Unit3 Avionics Mod

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Unit 3, Digital Avionics ArchitectureAvionics system architectureData buses MILSTD 1553 BARINC 429ARINC 629.1

SyllabusAvionics system architecture Data buses MILSTD 1553 B ARINC 429 ARINC 629.


OSI Model Data unit Host Data layers Layer 7. Application 6. Presentation 5. Session Segment Media Packet layers Frame Bit 4. Transport 3. Network 2. Data Link 1. Physical Function Network process to application Data representation and encryption Interhost communication End-to-end connections and reliability Path determination and logical addressing Physical addressing Media, signal3

Pave Pillar ArchitectureAn Hypothetical Architecture for an high performance Aircraft Which has the following performance requirement 1. Paying attention to take off and landing on flight controls 2. Having Two level maintenance & that has MTBF=70 Hrs & MTTR=1.25 hr 3.High percentage of Fault Detection & Fault Isolation=99 & 98%4

Major Avionic ArchitectureTypes, features and comparison


Scheme of General Avionic Control SystemInputs from Sensor 1.Positional Data 2.Environmental data Sensors 3.Aircraaft State DataACS-Avionic Control System Effector To Displays For Pilot Alerting





Federated Architecture= Dedicated & independent processing and communication system with no Data Sharing eg. Arinc 429 and Saras of NAL Integrated Modular Architecture- A real time computer system with data sharing between Sensors and Effectors integrated to flight control, landing gear, display control. - 1553 A/B eg. Airbus & Arinc 629 (partially IMA & Fed)


Features -Federated1. 2.



Stand-alone independent system with sensors, processing units and Effectors No Data Sharing between sensors, effectors and processing units Each system having own interfaces (CPU, I/O) to sensors and actuators (Effectors) Functions partitioned Eg. ARINC 4298

Federated Architecture Schematic


Components of Federated ArchitectureUser Interface for controlling the Effector 3 CPU-s each CPU for Sensor, Effectors, 5 I/O modules 4 Physical Communication Channel (1.User Interface to Effector, 2. UI to Sensor, 3.Sensor to Effector and 4. a Feedback from Sensor to UI)10

Components of Federated Architecture contd1. 2.

3. 4.

User interface = landing gear, processing unit, display and control Effector Used interface used for controlling the effector based upon feedback collected from a sensor Sensor 3 Units connected by dedicated communication channels.11

Advantages of Federated ArchitectureEach Function has its own fault tolerant computer and each box has a specific function, with specifically developed hardware and software Failure of one function has no effect on the other system Every system is a stand alone system


Disadvantages of Federated Architecture systemDeveloped from scratch, with the lack of technology re-use Suffering from obsolescence issues for hardware components Increased weight and power consumption Hence increasing the weight of the aircraft resulting in poor fuel efficiency this introduces dedicated communication channels and also13

Integrated Modular ArchitectureA real time computer airborne network system Core computer performing majority of avionics functions Distributed avionics functions are packaged into self-contained units IMA contain LRM ( Line Replacable Modules)14

Integrated Modular Architecture


Features of IMA1. 2.



6. 7.

Sensor data shared between several systems In Core computer several modules identified performing a specific function like the flight control, landing gear, display control, etc. Multiple Federated application integrated into a single platform Strong Partitioning of Software & Two layer Software Architecture Inter partitioning of Communication Facility & Client Server inter partition Protocol Displaying of Status Messages Input/Output message handling by Message Handler and System Executive16

Advantages of IMA

Each Avionic Computer has Open System Interface called Application Program Interface API with Plug and Play Flexible communication having a logical channel and communication channel Flexibility in Hardware Architecture All LRM lightening protected,EMC and environmentally protected Fault Tolerance in IMA Full Duplex Switched Ethernet17

Disdvantages of IMASpecific function for each LRM ( autopilot module, flight management module not interchangable) Modules not field replacable Multiple suppliers-not my problem


Air crtafts using IMA1.

2.3. 4.

F22 Raptor Airbus 380 & Airbus A400 Boeing 787 Sukhoi Super Jet 100


Two layer Software Architecture


Examples of IMA architectureAirbus A350 Airbus A380 Boeing 787 Dassault Falcon 900


Comparison between IMA & Fed1. 2. 3. 4.


Open System architecture with P&P Fully Duplex Only One Core Computer Field Replacable (LRM)except FM and Autopilot Highly fuel efficient and light weight


2. 3. 4. 5.

Closed System architecture with no P& P Not Duplex Many Distributed Computers Not Field Replacable Poor Fuel efficient and Bulky.


Aeronautical StandardsARINC429,629 & 1553 1773


Aeronautical StandardsARINC-Aeronautical Radio IncorporatedArinc 429 series Arinc 629, used by Boeing MIL std Military, MIL 1553 standard Airbus


ARINC 429In brief,


GeneralA physical and electrical interface of a two-wire data bus in most of the commercial and transport aircrafts One pair for TX and another pair for RX A data protocol to support an aircraft's avionics local area network. Use Star/Bus/Multiple bus topology26




Open Standard, with 32 bit word Transmission. A Simplex (TX & Rx on diff. ports) , Dedicated I/O with Point to Point, synchronous communication with 2 wire Operate on both discrete and analog signals Max 20 Receivers can be connected to the 2 wire. Sub Systems include FMS,ILS, VHF, Display system28

FEATURESAn Unidirectional Bus operating 12.5 or 14.5 or 100 kbps Use 32 Bit word with Odd Parity for error detection Waveform is RTZ bipolar It is Simplex Bus ,having RT, or Bus Monitor with no bus controller29


RTZ Bipolar Format


ARINC Avionic Data Bus in Boeing


Features of ARINC 429A standard that communicates between avionics equipment and systems connected with Twisted Pair wires Employs a Unidirectional Data Bus Standard called Mark 33 Digital Information system Data speed =12.5 or 100 kbps Transmission and reception on separate ports so that many wires required33

Point to Point structure


Components of Arinc 4291.

2.3. 4.

429 Transmitter- 2 transmit channels 429 Receiver-20 incoming channels Software Interface Graphical user Interface GUI


ARINC 429 Architecture




Word Format Characterestic32 bit word by two wire transmission containing 5 fields Protocol= Point to Multi- Point Protocol Has both low speed and high speed Parity Bit = MSB Five fields ; 2 for numerical data, 1 for discrete data, 2 for alphanumeric data Data = BCD38

Word Format


Word Format

32 BIT Format 1-8 for Label (for maintenance purpose) 9 & 10 for SDI ( Source Destination Identifier)-1 TX and 20 RX 11 to 29 Data both discrete and Numerical data 30 & 31 for SSM( Sign/Status Matrix) for reporting repair/fault on hardware status of en equiment 32 for Parity for error detection and correction.40

ARINC 629General Features,Protocol Layer,Timing Diagram (Periodic and Aperiodic) Comparison between 429 & 629


Schematic of Basic Protocol for Flight control


General Features of ARINC 629

A Multipoint system- one transmitter to Multi receivers Has two independent MAC protocols for communications across a 2 Mbps Serial data bus Use High Speed Bi directional Bus Duplex Has periodic and a-periodic transmissions Has 2 Protocols-Basic Protocol and Combined protocol; Basic protocol for flight controls, Combined protocol for flight management system No bus Controller required


Combined Protocol Layer4


2 2


4 Protocol layers of Arinc 629Physical layer- 2 Mbps Serial Data Transmission on Twister pair cable for collision avoidance 2. Data Link Layer- single source to many terminals for using TDMA Having Basic Protocol and Combined protocol existing in the same bus 3. Network Layer- 20 bit words upto 256 data words 4. Upper Layer-presenting application, session, presentation and transport layer for IMA architecture1.45

Basic Protocol features-in flight control1.


Transmitting only at aperiodic mode Normally Terminals transmit on periodic mode on no overload Even if there is overload, it is transmitting on aperiodic mode


Combined Protocol-CP - FMS systemShortfalls in BP for Periodic and Sporadic data transmissions corrected Transmitting both on periodic and aperiodic mode Terminals given equal opportunity to switch when there is overload Periodic Data compressed into Burst, separated by Transmit Internal T147

Difference between BP & CPBPTransmitting either Periodic or aperiodic Terminals transmit at periodic only when there is no overload Terminals not given equal opportunity for overload

CPTransmitting both periodic and aperiodic Terminals transmit at periodic mode even if there i