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Modular Avionics Introduction to Integrated Modular Avionics Integrated Modular Avionics (IMA) is a blanket term used to describe a distributed real-time computer network aboard an aircraft which consists of a number of computing modules (hardware) capable of supporting numerous applications (softwa...
Modular Avionics Introduction to Integrated Modular Avionics Integrated Modular Avionics (IMA) is a blanket term used to describe a distributed real-time computer network aboard an aircraft which consists of a number of computing modules (hardware) capable of supporting numerous applications (software) of differing safety criticality levels. The IMA approach has shaved 2000 pounds off the avionics suite of the new 787 Dreamliner and halved the part numbers of processor units for the new A380 avionics suite. Advantages of the Integrated Modular Avionics Concept As a consequence, the IMA concept reduces maintenance costs and increases reliability by using fewer computers, thus Giving economies in fuel savings and increasing the payload factor derived from less weight. Reducing work load for flight crew and maintenance personnel due to less operational activities. Enabling multiple functions to be achieved with a single LRU. Integrated modular avionics concept 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 39 of 136 Typical Integrated Modular Avionics Architecture EMBRAER 170/190 Modular avionics unit (EMB170/190) On Embraer 170/190 the IMA system consists of Modular Avionics Units (MAUs) linked by data buses and discretes to various aircraft systems. 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 40 of 136 Modular Avionics Unit Modular avionics unit (EMB170/190) The MAUs incorporate new hardware and software technologies, hosting independent applications in the same computing and memory resources, and also supply an input/output interface service to some of the conventional avionics. Single unit handles different systems 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 41 of 136 The MAU is a metal cabinet solidly grounded to the aircraft frame which houses different line replaceable modules (LRM). The cabinet only connects to the aircraft system wiring through the front connectors on the Line Replaceable Modules (LRM). For redundancy, each MAU houses two independent processing systems called channels. Each Modular Avionics Unit (MAU) channel consists of the following: 1. Backplane – LRMs are plugged in to make contact with a virtual back plane bus for power and communication. 2. Power supply – The Power Supply translates aircraft power to back plane conditioned power which supports all MAU boards. 3. One Network Interface Controller (NIC) – The NIC acts as a gateway for modules to access the ASCB/LAN data buses. Basically, the NIC supplies the interface between the internal backplane bus and external bus systems. 4. User modules – Third-party modules that perform various aircraft control and monitoring functions. This is achieved using a Digital Engine Operating System (DEOS) compliant processing system and various aircraft sensor and system inputs and outputs (termed custom and generic I/O). MAU 1 2 B 2 B 2 B 2 B 2 B P0125 P0123 P0121 A 1 CUSTOM I/O 1 NIC 2 (ID=62) PROC 2 A 1 GENERIC I/O 1 AIOP B1 A 1 A 1 PROC 1 NIC 1 (ID=1) A 1 A 1 FCM 2 A 1 A 1 A 1 CONTROL I/O 1 BRAKES (OUTBD) PSEM 1 AIOP A1 P0117 P0115 P0113 P0111 A 1 A 1 SUB POWER SUPPLY ESS1 P0131 P0129 HC HC SUB NIC 1 8 2 B 7 6 5 4 3 2 1 PS 1 CMC GPS 1 POWER SUPPLY ESS1 FCM 1 SUB B 2 B 2 B 2 B HC HC PS 2 16 15 14 13 NIC 2 12 11 10 9 SUB PS 3 20 19 18 17 POWER SUPPLY DC 1 AGM 1 (optional) P0109 P0107 P0243 P0105 P0101 P0099 P0097 P0095 P0093 P0103 P0091 Example of MUA boards/LRUs 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 42 of 136 Communication in the MAU is managed by the Network Interface Controller (NIC). The NIC transmits and receives ASCB and LAN data and makes this data available to other modules (termed clients) in the MAU through the Backplane Interface Controller (BIC). MAU boards The client modules that need to communicate with the NIC are connected to the backplane bus through an internal circuit called the BIC (Bus Interface Controller) frame buffer. This buffer is a dualport RAM (Random Access Memory) that can be read from and written to by both the NIC and client module. The clients may be a processor, Input/Output (I/O), memory or other hybrid modules. NIC modules have Aircraft Personality Modules (APMs) installed in their backshells. Aircraft Personality Modules (APMs) are programmed with system identification data, options data, system settings data, and rigging data. The data content is custom for the aircraft. For security reasons, software firewalls protect the MAUs from malicious data coming from other common applications. 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 43 of 136 Data Communications The MAUs use the following data buses, networks and components for data processing and MAU operations: Avionics Standard-Communication Bus (ASCB) ASCB coupler ASCB terminators Local Area Network (LAN) Controller Area Network (CAN) data bus. The Avionics Standard-Communication Bus The Avionics Standard-Communication Bus (ASCB) is the primary communications path between the major subsystems of the avionics systems. It is a high-speed serial data bus (10 Mb/s) using a singleshielded twisted pair of wires with resistor terminations to stop signal reflections. Data on the ASCB is transmitted in data frames of 12.5 milliseconds (mS). Each frame is divided into blocks or time slots. The transmission timing is controlled by the NICs and is synchronised across each bus by a master network interface controller. ASCB data frame For redundancy, the network is made up of four data buses: Left primary Right primary Left backup Right backup. 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 44 of 136 Avionics Standard-Communication Bus Coupler The bus coupler isolates onside primary, onside backup and cross-side primary buses which are fed to the NICs within the MAU. It uses a transformer coupler for isolation (to prevent a short circuit on one bus from having an effect on the other buses) and to impedance-match the ASCB and the applicable NIC. Avionics standard-communication bus coupler ASCB MAU connections 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 45 of 136 Avionics Standard-Communication Bus Terminators The ASCB terminators are devices attached to the endpoints of each ASCB with the purpose of absorbing signals so that they do not reflect back down the line. ASCB terminator 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 46 of 136 Local Area Network Introduction to Local Area Network The NIC controls data transmission on the Local Area Network (LAN) bus. This serial data bus is physically and electrically separate from the ASCB. The LAN is used for development, maintenance and software loading. It supplies an additional communication path to be used between the display units, the MAU and peripheral items such as the printer and the data-loader. The LAN is a thin coaxial cable, which is Ethernet based and uses the Transfer Control Protocol/Internet Protocol (TCP/IP). This protocol makes it possible for peripheral computers/communication devices to interface with the NIC over the LAN. Controller Area Network Data Bus The Controller Area Network (CAN) bus is an industry standard bus which uses controller-integrated circuits operating at 500 kHz. The CAN is a serial bidirectional bus that uses the same wire and harness construction as the ASCB (twisted, shielded pair with terminators). The CAN consists of multi-point serial synchronous digital communications. Controller area network bus network This means that there is no master that controls when individual users (known as nodes) have access to read and write data on the CAN bus. When a CAN node is ready to transmit data, it checks to see if the bus is busy and then simply writes a CAN frame onto the network. The CAN frames that are transmitted do not contain addresses of either the transmitting node or any of the intended receiving node(s). Instead, an arbitration ID that is unique throughout the network labels the frame. All nodes on the CAN network receive the CAN frame, and depending on the arbitration ID of that transmitted frame, each CAN node on the network decides whether to accept the frame. 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 47 of 136 If multiple nodes try to transmit a message onto the CAN bus at the same time, the node with the highest priority (lowest arbitration ID) automatically gets bus access. Lower priority nodes must wait until the bus becomes available before trying to transmit again. Error Capabilities The CAN specification includes a method of error checking on each frame’s contents. Frames with errors are disregarded by all nodes, and an error frame can be transmitted to signal the error to the network. The transmitting node will once again retransmit the data. If too many errors are detected, individual nodes can stop transmitting errors or disconnect themselves from the network completely. Typical Integrated Modular Avionics Version of Flight Guidance System (E170/190) The following example provides insight into the operation of IMA within an aircraft system. The Embraer 190 autopilot function resides as part of the Flight Guidance Control System (FGCS) application. Flight guidance system (EMB 170/190) The FGCS drives the autopilot control systems via clutched electro-mechanical servo assemblies (lateral and longitudinal) that operate in parallel with the normal pilot commands when engaged. The additional feature of this Automatic Flight Controls System (AFCS) is that it uses Actuator InputOutput Processors (AIOPs) which are Line Replaceable Modules (LRMs) within the Module Avionics Unit (MAU). 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 48 of 136 The Actuator Input-Output Processor (AIOP) modules do all of the necessary computations and data processing for the autopilot and Yaw Damper (YD) functions. AIOP modules collect the necessary data from avionic and flight control systems via the Avionics Standard-Communication Bus (ASCB) or from other Flight Guidance Control System (FGCS) inputs. Autopilot servo operation The AIOP modules send position data to the servos through a bidirectional Controller Area Network (CAN) data bus. Two AIOP modules operate in each channel. These modules are identified as lane A and lane B. The modules in these two lanes have the same software but do separate, complementary and similar functions that depend on the lane. The AIOP modules in lane A and lane B must operate at the same time for the servos in that channel to be active and engaged. With any control system, there must be feedback. 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 49 of 136 Autopilot feedback The Linear Variable Differential Transformers (LVDTs) provide analogue feedback to the Primary Actuator Control Electronics (P-ACE) System. The P-ACE does an analogue-to-digital conversion and the digital feedback data is then sent via a CAN bus to the Flight Control Module (FCM) and forwarded to the autopilot AIOP (for use in calculations) within the MAU. There are no mechanical rudder inputs from the autopilot. The FGCS provides yaw damper and turn coordination signals to the Flight Control Modules (FCMs), which then transmit the commands to the P-ACE module via the CAN bus interface. The commands are summed with the rudder pedal LVDT signal to drive the rudder actuator. Autopilot pitch trim commands (auto-trim and Mach trim), are also sent to the FCMs, which are combined with the configuration trim and transmit as a consolidated command to the horizontal stabiliser via the CAN bus interface. 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 50 of 136 Types of Integrated Modular Avionics The types of IMAs depend on the aircraft type and its systems. Within a given type, all IMAs are interchangeable but may require a software reconfiguration. Each type hosts avionics applications. For example, a B787 has IMAs dedicated for: Avionics: Displays and crew alerting, flight data acquisition and recording, flight management, thrust management, communication management, health management, data loading, configuration management. Environment control systems: Protective, air conditioning, pressurisation, e/e cooling systems control and indication. Electrical systems: System control and indication, secondary electrical power distribution, proximity sensing, window heat. Fuel systems: System indication, fuel quantity, nitrogen generation system. Hydraulics: System control and indication Mechanical systems: Brake, landing gear, and steering systems control and indication. Payloads: Lavatories, potable water, crew and passenger oxygen, vacuum waste. Propulsion/APU: Engine and APU fire detection and extinguishing control and indication, thrust reverser control and indication. 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 51 of 136 Comparison of Boeing B777 and B787 Avionics Systems Comparison of B777 and B787 avionics 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 52 of 136 Difference between EMB 170/190 and A380 Integrated Modular Avionics On the Embraer 170/190, each IMA is a metal cabinet solidly grounded to the aircraft frame. This cabinet called as Modular Avionics Unit (MAU), and it contains different line replaceable modules (LRM) for different avionics applications. Alternatively, the A380 has independent LRMs to host different avionics applications. Some LRMs merge three to four aircraft systems and handle these systems individually. Difference between EMB 170/190 and A380 IMA system 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 53 of 136 Integrated Modular Avionics System on the A380 On the A380, the independent applications are hosted in shared IMA modules called Core Processing Input/Output Modules (CPIOMs), and in order to accommodate and link with the conventional avionics, additional modules are placed in the system, called Input/Output Modules (IOMs). Both CPIOMs and IOMs are LRMs. These LRMs dialogue through the Avionics Data Communication Network (ADCN) by the means of a communication technology developed from a non-aeronautical standard which has been adapted to aviation constraints. This technology is called Avionics Full DupleX (AFDX) switched ethernet. The major components of the A380 IMA system are Core Processing Input/Output Modules (CPIOMs) Input/Output Modules (IOMs) Avionics Data Communication Network (ADCN). Integrated modular avionics concept on A380 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 54 of 136 Core Processing Input/Output Module Introduction to Core Processing Input/Output Module The Core Processing Input/Output Module (CPIOM) integrates shared memory and computing resources to independently execute its hosted avionics applications. In addition, the CPIOM independently processes specific input/output data for each application. This data is AFDX data. When the applications dialogue through ADCN and non-AFDX data when they dialogue directly with conventional LRUs. There are seven types of CPIOM, each one identified by a letter (A to G), for the following systems: Pneumatic applications (X4) Engine bleed air system, overheat detection system, pneumatic air distribution system. Air conditioning applications (X4) Air generation system, avionics ventilation system, cabin pressure control system, temperature control system, ventilation control system. Cockpit and flight controls applications (X2) Flight control, weight and balance computation, flight warning system. Data link applications (X2) Air traffic control system, avionics communication. Energy applications (X2) Circuit breaker monitoring system, electrical load management system. Fuel applications (X4) Fuel CG measurement COM, fuel management. Landing gear applications (X4) Braking control system, steering control system, landing gear extension and retraction system. 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 55 of 136 Core processing input/output module (CPIOM) Input/Output Module The Input/Output Module (IOM) does not host avionics applications. The IOM converts non-AFDX data coming from conventional LRUs into AFDX data used within the Avionics Data Communication Network (ADCN) and vice versa. All IOMs are fully interchangeable. Input/output module 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 56 of 136 Avionics Data Communication Network Subscribers The A/C system computers connected directly to the Avionics Data Communication Network (ADCN) are the LRMs, which are Core Processing Input/Output Modules (CPIOMs) or Input/Output Modules (IOMs). These computers are called ADCN subscribers. Communication between the ADCN subscribers is done through the AFDX technology. Avionics data communication network subscribers subscribers 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 57 of 136 ADCN and AFDX Technologies The ADCN is supported by the AFDX technology. AFDX is a communication technology based on commercial Ethernet protocol adapted to aeronautical constraints to meet the avionics requirements. It gives the following advantages: Secure and reliable communications High data rate of 10 and 100 Mb/s Flexibility for future developments of system architecture Less wiring. The ADCN is made of AFDX switches and AFDX cables. The AFDX switches are electronic devices. They manage the data traffic on the network between the connected subscribers. Avionics full duplex switches 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 58 of 136 Avionics full duplex configuration The AFDX cable is a full-duplex physical link between a subscriber and an AFDX switch. (The term full-duplex means that the subscriber can simultaneously transmit and receive on the same link.) This link is a quad cable, composed of four wires uniformly twisted, one pair for transmission and one pair for reception. Avionics full duplex cable 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 59 of 136 ARINC600 connector of a core processing input/output modules The ADCN implements a redundant network where all subscribers have connections to both network A and B with an auto switching system. ADCN network 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 60 of 136 ADCN A and B networks A subscriber simultaneously transmits the same information frame on both networks (A and B). The receiving subscriber will obtain two identical data frames, one from network A and one from network B, and simply rejects one. If a switch fails within the network, a data path is still established through the redundant network. ADCN redundancy 2022-12-13 B1-11k Turbine Aeroplane Aerodynamics, Structures and Systems CASA Part Part 66 - Training Materials Only Page 61 of 136
