1. technology and computing
2. hardware
3. computer components
4. chips and processors

AE 64 – AVIONICS QUESTION BANK
DEPARTMENT OF AEROSPACE ENGINEERING, NOORULISLAMUNIVERSITY 2011
Questions and Answers Bank
AVIONICS ,Semester:6
Prepared by N.Subash (Lecturer, Department of Electronics And
Communication Engineering, Noorul Islam University).
DEPARTMENT OF AEROSPACE ENGINEERING, NOORUL ISLAM UNIVERSITY
2011
Questions and Answers Bank
AVIONICS
Prepared by N.Subash (Lecturer, Department of Electronics And
Communication Engineering, Noorul Islam University).
Unit-I
Part-I
1. Define the term Avionics systems.
Ans:- All electronic and electromechanical systems and subsystems
(hardware and software) installed in an aircraft that are dependent on
flight crew to carry out the aircraft mission safely and to meet the mission
requirements with minimum flight crew
2. Explain briefly Flight management system (FMS)
Ans:- Outputs from the GNSS sensors, air data sensors and other on-board
sensors are used by FMS to perform the necessary navigation calculations
and provide information to the flight crew via a range of display units. The
flight management system provides the primary navigation, flight planning,
and optimized route determination and en route guidance for the aircraft
and is typically comprised of the following interrelated functions: navigation,
flight planning, trajectory prediction,performance computations, and
guidance. To accomplish these functions the flight management system
must interface with several other avionics systems.
3. Explain FBW control system.
Ans: Enables a lighter, higher performance aircraft designed with relaxed
stability. Good consistent handling which is sensibly constant over a wide
flight envelope and range of load conditions Continuous automatic
stabilization of the aircraft by computer control of the control surfaces. Auto
pilot integration
Care free maneuvering characteristics
Ability to integrate additional controls automatically such as
o Leading edge slats/flaps and trailing edge flaps to generate additional lift
o Variable wing sweep
o Thrust vector control nozzles and engine thrust
Elimination of mechanical controls runs - friction, backlash
Small control stick
Ability to exploit aerodynamically unstable configuration
Aerodynamics versus stealth - the concept of reducing the radar cross
section
Very high integrity, a failure survival system.
4. What do you mean by House keeping management?
Ans:- The term 'house keeping' management has been used to cover the
automation of the background tasks which are essential for the aircraft's
safe and efficient operation
Such tasks include
Fuel management
Electrical power supply system management
Cabin/cockpit pressurization systems
Environmental control system
Warning systems
Maintenance and monitoring systems.
5. What are the main characteristics of touch screens?
Ans:- Fully Connected Speech
Must Be Able to Operate in the Cockpit Environment
Vocabulary size - required size is around 200-300 words
Speech template duration - Speech Template Duration is around 5 Seconds
Vocabulary duration - Maximum duration of the total vocabulary is around
160 seconds
Syntax nodes - max. no. of syntax nodes required is 300
Duration of utterance - no restriction on the max. duration of an input
utterance
Recognition response time - this must be in real time.
6. What is the function of inertial sensor systems? What are the various
inertial sensor systems used in aircraft?
Ans:- They provide attitude and heading information which are essential for
a/c mission. Various inertial sensor systems are- Gyros - mechanical electromechanical - RLG-FOG
Accelerometer. AHRS(Attitude Heading Reference Systems)
o Strap Down o Gimballed systems
7. Explain Radar systems.
Ans:-• Installed in all civil airliners & in many general
aviation aircraft
• To detect water droplets and provide warning of storms, cloud turbulence
and severe precipitation-aircraft can alter course and avoid such turbulent
conditions
• It should be noted that in severe turbulence, the violence of the vertical
gusts can subject the aircraft structure to very high loads and stresses
• These radars can also generally operate in ground mapping and terrain
avoidance modes. • In the airborne interception mode, the radar, must be
able to detect aircraft upto 100 miles away and track while scanning and
keeping tabs on several aircraft simultaneously • The radar must also have
a 'look down' capability and be able to track low flying aircraft below it.
8. What are the different methods of navigation?
Ans:- Classic dead-reckoning navigation using air data and magnetic,
together with Doppler or LORAN-C; Radio navigation using navigation aids –
ground-based radio-frequency beacons and airborne receiving and
processing equipment;
Barometric inertial navigation using a combination of air data and inertial
navigations (IN) or Doppler; Satellite navigation using a global navigation
satellite system (GNSS), more usually a global positioning system (GPS);
Multiple-sensor navigation using a combination of all the above.
9. Explain briefly radio navigation.
Ans:- The primary means of navigation over land was by means of radio
navigation routes defined by VHF omni ranging/distance measuring
equipment (VOR/DME) beacons. By arranging the location of these beacons
at major navigation or crossing points, it was possible to construct an entire
airway network that could be used by the
flight crew to define the aircraft flight from take-off to touchdown. Other
radio frequency aids include distance measuring equipment (DME) and nondistance beacons (NDB).
10. Describe briefly inertial navigation
Ans:- Using inertial navigation systems (INS), flight crew are able to navigate
by autonomous means using an on-board INS with inertial sensors. By
aligning the platform to earth-referenced coordinates and present position
during initialization, it is possible to fly for long distances without relying
upon LORAN, VOR/DME or TACAN beacons. Waypoints could be specified
in terms of latitude and longitude as arbitrary points on the globe, more
suited to the aircraft’s intended flight path rather than a specific geographic
feature or point in a radio beacon network.
11. What do you mean by Engine control and management?
Ans:-Control and the efficient management and monitoring of the engines
Automatically controls the flow of fuel and respond to throttle command
Control system ensures the engine limits in terms of temperatures, engine.
speeds and accelerations are not exceed and the engine respond in an
optimum manner to the throttle command. Full authority in terms of the
control it can exercise on the engine and a high integrity failure survival
12.Explain the term Avionics systems
. A system in aircraft is dependent on electronics for its operation, although the system may
contain electromechanical elements is called avionics systems. All electronic and
electromechanical systems and subsystems (hardware and software) installed in an aircraft or
attached to it. (MIL-1553A-HDBK)
2. Equipments in Avionics systems are different from ground based equipments in many
ways. Justify.
1. The importance of achieving minimum weight.
2. The adverse operating environment particularly in military aircraft in terms of operating
temperature range, acceleration, shock, vibration, humidity range and electro-magnetic
interference.
3. The importance of very high reliability, safety and integrity.
4. Space constraints particularly in military aircraft requiring an emphasis on miniaturisation and
high packaging densities.
13.What are the major drivers for Avionics systems in a typical civil transport aircraft?
The avionics systems are essential to enable the flight crew to carry out the aircraft mission
safely and efficiently. The mission is the carrying of the passengers to their destination in the
case of a civil airliner. Other important drivers for avionics systems are 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
. 14. List the various mission phases for military and civil aircraft.
Mission phases --Air superiority --Ground Support --Passenger Transport
15. What are the typical Avionics system requirements for cruise phase and air-to-air military
mission?
Requirements for cruise phase ---Minimum Fuel Consumption ---Maximum Range --Maximum Endurance ---Accurate Navigation, Guidance and Control
16. What are the top level requirements for designing avionics systems in a civil aircraft?
The aircraft manufacturer makes a very careful analysis of the potential customer
structure, image, and operating philosophies to determine the customer
future operating environment.
The manufacturer then designs an aircraft that provides an optimum, balance response to the
integrated set of needs
Safety is always the highest priority need and economical operation is a close second
16. What are the steps involved in Avionics system design?
1. Requirement Analysis
2. Preliminary design
3. Detailed design
4. Testing and maintenance
16. Why weight saving is important in aircraft?
A weight saving of 10 kg enables an increase in the payload capability of the order of 100 kg.
17. List the functions carried out by the FMS(Flight Management System)
Flight Planning
Navigation Management
Engine control to maintain the planned speed of mach number
Control of the aircraft flight path to follow the optimised planned route.
Minimising fuel consumption
18. Briefly describe about the communication systems used in aircraft.
The communication radio suite on modern aircraft is a very comprehensive one and covers
several operating frequency bands. Long range communication is provided by high frequency
radios operating in the band 2 – 30 Mhz. Near to medium range communication is provided in
civil aircraft by very high frequency (VHF) radios operating in the band 30-100 Mhz, and in
19. What are the advantages of system integration by using digital data buses?
It reduces the no of wiring requirements for integrating the subsystems. So that it reduces the
faults and weight of the total system
Greater information sharing can be achieved between subsystems
20. Define the term LRU?
Line Replacement Unit, a single stand-alone unit with a unique part number that can be installed
or removed from an aircraft by line maintenance personnel while the aircraft is on the flight line
Unit-II
Part-A
1. What is sampling frequency?
Sampling is a process of converting continuous time signals into discrete time signals. The time
period between two successive samples are called as sampling period (Ts). Sampling Frequency
(Fs) is equal to 1/Ts.
2. List few advantages of digital systems over analog systems
. Hardware Economy Reduction in weight and volume is of the order of 5:1 for a system of
modest complexity Flexibility Control laws and gains can be changed Reduced nuisance
disconnects Sophisticated voting and consolidation algorithms enable unwanted disconnections
of redundant systems Built in test capability Comprehensive self test capabilities Digital data
buses Large reduction in weight, high integrity data transmission
3. Discuss the problems encountered in digital data.
1. Aliasing
2. Quantization Noise
4. Describe flip-flop as a storage element
. Flip-Flop is a memory element which is capable of storing one bit binary information
5. Give some features of 8085 microprocessor.
1. It is an 8-bit Microprocessor.
2. It has 16 address lines, hence it can access 64 Kbytes of memory.
3. It provides 8 bit I/O addresses to access 256 I/0 ports
4. It supports 74 instructions with the following addressing modes:
a) Immediate addressing
b) Register addressing
c) Direct addressing
d) Indirect addressing
e) Implied addressing
6. What is the function of Program Counter?
The program Counter is a special purpose register which, at a given time stores the address of the
next instruction to be fetched. Program counter acts as a pointer to the next instruction
. 7. What is the function of instruction decoder?
The processer first fetches the opcode of instruction from the memory and stores this opcode in
the instruction register. It is send to the instruction decoder. The instruction decoder decodes it
and accordingly gives the timing and control signal which controls the register, the data buffers,
ALU and external peripheral signals depending on the nature of the instruction.
8. Explain the function of interrupts.
A more desirable method would be the one that allows the microprocessor to be executing its
main program and only stop to service peripheral devices when it is told to do so by the device
itself, In effect, the method, would provide an external asynchronous input that would inform the
processer that it should complete whatever instruction that is currently being executed and fetch a
new routine that will service the requesting device. Once this servicing is completed, the
processer would resume exactly where it left off. This method is called interrupt method.
9. What is the difference between Microprocessors and Microcontrollers?
Microprocessors
1. Microprocessor contains ALU, general purpose registers, stack pointer, program counter, clock
Microcontrollers
. Microcontroller contains the circuitry of microprocessor and in addition it has built-in ROM,
RAM, I/O devices, timers and counters
. Less flexible in design point of view.
. Microcontroller based system requires less hardware reducing PCB size and increasing the
reliability.
10. What is memory mapping?
Memory mapping is a process of connecting external memory to the microprocessor. It gives the
starting address and ending address of the connected memories
11. What are the needs of memory address lines? The memory capacity is directly proportional to
the no of address lines. If memory is having 12 address lines and data lines, then Number of
registers/memory locations = 4096. Microprocessor 8085 can access 64Kbytes memory since
address bus is 16-bit. But it is not always necessary to use full 64Kbytes address space. The total
memory size depends upon the application.
12. What is memory word size?
1 word = 8 bits
13. What are the classifications of memories?
Memory
. Read Only Memory(ROM)
. Masked ROM
. PROM
. EPROM
. EEPROM
. Read/write memory(RAM)
. Static RAM
. Dynamic RAM
14. What is aliasing affect?
When, the spectrum of the samples overlapping with each other. This is called aliasing effect =
maximum frequency component present on the signal
15. What is the difference between volatile and non-volatile memory?
The volatile memory retains its contents after switch off the power supply. But the non-volatile
memory losses its contents when the power is switched off.
16. What is the function of multiplexer?
A multiplexer is a digital switch which routes inputs from several sources to only one sink. The
selection of input is achieved by suitable bit combinations of selection lines
17. What is the purpose of accumulator in Intel 8085 microprocessor?
Registers are small memories within the CPU. They are used by the
microprocessor for temporary storage and manipulation of data and
instructions.
The register A is the accumulator in Intel 8085 microprocessor. This is for
temporary storage used during the execution of a program. It holds one of
the operands. The other operand may be either in the memory or in one of
the registers.
18. What are the status flags in 8085 microprocessor?
Ans:- The following status flags have been provided in Intel 8085:
(i) Carry(CS):- If there is a carry from addition or a borrow from subtraction
or comparison, the carry flag CS is set to 1; otherwise 0.
(ii) Zero(Z):- The zero status flag Z is set to 1 if the result of an arithmetic or
(iii) Sign(S):- The sign status flag is set to 1 if the most significant bit of the
result of an arithmetic or logical operation is 1, otherwise 0.
(iv) Parity(P):- The parity status flag is set to 1 when the result of the
operation contains even number of 1s. It is set to 0 when there is odd
number of 1s.
(v) Auxillary Carry(AC):- The auxillary carry status flag holds carry out of bit
3 to 4 resulting from the execution of an arithmetic operation.
19. What is the purpose of the ALE output line in 8085 µP?
Ans:- ALE is an address latch enable signal. The 8085 microprocessor, to
work properly, needs one or more memory chips connected to it. Each
memory chip has its own MAR(Memory address register), usually called an
address latch. This latch stores the incoming address from the address bus
and address-data bus. The falling edge of the ALE signal loads the address
on the address bus into the MAR or address latch of the memory chips.
20. What is the size of the memory space for an 8-bit microprocessor with a
16-bit
address word?
Ans:- 216 (= 65536=64Kilobytes(K), where 1K=1024 bytes) memory locations
can be addressed by an 8-bit microprocessor with a 16-bit address word.
Each memory location contains 1 byte of data.
21. State the functions of the following lines in 8085 µP chip, (i) SOD, SID
(ii) READY
Ans:- (i) Some times, I/O devices work with serial data rather than parallel.
SOD stands for serial out data. This serial data comes out of pin 4, can be
connected to a serial output device. SID stands for serial in data.
(ii) Some peripheral devices are slow; they are unable to run at the same
speed as 8085. One way to slow down the 8085 is with the READY signal. If
the device is not ready, it will return a low READY bit to the 8085. The 8085
then generates a number of WAIT states. When the peripheral device is
ready, it will send a high READY signal to µP. Then µP can complete the
data transfer.
22. How is address information outputted in 8085 microprocessor?
Ans:- The Intel 8085 requires a 16-bit wide address bus as the memory
addresses are of 16 bits. The 8 most significant bits of the address are
transmitted by the address bus, A-bus(pins A8 to A15). The 8 least
significant bits of the address are transmitted by address/data bus, AD-bus
moment, it transmits either data or address. This technique is called
multiplexing. First of all 16-bit memory address is transmitted by the
microprocessor; the 8 MSBs of the address on the A-bus and the 8 LSBs of
the address on AD-bus. Then the 8 LSBs of the address is latched so that
the complete 16-bit address remains available for further operation.
23. Define Opcode and Operand, and specify the Opcode and the Operand in
the
instruction MOV A, B.
Ans:- Each instruction contains two parts: operation code(opcode) and
operand. The first part of an instruction which specifies the task to be
performed by the computer is called opcode. The second part of the
instruction is the data to be operated on, and it is called operand. The
operand given in the instruction may be in various forms such as 8-bit or
16-bit data, 8-bit or 16-bit address, internal registers or a register or
memory location. In the instruction, MOV A, B, MOV is the opcode and A &
B are operands.
24. Explain (i) One byte instruction (ii) Two byte instruction
Ans:- A digital computer understands instructions written in binary codes or
machine codes. The machine codes of all instructions are not of the same
length. The instructions whose word size is of one byte (8 bits) are called one
byte instructions. Eg:- MOV A,B
The instructions whose word size is of two bytes (16 bits) are called two byte
instructions.
Eg:- MVI A, 05
25. Differentiate between Direct and indirect addressing.
Ans:- In direct addressing mode, the address of the operand is given in the
instruction itself.
Eg: STA 2400H--------Store the content of accumulator in location 2400H.
In indirect addressing mode, the address of the operand is not given in the
instruction explicitly.
Eg: RST 4----------------This instruction takes the program to the address
0020(4
x8=32)-------> (0020)hex.
26. What operations can be performed with the following instructions, (i)
DAA (ii) DAD
Ans:- (i) DAA instruction is used in the program after ADD or ADC
hexadecimal and it is placed in the accumulator. DAA instruction operates
on this result and gives the final result in decimal system.
(ii) During the execution of DAD B instruction, the contents of B-C register
pair are added to the contents of H-L pair and the sum is placed in H-L pair.
27. Differentiate between hold and halt states of the 8085 microprocessor.
Ans:- If the HOLD line of 8085 found high, the µP enters a HOLD state and
issues out a HLDA(Hold acknowledge) signal. After recognizing the HOLD
signal, the µP suspends executing any further machine cycles and tri-states
the A and AD buses and also the IO/M, RD and WR lines. During the HOLD
state, the peripheral devices can gain control of the data and address buses
for transferring data to or from the memory directly. This mode of operation
is called Direct memory access(DMA). When a HLT instruction is executed,
the µP enters a HALT state. It will stops the microprocessor. The registers
and status flags remain unaffected. The µP can get out of this state only one
clock cycle after a valid interrupt is recognized or a RESET occurs.
28. What is WAIT state?
Some peripheral devices are slow; they are unable to run at the same speed
as 8085. One way to slow down the 8085 is with the READY signal. If the
device is not ready, it will return a low READY bit to the 8085. The 8085
then generates a number of WAIT states. When the peripheral device is
ready, it will send a high READY signal to µP. Then µP can complete the
data transfer.
29. What are the major components of a CPU?
Ans: - The major components of CPU are:(1) Arithmetic and Logic Unit (ALU):- The function of ALU is to perform
arithmetic operations such as addition and subtraction; logical operations
such as AND, OR and EX-OR. (2) Timing and control unit:- It generates
timing signals for the execution of instruction and control of peripheral
devices.
(3) Accumulator and General purpose registers:- The accumulator is a
register which contains one of the operands and stores results of most
arithmetic and logical operations. General purpose registers are used for
temporary storage of data and intermediate results while computer is
making execution of a program.
30. List the different categories of instructions that manipulate data.
Ans: - Data transfer group, Arithmetic group, Logical group, Branch control
Data transfer group:- Instructions which are used to transfer data from one
register to another register, from a memory location to a register or register
to memory, between an I/O device and accumulator or between a register
pair and stack come under this group.
Arithmetic group: The instructions of this group perform arithmetic
operation such as addition, subtraction, increment or decrement data in
register or memory.
Logical group:- The instructions under this group perform logic operations
such as AND, OR, compare, rotate etc.
Branch Control group:- It includes the instructions for conditional and
unconditional jump, subroutine call and return and restart.
I/O and machine control group:- This group includes the instructions for
input/output ports, stack and machine control.
31. Explain subroutines
Ans:- While writing a program, certain operations may occur several times
and they are not available as individual instruction. The program of such
operations is repeated again and again in the main program. The concept of
subroutines is used to avoid the repetition of smaller programs. The small
programs for particular tasks are called subroutines. They are written
separately and stored in the memory. They are called at various points of the
main program by CALL instruction where they are required. After the
completion of a subroutine, the main program begins from the instruction
immediately following the CALL instruction.
32. Differentiate between maskable and non-maskable interrupts.
Ans:- At many occasions, the programmer may like to prevent the
occurrence of a few of several interrupts while µP is performing certain
tasks. This is done by masking off those interrupts which are not required to
occur when certain task is being performed. The interrupts which can be
masked off are called maskable interrupts. Eg:- RST 7.5, RST 6.5 & RST 5.5.
The TRAP is a non-maskable interrupt. It need not be enabled. It cannot be
disabled.It is not accessible to user. It is used for emergency situation such
as power failure and energy shut off.
33. What is memory mapped I/O scheme?
Ans: - In this scheme, the addresses for I/O devices are different from the
addresses which have been assigned to memories. The memory addresses
which have not been assigned to memories can be assigned to I/O devices.
both memory as well as I/O devices.
Eg:- MOV A,M will be valid for data transfer from the memory location or
I/O device whose address is in H-L pair. If the H-L pair contains the address
of a memory location data will be transferred from the memory location to
the accumulator. If the H-L pair contains the address of an I/O device, data
will be moved from the I/O device to the accumulator.
34. Describe flip flop as a storage element.
Ans:- A digital computer needs devices which can store information. A
flip flop is a binary storage device. It can store binary bit either 0 or 1. It
has two stable states: HIGH and LOW, ie 1 and 0. It has the property to
remain in one state indefinitely until it is directed by an input signal to
switch over to other state. It is a basic memory element. In the case of Dflip flop, when CLK is high, the flip flop sets. When CLK is low, the flip
flop resets.
Unit_III
Part-A
1. What is the need for two different speeds in ARINC429?
ARINC429 operates at two different speeds. There are
1. Low Speed(12 – 14 kbps)
For general purpose low critical applications
High Speed(100Kbps)
For flight critical applications
2. Differentiate between centralized, Federated and Distributed architectures
Centralized 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
Federated Data conversion occurs at the system level and the data
digital form – called Digital Avionics Information Systems (DAIS) Distributed It has
multiple processors throughout the aircraft that are designed for computing takes on a
real-time basis as a function of mission phase and/or system status. Data Processing is
performed in the sensors and actuators.
3.What is the need for Manchester II Bi-phase encoding?
It provides a self-clocking waveform with equal positive and negative values and suitable
for transformer coupling
4.What is DATAC?
Digital Autonomous Terminal Access Communication (DATAC). A carrier sense,
multiple access, collision avoidance two-way data bus concept with an operating
frequency and word structure identical to MIL-STD-1553B data buses but without a bus
controller. Now it is called ARINC629.
5.What is distributed architecture?
It has multiple processors throughout the aircraft that are designed for computing takes on
a real-time basis as a function of mission phase and/or system status. Data Processing is
performed in the sensors and actuators.
6.In Which Data Bus Dynamic bus – control acceptance is used and why?
Dynamic bus – control acceptance is used in MIL-STD-1553B. The operation of a data
bus system in which designated terminals is offered control of the data bus (The bus
controller gives permission to another terminal for act as a Bus Controller).
7.What are the similarity between ARINC 629 and MIL-STD-1553B?
Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA). Each and every
terminal on the bus transmits the data autonomously without a Bus Controller.
9.What is the difference between Simplex bus and Duplex bus?
In simplex mode, the communication is unidirectional, as on a one way street. Only one
of the two stations on a link can transmit; the other can only receive. Keyboards and
traditional monitors are both examples of simplex devices. The keyboard can only
introduce input; the monitor can only accept output. In half duplex mode, each station can
both transmit and receive, but not at the same time. When one device is sending, the other
can only receive, and vice versa. Walkie-talkies and
CB (citizen
-duplex systems.
10. What are the couplings methods used in MIL-STD-1553B and write the difference between
them?
1. Transformer Coupling
2. Direct Coupling
Differences The primary difference between the two beings that the transformer coupled
method uses an isolation transformer for connecting the stub cable to the main bus cable. In
the direct-coupled method, the resistors are typically located within the terminal, whereas in
the transformer-coupled method, the resistors are typically located with the coupling
transformer in boxes called data bus couplers. Another difference between the two coupling
methods is the length of the stub. For the direct-coupled method, the stub length is limited to
a maximum of one foot. For the transformer-coupled method, the stub can be up to a
maximum of twenty feet long.
11.What are the disadvantages of MIL-STD-1533B Data bus?
Certification is a biggest problem present in MIL-STD-1533B.Single point failure in
1553B leads to certificability problem in civil aircraft and Addition of remote terminal
requires changes in BC software which requires frequent certification standard
12.What is centralized architecture?
A system design characterized by signal conditioning and computations are taking place
in one computer or several very tightly coupled computers in (usually) one line
replaceable unit located in the avionics bay, with signals transmitted over one-way data
bus.
13.What is Time division Multiplexing Access?
TDM enables information from several signal channels to be transmitted through one
communication system by staggering the different channel samples in time to form a
composite pulse train. Each signal channel is transmitted as a serial digital pulse train at a
given time slot in a clock cycle. Thus given the clock time information and the address of
the signal (suitably pulse coded), the receiver can then decode and distribute the
individual signals. Hence if there are, say, 30 different signals to be transmitted between
two units, only two wires are required in principle when the data is multiplexed compared
with 60 wires.
14. Briefly explain the evaluation Avionics Systems Architecture. First Generation Architecture
(1940 –1950
Disjoint or Independent Architecture ( MiG-21)
Centralized Architecture (F-111)
Second Generation Architecture (1960 –1970
Federated Architecture (F-16 A/B)
Distributed Architecture (DAIS)
Hierarchical Architecture (F-16 C/D, EAP)
Third Generation Architecture (1980 –1990
Pave Pillar Architecture ( F-22)
Fourth Generation Architecture (Post 2005)
Pave Pace Architecture- JSF
Open System Architecture
15.. What is protocol?
Protocol is a set of formal rules and conventions governing the control of interaction
2. High-level protocol
It deals with the data formatting, including the syntax of messages and its format.
16. What is the function of instrumentation bit?
The instrumentation bit, in position 10, always shall be set to a logical 0 to allow
distinction of a status word from a command word. (In a command word bit 10 is always
set to a logical 1 if the instrumentation bit is being used.)
17. Explain Manchester-II-bi-phase encoding?
A bi-phase method of encoding binary digits. A binary 1 begins with a positive voltage
and swings negative at mid-bit. A binary O begins with a negative voltage and swings
positive at mid-bit.
18. What is the function of mode code „00000
Dynamic Bus Control. Dynamic bus – control is used in MIL-STD-1553B. The operation
of a data bus system in which designated terminals is offered control of the data bus. (The
bus controller gives permission to another t erminal for act as a Bus Controller).
19. Why MIL-STD 1553 is not used in civil aircrafts?
Getting certification for civil aircraft is very difficult comparing to military aircraft.
Single point failure in 1553B leads to certificability problem in civil aircraft. Addition of
remote terminal requires changes in BC software which requires frequent certification.
20. What are the disadvantages of Centralized architecture?
1. Vulnerability – „all the eggs in one basket
computer affected all the subsystems sharing its computing facilities.
2. Inflexibility – changes in an individual sub – system could involve changes in the main
computer software with possible ramifications and „knock on
sub – systems sharing the computing facility.
3. Cost and weight of redundant central computer configurations was unacceptable.
21. What are the functions of Mode codes in MIL-STD1553B data bus?
Mode codes are used only to communicate with the bus hardware and to manage
information flow, not to transfer data.
22. Differentiate between MIL and ARINC 429 standard in terms of RT?
MIL-STD-1553B
All the remote terminals can able to transmit and receive the data
Maximum no of remote terminals is 31
ARINC
All the remote terminals can only receive the data
Maximum no of remote terminals is 20
23. What is the function of status word in MIL-STD-1553B?
The status words are used to give information about the status of the subsystems
. 24. What is the function of Source destination Identifier (SDI) bit in ARINC429?
ARINC429 is a Simplex Data Bus using only one transmitter and up to 20 data receivers.
•
To identify which source in the multisystem is transmitting the data
•
To direct which sink in the multisystem should recognize the data
25. Explain briefly magnetic bubble type memories.
Ans:- Magnetic bubble type memory is a solid state device having high
reliability, small size, light weight, ruggedness and limited power
dissipation. It is a static device. It has no rotary parts. It has very high
storage capacity in compact space. It is a non-volatile semi-random access
type memory. It possesses the property of non-destructive read-out, which
means that the read operation does not alter the stored information. It
stores the data in magnetic bubbles created in a thin film of magnetic
26. Differentiate between semiconductor and magnetic memories.
Ans:- Semiconductor memories are used as the main memory of a computer.
They are faster, smaller, and lighter and consume less power. Magnetic
memories are used as the secondary memories of a computer for bulk
storage of data and information. They are slower, but cheaper than
semiconductor memories.
27. What is the need for Manchester II bi-phase encoding?
Ans: - In MIL-STD 1553 data bus, all words are constructed using
Manchester coding. A logical 1 begins +ve and transitions to -ve at mid-bit
and a logical 0 begins –ve and transitions to +ve at mid-bit. Manchester
coding is chosen since it is compatible with transformer coupling and is self
clocking.
28. Differentiate between Disjoint and Centralized Architectures.
Ans:- In disjoint architecture, the system was integrated by the air-crew who
had to look at various dials and displays connected to disjoint sensors,
correlate the data provided by them, apply error corrections, orchestrate the
functions of the sensors and perform mode and failure management in
addition to flying the aircraft. In centralized architecture, a central computer
was added to integrate the information from the sensors and subsystems.
Data is transmitted from the systems to the central computer and the data
conversion takes place at the central computer.
29. What are the three types of terminals in MIL-STD 1553 data bus?
Ans:- The three terminals in MIL-STD 155
3 data bus are Bus Controller, Remote Terminal and Bus monitor.The bus
controller is responsible for directing the flow of data on the bus.It initiates
all information transfers. Bus controller also monitors the status of the
system. A bus monitor receives and stores selected bus traffic. It will not
respond to any traffic received, unless the traffic is specifically addressed to
it. They are generally used to receive and extract data for off-line purposes
such as flight test, maintenance or mission analysis. Remote terminals (RTs)
are the largest fraction of units in a 1553 bus system. Because of the 5-bit
address field, there can be only upto 31 RTs on a given bus.
RTs respond only to valid commands specifically addressed to them or to
valid broadcast commands.(all RTs simultaneously addressed)
30. What are the two coupling methods used in MIL-STD 1553 data bus?
Ans:- Figure shows the two methods, the primary difference between the two
for connecting the stub cable to the main bus cable. In both methods, two
isolation resistors are placed in series with the bus. In the direct coupled
method, the resistors are typically located within the terminal, where as in
the transformer coupled method, the resistors are typically located with the
coupling transformer in boxes called data bus couplers. Another difference
between the two coupling methods is the length of the stub. For the direct
coupled method, the stub length is limited to a maximum of 1 ft. For the
transformer coupled method, the stub can be up to a maximum length of 20
ft.
31. Differentiate between command word and status word.
Ans:- A command word is always the first word in a message and is
transmitted only by the bus controller. Following the synchronization code,
which is a + 112 bit times followed by a -112 bit times, there are 5 address
bits. Every RT must have a unique address. The transmit/receive bit is set
to logical 0 if the RT is to receive and to logical 1 if the RT is to transmit. The
next 5 bits(10-14) are used to designate a subaddress to the RT or use of
mode codes to the equipment on the bus. If bits 10 through 14 are
subaddresses, bits 15 through 19 are the data word count. f bits 10 through
14 are either 00000 or 11111, bits 15 through 19 are mode codes. Bit 20 is
parity bit. A status word is always the first word in a response by a remote
terminal. Bit positions 1 through 3 are the synchronization code that is
identical to that of a command word. Bits 4 through 8 are the address of the
terminal transmitting the status word. Bits 9 through 19 are the RT status
field. If the instrumentation bit in the status word is used, the available
subaddresses are reduced to 15. Bit 20 is parity bit.
32. What is the function of bus controller in MIL-STD 1553 data bus?
Ans:- The bus controller is responsible for directing the flow of data on the
bus. It initiates all information transfers. Bus controller also monitors the
status of the system.
33. What is the function of bus monitor in MIL-STD 1553 data bus?
Ans:- A bus monitor receives and stores selected bus traffic. It will not
respond to any traffic received, unless the traffic is specifically addressed to
it. They are generally used to receive and extract data for off-line purposes
such as flight test, maintenance or mission analysis.
34. What is the need of two different data rates in ARINC 429?
Ans:- Two different data rates are used in ARINC-429. They are 12-14.5
is used for general-purpose, low criticality applications. High speed bus is
used for transmitting large quantities of data or flight critical information.
35. Differentiate between Manchester encoding and bipolar-RZ encoding.
Which encoding format is used in ARINC-429?
Ans:- In Manchester coding, a logical 1 begins +ve and transitions to -ve at
mid-bit and a logical 0 begins –ve and transitions to +ve at mid-bit. In
bipolar return-to-zero encoding format, the voltage levels are used for
representing logic 1 and 0 as shown in the figure.
36. What are the five primary fields in ARINC 429 word format?
Ans:- ARINC-429 word format includes five primary fields, namely Parity,
SSM, Data, SDI, and Label.
Parity:- The MSB is always the parity bit for ARINC 429. Parity is normally
set to odd except for certain tests.
SSM:- Bits 31 and 30 contain the Sign/Status Matrix or SSM. This field
contains hardware equipment condition, operational mode, or validity of
data content.
Data:- Bits 29 through 11 contain the data, which may be in a number of
different formats such as BCD, BNR etc.
SDI:- Bits 10 and 9 provide a Source/Destination Identifier or SDI. This is
used for multiple receivers to identify the receiver for which the data is
destined.
Label:- The label is an important part of the message. It is used to determine
the data type of the remainder of the word. All BCD and BNR data words
have a five- character label assigned in 429.
37. How is ARINC-629 different from MIL-STD 1553?
Ans:- ARINC-629 uses word formats that are very similar to those in MILSTD- 1553, but it does not have a bus controller. Instead, ARINC-629 gives
each terminal autonomous access to the bus based upon meeting three
timing conditions stored in a Transmit Personality programmable read-only
memory, or PROM (XPP) in the host terminal. One of these timing conditions
is unique to the terminal. Another difference from MIL-STD-1553 is the use
of a Receive Personality PROM (RPP) to identify the labels of messages to be
recorded from the bus.
38. Why we need different standards for military and civil aircraft data
buses?
Ans:- Once the equipments are standardized, equipments are easily
Also safety measure is different for military and civil aircrafts. So we need
different standards for military and civil aircrafts. Standardization of
equipments are based on the document Military Standard (MIL-STD) and
Aeronautical Radio Inc. (ARINC) specifications and Reports.
39. What are the functions of Terminal controller in ARINC-629?
Ans:- Terminal controller provides Protocol Function and Data Validation. It
acts as Subsystem/SIM Interface. It converts subsystem data to Manchester
for SIM and decode Manchester data from SIM for subsystem. It also
provides message and word sync pulses. It provides inter-word string gaps.
40. What are the functions of Serial Interface Module (SIM)?
Ans:- Convert between Manchester < ----- > Doublets Transmit /Receive
Doublets to/from Coupler Power Management
- Apply /remove/reverse power
- Over current detection and shutdown
Fault Monitoring and Management
- Checks its own output waveform
- Checks received waveform - Causes/verifies coupler channel switching Inhibits coupler transmission, if necessary - Outputs fault information to
Terminal Controller
41. What are the functions of current mode coupler in ARINC-629?
Ans:- Provides Non-intrusive connection to the Bus
Transmits/Receives Doublets onto/from the Bus
Provides Low Impedance to Bus under all conditions
Decodes SIM Doublet Polarity for Channel selection
Provides appropriate Receive Doublet Polarity for SIM
Shuts Down Transmitters on Power Reversal
42. Differentiate between Basic protocol and combined protocol.
Ans:- Basic Protocol (BP)
- Periodic Mode or Aperiodic Mode
It provides an equal priority access for each terminal to transmit either
periodic or aperiodic data. If no bus overload exists and transmission
lengths are constant, terminals transmit at a constant interval (Periodic
Mode). If the bus is overloaded, it will automatically switch to an aperiodic
mode with no loss of data Combined Protocol (CP)
- Periodic and Aperiodic Mode
- Allows Prioritized Data
levels of lower priority access for Aperiodic data transmission (Levels 2 & 3).
At each level all terminals are given equal opportunity to access the bus. It
allows substantial levels of aperiodic data to be transmitted without risk of
affecting the frequency of periodic
transmission.
43. The unique feature of ARINC 629 is that access to the bus to transmit by
a given terminal is based on meeting three timing conditions. What are
they?
Ans:- The three timing conditions are Transmit Interval (TI), Terminal Gap
(TG) and Synchronization Gap (SG).
Transmit Interval (TI) is a global Bus Parameter. For a particular terminal,
TI begins the moment the terminal starts transmitting. Once it has
transmitted, it must wait the length of time specified by the TI before it can
transmit again (0.5 to 64 ms).Terminal Gap(TG) is an unique timer assigned
to each terminal on the Bus. TG begins only after the SG has elapsed and
only if no carrier is present. TG and SG cannot overlap in time, they must
run consecutively(4 to 128 µs). Synchronization Gap(SG) is a global access
parameter. SG is the second longest timer and is set to the same value in all
terminals. SG starts the moment the bus is quiet, it is reset if a carrier
appears on the bus before it has elapsed.
44. Explain Synchronization gap.
Ans:- The unique feature of ARINC 629 is that access to the bus to transmit
by a given terminal is based on meeting three timing conditions. They are
Transmit Interval (TI), Terminal Gap (TG) and Synchronization Gap (SG).
Synchronization Gap is a Global Access Parameter. It is the second longest
timer and is set to the same value in all terminals. SG starts the moment
the bus is quiet, it is reset if a carrier appears on the bus before it has
elapsed.
45. What do you mean by CID(Source channel identification)?
Ans:- In ARINC-629, messages are composed of a series of word strings. The
first word of any word string is the label word with its unique
synchronization pattern followed by the Source channel identification (CID),
the word string label and the parity bit. CID is used to identify a unique
unit when there are two or more identical, redundant units on the same bus
such as triple redundant inertial reference units
Unit-IV
DISPLAYS AND INTERFACES
1. What is a function of combiner in HUD?
The optical element of the HUD through which the pilot views the outside world and which
combines the collimated display image with the outside world scene is called combiner
2. What is instantaneous field of View?
The angular coverage of the imagery which can be seen by the observer at any specific
instant is called instantaneous field of View.
3. What is Total field of view?
The total angular coverage of the display imagery which can be seen by moving the
observer
4. What are the limitations of single element beam combiner HUDs?
Transmission of the outside scene is higher in a single-element combiner than in a three –
element combiner.
5. What are the advantages of three element beam combiner HUDs?
A three element combiner design is used on some high performance aircraft to achieve
better producibility, simpler overall HUD design, freedom from secondary reflections and
large field of view
6. What are the advantages of HUDs?
A HUD basically projects a collimated display in the pilots head up forward line of sight so
that he can view both the display information and the outside world scene at the same time.
There is no parallax errors and aiming symbols for either a flight path director, or for weapon
aiming in the case of a combat aircraft, remain overlaid on a distant „target
the pilot
1. Increased safety in landing the aircraft in conditions of severe wind shear
2. To display automatic landing guidance to enable the pilot to land the aircraft safely in
conditions of very low visibility due to fog, as a back up and monitor for the automatic
landing system.
7. Explain Label word
Ans:- Label word is characterized by a synchronization pattern that
starts in a high state and transitions to a low state in the middle of the
second bit time. All other words follow the reverse pattern; thus the
synchronization pattern alone is sufficient to identify a label word. For
label words, the 16 bits between the synchronization pattern and the
parity bit are designated as label bits (LBs). Label bits are numbered in
reverse order from the basic word bit positions
8. Explain briefly about Light Emitting Diode (LED).
Ans: - An LED is a solid- state device comprising a forward –biased p-n
junction transistor formed from a slice or chip of gallium arsenide
phosphate (GaAsP) mounted into a transparent covering. When the
current flows through the chip it emits light which is in direct proportion
to the current flow. Light emission in different colors of spectrum can be
obtained by varying the proportions of the elements comprising the chip,
and can also be obtained by using the technique called doping with other
elements, e.g. Nitrogen.
9. What do you know about Liquid Crystal Display (LCD)?
Ans: - LCD consists of two glass plates coated on their inner surfaces
oxide. The material on the front plate is etched to form the seven
segments, each of which forms an electrode. A mirror image is also
etched into the oxide coating of the back glass plate. The space between
the plates is filled with a liquid crystal compound, and the complete
assembly is hermitically sealed with a special thermoplastic material to
prevent contamination.
10. Explain the working of HUD.
Ans: - A head-up display (HUD) is one in which vital in-flight data are
presented at the same level as a pilot’s line of sight when he is viewing
external references ahead of the aircraft. The principle adopted in a HUD
system is to display the required data on the face of a CRT and to project
them through a collimating lens as a symbolic image on to a transparent
reflector plate, such that the image is superimposed on a pilot’s normal
view, through the window screen, of the terrain ahead. The display is a
combined alphanumeric and symbolic one, and since it is focused at infinity
it permits simultaneous scanning of the ‘outside world’ and display without
refocusing the eyes.
11. What are the properties of a Combiner? How it is constructed?
Ans: The combiner is a mirror with several unusual properties: The reflective
coating is highly wavelength selective, centered on the wavelength of the
emission from the CRT phosphor and clear to other wavelengths, and the
coating is also highly selective in angle of incidence so that only that light
impinging within a very narrow range of angles will be reflected. Combiners
are constructed photographically by exposing a film of dichromated gelatin
to crossed laser beams and then developing the resulting diffraction pattern
image. Since the gelatin is organic, it must be protected from the
environment, especially from high temperatures.
12. Designing an HMD requires careful consideration of two factors. What
are they?
Ans: Two factors are:- Weight and Helmet aerodynamics. During high
vertical acceleration maneuvers such as tight turns and ejection from the
aircraft, the helmet can become a very heavy object, which leads to the
mandate to design absolutely minimum-weight helmet mounted optics.
Immediately following ejection, the helmet is exposed to a high-speed airflow
which can generate substantial lift when flowing over a properly shaped
object. Thus, the designer must ensure that the helmet is poorly designed
any lift and thereby suddenly pull on the pilot’s neck immediately following
ejection.
13. How multifunction keyboards can be designed using LEDs?
Ans: Designs using LEDs have arrays of standard-sized push button
switches with legends built into the surface of the switches. These legends
are generated by small arrays of matrix addressable LEDs in the switch
cover. Color can be used if desired. The legends are changed by the user or
automatically by the aircraft as the mission
phase changes.
14. How multifunction keyboards can be designed using LCDs?
Ans: For MFKs designed using LCDs, the panel is usually a continuous
smooth surface with the individual switch function and area established by
the matrix addressed LCDs. Since LCDs have a graphics capability, it is also
possible to enter a numerical value by pressing the surface of an LCD panel
in the area where a portion of a curve is displayed rather than entering a
numerical value by using a keyboard.
15. Explain multifunction displays.
Ans: In multifunction displays, CRT displays serve as MFKs. The most
common way is for the CRT face to contain function labels correlated with
adjacent switches mounted in the bezel surrounding the CRT. It is easy
through software to change the switch function and the associated label on
the CRT. The second method of implementing MFKs on CRTs is to overlay
the CRT face with a touch-sensitive screen. The CRT face contains various
switch function legends and the corresponding function is selected by
touching that portion of the screen over the switch label.
16. Explain DVI concept in cockpit.
Ans: - Speech recognition systems are capable of performing non-critical
tasks such as requesting system status, tuning radios, and requesting maps
to be displayed on a CRT. The most important figure of merit in a speech
recognition system is the fraction of correct word recognitions. When a word
is spoken, there are three possible responses by the system: correct
recognition, confusion with a rhyming word and rejection. Most systems can
achieve correct recognition rates in the mid-90 percent in the case of a pilot
experienced in interacting with a speech recognition system in a benign
flight environment. As acceleration increases, the recognition rate decreases
to less than 80% for a 9-g load on the pilot. Another important consideration
individually, with a pause between successive words.
17. Explain voice synthesis systems.
Ans: - The preferred use of voice synthesis systems is during high-work load
periods. Messages should be brief and in a telegraphic format. Messages
should be restricted to conditions that (1) require immediate corrective
action or have an immediate impact on the safety of flight or (2) will soon
reach this condition if not corrected by the pilot. These messages should be
preceded by a warning tone and have a concurrent visual display. Voice
synthesis systems must include logic in the central processor that will
resolve conflicts between nearly simultaneously received messages to be
converted into synthetic voice. This resolution is generally achieved by a first
in first out protocol.
18. Explain Head Level displays?
Ans: An HLD avoids the physiological limitation on eye refocusing time by
placing directly below the HUD or top edge of the instrument panel a display
in which an image and supplemental alphanumeric information are focused
at a long distance. Thus, the need for the pilot to refocus his or her eyes to
scan at least some information inside the cockpit is eliminated. Typically the
HLD will contain a radar or infrared image of the outside scene. An HLD
uses a high-intensity lamp coupled with dichroic filters to sort the white
light into red, green and blue and with optics to collimate and fold the light.
The red and green bands are each modulated by liquid crystal shutters in
which each pixel is either opaque or transparent as required to generate a
color image
Part-B
1. Compare the different avionics system architectures and bring out their merits and demerits.
Centralized Architecture
 Simple design
 Software can be written easily
 Computers are located in readily accessible bay
Disadvantages
 Requirement of long data buses
 Low flexibility in software
 Increased vulnerability to change
 Different conversion techniques are needed at the central computer
Federated Architecture
2.With neat-sketch Explain about the Pave-Pillar Architecture
 Increased Information Fusion
 Higher levels and complexity of software
 Standardization for maintenance simplification Lower costs
 Backward and growth capability while making use of emerging technology – VHSIC, Voice
 Provides capability for rapid flow of data in, through and from the system as well as between
and within the system
 Higher levels of avionics integration and resource sharing of sensor and computational
capabilities
 Pilot plays the role of a WEAPON SYSTEM MANAGER as opposed to subsystem
operator/information integrator
 Able to sustain operations with minimal support, fly successful mission day and night in any
type of weather
 Face a numerically and technologically advanced enemy aircraft and defensive systems
Advantages
 Component reliability gains
 Use of redundancy and resource sharing
 Application of fault tolerance
 Reduction of maintenance test and repair time
 Increasing crew station automation
 Enhancing stealth operation
 Wide use of common modules (HW & SW))
 Ability to perform in-aircraft test and maintenance of avionics
 Use of VHSIC technology and Capability to operate over extended periods of time at austere,
deployed locations and be maintainable without the Avionics Intermediate Shop
3. a) Compare
and Contrast the
characteristics of
MIL-STD1553B,
ARINC429 and
ARINC629.
S.No
1.
Characteristics
MIL-STD1553B
ARINC 429
Data Rate
1Mbps
2.
3.
4.
Word length
Low speed (12.5 2 Mbps
kbps) High
Speed (100
kbps)
32 bits
20 bits
32 data words
Simplex
Half duplex
5.
20 bits
Message length
Transmission
Half duplex
mode
Operation
Asynchronous
Encoding
Manchester Bi
Phase
7.
Protocol
8.
Transmission
Media
Coupling
5.
9.
10
Maximum no
terminals
connected on the
bus
ARINC 629
Asynchronous
Bi polar return
to zero
Asynchronous
Manchester Bi
Phase
Command/Resp
onse
Twisted Pair
cable
Transformer and
Direct coupling
Point-to-point
CSMA/CA
Twisted Pair
cable
Direct coupling
31
20
Twisted Pair
cable
Current mode
coupling (
Similar to
transformer
coupling)
120
Advantages
 Contrast to analog avionics – DDP provide precise solutions over long range of flight , weapon and
sensor conditions
 Sharing of Resources
 Use of TDMA saves hundreds of pounds of wiring
 Standardization of protocol makes the interchangeability of equipments easier
 Allows Independent system design and optimization of major systems
 Changes in system software and hardware are easy to make
 Fault containment – Failure is not propagated
3. Explain the word formats of ARINC 629
Label Word
System Status Word
Function Status
. Parameter Validity Word
. . Explain the function of various timers in ARINC 629
. CSMA/CA is achieved by use of three timers
 Transmit Interval (TI)
 Terminal gap (TG)
 Synchronization gap (SG)
Transmit Interval (TI)
 This timer is same for all terminals
 The timer starts every time the terminal starts transmitting
a terminal has transmitted, it must wait the length of time specified by the TI before it can transmit again
Terminal Gap (TG)
 Unique Timer assigned to each terminal on the Bus. It is used to differentiate between terminals since
timer is unique. Thus timer starts only after the SG has elapsed and only if no carrier is present (for
collision avoidance). This timer is reset by the presence of carrier.
Synchronization Gap (SG) This timer is same for all terminals. It starts the moment the bus is quiet. It is
reset if a carrier appears on the bus before it has elapsed (CARRIER SENSING). Once the timer has
elapsed, it cannot be reset by the presence of a carrier. It can only be reset, when that terminal begins
transmitting. Terminal Access Flow Chart
Disadvantages
 Wastage of resources
 It is based on the TREE Topology
Advantages
 Critical functions are placed in a separate bus and Non-Critical functions are placed in another bus
 Failure in non – critical parts of networks do not generate hazards to the critical parts of network
 The communication between the subsystems of a particular group are confined to their particular group
 The overload of data in the main bus is reduced
1. With neat sketch explain the operation of single element combiner and double element combiner HUD
also give its advantages and disadvantages?
Tree element combiner HUD
 It is used in high performance aircrafts
 Simpler overall HUD design
 Freedom from secondary reflections
 Large field of view.
Part-A
Unit-V
1. Explain Weather radar.
Ans: • Installed in all civil airliners & in many general aviation aircraft
• To detect water droplets and provide warning of storms, cloud turbulence and
severe precipitation-aircraft can alter course and avoid such turbulent conditions
• It should be noted that in severe turbulence, the violence of the vertical gusts can
subject the aircraft structure to very high loads and stresses
• These radars can also generally operate in ground mapping and terrain avoidance
modes.
• In the airborne interception mode, the radar, must be able to detect aircraft upto
100 miles away and track while scanning and keeping tabs on several aircraft
simultaneously (typically at least 12 aircraft)
• The radar must also have a 'look down' capability and be able to track low flying
bands. The main role of electronic warfare is to search these radio-frequency bands
in order to gather information that can be used by intelligence analysts or by frontline operators. The information gained may be put to immediate effect to gain a
tactical
advantage on the battlefield; it may be used to picture the strategic scenario in
peace time, in transition to war, or during a conflict. It may also be used to devise
countermeasures to avoid a direct threat or to deny communications to an enemy.
The cycle of intelligence begins with a requirement to gather information on a
particular scenario. Intelligence is collected from a number of different sources to
form a strategic picture.
3. Explain the need of accurate navigation.
Ans:Effective operation of any a/c Automatic because of speed
Density of air traffic on major air routes to fly in a specified corridor defined by ATC
authorities - high accuracy NAV is essential & forms part of FMS
For military operation - to enable the a/c to fly low & take advantage of terrain
screening from enemy radar
Use of weapon - released from several Kms away from target also requires an
accurate knowledge of the a/c position in order to indicate the mid course inertial
guidance of the missile.
4. Describe the various dead reckoning navigation systems used in aircraft.
Ans:- DR navigation systems used in aircraft are
Air data/heading reference system - lower accuracy
Doppler/heading reference systems - widely used in helicopters
Inertial Navigation systems - most accurate and widely used systems
Doppler/Inertial navigation system - combination
5. Explain radio navigation systems
Ans:- Two types of radio navigation systems are position fixing systems and
hyperbolic radio navigation systems
POSITION FIXING SYSTEMS
Range and bearing (R/q) radio navigation aids VOR/DME
TACAN- Accuracy of 1-2 miles
HYPERBOLIC RADIO NAVIGATION SYSTEMS
LORAN C - positional accuracy of around 150 m 8 LORAN C chains comprising 34
6. Explain the various communication systems used in aircraft.
Ans:- High-frequency (HF) communications;
Very high-frequency (VHF) communications;
Ultrahigh-frequency (UHF) communications;
Satellite communications (SATCOM);
Data links.
7. Differentiate between HF and VHF communication systems.
Ans:- High frequency (HF) covers the communications band between 3 and 30 MHz
and is a very common communications means for land, sea and air. The utilized
band is HF SSB/AM over the frequency range 2.000–29.999 MHz using a 1 kHz
(0.001 MHz) channel spacing. The primary advantage of HF communications is that
this
system offers communication beyond the line of sight. The VHF band for
aeronautical applications operates in the frequency range 118.000– 135.975 MHz
with channel spacing in past decades of 25 kHz (0.025 MHz). In recent
years, to overcome frequency congestion and taking advantage of digital radio
technology, channel spacing has been reduced to 8.33 kHz (0.00833 MHz) which
permits 3 times more radio channels in the available spectrum. VHF signals will
only propagate over line of sight. That is, the signal will only be detected by the
receiver when it has line of sight or can ‘see’ the transmitter. This line-of-sight
property is affected by the relative heights of the radio tower and aircraft.
8. Explain satellite communication systems.
Ans:- Satellite communications provide a more reliable method of communications
using the International Maritime Satellite Organization (INMARSAT) satellite
constellation. The aircraft communicates via the INMARSAT constellation and
remote ground earth station by means of C-band uplinks and downlinks to/from
the ground stations and L-band links to/from the aircraft. In this way,
communications are routed from the aircraft via the satellite to the ground station
and on to the destination. Conversely, communications to the aircraft are routed in
the reverse fashion. The airborne SATCOM terminal transmits on frequencies in the
range 1626.5– 1660.5 MHz and receives messages on frequencies in the range
1530.0– 1559.0 MHz. The coverage offered by the INMARSAT constellation was a
total of four satellites in 2001. Further satellites are planned to be launched in the
near future. The INMARSAT satellites are placed in earth geostationary orbit above
9. Describe data links.
Ans:- Many of the data links are limited to line-of-sight operation owing to the
transmission characteristics of the RF frequencies being employed. However, the use
of communications satellites to perform a relay function permits transmission of
data over the horizon (OTH), thereby enabling intra- and inter-theatre
communications.
Typical data packages that may be delivered by data links include:
Present position reporting;
Surveillance;
Aircraft survival, EW and intelligence information;
Information management; Mission management; Status.
The primary data links used for communications between airborne platforms and
space and surface platforms areLink-16 - This is the most commonly used avionics data link and is usually
manifested in avionics systems as the joint tactical information distribution system
(JTIDS).
Link-11 - a data link commonly used by naval forces.
16 marks:
1)Discuss the bus protocol in MIL-STD 1553B and the word formats. (16)
Hint:- Bus protocol in MIL-STD-1553 includes message formats and word structure.
Important message formats include BC-RT transfer, RT-BC transfer and RT-RT
transfer.
Three word formats include command word, status word and data word. Explain
each of
them as given in note
10. (i) Explain ARINC-629 protocols (8)
Hint:- There are two ARINC-629 protocols. They are basic and combined. Explain
each briefly as given in note
(ii)Explain ARINC-429 word format (8)
Hint:- ARINC-429 word format includes five primary fields, namely Parity, SSM,
Data, SDI, and Label.
Data, SDI, and Label. Bits 31 and 30 contain the Sign/Status Matrix or SSM. This
field contains hardware equipment condition, operational mode, or validity of data
content.
(ii) Discuss the communication systems used in aircrafts. (8)
Hint:- Various communication systems used in aircrafts include HF, VHF,
UHF,SATCOM, Data links etc.
12. What are the advantages of Inertial Navigation Systems?
It is completely self-contained navigation system.
. High accuracy
. It doesn
13What is electronic warfare?
Electronic Warfare encompasses all actions involving the use of electromagnetic energy to
DETERMINE, EXPLOIT, REDUCE Or PREVENT HOSTILE USE OF ELECTROMAGNETIC
SPECTRUM and actions which RETAIN FRIENDLY USE of the electromagnetic Spectrum
. 14. What is data fusion?
It is the name given to the process of combining data from number of different sources to provide
information which is not present in the individual sources
. 15. What are the different types of communication systems in Aircraft?
High-frequency (HF) communications; 2. Very high-frequency (VHF) communications; 3. Ultrahighfrequency (UHF) communications; 4. Satellite communications (SATCOM); 5. Data links
. 16. What are the various classification of Navigation system?.
1. Navigation by Pilotage
2. Celestial Navigation
3. Navigation by Dead-Reckoning
4. Radio Navigation
5. Satellite Navigation
17. Justify the need for certification.
Certification is a critical element in the safety-conscious culture on which civil aviation is based.
The legal purpose of avionics certification is to document a regulatory judgment that a device meets
all applicable regulatory requirements and can be manufactured properly
18. Describe Fly-by-Wire flight control systems?
A flight control system where all the command and control signals are transmitted electrically and the
aerodynamic control surfaces are operated through computers which are supplied with the pilots
command signals and the aircraft state from appropriate motion sensors
19. Explain Electromagnetic Interference.
1. Any electromagnetic energy which interrupts, obstructs, or otherwise degrades or otherwise
degrades or limits the effective performance of telecommunicating (communication-electronic)
equipment.
2. 9. What is navigation?
3. Navigation is an art of finding the position of the vehicle with respect to some reference frame.
10. What is Celestial Navigation? Celestial Navigation is accomplished by measuring the
angular position of celestial bodies. Almanacs giving the position of celestial bodies at various
times are readily available. The navigator measures the elevation of the celestial body with a
sextant and notes the precise time at which the measurement is made with a chronometer.
These two measurements are enough to fix the position of the vehicle on a circle on the face of
the globe. 11. What is dead-reckoning Navigation? In this method of navigation, the position of
electromagnetic waves to find the position of the craft. All the systems depend upon the
transmitters and receivers at known locations on the earth
receivers working in co junction with them in a vehicle. This type of navigation depends on the
external aids and it is not self contained The positional information may be related to
4.  Measurement of direction
5.  Measurement of distance
6.  Difference of distance between two transmitters
20. What is satellite Navigation?
The satellite navigation system depends on the measurement of the exact distance of the receiver
from the satellite and the locus is the intersection of a spherical surface with the earth (or a
concentric sphere in the case of aircraft flying over the earth). And again the intersection of two or
more loci establishes the position of the receiver. 14. What is the difference between Navigation
and Guidance? A navigation system is one that automatically determines the position of the
vehicle with respect to some reference frame. A guidance system, on the other hand,
automatically makes the necessary correction to keep the vehicle on course by
Part B
Unit-I
1. i) Explain the need for avionics in civil and military aircrafts.
development and introduction of avionics systems
navigator and Flight engineer.
achievement of safe
expenses and training costs.
(Navigator/Observer/Radar-Operator)
1. ii) Explain integrated avionics systems and weapon systems
(i)Explanation
(ii)Diagram
2. i) What are the major design drivers for avionics system?
designing a digital avionics system
development methods in civil and military avionics.
– The customer prepares the statement of need and top-level description of possible missions
– The requirement describes the gross characteristic of a hypothetical aircraft that could fly the
mission
–
The Customer may also describe the mission environment and define strategic and tactical philosophies
and principles and rules of engagement.
Top – level requirements for the successor to the A-10 Aircraft Minimum Goal
2.ii) Describe the various “illities” in avionics systems
Survivability Capability of systems
MIL-STD-2069 Maintainability
MIL-STD-721C Vulnerability
MIL-STD-2069 Accessibility
3. With a neat block diagram explain the integration of different avionics system.
Major avionic systems
„System Integration .
4. i) Explain clearly the top down design procedure that is adopted in Avionics system design
The overall plan must contain the following
1) A detailed milestone chart
2) A synthesis and analysis plan
3) A verification plan
4) Flight safety, Reliability, Vulnerability and Maintainability analyses plans
5) A functional mock up test plan
6) A ground test plan including test procedures
7) A flight test plan including test procedures
6. Explain the Various Typical Avionics
Sub systems.
Displays
pilot crew
Airframe data Warning information
Weapon aiming Threat warnings
Unit-II
1. Explain the operation of digital computers
INPUT/OUTPUT
Central Processing Unit
input/ output devices
control unit.
Arithmetic/ Logic Circuit
MPU.
2.With Neat Sketch explain the architecture of 8085 Microprocessor
The architecture of 8085 includes ALU,
Timing and control unit
, Instruction register and decoder
,
Register array,
Interrupt Control and Serial I/O control. General purpose
.
.
3.Explain the different types of Interrupts and its functions in 8085
Vectored Interrupts
Maskable and Nonmaskable interrupts
1) Hardware Interrupts
2) Software Interrupts
 Non-maskable interrupt
 It has highest priority
 Non Vectored interrupt
b) INTR
 Maskable Interrupt
 Vectored Interrupt
 It has second Highest priority
c) RST 7.5
 Maskable Interrupt
 Vectored Interrupt
 It has second highest priority
d) RST6.5 & 5.5
 Maskable interrupt
 Vectored interrupt
 RST 6.5 has the third priority
 RST 5.5 has the fourth priority
4.Explain the method of Memory Interfacing, and various steps involved in interfacing memory devices
with 8085 microprocessor.
The memory interfacing requires
1. Select the chip
2. Identify the register
3. Enable the appropriate buffer
1) Connect the required address lines of the address bus to the address lines of the memory chip.
2) Decode the remaining address lines of the address bus to generate the chip select signal and
connect the signal to select the chip.
3) Create control signals MEMR and MEMW by combining RD and WR signals with, IO/M,
and use them to enable appropriate buffers.
5. Explain the method of I/O Interfacing, and various steps involved in interfacing I/O devices with
8085 microprocessor.
 Combine the device address pulse with the control signal to generate a device select (I/O
select) pulse that is generated only when both signals are asserted.
 Use the I/O select pulse to activate the interfacing device (I/O port)
 Decode the address bus to generate the device address pulse.
 AND the control signal with the device address pulse to generate the device select pulse
 Use the device select pulse to enable the I/O port.
Unit-III
1.Explain dead-reckoning navigation with one example
Inertial Navigation
Measurement of direction (RDF)
Measurement of Distance (DME)
.
Difference of distance between two transmitters (LORAN, TACAN, etc)
Space segment
Almanac - Coarse time information
Ephemeris – orbital Information
Clock information
C/A code ( available to public)
–
P-code ( reserved for US military purpose)
Control Segment
2.. Explain the various functions involved in Electronic Warfare.
Electronic Warfare encompasses all actions involving the use of electromagnetic energy to
DETERMINE, EXPLOIT, REDUCE Or PREVENT HOSTILE USE OF ELECTROMAGNETIC
SPECTRUM and actions which RETAIN FRIENDLY USE of the electromagnetic Spectrum.
Divisions of Electronic warfare
Signals Intelligence Intelligence is collected from a number of different sources to form a strategic
picture. These sources include:
 Electronic Intelligence
Communication Intelligence
Electronic Intelligence
2. Image Intelligence
3. Photographic intelligence
 The locations of groups of transmitters and the numbers in the groups
 The frequency of the transmitter carrier
 The style of the operator
The relative intensity of messages.
Electronic Support measures (ESM) ESM is that division of EW involving actions taken
to search for, I ntercept, locate and immediately identify radiated electro-magnetic energy
for the purposes of immediate thread recognition and the tactical employment of forces. It
has the following divisions
 Threat warning
Electronic Counter Measures (ECM) Electronic counter measures encompass all actions taken to
introduce signals into an electronic system which degrades the performance of that system so that it is
unable to perform its intended mission. It has the following divisions
 Noise Jamming
Deception Jamming
1. Noise Jamming Injects an interference signal into the enemy
actual signal is completely submerged by the interference. Optimum jamming signal should have the
characteristics of victim receiver noise. Minimum details of victim radar is required. Deception
Jamming The objective is to mask the real signal by injecting a suitably modified replica of the real
signal in to the victim radar system. Deception jamming attempts to jam victim radar both in range and
in angle. Some deception jamming also attempts to jam velocity tracking circuits to prevent cross
checking between Doppler measurements and differentiated range measurement.
Electronic Counter-Counter Measures Electronic Counter-Counter measures all actions taken to
introduce signals into an electronic system which prevents the performance of friendly ECM & ESM
system so that it is able to perform its intended mission. It has the following divisions
 Anti-ESM
Anti-ECM
 Transmitting more average power
 Increasing antenna gain
 Homing longer on the target
– Reducing data rate
– Adaptive scan rate
. 3. Explain Maintenance and Reliability analysis of avionics systems and the various steps followed for
reducing the difficulties involved in avionics system maintenance?
Maintenance t
.Who will be doing the work?
 Skill level of maintenance personnel is a major consideration
 This necessitates a straight forward design which can be easily understood with BITE, procedures and
associated displays
 Experience level of military personnel will be substantially less than those of their civil counterparts
When will it be done?
 Amount of time required for maintenance is one of the factor to be considered
 Reducing this time will yield an equal reduction in sortie turnaround time
 Architecture should be designed to allow the aircraft to be dispatched with an inoperative unit and
repaired during a scheduled maintenance
Where will it be done?
 Maintenance tasks may be performed in Flight line and Maintenance depot.
 Distribution of maintenance tasks between the flight line and the maintenance depot must be established
easy in the design.
The distribution will have a major influence on the design of built-in-test equipment and accessibility to
the LRU
4.Designing for Easy Maintenance
 Use of standard units for design
 Accessibility of LRUs in both flight line and shop
 Each function should be implemented on asingle replaceable unit
 ESD sensitive devices should have protection facilities built in to the LRUs
1. BITE is a powerful maintenance tool that takes advantage of the intrinsic capabilities of digital
avionics. BITE has become used in more LRU
avionics architectures, there has been a trend toward the development of CFDS that display and store
fault data for all BITE equipped LRU
indispensable maintenance needs. BITE should be able to
recognize and correctly identify at least 95% of possible faults. Failure of BITE should also be clearly
indicated. Reliability
 The duration or probability of failure-free performance under stated conditions
 The probability that an item can perform its intended functions for a specified interval under stated
conditions
 Well known method is to use failure prediction methods
 Rate gyroscopes : Rate of rotation about roll, pitch and yaw axes.
 Linear accelerometers : Normal and Lateral acceleration.
 Air data sensors : Height and Airspeed.
 Airstream sensors : Incidence angles in longitudinal and lateral planes.
Features
 Electrical Signal Transmission
.
4.Explain the requirements for Civil Avionics certification?
a) The equipment, systems and installations whose function is required by this subchapter must be designed
to ensure that they perform their intended functions under any foreseeable operating conditions.
b) The airplane systems and associated components, considered separately and in relation to other systems,
must be designed so that
1) The occurrence of any single failure condition which would prevent the continued safe flight and landing
of the airplane is extremely improbable, and
2) The occurrence of any data failure condition which would reduce the capability of the airplane or the
ability of the crew to cope with adverse operating conditions is improbable.
c) Warning information must be provided to alert the crew to unsafe system operating conditions and to
enable them to take appropriate corrective action. Systems, controls and associated monitoring and warning
means must be designated to minimize crew errors which would create additional hazards.
d) Compliance with the requirements of paragraph (b) of this section must be shown by analysis and where
necessary, by appropriate ground, flight, or simulator tests. The analysis must consider
1) Possible mode of failure, including malfunctions and damage from external sources.
2) The probability of multiple failures and undetected failures.
3) The resulting effects on the airplane and occupants, considering the stage of flight and operating
conditions, and
4) The crew warning cues, corrective action required, and the capability of detecting fault
Unit-IV
.
1. Compare the different avionics system architectures and bring out their merits and demerits.
Centralized Architecture
 Simple design
 Requirement of long data buses
 Low flexibility in software
 Increased vulnerability to change
 Different conversion techniques are needed at the central computer
Federated Architecture
2.With neat-sketch Explain about the Pave-Pillar Architecture
 Increased Information Fusion
 Higher levels and complexity of software
 Standardization for maintenance simplification Lower costs
 Backward and growth capability while making use of emerging technology – VHSIC, Voice Recognition
/synthesis and Artificial Intelligence
 Provides capability for rapid flow of data in, through and from the system as well as between and within
the system
 Higher levels of avionics integration and resource sharing of sensor and computational capabilities
 Pilot plays the role of a WEAPON SYSTEM MANAGER as opposed to subsystem operator/information
integrator
 Able to sustain operations with minimal support, fly successful mission day and night in any type of
weather
 Face a numerically and technologically advanced enemy aircraft and defensive systems
Advantages
 Component reliability gains
 Use of redundancy and resource sharing
 Application of fault tolerance
 Reduction of maintenance test and repair time
 Increasing crew station automation
 Enhancing stealth operation
 Wide use of common modules (HW & SW))
 Ability to perform in-aircraft test and maintenance of avionics
 Use of VHSIC technology and Capability to operate over extended periods of time at austere, deployed
locations and be maintainable without the Avionics Intermediate Shop
3. a) Compare
and Contrast the
characteristics of
MIL-STD1553B,
ARINC429 and
ARINC629.
S.No
1.
Characteristics
MIL-STD1553B
ARINC 429
Data Rate
1Mbps
2.
3.
4.
Word length
Low speed (12.5 2 Mbps
kbps) High
Speed (100
kbps)
32 bits
20 bits
32 data words
Simplex
Half duplex
5.
5.
20 bits
Message length
Transmission
Half duplex
mode
Operation
Asynchronous
Encoding
Manchester Bi
Phase
Asynchronous
Bi polar return
to zero
ARINC 629
Asynchronous
Manchester Bi
Phase
8.
9.
10
Transmission
Media
Coupling
Twisted Pair
cable
Transformer and
Direct coupling
Twisted Pair
cable
Direct coupling
Maximum no
terminals
connected on the
bus
31
20
Twisted Pair
cable
Current mode
coupling (
Similar to
transformer
coupling)
120
Advantages
 Contrast to analog avionics – DDP provide precise solutions over long range of flight , weapon and sensor
conditions
 Sharing of Resources
 Use of TDMA saves hundreds of pounds of wiring
 Standardization of protocol makes the interchangeability of equipments easier
 Allows Independent system design and optimization of major systems
 Changes in system software and hardware are easy to make
 Fault containment – Failure is not propagated
3.Explain the word formats of ARINC 629
Label Word
System Status Word
Function Status
. Parameter Validity Word
.5. Explain the function of various timers in ARINC 629
. CSMA/CA is achieved by use of three timers
 Transmit Interval (TI)
 Terminal gap (TG)
 Synchronization gap (SG)
Transmit Interval (TI)
 This timer is same for all terminals
 The timer starts every time the terminal starts transmitting
a terminal has transmitted, it must wait the length of time specified by the TI before it can transmit again
Terminal Gap (TG)
 Unique Timer assigned to each terminal on the Bus. It is used to differentiate between terminals since timer is
unique. Thus timer starts only after the SG has elapsed and only if no carrier is present (for collision avoidance).
This timer is reset by the presence of carrier.
Synchronization Gap (SG) This timer is same for all terminals. It starts the moment the bus is quiet. It is reset if
a carrier appears on the bus before it has elapsed (CARRIER SENSING). Once the timer has elapsed, it cannot
be reset by the presence of a carrier. It can only be reset, when that terminal begins transmitting. Terminal Access
Flow Chart
Disadvantages
 Wastage of resources
 It is based on the TREE Topology
Advantages
 Critical functions are placed in a separate bus and Non-Critical functions are placed in another bus
 Failure in non – critical parts of networks do not generate hazards to the critical parts of network
 The communication between the subsystems of a particular group are confined to their particular group
 The overload of data in the main bus is reduced
1. With neat sketch explain the operation of single element combiner and double element combiner HUD also give
its advantages and disadvantages?
Tree element combiner HUD
 It is used in high performance aircrafts
 Simpler overall HUD design
 Freedom from secondary reflections
 Large field of view.
1. Compare the different avionics system architectures and bring out their merits and demerits.
Centralized Architecture
6. . Explain the function of various timers in ARINC 629
. CSMA/CA is achieved by use of three timers
 Transmit Interval (TI)
 Terminal gap (TG)
 Synchronization gap (SG)
Transmit Interval (TI)
 This timer is same for all terminals
 The timer starts every time the terminal starts transmitting
a terminal has transmitted, it must wait the length of time specified by the TI before it can transmit again
Terminal Gap (TG)
 Unique Timer assigned to each terminal on the Bus. It is used to differentiate between terminals since timer is
unique. Thus timer starts only after the SG has elapsed and only if no carrier is present (for collision avoidance).
This timer is reset by the presence of carrier.
Synchronization Gap (SG) This timer is same for all terminals. It starts the moment the bus is quiet. It is reset if
a carrier appears on the bus before it has elapsed (CARRIER SENSING). Once the timer has elapsed, it cannot
be reset by the presence of a carrier. It can only be reset, when that terminal begins transmitting. Terminal Access
Flow Chart
Disadvantages
 Wastage of resources
 It is based on the TREE Topology
Advantages
 Critical functions are placed in a separate bus and Non-Critical functions are placed in another bus
 Failure in non – critical parts of networks do not generate hazards to the critical parts of network
 The communication between the subsystems of a particular group are confined to their particular group
 The overload of data in the main bus is reduced
Unit-V
1. With neat sketch explain the operation of single element combiner and double element combiner HUD also give
its advantages and disadvantages?
Tree element combiner HUD
 It is used in high performance aircrafts
 Simpler overall HUD design
 Freedom from secondary reflections
 Large field of view.
2. Explain dead-reckoning navigation with one example
Inertial Navigation
 Measurement of direction (RDF)
 Measurement of Distance (DME)
 Difference of distance between two transmitters (LORAN, TACAN, etc)
. Space segment
 Ephemeris – orbital Information
 Clock information
– C/A code ( available to public)
– P-code ( reserved for US military purpose)
Control Segment
1. The spherical range of the user from the individual transmitting satellite can be determined by measuring the
time delay for the satellite transmission to reach the user. Multiplying the time delay by the velocity of light
then gives the spherical range ρ of the user from the transmitting satellite. The measurement of the time delay
is thus made up of two components. The first component is the transit time of the ranging signal and the
second component is the offset between the transmitter clock and receiver clock due to the nonsynchronization of the
2. clock. Measuring the spherical ranges from four satellites as shown in fig enables the user
determined and yields four equations containing the four unknowns, viz the three position co-ordinates of the
user and the time bias in the user
d waveforms and
illustrates the user time bias △T, and the time delays △t1, △t2, △t3, △t4 for the signals transmitted from the
satellites to reach the user.
3.
4. The position of user can be find out by solving the below three simultaneous spherical equations. A Cartesian
coordinate is constructed for the mathematical analysis of GPS operation by using earth centre of gravity as
centre of axis system. The orbital position of the satellites satellite1, satellite2 and satellite3 are represented as
(X1, Y1, Z1), (X2, Y2, Z2) and (X3, Y3, Z3). The user position on the earth can be represented as
(Xu,Yu,Zu). Four pseudo ranges , , and to the four satellites satellite1, satellite2, satellite3 and satellite4 can
be determined = C*△t1 = C*
5. Let the range equivalent to the user clock offset, The four spherical ranges,,and can be determined from the
below spherical equations These four equations with four unknowns can thus be solved and yield the users
position coordinates (Xu, Yu, Zu) and the users time offset △T. The satellite clocks are therefore
mathematically synchronized to d defined GPS master time which is maintained at the master control station. n
3. Explain the various functions involved in Electronic Warfare.
1. Electronic Warfare encompasses all actions involving the use of electromagnetic energy to DETERMINE,
EXPLOIT, REDUCE Or PREVENT HOSTILE USE OF ELECTROMAGNETIC SPECTRUM and actions
which RETAIN FRIENDLY USE of the electromagnetic Spectrum.
2. Divisions of Electronic warfare
Signals Intelligence Intelligence is collected from a number of different sources to form a strategic picture. These
sources include:
 Electronic Intelligence
 Communication Intelligence
Electronic Intelligence Confirmation of electronic warfare intelligence is usually performed by comparison with
local information collection and photographic evidence, including
1. Human Intelligence
2. Image Intelligence
3. Photographic intelligence
The human intelligence and image intelligence are often gathered by high-flying EW aircraft on long duration
patrols, usually flying a patrol on the friendly side of a border and beyond missile engagement range. The
photographic intelligence is used to obtain the existence and precise location and types of target. Communication
intelligence
1. Communication intelligence is gathered by scanning the normal communication frequency bands and looking
on to detected transmissions. In peace time it may be possible to receive in clear speech, but this is extremely
unlikely in times of tension or during conflict. Howeve
great deal of intelligence can be obtained from the following characteristics of communications activity.
 The locations of individual transmitters
 The locations of groups of transmitters and the numbers in the groups
 The frequency of the transmitter carrier
 The style of the operator
 The relative intensity of messages.
Electronic Support measures (ESM) ESM is that division of EW involving actions taken to search for, intercept,
locate and immediately identify radiated electro-magnetic energy for the purposes of immediate thread recognition
and the tactical employment of forces. It has the following divisions
 Threat warning
 Homing
 Target Acquisition
Electronic Counter Measures (ECM) Electronic counter measures encompass all actions taken to introduce
signals into an electronic system which degrades the performance of that system so that it is unable to perform its
intended mission. It has the following divisions
 Noise Jamming
 Deception Jamming
2. Noise Jamming Injects an interference signal into the enemy
signal is completely submerged by the interference. Optimum jamming signal should have the characteristics
of victim receiver noise. Minimum details of victim radar is required. Deception Jamming The objective is to
mask the real signal by injecting a suitably modified replica of the real signal in to the victim radar system.
Deception jamming attempts to jam victim radar both in range and in angle. Some deception jamming also
attempts to jam velocity tracking circuits to prevent cross checking between Doppler measurements and
differentiated range measurement.
Electronic Counter-Counter Measures Electronic Counter-Counter measures all actions taken to introduce
signals into an electronic system which prevents the performance of friendly ECM & ESM system so that it is able
to perform its intended mission. It has the following divisions
 Anti-ESM
 Anti-ECM
We know that the performance of the ESM and ECM can be degraded by noise jamming and deceptive jamming
 Increasing antenna gain
 Homing longer on the target
– Reducing data rate
– Adaptive scan rate
 Increase the transmitter frequency to narrow the antenna
blanked by the main lobe noise jamming and also provides a strobe in the direction of the jammer.
The effect of deception jamming is minimized by using the below techniques. The false target return must follow
the return from the jammer carrying target and in any event must lie in the same direction within a radar pulse
repetition interval. To encounter this radar employ leading edge tracker which tracks the target pulse which is
ahead of false target pulse. If the deception jammer uses a delay which is greater than Pulse repetition interval to
generate an anticipatory false target return, then pulse to pulse frequency agility eliminates the false targets and
pulse to pulse PRI jitter identifies the false target returns
. 4. Explain Maintenance and Reliability analysis of avionics systems and the various steps followed for reducing
the difficulties involved in avionics system maintenance?
Maintenance Measure of ability of an item to be retained in or restored to specified condition when maintenance
 This necessitates a straight forward design which can be easily understood with BITE, procedures and associated
displays
 Experience level of military personnel will be substantially less than those of their civil counterparts
When will it be done?
 Amount of time required for maintenance is one of the factor to be considered
 Reducing this time will yield an equal reduction in sortie turnaround time
 Architecture should be designed to allow the aircraft to be dispatched with an inoperative unit and repaired during
a scheduled maintenance
Where will it be done?
 Maintenance tasks may be performed in Flight line and Maintenance depot.
 Distribution of maintenance tasks between the flight line and the maintenance depot must be established easy in
the design.
 The distribution will have a major influence on the design of built-in-test equipment and accessibility to the
LRU
Designing for Easy Maintenance Avionics designed for easy maintenance are major contributors for increasing
the mission effectiveness while reducing operating costs
 Make maintenance manuals, procedures, and equipments easy to use and understand
 Use of standard units for design
 Accessibility of LRUs in both flight line and shop
 Each function should be implemented on a single replaceable unit
 ESD sensitive devices should have protection facilities built in to the LRUs
 No connectors should be on the front of the LRUs according to DOD-STD-1788 and ARINC 600 standard
Testing a good unit is as expensive as testing a bad unit BITE (Built In Test Equipment)
2. BITE is a powerful maintenance tool that takes advantage of the intrinsic capabilities of digital avionics. BITE
has become used in more LRU
there has been a trend toward the development of CFDS that display and store fault data for all BITE equipped
LRU
be able to
recognize and correctly identify at least 95% of possible faults. Failure of BITE should also be clearly indicated.
Reliability
 The duration or probability of failure-free performance under stated conditions
 The probability that an item can perform its intended functions for a specified interval under stated conditions
 Well known methodis to use failure prediction methods
1. n Equip =
i
Gi
i-1 Where λEquip = total equipment failure rate Gi = generic failure rate for the
generic part type
= quality factor for ith generic part type Ni = quantity of ith generic part type n = number
of different generic part types 5. Explain the features and benefits of Fly-by-wire flight control system FBW
control has come into use in production aircraft since the late 1970s and can enable a major increase in flight
control capability to be achieved. One of the unique benefits of a FBW control system is the ability to fly
aircraft configurations which have minimal stability margins, or which may be aerodynamically unstable over
part or even the whole of the flight envelope. Higher agility can be achieved with an aerodynamically unstable
compared with a conventional stable configuration, agility being defined as the ability to change the direction
of the aircraft
surfaces on the wings and tail. The controls and flight surfaces are directly connected. Mechanical links are
also used for the engine control. The below fig shows the conventional flight control system configuration.
 Air data sensors : Height and Airspeed.
 Airstream sensors : Incidence angles in longitudinal and lateral planes.
Features
 Electrical Signal Transmission
– Pilot
commanded control surface angles are transmitted electrically.
 Motion Sensor Feedback
1. Failure survival,
.
 Linear accelerometers : Normal and Lateral acceleration.
 Air data sensors : Height and Airspeed.
 Airstream sensors : Incidence angles in longitudinal and lateral planes.
Features
 Electrical Signal Transmission
– Pilot
ntrol surface actuator position signals and
commanded control surface angles are transmitted electrically.
 Motion Sensor Feedback
Failure survival, redundant configuration of motion sensors
Advantages
 Good consistent handling
 Automatic stablisation
5.  Ease of autopilot integration
1.
2.
3.
4.
6. – High Bandwidth manoeuvre command “inner loop” ensures response to outerloop autopilot commands is
fast.
7.  Carefree manoeuvring
8. – Automatically limit pilot
r control limits.
9.  Ability to integrate additional controls automatically
10.  Leading edge slats/flaps and trailing edge flaps are controlled automatically to generate lift
11.  Variable wing sweep
12.  Thrust vector control nozzles and engine thrust
13.  Elimination of mechanical control runs
14. – Bulk, weight and mechanical complexity of control rods are eliminated
15. – Problems of friction, backlash and flexure of the airframe structure can also be overcome
16.  Pilot workload reduction
17. – The fly-by-wire system provides a more usable interface and takes over some computations that previously
would have to be carried out by the pilots.
18.
19. ● Airframe safety
20. – By mediating the control commands, the system can ensure that the pilot cannot put the aircraft into a state
that stresses the airframe or stalls the aircraft.
21.
22. ● Weight reduction
23. – By reducing the mechanical linkages, a significant amount of weight (and hence fuel) is saved.
24.  Small control stick
25. – Location can be a “side arm” or central mounting
26.  Abilityto exploit aerodynamically unstable aircraft configuration.
27.  Aerodynamics Vs Stealth
28. – Reducing the radar cross section
29. – Engine intake design
30. – Extensive use of radar energy absorbing materials
31. Redundancy and Failure Survival
32. 
33.
FBW control system must be no less safe than the simple mechanical control systems which it replaces.
 The safety levels required are specified in terms of probability of a catastrophic failure occuring in the system
from any cause which could result in loss of control of the aircraft.
 Probability of catastrophic failure
 Military < 10-7/hr
 Civil <10-9/hr
 MTBF of a single channel FBW system is in the region of 3000 hours.
1. 6. Explain the requirements for Civil Avionics certification?
2. Certification is the most difficult part for civil avionics designers.
a) The equipment, systems and installations whose function is required by this subchapter must be designed to
ensure that they perform their intended functions under any foreseeable operating conditions.
b) The airplane systems and associated components, considered separately and in relation to other systems, must be
designed so that
1) The occurrence of any single failure condition which would prevent the continued safe flight and landing of the
airplane is extremely improbable, and
2) The occurrence of any data failure condition which would reduce the capability of the airplane or the ability of
the crew to cope with adverse operating conditions is improbable.
c) Warning information must be provided to alert the crew to unsafe system operating conditions and to enable
them to take appropriate corrective action. Systems, controls and associated monitoring and warning means must
be designated to minimize crew errors which would create additional hazards.
d) Compliance with the requirements of paragraph (b) of this section must be shown by analysis and where
necessary, by appropriate ground, flight, or simulator tests. The analysis must consider
1) Possible mode of failure, including malfunctions and damage from external sources.
2) The probability of multiple failures and undetected failures.
3) The resulting effects on the airplane and occupants, considering the stage of flight and operating conditions, and
4) The crew warning cues, corrective action required, and the capability of detecting faults.
1.