5.01 Electronic Instrument Systems.pdf

Electronic Instrument Systems (5.1) Learning Objectives 5.1.1 Describe typical arrangements of electronic instrument systems (Level 2). 5.1.2 Describe a typical cockpit layout of electronic instrument systems (Level 2). 2022-07-22 B1-05b Digital Techniques / Electronic...

Electronic Instrument Systems (5.1) Learning Objectives 5.1.1 Describe typical arrangements of electronic instrument systems (Level 2). 5.1.2 Describe a typical cockpit layout of electronic instrument systems (Level 2). 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 8 of 172 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. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 9 of 172 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 10 of 172 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 (early model) 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. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 11 of 172 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 cathode 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 12 of 172 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 all the primary aircraft operational information on display screens. This reduces the number of devices that aircrew have to scan and also 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 (NDs) Navigation Displays. 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. In the following example, 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. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 13 of 172 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 incorporate the Basic T configuration system to minimise training times and make finding an instrument intuitive. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 14 of 172 CASA Part 66 - Training Materials Only  EADI and EHSI in one display 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 15 of 172 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 16 of 172 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). 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 17 of 172 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 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 Pressure of the day (1013.25 mb = 1013.25 hPa = 29.92 inHg). 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 18 of 172 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 19 of 172 CASA Part 66 - Training Materials Only  EADI and EHSI on a Boeing 737, among Conventional Instrumentation A PFD and ND on a Boeing 777 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 20 of 172 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 21 of 172 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 22 of 172 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. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 23 of 172 CASA Part 66 - Training Materials Only  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 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 analogue to digital converters (ADCs) and receive instructions through digital to analogue 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. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 24 of 172 CASA Part 66 - Training Materials Only  Aviation Australia Data buses are usually duplicated for redundancy 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 25 of 172 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 26 of 172 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. 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. If 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 it's 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. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 27 of 172 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. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 28 of 172 CASA Part 66 - Training Materials Only  Electronic Centralised Aircraft Monitoring (Airbus) 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 29 of 172 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. 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 Engine Indicating and Crew Alert System (Boeing) 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. 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 30 of 172 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 Engine system displays of three different aircraft types 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 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 2022-07-22 B1-05b Digital Techniques / Electronic Instrument Systems Page 31 of 172 CASA Part 66 - Training Materials Only