party.
55. Explain Reliability.
• The idea that something is fit for purpose with respect to time;
• The capacity of a device or system to perform as designed;
• The resistance to failure of a device or system;
• The ability of a device or system to perform a required function under stated conditions for a specified period of time;
• The probability that a functional unit will perform its required function for a specified interval under stated conditions.
• The ability of something to "fail well" (fail without catastrophic consequences)
56. Explain maintainability.
The probability that a failed system can be made operable in a specified interval or downtime is called as maintainability.
57. Explain Electronic warfare.
Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy. The purpose of electronic warfare is to deny the opponent the advantage of, and ensure friendly unimpeded access to, the EM spectrum. EW can be applied from air, sea, land, and space by manned and unmanned systems, and can target communication, radar, or other services. EW includes three major subdivisions: Electronic Attack (EA), Electronic Protection (EP), and Electronic warfare Support (ES).
58. Explain the specific advantages of INS.
• It is the self contained, autonomous and unjammable.
• It is faster than the data given by the GPS.
• INS is very accurate over the short distance.
59. Explain Gimbaled INS.
Gimbaled systems have a platform in the device that is mounted in gimbals. This device has 2 or more mechanical gyroscopes (not likely there are more than 3) that keep this platform level. On the platform, in addition to the gyroscopes, are usually three accelerometers, one in each direction. This was the earlier type of INS. It does not need accurate gyroscope orientation sensing, they only need mechanical gyroscopes to keep a platform level -- a much less demanding task for the gyroscopes. Additionally, since the accelerometers are already oriented (usually north/south, east/west, and up/down) the actual integration to obtain velocity and then position can be done by simpler, analog electronics.
60. Give few examples of integrated avionics system used in weapon system.
• Hemet Mounted Display (HMT)
• Head Level Display (HLD)
• Night Vision Goggles (NGV)
• Forward Looking Infra Red Displays (FLIR)
61. Give few examples of Standards used in design of avionics system.
Military standards - MIL-STD-1629A (Hardware FMEA), MIL STD-882 (systems safety program requirements) ARINC 429, 629 (Civilian a/c data bus) and MIL-STD-1553A, 1773
(Military a/c data buses)
• Civil Standards - FAR 25 : 1309 A (equipments, systems and installation), FAR 25 : 581 (lightning protection systems), FAR 25 : 571 (control systems), FAR 25: 572 (stability augmentation systems)
62. Give few examples of integrated avionics system used in civil airlines.
• INS & GPS (Navigation)
• MFKs and MFDU (Display I/O)
• HUD
• Glass Cockpit
63. Explain the steps of certification.
• Assessment
• Validation
• Verification
Other major steps like
• Functional Hazard Assessment (FHA)
• Fault Tree Analysis (FTA)
• Failure Mode Effect Analysis (FMEA)
64. Explain the document support for Certification.
• In Military aircrafts, the documents support for certification
i. MIL-STD-1629A (Hardware)
ii. DOD-STD-2167 (Software)
• In Civil aircrafts, the document support for certification
o FAR 25 : 1309A (systems)
o RTCA-DO-178A (Software)
Within the overall task of hardware assessment and validation,
Certification is perhaps the most difficult part for civil/military avionics designers. Certification is the challenging process of negotiation and compromise between the designers and the regulatory authorities buttressed by technical analysis and expertise on both sides.
65. Explain the advantage of GPS over conventional navigation.
• Global coverage and assessment
• More precise
• High integrity and portable simple system
• Augments the accuracy of the self contained systems
66. Explain FBW over FBL.
• FBW: (FLY BY WIRE) It’s a concept of utilizing digital data bus for the transmission of mechanical movements from pilot’s joystick to the Mechanical actuators near by the control surface in the form of electronic signals using suitable transducers. It eliminates majority of the weight in handling control rods, push pull systems. Because of this weight elimination the redundancy level of FBW can be raised.
• FBL: (FLY BY LIGHT) It’s a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilot’s joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers. It eliminates the amplification units, filter circuits, modulator units etc., which are at high redundant levels in the FBW. FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft.
67. What is FBL?
• FBL: (FLY BY LIGHT) It’s a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilot’s joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers. It eliminates the amplification units, filter circuits, modulator units etc., which are at high redundant levels in the FBW. FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft.
68. Compare INS and GPS.
Sl. No. INS GPS
01 Self contained system Not a self contained system
02 Accuracy degrades with time Accuracy level is high always
03 Being a self contained system, weight is more Weight is less comparatively
04 No signal transmission/reception Signal is transmitted/received
69. What is usage of night vision goggles?
• Night time flight is possible (As pilot can see the terrain like a near morning)
• Close Ground Support during night time attack is enabled in rotor and fighter planes
• Night time reconnaissance and surveillance is possible on NVG enabled cameras
70. Explain advantage of EL over Plasma display.
• Less flickering
• Sustainable luminosity even during aging
• Light weight than plasma displays
• Simple light weight component
• Available in smaller size (unlike plasma displays, which are available only at 32”)
71. Explain the need of communication system in airline.
• Renders a clear picture of aircrafts health during the complete mission
• Ensures safety landing and take-off guidance • Provides suitable environment awareness to the crew members of flight to direct the flying machine
• Acts as primary interfacing unit between pilot and the ATC or ground station.
72. Explain the advantage of HMD over MUD?
• In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which he/she moves/looks, thus facilitating him/her to watch the primary data always.
• HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target.
73. Explain MFK and its usage.
• As the cockpits of modern aircraft have more controls jammed into them, the point reached where there is no more space. Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected.
• Multifunction keyboards can be implemented in several ways. The first two ways use LEDs or LCDs in panels in a central location. Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with
legends built into the surface of the switches.
74. Differentiate between Civil and military communication standards.
Sl. No. Civil Communication Standards Military Communication Standards
01 Speed level in data bus is generally slow Speed level in the data bus is high
02 Frequency band is in common range of communication devices Frequency band is in isolated or restricted range of communication devices. It varies between nation to nation
03 Redundancy and integrity level is moderate Redundancy and integrity level is high
04 Maintenance is spoken in terms of Cost Of Ownership (COO) Maintenance is spoken in terms of Life Cycle Cost (LCC)
05 Ex: ARINC 429, FAR-25-1309A Ex: MIL-STD-1553A, MIL-STD-16629A
75. Differentiate between ARINC 429 and ARINC 629.
Sl. No. MIL-STD-1553A ARINC 429 ARINC 629
01 Adopted in 1970 Adopted in 1977 Adopted in 1989
02 Half duplex data bus Simplex data bus Duplex data bus
03 SPEED 1 Mb/s SPEED Critical data 100 Kb/s Non critical data 12-14.5 Kb/s SPEED 2 Mb/s
04 Command/Response protocol Williamsberg protocol Protocol: CSMA/CA – Carrier sense multiple access/ Collision avoidance
05 Called as Digital Time Division Command/Response Multiplex Data bus Called as Digital Data
CompendiumCalled as DATAC- Digital Autonomous Terminal Access Control
06 31 RTs can be accessed
76. Explain the major components of microprocessor.
• Arithmetic and Logical Unit
• Timing and Control Unit
• Register sets
77. What is fetching?
• Fetching means getting/bringing/taking/carrying/obtaining the value/address from the specific memory location/register pair.
• Assembly language code MOV B,A says that fetch the 8 bit data from accumulator to B register.
78. Give the need for standard documents in the design of avionics system. • In most of the aircrafts, the most important avionics function is flight controls, frequently in flight critical manner, that is, if the avionics fail, the aircraft is lost. Because of the critical role for the avionics, it is essential to take early surveys to formulate standards.
• Those standards must ensure the aircraft safety even during the critical failure of its avionics components.
• Those accepted standards have to be documented so that in future avionics design for various aircraft it would be considered as reference to build it.
• Ex. MIL-STD-9490, 1629, 810 etc.,
79. Give the advantages of digitization.
• Digitizing or digitization means converting the analogue data in to discrete or digital data source.
• Converting the details about a picture/sound/scene in to a discrete form is called as digitizing.
80. What are major drivers for avionics in civil transport aircraft?
• Major drivers for avionics in civil transport aircraft are:
i. Capability
ii. Reliability
iii. Maintainability
iv. Certificability
v. Cost of Ownership vi. Technical risk
vii. Power and Weight
81. Explain the usage of microprocessors in Avionics system.
• In ground station, the complete avionics on ATC (AIR TRAFFIC CONTROL) is running on the backbone of microprocessor for various data computation. (weather data computation)
• Sensors on the airborne equipments are interrupted and computed to the understandable values and displayed on the panels only through the use of microprocessor. (Temperature monitoring system)
• And most of the avionics system in fighter planes utilizes microprocessor for data computation and presentation. (HMT, HUD)
82. How are reliability and maintainability related to each other?
• When a system is said to be more reliable and maintainable then it is readily available.
• A more reliable system requires less maintenance and a less reliable system requires more maintenance. Hence a suitable trade-off has to be made between these two things to save money.
• Both increase in reliability and maintainability requires more money in turn.
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