Electronic Instrument Systems PDF - CASA B2-05b

MODULE 05 Category B2 Licence CASA B2-05b Digital Techniques / Electronic Instrument Systems II Copyright © 2020 Aviation Australia All rights reserved. No part of this document may be reproduced, transferred, sold or otherwise disposed of, without the written permission of Aviation Australia. CONTROLLED DOCUMENT 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 2 of 167 CASA Part 66 - Training Materials Only Knowledge Levels Category A, B1, B2 and C Aircraft Maintenance Licence Basic knowledge for categories A, B1 and B2 are indicated by the allocation of knowledge levels indicators (1, 2 or 3) against each applicable subject. Category C applicants must meet either the category B1 or the category B2 basic knowledge levels. The knowledge level indicators are defined as follows: LEVEL 1 Objectives: The applicant should be familiar with the basic elements of the subject. The applicant should be able to give a simple description of the whole subject, using common words and examples. The applicant should be able to use typical terms. LEVEL 2 A general knowledge of the theoretical and practical aspects of the subject. An ability to apply that knowledge. Objectives: The applicant should be able to understand the theoretical fundamentals of the subject. The applicant should be able to give a general description of the subject using, as appropriate, typical examples. The applicant should be able to use mathematical formulae in conjunction with physical laws describing the subject. The applicant should be able to read and understand sketches, drawings and schematics describing the subject. The applicant should be able to apply his knowledge in a practical manner using detailed procedures. LEVEL 3 A detailed knowledge of the theoretical and practical aspects of the subject. A capacity to combine and apply the separate elements of knowledge in a logical and comprehensive manner. Objectives: The applicant should know the theory of the subject and interrelationships with other subjects. The applicant should be able to give a detailed description of the subject using theoretical fundamentals and specific examples. The applicant should understand and be able to use mathematical formulae related to the subject. The applicant should be able to read, understand and prepare sketches, simple drawings and schematics describing the subject. The applicant should be able to apply his knowledge in a practical manner using manufacturer's instructions. The applicant should be able to interpret results from various sources and measurements and apply corrective action where appropriate. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 3 of 167 CASA Part 66 - Training Materials Only Table of Contents Electronic Instrument Systems (5.1) 8 Learning Objectives 8 Conventions and Development 9 Early Instrument Systems 9 Electronic Instrument Display Technology 11 Arrangements of Electronic Instrument Systems 13 Electronic Flight Instruments System 13 EADI and EHSI 15 PFD and ND 16 Cockpit Layout of Electronic Instrument Systems 21 The Boeing System 21 The Airbus System 21 Multifunction Displays and Digital Data Bus 23 Symbol Generators 24 Basic Operation of Aircraft Display Systems 25 Airbus’ Electronic Centralised Aircraft Monitoring 27 Boeing’s Engine Indicating and Crew Alert System 29 Main or Upper EICAS Display 30 Auxiliary EICAS Display 31 Software Management Control (5.13) 32 Learning Objectives 32 Classification of Aircraft Software Systems 33 Software Use 33 Software Control 34 Software Levels 35 Software Types 37 Explanation of Software Terms 41 Loadable Software Aircraft Part 41 Non-Loadable Software Aircraft Part or Aeronautical Database 41 Databases 42 Operator Modifiable Software 43 Supplier Controlled Software 45 Software Media 46 Target Hardware 47 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 4 of 167 CASA Part 66 - Training Materials Only Software Data Loading 51 Data Loaders 51 FLS Loading and Certification 53 Electronic Distribution of Software 53 Field-Loadable Software Procurement and Documentation 54 FLS Storage Media Handling 55 Replication of FLS 56 Procedures 57 Case Study 58 Electromagnetic Environment (5.14) 60 Learning Objectives 60 Electromagnetic Interference in Electrical Systems 61 Electromagnetic Environment Terminology 61 Electromagnetic Interference 62 Elements of an EMC Problem 64 Electric and Magnetic Fields 66 Leakage and Antenna Effect of Conductors 67 Natural Sources of EMI 71 Lightning Strikes and Lightning Protection 71 Electrical Bonding 72 Man-Made Sources of EMI 73 High-Intensity Radiated Field 76 EMI Management 79 Addressing EMI Problems 79 EMI Permeation 80 EMI Shielding 80 Cable Shielding 81 Effect of Multi-Shielding 84 EMC/EMI Problems 85 EMI Minimisation 87 Balanced Circuits 87 PCB Continuous Ground Plane 88 Structure Shielding 88 Static Discharging 90 General Precautions 90 Fibre Optics 92 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 5 of 167 CASA Part 66 - Training Materials Only Typical Electronic / Digital Aircraft Systems I (5.15) 94 Learning Objectives 94 Integrated Test Equipment 95 Aircraft Diagnostics 95 BITE Systems 95 BITE Philosophy 96 BITE Function 98 Maintenance Control Display Unit (MCDU) 100 MCDU Utilisation 101 Simple BITE Circuit 103 Aircraft Communications Addressing and Reporting System (ACARS) 106 ACARS Introduction 106 ACARS Components 106 Data Bus Fundamentals 108 Airbus’ Electronic Centralised Aircraft Monitoring (ECAM) 110 ECAM Introduction 110 ECAM Displays 110 ECAM System Operation 111 Electronic Flight Instrument System (EFIS) 113 EFIS Purpose 113 Primary Flight Display (PFD) 113 Multifunction or Navigation Display (MFD or ND) 114 Boeing’s Engine Indicating and Crew Alerting System (EICAS) 116 EICAS Introduction 116 EICAS Upper Display 117 EICAS Lower Display 118 EICAS System Operation 119 EICAS Control Panel 120 EICAS Maintenance Control Panel 121 EICAS BITE Tests 121 Fly-By-Wire Flight Control System 123 Fly-By-Wire General Arrangement 123 Flight Management System (FMS) 125 FMS General Arrangement 125 FMC Operation 125 Control Display Unit (CDU) 126 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 6 of 167 CASA Part 66 - Training Materials Only FMS BITE 127 Global Positioning System (GPS) 129 GPS Introduction 129 Airborne GPS Components 129 Receiver BITE Test 131 Inertial Reference System (IRS) 132 IRS Introduction 132 IRS Components 132 IRS BITE 134 Traffic Alert and Collision Avoidance (TCAS) 136 TCAS Introduction 136 TCAS BITE 137 Typical Electronic / Digital Aircraft Systems II (5.15) 139 Learning Objectives 139 Integrated Modular Avionics (IMA) 140 Background 140 IMA Advantages 140 Cabin Systems 144 Overview 144 Cabin Core System 144 Basic CIDS Operations 145 CIDS Architecture 147 Cabin Monitoring System: Communication Functions 150 Cabin Monitoring System Control Functions 153 In-Flight Entertainment (IFE) System 156 IFE System Architecture 157 IFE Components 158 Overhead Equipment 162 Cabin Systems BITE Testing 162 Information Systems 164 Aircraft Information Systems 164 Health Management Systems 164 Electronic Logbook (e-Logbook) 166 Information System BITE Testing 167 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 7 of 167 CASA Part 66 - Training Materials Only Electronic Instrument Systems (5.1) Learning Objectives 5.1.1 Demonstrate typical arrangements of electronic instrument systems (Level 3). 5.1.2 Demonstrate a typical cockpit layout of electronic instrument systems (Level 3). 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 8 of 167 CASA Part 66 - Training Materials Only Conventions and Development Early Instrument Systems In the early days of aviation, aircraft had a clock (optional) and a compass, which was acceptable for flights in daytime in clear weather. Next came an altimeter, then a simple attitude instrument. Aviation Australia Early aircraft basic instrument cluster As more instruments became available, the individuals involved laid out the instrument panel as they wanted, squeezing instruments in where they could. This became a problem for pilots who flew more than one type of aircraft as they had to relearn the instrument position before the flight. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 9 of 167 CASA Part 66 - Training Materials Only NY2 Huskey first blind flying cockpit After 1950 most aircraft cockpit instrument systems were arranged in the Basic T configuration. Every aircraft had an Airspeed Indicator (ASI), Attitude indicator (AI) and altimeter in a row, which made the information required in an emergency immediately identifiable. With the compass below these instruments, the pilot could now fly in the dark or in poor weather without becoming disoriented. The basic 'T' configuration 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 10 of 167 CASA Part 66 - Training Materials Only Additions to the Basic T included a turn coordinator (or a turn and slip indicator) and a Vertical Speed Indicator (VSI) at the bottom left and bottom right respectively. These were added to give the pilot more accurate immediate information. Due to the difficulty in seeing a 1° bank on an ADI, the pilot would notice a gradual drift in heading and have to correct by banking in the other direction. The turn co-ordinator now shows an accurate wing level position and therefore fewer corrections are required. Basic six instrument cluster Larger aircraft such as the 747 Classic use the same Basic T configuration, except with the addition of a rad alt, standby instruments and special features on the standard instruments such as ILS, VOR guidance indicators and a rising runway. In these cases, the additional functionality has resulted in the Artificial Horizon and Directional Gyro being renamed to the Attitude Direction Indicator (ADI) and the Horizontal Situation Indicator (HSI) respectively. Standby instruments and engine instrumentation are conventionally placed in the centre of the panel, one set being easily readable by both pilots. Aircraft instrumentation will be covered in 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 11 of 167 CASA Part 66 - Training Materials Only Electronic Instrument Display Technology Types of electronic displays commonly used in aircraft: Light-emitting diodes Liquid crystal displays. Some older displays may still use cathod ray tube technology however this technology is becoming rarer due to the reliability, physical size, and service life of this technology. The signals produced by sensors, and the digital signals transmitted over a digital data bus, are incapable of generating a display on a screen. The signals simply convey information about certain parameters. Display units must be supported by processors and electronic devices to interpret the data provided by sensors and avionics data buses. Then, they generate signals to produce information on the screen. Cockpit with LCD screens 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 12 of 167 CASA Part 66 - Training Materials Only Arrangements of Electronic Instrument Systems Electronic Flight Instruments System The purpose of the EFIS display system is to provide the flight crew with the information required to operate the aircraft. Instead of using large numbers of analogue instruments, the EFIS is used to display the all the primary aircraft operational information on display screens. This allows reduces the devices that aircrew have to scan and reduces the instrument clutter that is common in analogue instrument-based cockpits. It also provides a maintenance advantage as fewer mechanical instruments are required for the system, which increases reliability and serviceability. A typical EFIS system consists of four interchangeable displays: an EADI (Electronic Attitude Director Indicator) and EHSI (Electronic Horizontal Situation indicator) each for the Captain and First Officer, three symbol generators, two control panels and two source selection panels. A third (centre) symbol generator may be incorporated if a primary symbol generator fails. In aircraft with an avionics digital data bus and multifunction displays, the EFIS displays directly in front of the pilots are not restricted to only displaying EADI and EHSI information. The EFIS typically contains four large colour displays – two PFDs (Primary Flight Displays) and two MFDs (Multifunction Displays) or Navigation Displays (NDs). The modern display systems include the following advantages: Large, uncluttered displays enhance crew efficiency and situational awareness. Versatile formats allow displays to be used interchangeably as a PFD (Primary Flight Display), MFD (Multifunction Display) or EICAS/ECAM display. PFDs include attitude, air data, navigation references and Traffic Collision Avoidance System (TCAS) resolution advisories. MFDs include navigation maps, weather radar, TCAS traffic and maintenance data. Operation can be broken down into two distinct functions: Electronic Flight Instruments System (EFIS) – PFD and MFD Engine Indication and Crew Alerting System (EICAS – Boeing) or Electronic Centralised Aircraft Monitoring (ECAM – Airbus). The two central displays are commonly aligned to either EICAS or ECAM systems, but all six displays can be interchangeable depending on the aircraft. Both cockpit images are of the same single engine aircraft. The top image was taken before installation of the glass cockpit. In the lower image the number if instruments have been significantly reduced by the modification but the same information is displayed. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 13 of 167 CASA Part 66 - Training Materials Only Single engine aircraft illustrated before (conventional instruments) and after a 'glass cockpit' modification Even the latest aircraft models with the most up-to-date systems use the Basic T configuration system to minimise training times and make finding an instrument intuitive. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 14 of 167 CASA Part 66 - Training Materials Only EADI and EHSI in one display 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 15 of 167 CASA Part 66 - Training Materials Only EADI and EHSI The ability to manufacture display screens in the required size resolution and reliability improvements resulted in the mechanical ADI and HSI being replaced by the Electronic Attitude Direction Indicator (EADI) and Electronic Horizontal Situation Indicator (EHSI). An EADI and EHSI 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 16 of 167 CASA Part 66 - Training Materials Only PFD and ND It was not long before manufacturers realised the full potential of electronic instrumentation. The EADI was integrated with airspeed (IAS) information (in tape form) with stall and overspeed visual warnings, altitude and vertical speed information (in tape form), along with autopilot and other annunciations. All information required to fly the aircraft is supplied on one screen. The name was changed to the more appropriate Primary Flying Display (PFD). Primary Flight Display (PFD) and Navigation Display (ND) - Boeing example The EHSI was integrated with ADF, ILS, VOR and flight plan MAP information, colour coded for easier and more instantaneous mode recognition; aircraft speeds (GS and TAS) and heading/track information in digital format; and annunciation of which NAV equipment is supplying the data. All information required to navigate the aircraft is supplied on one screen. Selectable alternative configurations enable the pilot to view the display in either full rose, with variable ranging rings indicated. The name was changed to the more appropriate Navigation Display (ND). 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 17 of 167 CASA Part 66 - Training Materials Only Conventional instruments replaced by the PFD The PFD replaces many analogue instruments: Attitude Director Indicator (ADI), including Flight Director (FD), Air Speed Indicator (ASI), Machmeter, Compass or Directional Gyro (DG), true or magnetic, Altimeter, and Vertical Speed Indicator (VSI). As well as these basics, the PFD now displays other indications: Autopilot mode information, Track, Flight plan (speed or Mach, track) Traffic collision avoidance system (TCAS) information, and Pressure of the day (1013.25 mb = 1013.25 hPa = 29.92 inHg). 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 18 of 167 CASA Part 66 - Training Materials Only Examples of Airbus PFD and ND The ND can be integrated with terrain information from a worldwide mesh terrain database, (EGPWS), with weather radar information (including local ground mapping) and traffic information (ACAS/TCAS). In the case of the latter, the PFD and ND provide Resolution Advisories in the event of a collision threat. The ND displaying terrain information and weather radar information 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 19 of 167 CASA Part 66 - Training Materials Only EADI and EHSI on a Boeing 737, among Conventional Instrumentation A PFD and ND on a Boeing 777 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 20 of 167 CASA Part 66 - Training Materials Only Cockpit Layout of Electronic Instrument Systems The Boeing System The Boeing system uses the Engine Indicating and Crew Alert System (EICAS) to provide airframe and engine data. The primary and secondary (upper and lower) screens display primary and secondary engine data, respectively, and indicate visual cautions, warnings and memos regarding aircraft system status. System synoptics are also displayed on these screens. More information on the EFIS and EICAS is provided in Module 5 Topic 15. Aviation Australia Boeing instrument panel layout with EFIS and EICAS displays 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 21 of 167 CASA Part 66 - Training Materials Only The Airbus System The Airbus flight deck display system uses the Electronic Centralised Aircraft Monitor System (ECAM) to provide the engine, system and synoptic information. The primary and secondary (upper and lower) screens display primary and secondary engine data, respectively, and indicate visual cautions, warnings and memos regarding aircraft system status. System synoptics are also displayed on these screens. Airbus A320 flight deck Aviation Australia Airbus EFIS instrument display layout 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 22 of 167 CASA Part 66 - Training Materials Only Aviation Australia Airbus - Electronic Centralised Aircraft Monitor System (ECAM) primary and secondary displays More information on the EFIS and ECAM is provided in Module 5 Topic 15. Multifunction Displays and Digital Data Bus The use of digitally based microprocessor electronics in flight instruments enables the display of information on one or more Multifunction Display (MFDs) or Digital Display Indicators (DDIs). The data to and from numerous aircraft systems and components is communicated via a digital data bus. A symbol generator connected to the data bus communicates with other devices either directly from the sensors (ARINC 429 and 629) or by a Bus Controller (MIL-STD 1553). Aviation Australia Multifunction displays and digital data bus 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 23 of 167 CASA Part 66 - Training Materials Only Each of the systems passing information for indication is connected to a data bus and transmits its information to all other systems requiring it. Although most systems are digital, a few simple systems may have an output that cannot be transmitted on the data bus. These systems can still pass information to the digital systems through analog to digital converters (ADCs) and receive instructions through digital to analog converters(DACs). The data buses are usually duplicated for redundancy: if one data bus fails, the second bus carries the same information so the whole system is still operational. These separate buses in parallel are called channels of the bus. In an aircraft they can be referred to as channels A and B or channels 1 and 2. The most common failures occur when a terminal or connector is shorted to earth, an LRU fails and continually transmits, or a connector is not installed correctly. Aviation Australia Data buses are usually duplicated for redundancy 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 24 of 167 CASA Part 66 - Training Materials Only Symbol Generators The symbol generation is the centre of the electronic display system. Commercial aircraft typically have at least two (Captain’s symbol generator and First Officer’s symbol generator), and some systems have an additional symbol generator for redundancy. The symbol generator or symbol generator unit (SGU) receives all aircraft sensor inputs and is the centre of an Electronic Display System. The sensor information is processed and transmitted to the electronic displays. Symbol generators provide the analogue, discrete and digital signal interfaces between an aircraft’s systems, and the display units. They also perform the main functions of power control, symbol generation, and system monitoring. Aviation Australia Symbol generator is the centre of an electronic display system 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 25 of 167 CASA Part 66 - Training Materials Only Basic Operation of Aircraft Display Systems Within the electronic instrument display system, the symbol generators receive the information from the data bus and send it to the display, as selected by the aircrew. There are left and right symbol generators and may be a third for redundancy. All symbol generators receive the same data from the data bus; even the centre symbol generator has the same functionality. This allows the back-up unit to take the place of a failed unit before the pilot has had time to realise there was a failure. Display systems use up to three separate channels of a data bus so two channels of a bus fail, the other symbol generators can still function. The symbol generator processes the received information and sends it to the display via a dedicated display bus. Aviation Australia Example of a electronic instrument display and its data buses Data is sent from the symbol generator to the I/O processors, which extract the different data and allocate storage locations in the RAM. When this information is to be displayed, the display controller recalls the information from RAM. So that there are no clashes between I/O writing to memory and the display controller reading from memory, the main processor controls all activities. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 26 of 167 CASA Part 66 - Training Materials Only Aviation Australia Display system schematic There are two types of data to be written on the screen: raster and stroke. The raster data are overwritten onto the Weather Radar (WXR) Memory as the WXR is also raster information. In this memory is a location for each pixel on the screen, containing colour and brightness information. First the weather radar information is written into the WRX memory directly from the WXR. Then the data from the symbol generator are written over the top so that when it appears on the screen, you can read this information without it being affected by the radar picture. The stroke data are a method of drawing on the screen so that circles and lines do not have a jagged appearance. This information is not laid out by pixel as the raster is; it is more a location on the screen where a line must be drawn and is done at the end of each row of pixels of the raster scan. Therefore, the Raster Generator is the master timing device for both types of information. The display types and operation will be covered more fully in Topic 5.11. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 27 of 167 CASA Part 66 - Training Materials Only Airbus’ Electronic Centralised Aircraft Monitoring ECAM displays are typically located in the centre of the instrument panel, corresponding to where analogue engine instruments have been traditionally located. In older model Airbus aircraft, the ECAM displays are dedicated to display only data generated by the Flight Warning Computers (FWC) and ECAM symbol generators. In these aircraft, the displays directly in front of the pilot are typically dedicated to providing EFIS information. In aircraft with data bus technology, the ECAM display is not restricted to centre displays; it can be displayed in front of either pilot in place of EFIS displays if selected. Electronic Centralised Aircraft Monitoring (ECAM) Aviation Australia Electronic Centralised Aircraft Monitoring (ECAM) data bus system 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 28 of 167 CASA Part 66 - Training Materials Only ECAM Control Panel The ECAM control panel has two display brightness control knobs and the remaining switches are of the push-button type. Synoptic display switches permit individual selection of synoptic diagrams corresponding to the systems and illuminate when pressed. Symbol Generator Unit (SGU) selector switches, that may be mounted remotely, control the respective SGUs. A fault light will come on if an SGU failure is detected, and the failed SGU can then be isolated. A Flight Warning Computer (FWC) maintenance panel is incorporated into the system. System tests of ECAM displays and symbol generators can be initiated from this panel. ECAM control panel 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 29 of 167 CASA Part 66 - Training Materials Only Boeing’s Engine Indicating and Crew Alert System Although all electronic displays require a device or circuitry to interface data (from analogue sensors or from a digital data bus) to the visual display unit (to produce raster/stroke signals), the circuitry may be incorporated into a system processor (for example, within the EICAS computer), or it may be housed within the display itself. Although symbol generators may not be included as discrete components within the system, the electronics to perform this function will be included somewhere. The EICAS system does not incorporate separate symbology generators. Symbol generation is performed by the EICAS computers. Aviation Australia Boeing EICAS system EICAS provides comprehensive monitoring of aircraft systems, dispatch information, storage of maintenance-related data, colour-coded displays and alert messages. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 30 of 167 CASA Part 66 - Training Materials Only Main or Upper EICAS Display The upper display normally shows primary engine indications, crew alert messages, flaps and landing gear status, fuel quantity and environmental control system information. The information displayed is determined by the aircraft type (physical configuration and software), was well as display control panel selections. Aviation Australia EICAS primary display variation Auxiliary EICAS Display The lower display normally shows the auxiliary EICAS formats. During normal flight, the lower display is blank. The available auxiliary EICAS formats are secondary engine parameters, secondary- partial, status page, synoptics and maintenance pages. In older aircraft the EICAS displays are mounted in the centre of the instrument panel and are dedicated to display only EICAS data generated by the EICAS computers. In these aircraft the CRTs directly in front of the pilots are typically dedicated to providing EFIS information. In the latest model aircraft with data bus technology, the EICAS display is not restricted to centre displays and can be displayed in front of pilots in place of EFIS displays if so selected. Aviation Australia Auxiliary EICAS display format options 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 31 of 167 CASA Part 66 - Training Materials Only Software Management Control (5.13) Learning Objectives 5.13.1.1 Describe the restrictions that apply to software management and control (Level 2). 5.13.1.2 Describe the airworthiness requirements for software management and control (Level 2). 5.13.1.3 Describe the possible catastrophic effects of unapproved changes to software programs (Level 2). 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 32 of 167 CASA Part 66 - Training Materials Only Classification of Aircraft Software Systems Software Use Software is used in aircraft systems to provide the programming information required by the computers. It is used by all computer-based systems on the aircraft and includes the following: Engine control systems Bleed air control systems Power generation and control systems Fire protection systems Aircraft instrument displays. Modern aircraft rely heavily on computer software It is also used to control the aircraft’s navigation and flight management systems. These systems require continuous software updates as navigational requirements of the aircraft constantly change. These changes can be a result of: Airline flight route changes Air traffic control changes Changes in the position of waypoints. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 33 of 167 CASA Part 66 - Training Materials Only Software is also used by the aircraft’s Built-In Test Equipment (BITE) to communicate with the other systems to test and identify problems associated with the aircraft. A Multifunction Control Display Unit (MCDU) is programmed with software that communicates with multiple systems to update or input data, test and identify faults 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 34 of 167 CASA Part 66 - Training Materials Only Software Control Each aircraft equipment and system requiring software is assigned a Software Level which relates to the severity of the effect of possible software errors within the equipment or system on aircraft safety, crew and/or passengers. Software levels are assigned in accordance with the criteria defined in DO-178C Software Considerations in Airborne Systems and Equipment Certification. This document is jointly prepared by the Radio Technical Commission for Aeronautics (RTCA) safety critical working group RTCA SC- 167 and the European Organisation for Civil Aviation Equipment EUROCAE WG-12. Airbou rne Software and Data YES Is the airbou rne so ftware or data included in the ai rcraft design, NO Airbourne Software OR requi red for aircraft produ ction, OR requi red for ﬂight ope ration s, Airbourne Support OR requi red for maintenan ce ope rations? Data A/C suppot d ata YES NO IFE ﬁles Is the software controlled at the ai rcraft level? A/L duty free store Hotels list Aircraft Controlled Software (ACS) Hardware Controlled Software (HCS) Conn exions (AOC convenience items) YES NO Field Loadable Software (FLS) Is the software loadable? or Loadable Software Part (LSP) Aircraft Controlled Loadable Reside nt Software (RS) Software Part (ACLSP) or Pre-loaded Software (CASR 21) YES Included in the NO aircraft type desi gn? (CASR 21) YES NO Is an ADB Loadable Software Aircraft Part YES (LSAP) Aeronautical D atabase (ADB) Requi red for ﬂight ope rations? NO (CASR 21) YES NO (CASR 175 ) Requi red for maintenan ce? Flight Ope rations Software (FOS) YES Instru ctions for Continued NO Ele ctronic Flight Book (EFB) Nav Charts, Airworthiness? Uncatego rised Supplier Controlled User Modiﬁable User Certiﬁed Software (SCS) Software (UCS) Software (UCS) Airport maps (CASR 21) Technical Publications Maintenan ce Ope rations OPS, OSS AMI, ASO Cabin database (Tech Pubs) Software (MOS) CDB AMM,TSM FIM Aviation Australia Aviation software management 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 35 of 167 CASA Part 66 - Training Materials Only Software Levels Software is assigned a level (A, B, C, D or E) based on its potential to cause safety-related failures identified by a system safety assessment. The software must also be designed to meet strict specifications (probability of failure) based on its assigned level. Aviation Australia Flight software design assurance levels and acceptable probabilities of failure Most of the software used is treated in the same manner as an aircraft component for the purposes of certification, major defect investigation and aircraft component control procedures. The five levels of certification and some examples of the systems controlled by software are provided as follows. Level A - Catastrophic Software whose failure would cause or contribute to a catastrophic failure of the aircraft. This includes software managing systems such as: Flight control computer Fly-by-wire Full authority digital engine control Flight displays Air data systems 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 36 of 167 CASA Part 66 - Training Materials Only Level B - Hazardous Software whose failure would cause or contribute to a hazardous/severe failure condition. This includes software managing systems such as: Autopilot Autothrottle Ice protection Standby flight displays Instrument landing system Landing gear control Level C - Major Software whose failure would cause or contribute to a major failure condition. This includes software managing systems such as: Navigation systems (such as GPS) Yaw damper Environmental control systems Level D - Minor Software whose failure would cause or contribute to a minor failure condition. This includes software managing systems such as: Flight data recorder Data acquisition system Cabin lighting Level E - No Effect Software whose failure would have no effect on the aircraft or on pilot workload. This includes software managing systems such as: In-flight entertainment 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 37 of 167 CASA Part 66 - Training Materials Only Software Types There are two main types of aircraft software: Field-Loadable Software (FLS) Preloaded or Resident Software. Airbou rne Software and Data YES Is the airbou rne so ftware or data included in the ai rcraft design, NO Airbourne Software OR requi red for aircraft produ ction, OR requi red for ﬂight ope ration s, Airbourne Support OR requi red for maintenan ce ope rations? Data A/C suppot d ata YES NO IFE ﬁles Is the software controlled at the ai rcraft level? A/L duty free store Hotels list Aircraft Controlled Software (ACS) Hardware Controlled Software (HCS) Conn exions (AOC convenience items) YES NO Field Loadable Software (FLS) Is the software loadable? or Loadable Software Part (LSP) Aircraft Controlled Loadable Reside nt Software (RS) Software Part (ACLSP) or Pre-loaded Software (CASR 21) YES Included in the NO aircraft type desi gn? (CASR 21) YES NO Is an ADB Loadable Software Aircraft Part YES (LSAP) Aeronautical D atabase (ADB) Requi red for ﬂight ope rations? NO (CASR 21) YES NO (CASR 175 ) Requi red for maintenan ce? Flight Ope rations Software (FOS) YES Instru ctions for Continued NO Ele ctronic Flight Book (EFB) Nav Charts, Airworthiness? Uncatego rised Supplier Controlled User Modiﬁable User Certiﬁed Software (SCS) Software (UCS) Software (UCS) Airport maps (CASR 21) Technical Publications Maintenan ce Ope rations OPS, OSS AMI, ASO Cabin database (Tech Pubs) Software (MOS) CDB AMM,TSM FIM Aviation Australia Aviation software management 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 38 of 167 CASA Part 66 - Training Materials Only Field-Loadable Software (FLS) Field-loadable software is used specifically to describe the software rather than the medium containing it. FLS is software, including data tables, which can be loaded on an aircraft by maintenance personnel without removing the system or equipment from its installation. Characteristics of FLS include the following: It has its own unique part number. It may be an aircraft part. The part number is verifiable on the aircraft by electronically accessing the target hardware memory. It does not change the target hardware part number. It can be uploaded regardless of the current software state and will not prevent a previous version from overwriting it. Portable FLS loader 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 39 of 167 CASA Part 66 - Training Materials Only Preloaded or Resident Software Preloaded software cannot be changed without physically removing the system or components of the system from the aircraft. Updates to the software or programming cannot be changed on the aircraft and require the unit to be removed and sent to a workshop environment for reprogramming. The reasons for using preloaded software are that some aircraft components or computers may not have software changes for long periods of time and loadable software is not an option as the component is in an inaccessible area or an area of high contamination. Additionally, the manufacturer of the software may not want the information to be released, so the original software will be preloaded by the manufacturer and any upgrade to it will be undertaken by the manufacturer. FADEC LRU containing pre-loaded software 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 40 of 167 CASA Part 66 - Training Materials Only Explanation of Software Terms Loadable Software Aircraft Part A Loadable Software Aircraft Part (LSAP) is software that is considered part of the aircraft approved design and therefore an aircraft part. A LSAP requires release documentation (EASA Form 1, FAA 8130-3), or an equivalent designated in agreement with the regulatory authority. FAA diagram LSAP loading and management 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 41 of 167 CASA Part 66 - Training Materials Only Non-Loadable Software Aircraft Part or Aeronautical Database Field-loadable software which is not part of the certified aircraft configuration is defined as a Non- LSAP part or an Aeronautical Database (ADB). These parts are commonly used for applications such as navigation, flight planning and terrain awareness. As they are not part of the aircraft Type Certificate, they may be routinely updated without a formal modification approval or Supplemental Type Certificate (STC) being required. It is still critical, however, that they are subject to rigorous configuration control. Aviation Australia Non-LSAP Aeronautical database version details presented on a CDU 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 42 of 167 CASA Part 66 - Training Materials Only Databases There are two significant types of databases: those which are aircraft parts (LSAP) and those which are Aeronautical Databases. The distinction between the two does not lie in the technologies and loading methods used, but in their regulatory status: Model/Engine Database (MEDB) is LSAP software that defines a customised performance database for the navigation system. The performance database includes performance values such as fuel flow, drag factor, manoeuvre margin, minimum cruise time and minimum rate of climb. Aeronautical Database (ADB) is not classified as an aircraft part and is sometimes referred to as a non-LSAP. An ADB may be managed using methods developed for LSAP. An example of an ADB is the Navigation Database (NDB), which provides navigation and route information for the Flight Management System (FMS) so that it can accomplish navigation tasks. In most cases the NDB is replaced every 28 days and contains two different databases, the current database and the previous NDB. Aviation Australia FLS classifications including databases 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 43 of 167 CASA Part 66 - Training Materials Only Operator Modifiable Software Operator-Modifiable Software (OMS) consists of User-Modifiable Software (UMS) and User- Certifiable Software (UCS). OMS permits operators to modify a system function to suit preferred operational procedures, existing operational infrastructure or local conditions. This can be achieved by providing a UMS partition within the executable software, within which the modified software is installed using the appropriate ground-based tools. The resulting software can then be loaded onto the aircraft as a separate software part for the equipment concerned. User Modifiable Software UMS is software intended for modification by the aircraft operator without review by the certification authority, the aircraft manufacturer or the equipment manufacturer. Modifications by the user may include modifications to data and/or executable code. Target hardware for UMS includes: Aircraft Communication and Reporting System (ACARS) Aircraft Condition Monitoring System (ACMS) Satellite Communications (SATCOM) In-Flight Entertainment System (IFE). Aviation Australia FLS classifications including databases 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 44 of 167 CASA Part 66 - Training Materials Only User-Certifiable Software User-Certifiable Software (UCS) is software that an operator or its designated party chooses to modify in accordance with approved guidelines. A change to UCS requires certification acceptable to the operator’s regulatory authority. Supplier Controlled Software Operational Program Software Operational Program Software (OPS) is software that contains the program instructions for a Line- Replaceable Unit (LRU). Each version of OPS has a unique software part number. Aviation Australia Types of field loadable software 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 45 of 167 CASA Part 66 - Training Materials Only Operational Program Configuration Operational Program Configuration (OPC) is software that determines the function of the LRU. It is a special purpose database that enables or disables optional functions of the OPS. It eliminates the requirement for pin programming of the LRU. Aviation Australia MCDU software version Aircraft Configuration List An Aircraft Configuration List (ACL) is a list of modules, including LRUs, which use LSAPs applicable to a specific aircraft. This list may be contained in a drawing supplied by the Type Certificate Holder, in a Service Bulletin, in a Service Information Letter, in an Illustrated Parts Catalogue (IPC) or as part of a separate tracking system. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 46 of 167 CASA Part 66 - Training Materials Only Software Media Software media is the means of transporting and distributing software for installation in the user equipment. The software media comes in many forms, including discs (floppy and CD-ROM), memory cards, tapes (mostly obsolescent) and via the internet. A single software medium may contain numerous LSAPs or Aeronautical Databases. FLS USB Stick Software Version The software version is the specific software item at a designated revision status. Within software versions, it is common for there to be a major and a minor version designation. Minor version designations usually reflect only minor changes to the software. Software version designation is often seen in the format A.BB, where A is the major version designation and BB is the minor version designation. Aviation Australia Software part number version identification 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 47 of 167 CASA Part 66 - Training Materials Only Target Hardware Target hardware identifies the hardware, such as LRUs or modules, for the purpose of loading new FLS. Target hardware for databases include: Enhanced Ground Proximity Warning System (EGPWS) Flight Control Computer (FCC) Flight Management Computer (FMC). The databases are used by the appropriate system to accomplish aircraft navigational and manoeuvring tasks. Aviation Australia Flight control computer 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 48 of 167 CASA Part 66 - Training Materials Only Target Hardware for LSAP The following list includes target hardware for LSAP: Display Electronics Unit (DEU) Flight Management Computer (FMC) Flight Control Computer (FCC) Digital Flight Data Acquisition Unit (DFDAU) Digital Flight Data Acquisition Management Unit (DFDAMU) Auxiliary Power Unit (APU) and Electronic Control Unit (ECU) Electronic Engine Control (EEC). Display Electronics Unit (DEU) 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 49 of 167 CASA Part 66 - Training Materials Only Digital Flight Data Acquisition Unit (DFDAU) Sourcing Software Software updates such as NDB, TDB and MEDB should be acquired from a source that is acceptable to the Target Hardware Manufacturer and accompanying documentation and Transport Storage Media containing the modified software should clearly identify this. The Transport Storage Media should also be annotated with the originator identification and quality/conformity markings. The responsibility for obtaining appropriate documentation confirming the authenticity, performance specification and accuracy of the software rests with the operator. It is also recommended that a ‘confidence’ check of the received navigation/performance data be accomplished to ensure that the changes made satisfy their intended use. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 50 of 167 CASA Part 66 - Training Materials Only Software Data Loading Data Loaders As with all computer systems, a means to load software and data updates is a necessity. To facilitate this, a software or data loader is required. Data loaders facilitate software loading to any programmable computer system except those whose software is stored on ROM, PROM and EPROM. For example, the FMC program is likely able to be reloaded using a data loader, but a FCC program is more likely to have a BIOS-type software program. This means it is less likely to become corrupted and cannot be erroneously modified or corrupted using a data loader. To change a ROM program, a computer chip within the computer must be physically replaced or reprogrammed. Data loaders will be linked to the FMC system or connected to a data bus coupler. Data loaders may be portable, allowing them to be taken to the aircraft and plugged in, or in the most up-to-date systems they may be integrated into the avionics system. Loading information is similar to loading software onto your home computer. If several programmable computers are incorporated into the avionics system, you may be required to select the computer intended to receive the software. Correct software loads and software configurations are critical to aircraft operations. A software mismatch or glitch as a result of incorrect loading procedures could cause a disastrous sequence of events, so it is imperative that maintenance manuals are strictly followed when loading software, and that software and system functional and confidence checks are performed following software loading. Data loaders 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 51 of 167 CASA Part 66 - Training Materials Only Data loaders are referred to as: ADLs (airborne data loaders) PDLs (portable data loaders) Portable Maintenance Access Terminals (PMATs) which can also provide data loading and fault-recording capability. Portable Maintenance Access Terminal (PMAT) The software data loader is used to download loadable software into the aircraft’s systems. It provides a high-speed data transfer capability to the aircraft. A data loader normally uses one of two media to transfer information into the aircraft, either a standard 3.5-in. disc (1.44 MB) or a CD-ROM (700+ MB). The disc is the most common method of software transfer as it has more than enough storage for the data required. The data loader can be permanently fitted to the aircraft or it can be an external device fitted only when new software is required. In an internal data loader, information can be downloaded by placing the media format (usually a disc) into the unit and following the loading procedures as defined by the systems operating manual. At the completion of the process, the disc is removed. In some other systems, the disc may be left and the system directly reads from the disc. This type is not very common and is mainly used by in-flight entertainment systems. An external device is usually connected via a high-speed data connection cable (an umbilical cord cable). This is usually done for software associated with the FMC. The process of downloading the information is carried out via the FMC. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 52 of 167 CASA Part 66 - Training Materials Only Aviation Australia Correct software loading is extremely important FLS Loading and Certification FLS is loaded into the target hardware using a PDL, ADL or off-aircraft data loader (workshop). After loading, the software should be verified on-board using the established processes and procedures detailed in the maintenance manual or associated approved maintenance or modification data. Any FLS loading should be recorded in the Aircraft Configuration List (ACL), and a copy kept on board the aircraft with a further copy also kept in the operator's aircraft maintenance records system. After any loading of LSAP, a Certificate of Release to Service must be issued by an appropriately authorised Line/Base Maintenance Certifying Staff. FLS loading and certification 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 53 of 167 CASA Part 66 - Training Materials Only Electronic Distribution of Software Electronic Distribution of Software (EDS) is a process whereby FLS is moved from the producer or supplier to a remote site (generally the operator) without the use of physical media. EDS is increasingly being utilised to transfer FLS from the supplier to an operator. The obvious advantages of this are speed of distribution and removal of the need for physical transport media. This should be accomplished to a standard acceptable to the regulatory authority. It is also recommended that a ‘confidence’ check of the received navigation/performance data be accomplished to ensure that the changes made satisfy their intended use. Electronic distribution of software 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 54 of 167 CASA Part 66 - Training Materials Only Field-Loadable Software Procurement and Documentation LSAP, databases and UMS are first delivered with the new aircraft and contained in the target hardware and in media sets in binders or storage bins. It must be realised, however, that the part number of target hardware does not necessarily indicate the loaded software part number when replacing affected LRUs. LSAP – Procured LSAP must be obtained from an approved source using the part number specified and be accompanied by a JAA Form 1 or FAA 8130-3. These can typically be found in documents such as the IPC, Service Bulletin, Service Letter or Approved Modification. Updating the A380 navigation with flash drives 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 55 of 167 CASA Part 66 - Training Materials Only FLS Storage Media Handling In order to ensure FLS and storage media reliability, storage media should be sealed in dust- and lint- free material in a closed box, should be clearly labelled as containing software media and the following should be avoided: Moisture, dust or airborne contaminants Magnetic fields Direct sunlight for prolonged periods Rate of temperature change greater than 20 °C/hr Temperature outside the range of -20 to +50 °C X-ray Magnetic or electromagnetic source. FLS storage media handling FLS and storage media known to contain defects should not be used and should be placed in quarantine for suitable disposal. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 56 of 167 CASA Part 66 - Training Materials Only Replication of FLS If LSAP copies are to be made, this should be accomplished using the aircraft Type Design Organisation-approved FLS storage media replication process. This replication should be recorded in an Aircraft Software Replication Register and be traceable to the original source from which copies were made. This is to ensure that this activity can be audited. A copy of the accepted release documentation, as appropriate, should accompany all LSAP storage media containing software copy. Duplicating data 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 57 of 167 CASA Part 66 - Training Materials Only Procedures It is essential that operators have appropriate procedures in place such that at any time it is possible to determine the equipment and software configuration of each aircraft in their fleet. Operators involved in the procurement, modification and embodiment of FLS shall produce a documented procedure within their company procedures, Maintenance Management Exposition (MME) or equivalent that describes their means of compliance with this notice. The procedure should cover the complete cycle, from procurement specification, distribution methodology (for example, EDS, media type and so on) and receipt inspection/assessment through to embodiment, subsequent testing and release to service. This process must also be included in the internal audit program. Maintenance management exposition Case Study Changing aircraft software can result in changes to the operating characteristics of the aircraft. Areas of the aircraft that can be affected by changing software include: Engine systems Navigational systems Flight control systems. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 58 of 167 CASA Part 66 - Training Materials Only Air New Zealand Flight 901 - Mt Erebus Disaster The following example highlights the possible catastrophic effects of unapproved changes to aircraft software. On 28 November 1979, Air New Zealand Flight 901 left Auckland Airport. On board were 237 passengers and 20 crew members bound for Antarctica. The plan gave co-ordinates for the trip to Antarctica and across McMurdo Sound which, when entered into the computerised navigation system, would be flown automatically by the plane. That morning, Collins and Cassin entered the series of latitude and longitude co-ordinates into the aircraft computer. Unknown to them, two of the coordinates had been changed earlier that morning, and when entered, shifted the flight path of the aircraft 45 km to the east. At 12:45 p.m., Collins advised McMurdo Centre he was descending farther, to 2000 ft. At this point he locked onto the computerised navigational system, but Flight 901 was not where the crew thought it was. The change in the two co-ordinates had put it on a path not across the flat ground of McMurdo Sound, but across Lewis Sound and towards the 12 300-ft-high active volcano Mount Erebus. The air was clear, and beneath the cloud layer the whiteness of the ice blended with the whiteness of the mountain, with no contrast to show the upwards slope of the land – a whiteout. At 12:49 p.m., the deck altitude device began to blare a warning, but there was no time for Collins to save the situation from disaster. Just 6 seconds later, Flight 901 hit the side of Mount Erebus and disintegrated. Air New Zealand Flight 901 crash site This shows the catastrophic effects of loading an unapproved NDB into an aircraft. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 59 of 167 CASA Part 66 - Training Materials Only Electromagnetic Environment (5.14) Learning Objectives 5.14 Understand how to minimise or prevent EMI/RFI from being generated by devices (S). 5.14.1 Explain the influence of the following phenomena on maintenance practices for electronic systems: EMC - electromagnetic compatibility (Level 2). 5.14.2 Explain the influence of the following phenomena on maintenance practices for electronic systems: EMI - electromagnetic interference (Level 2). 5.14.3 Explain the influence of the following phenomena on maintenance practices for electronic systems: HIRF - high intensity radiated field (Level 2). 5.14.4 Describe the influence of the following phenomena on maintenance practices for electronic systems: lightning and lightning protection (Level 2). 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 60 of 167 CASA Part 66 - Training Materials Only Electromagnetic Interference in Electrical Systems Electromagnetic Environment Terminology Throughout this topic a number of definitions, terms and acronyms will be referenced. Key Definitions Terms Deﬁnition Electromagnetic Environment (EME) The totality of electromagnetic phenomena existing at a given location. Electromagnetic Compatibility (EMC) Capability of equipment or systems to be operated in the intend operational electromagnetic environment at designed levels of efﬁciency without degradation due to electromagnetic interference. Electromagnetic Interference (EMI) Deﬁned by NATO as any electromagnetic disturbance that interrupts, obstructs or otherwise degrades or limits the effective performance of electronics/electrical equipment. High-Intensity Radiated Field (HIRF) Man-made sources of electromagnetic radiation generated exte to aircraft. Radio-Frequency Interference (RFI) Electromagnetic interference (EMI), also called radio -frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. Ⓒ Aviation Australia Electromagnetic Environment definitions, terms and acronyms Avionic Frequency Bands The frequency bands used by avionics systems span the electromagnetic spectrum from a few kilohertz to several gigahertz. VHF Omnidirectional Range (VOR) is a radio beacon used in point-to-point navigation. It operates from 108 to 118 MHz. Glideslope Systems used during landings operate in the 328 to 335 MHz range. Distance-Measuring Equipment (DME), which gauges the distance between the aircraft and ground- based transponders, operates at just over 1 GHz. Also in the spectrum above 1 GHz are global positioning, collision avoidance and cockpit weather radar systems. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 61 of 167 CASA Part 66 - Training Materials Only PED Frequency Bands Personal Electronic Devices (PEDs) operate at frequencies from 10 to 15 KHz for AM radios and up to 400 MHz for laptop computers. When the higher harmonics of these signals are taken into account, the emitted frequencies cover almost the entire range of navigation and communication frequencies used on the aircraft – and PEDs are just a single class of EMI emitters. When the full spectrum of other radiated and conducted EMI emitters is considered, it becomes clear that the entire system of electronic equipment aboard aircraft is at risk of EMI. But the fact that all avionics equipment and cabling which are critical to the functioning of aircraft are shielded against EMI raises an interesting question: How exactly does EMI, such as Radio Frequency Interference (RFI) from a passenger radio or laptop, permeate the system? EMI Permeation In many cases, the cause is simply inadequate shielding, or shielding which has been damaged during servicing or has degraded due to corrosion, thus increasing the resistance of the electrical connection to ground. As effective shielding depends on good grounding, any additional resistance in the system – for example, at a corroded backshell or a poorly installed shield termination crimp ring – can enable the wires to pick up interfering signals directly. Aircraft with navigation and communication antennas located outside the skin can also pick up EMI radiated through passenger windows and other unshielded openings in the plane. The pathway for RFI from a passenger PED would, in this example, be out the window, back into the plane via an unprotected or RFI-sensitive antenna, and then directly into a navigation receiver, autopilot computer or other avionics device. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 62 of 167 CASA Part 66 - Training Materials Only Electromagnetic Interference In the early 1980s, a British Harrier Jump Jet landed for the very first time on a U.S. aircraft carrier. On the flight deck, the carrier's yellow-shirted deck crew stood ready to secure the jet and roll it to the hangar deck elevator. On the bridge, a dozen pairs of eyes watched intently as the Harrier made its signature vertical landing. But as the powerful vectored thrust turbofan engine brought the aircraft down in its measured descent to the flight deck, a terrible accident occurred: Electromagnetic interference radiating from the carrier's massive island of electronic equipment disrupted the Harrier's electronic controls and triggered the pilot's emergency ejector seat. The pilot was propelled through the canopy of the jet with explosive force, killing him instantly. On the flight deck, emergency crews worked rapidly to control the now pilotless plane. But the damage was done. Electromagnetic Interference (EMI), defined by the North Atlantic Treaty Organisation (NATO) as an electromagnetic disturbance which interrupts, obstructs or otherwise degrades the effective performance of electronic or electrical equipment, had claimed another victim. Aircraft are designed and built to withstand interference from a broad range of electromagnetic fields. In fact, the outer shell of the plane as well as its internal electronic equipment and interconnect cabling are designed to prevent penetration of disruptive electromagnetic signals – both those generated internally and those emanating from external sources. Electromagnetic interference Effects of EMI Electromagnetic interference can jam sensitive equipment and burn out electric circuits. In aircraft, EMI can affect everything from fly-by-wire flight control systems to a cockpit fuel gauge, and in extreme cases it can send a plane into an uncommanded dive or shut down a critical avionics system. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 63 of 167 CASA Part 66 - Training Materials Only Electromagnetic Compatibility EMC is the ability of equipment to operate satisfactorily in its EM environment without introducing intolerable EM disturbances to other electrical devices in that environment. Aviation Australia Electromagnetic compatibility 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 64 of 167 CASA Part 66 - Training Materials Only Elements of an EMC Problem There are three essential elements to any Electromagnetic Compatibility (EMC) problem: A source of an electromagnetic phenomenon A receptor (or target) that cannot function properly due to the electromagnetic phenomenon A path between them that allows the source to interfere with the receptor. Each of these three elements must be present, although they may not be readily identified in every situation. EMC problems are generally solved by identifying at least two of these elements and eliminating (or attenuating) one of them. Aviation Australia Three elements of an EMC problem Potential Sources Potential sources of EMC problems include radio transmitters, power lines, electronic circuits, lightning, lamp dimmers, electric motors, arc welders, solar flares and just about anything that utilises or creates electromagnetic energy. Potential Receptors Potential receptors include radio receivers, electronic circuits, appliances, people and nearly any object that utilises or can detect electromagnetic energy. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 65 of 167 CASA Part 66 - Training Materials Only Coupling Path Methods of coupling electromagnetic energy from a source to a receptor fall into four categories: Conducted (electric current) Inductively coupled (magnetic field) Capacitively coupled (electric field) Radiated (electromagnetic field). Coupling paths often utilise a complex combination of these methods, making the path difficult to identify even when the source and receptor are known. There may be multiple coupling paths, and steps taken to attenuate one path may enhance another. EMI coupling paths 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 66 of 167 CASA Part 66 - Training Materials Only Electric and Magnetic Fields An electric field has the ability to exist with only one pole. All magnetic material exists with two poles. In this way, an electric field is not like a magnetic field. The lines of force of a magnetic field go from north to south in a curved manner. Electric fields do the same with opposite charges present. In this case, electric force naturally travels in straight lines from the centre of its point of origin outward, no matter its size. Aviation Australia Electric force Electric (E) fields are created by voltages on conductor areas, and magnetic (M) fields are created by currents flowing (in loops, as they always do). All electrical signals create both types of fields with their conductors, so all conductors leak their signals to their external environment and allow external fields to leak into their signals. 2024-05-27 B2-05b Digital Techniques / Electronic Instrument Systems Page 67 of 167 CASA Part 66 - Training Materials Only Leakage and Antenna Effect of Conductors The frequencies in common use in daily life range from AC power lines through audio frequencies; long, medium, and short-wave radio; FM and TV broadcast; to 900 MHz and 1.8 GHz for mobile phones. The real spectrum is busier than this – all of the range above

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