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ATR 42/72-600 Systems Guide — Chapter K: Flight Instruments

2026-06-23

Chapter K. FLIGHT INSTRUMENTS (FCOM DSC 31, 34)

1. ELECTRONIC INSTRUMENT SYSTEM (EIS) SCHEMATIC ARCHITECTURE (Page 116)

The Electronic Instrument System (EIS) processes raw sensory inputs and telemetry data to drive the primary cockpit displays, using an integrated modular layout.

  EIS COMPONENT SIGNAL MAP
  ┌────────────────────────────────────────────────────────┐
  │               AIRCRAFT SYSTEMS & TELEMETRY             │
  │     (ADCs, AHRS, FMS, Engines, Radios, Fuel Nodes)     │
  └───────────────────────────┬────────────────────────────┘
                              │
                              ▼ [High-Speed ARINC 429 Bus]
  ┌────────────────────────────────────────────────────────┐
  │               INTEGRATED MODULAR AVIONICS              │
  │        (IMA Processing Cabinets & Data Modules)        │
  └───────────────────────────┬────────────────────────────┘
                              │
               ┌──────────────┼──────────────┐
               ▼              ▼              ▼
         ┌───────────┐  ┌───────────┐  ┌───────────┐
         │   PFD 1   │  │    EWD    │  │   PFD 2   │
         │ (Capt Air)│  │(Engine/FWS│  │ (F/O Air) │
         └─────┬─────┘  └───────────┘  └─────┬─────┘
               │                             │
               ▼                             ▼
         ┌───────────┐                 ┌───────────┐
         │   MFD 1   │                 │   MFD 2   │
         │ (Left ND) │                 │(Right ND) │
         └───────────┘                 └───────────┘

1.2. Physical Display Configurations

The instrument suite consists of five interchangeable $6 \times 8 \text{ inch}$ Liquid Crystal Display (LCD) units configured side-by-side across the Main Instrument Panel (MIP). Each unit features an independent brightness dimmer knob and dedicated circuit breaker paths.

2. PRIMARY FLIGHT DISPLAY (PFD) OPERATIONAL REGIONS (Page 117)

The Primary Flight Display (PFD) centralizes critical safety data, attitude parameters, and spatial orientation elements into a unified viewing space.

  PFD DISPLAY INTERFACE DIVISION
  ┌────────────────────────────────────────────────────────┐
  │ [ FMA FLIGHT GUIDANCE STRIP BANNER ]   (Top Section)   │
  │                                                        │
  │ ┌──────────┐   ┌────────────────────┐   ┌────────────┐ │
  │ │ Airspeed │   │                    │   │ Altimeter  │ │
  │ │  Tape    │   │  ATTITUDE DIRECTOR │   │   Tape     │ │
  │ │  Scale   │   │  INDICATOR (ADI)   │   │   Scale    │ │
  │ └──────────┘   │                    │   └────────────┘ │
  │                └────────────────────┘   ┌────────────┐ │
  │                                         │ Vert Speed │ │
  │                                         └────────────┘ │
  │               [ HSI ROSETTE COMPASS ]                  │
  └────────────────────────────────────────────────────────┘

2.1. Scale Layout Characteristics

  • Attitude Director Indicator (ADI): Provides an artificial horizon display mapping aircraft pitch and roll angles, overlaid with Flight Director guidance commands.
  • Airspeed Tape Display: Vertical strip tracking live indicated airspeed parameters. Features dynamic color markings mapping structural minimum speeds ($V_{MS}$), structural flap limits ($V_{FE}$), maximum operational speed bounds ($V_{MO}$), and high angle-of-attack ($V_{AOA}$) warning combs.
  • Altimeter and Vertical Speed Tape: Right-hand layout tracking barometric target pressure altitude metrics, target altitude capture bugs, and real-time vertical rate trends.
  • Horizontal Situation Indicator (HSI): Ground orientation tracking compass showing selected heading vectors, VOR/ILS course deviations, and distance tracking numbers.

3. MULTI-FUNCTION DISPLAY (MFD) DESIGN CONFIGURATIONS (Page 118)

The Multi-Function Display (MFD) units flank the primary displays to provide navigation maps and granular aircraft system tracking pages.

3.1. Primary Operational Profiles

  1. Navigation Display (ND) Modes: Driven via settings on the Electronic Flight Control Panel (EFCP).
  2. Rose Mode: Displays a $360^\circ$ compass wheel overlay tracking VOR/ADF needles.
  3. Arc Mode: Displays a $90^\circ$ forward-looking map sector to maximize flight path visibility down track.

  4. Map Mode: Couples display tracking directly to active FMS waypoint tracks and terminal database paths.

  5. Systems Synoptic Monitoring Display (SD): Replaces the map view to display real-time interactive schematics. Crews can cycle through individual system layers using the panel selection keys:

  6. ELEC (Electrical generation, line distribution profiles).
  7. HYD (Fluid volumes, operating pressures).
  8. FUEL (Tank quantities, feed lines, cross-feed states).
  9. CABIN (Air conditioning flows, zone temperatures, pressurization).
  10. ENG ( granular engine diagnostics, vibration indexes).

4. ENGINE AND WARNING DISPLAY (EWD) LAYOUT TERMINOLOGIES (Page 119)

Mounted permanently in the center of the main instrument panel array. This display provides continuous monitoring of engine parameters and system alert structures.

  EWD PERMANENT SCREEN ALLOCATION
  ┌───────────────────────────────┬────────────────────────┐
  │                               │  TQ %   [ 82.5 ] [ 82.1]│
  │                               ├────────────────────────┤
  │      FLIGHT WARNING SYSTEM    │  ITT °C [  742 ] [  738]│
  │       ACTIVE MEMO WINDOW      ├────────────────────────┤
  │                               │  Np %   [ 82.0 ] [ 81.9]│
  │   - Alerts displayed in       ├────────────────────────┤
  │     order of urgency          │  Nh %   [ 92.5 ] [ 92.4]│
  │   - Explicit instruction      ├────────────────────────┤
  │     and clearing tracking     │  FF kg  [  245 ] [  242]│
  │                               ├────────────────────────┤
  │                               │  FUEL T.[   1840 kg  ] │
  └───────────────────────────────┴────────────────────────┘

4.1. Core Propulsion Indexes Tracking Laws

  • Torque Display (TQ%): The primary engine power reference index. Displays high-precision torque values delivered to the propeller assemblies.
  • Interstage Turbine Temperature (ITT): Displays engine thermal data. Exceeding nominal thermal limits triggers amber or red alert transitions.
  • Rotational Speed Gauges ($Np$ & $Nh$): Track the operating speed of the low-pressure propeller shaft ($Np$) and high-pressure engine gas generator spool ($Nh$).

5. NAVIGATION OVERLAY INTERFACE & SOURCE FAILURE ALERT LOGIC (Page 120)

The display system integrates cross-talk validation circuits to verify the integrity of displayed sensory data lines before rendering them to the crew.

5.1. Sensor Input Overlays

  • Weather Radar (WXR) injection: Superimposes raw precipitation returns directly over the active ND navigation tracking map.
  • Terrain Awareness Display (TAWS): Projects color-coded elevation contours onto the ND, mapping geographic high points against the current altitude profile to prevent Controlled Flight Into Terrain (CFIT).

5.2. Source Failure Alert Logic

If a critical sensor or data line experiences an electrical dropout or code corruption error, the Integrated Modular Avionics (IMA) invalidates the data stream. The display screen immediately flags the failed data block using highly visible, standardized red indicator labels:

  PFD DATA DROP INDICATORS
  ┌────────────────────────────────────────────────────────┐
  │   [ ATT FAIL ]   ──► Attitude Gyro Telemetry Loss       │
  │   [ HDG FAIL ]   ──► Heading Sensor Input Loss          │
  │   [ ADC FAIL ]   ──► Air Data Computer Line Interruption│
  └────────────────────────────────────────────────────────┘

System Action: When a failure alert displays, the respective tape scale or pointer vanishes from the screen, preventing the flight crew from executing adjustments based on corrupted or trailing data strings. Crews must use the adjacent Display Switching Panel to cross-feed data lines from the opposite, healthy side computer.

Chapter K. FLIGHT INSTRUMENTS (CONTINUED)

4.2. EWD TEMPORARY AND SECONDARY PARAMETERS LOGIC (Page 121)

While primary propulsion indexes remain permanently fixed on the right half of the Engine and Warning Display (EWD), secondary diagnostic values follow an automated presentation law to keep screen layout clean.

  • Monitored Secondary Parameters: Engine Oil Pressure, Oil Temperature, Fuel Temperature, and Engine Core Vibration Indexes.
  • Automated Display Triggers: These indicators are normally hidden during routine cruise flight. They will automatically open and display below the primary tapes under three conditions:
  • Engine Start Phase: Displays during the initial engine motoring profile until the high-pressure spool stabilizes at idle parameters.
  • Engine Shutdown Phase: Displays when a Condition Lever is moved toward the FEATHER or FEATHER/SHUT OFF gate.
  • Parameter Exceedance Alert: Displays instantly if any secondary sensor tracks a value that breaches normal operating safety limits (e.g., oil pressure drops below green limits or core vibration spikes). The affected digital value flashes amber or red depending on the severity of the trend.

5.3. DISPLAY SWITCHING PANEL AND DATA RECONFIGURATION (Page 122)

The flight deck includes automated and manual fallback mechanisms to handle a complete display screen failure (blanking) or data line corruption.

  • Automatic Screen Transposition: If a primary display screen (like PFD 1) suffers an internal power failure and goes completely blank, the adjacent multi-function display screen (MFD 1) senses the data loss. It immediately drops its active navigation map and draws the primary flight profile tape architecture onto its display face to maintain pilot orientation.
  • Data Source Miscompares: If Air Data Computer 1 (ADC 1) and Air Data Computer 2 (ADC 2) deliver conflicting metrics to the processing cabinets, the system displays an amber flashing MISCOMP alert line across both airspeed and altitude tapes. This warns the crew to cross-check parameters against the standalone standby instruments before selecting a master control source.

7. SWITCHING PANEL (Page 123)

Source: direct reading of PNG page 125 (printed 123)

ATA 34

  CAPT SWITCHING
  ┌────────────────────────────────────────────────┐
  │   ATT/HDG        ADC          DISPLAY          │
  │   [F/O  ]      [F/O  ]        PFD             │
  │   [SYS 2]      [SYS 2]        MFD             │
  │                                EWD             │
  └────────────────────────────────────────────────┘
  • ATT/HDG pb: Enables use of AHRS 2 information. When captain pb is depressed, SYS 2 illuminates white on CAPT pb, CAPT 2 illuminates green on F/O pb.
  • ADC pb: Enables use of ADC 2 information. When captain pb is depressed, SYS 2 illuminates white on CAPT pb, CAPT 2 illuminates green on F/O pb.
  • DISPLAY pb: In normal conditions, enables cycling the three formats (PFD, MFD, EWD) on DU 2 (capt switching) or DU 4 (F/O switching). In case of failure of any DU (DU 1 or 2 on capt side, or DU 4 or 5 on F/O side), enables cycling the three formats on the remaining DU.

7. ELECTRONIC FLIGHT CONTROL PANEL (EFCP) INTERFACE (Page 124)

Mounted on the outboard glaresheld sections (Left for Captain, Right for First Officer). Controls individual Navigation Display (ND) configurations.

  ELECTRONIC FLIGHT CONTROL PANEL (EFCP)
  ┌────────────────────────────────────────────────────────┐
  │   MODE SEL        RANGE SEL        ND NAVIGATION CODES │
  │    (ROSE)          ( 20 )           [WPT ]   [ARPT]    │
  │    (ARC )          ( 40 )                              │
  │    (MAP )          ( 80 )           [WXR ]   [TERR]    │
  │                    (160 )                              │
  └────────────────────────────────────────────────────────┘
  • MODE SEL Knob: Rotary selector to cycle through different map layout configurations:
  • ROSE: Renders a fixed, complete 360-degree compass wheel optimized for traditional raw data VOR/ADF navigation and holding pattern tracking.
  • ARC: Provides a high-visibility 90-degree forward-looking pie segment, maximizing the visible terrain map space downstream along the flight path vector.

  • MAP: Couples display tracking directly to active FMS navigation waypoints and active route trajectory strings.

  • RANGE SEL Knob: Scales the geographic distance rings visible on the ND screen across a selectable spectrum from a minimum of 5 nautical miles up to a maximum of 320 nautical miles.

  • ND Navigation Display Overlay Pushbuttons: Independent toggles that inject real-time graphical data layers directly over the active navigation map:
  • WPT: Displays non-route geographic intersection waypoints stored in the navigation database.
  • ARPT: Projects location markers and airfield identification text codes for regional airports.
  • WXR: Energizes receiver lines and embeds colored weather radar precipitation returns.
  • TERR: Activates real-time terrain sweep data maps to provide structural terrain clearance tracking.

8. WEATHER RADAR CONTROL PANEL SPECIFICATIONS (Page 125)

Located on the center pedestal control group. Manages the Primus 660 radar array sweeps.

  WEATHER RADAR INTERFACE BLOCK
  ┌────────────────────────────────────────────────────────┐
  │  WXR MODE      GAIN ADJ       TILT UP/DN    STAB AREA  │
  │  ( OFF  )       ( O )           ( O )        [ NORM ]  │
  │  ( STBY )     MIN   MAX       +15   -15      [ STAB ]  │
  │  ( TEST )                                              │
  │  (  ON  )       [ TGT ALRT ]                           │
  └────────────────────────────────────────────────────────┘

Component Functional Logic and Display Targets:

  • WXR MODE Dial:
  • OFF: Removes power from the nose-mounted radar transceiver.
  • STBY (Standby): Warms up internal transceiver circuitry while blocking active wave generation to protect ground crew from radiation hazards.
  • TEST: Injects a multi-colored geometric test calibration pattern across the display screen to confirm receiver sensor health.

  • ON: Initiates live active sweeps through the nose cone.

  • GAIN ADJ Potentiometer: Fine-tunes the sensitivity threshold of the receiver array to amplify or suppress weak precipitation returns.

  • TILT Wheel: Manually pitches the radar antenna assembly up or down through an operating range of +15 degrees to -15 degrees to track specific storm cell cores relative to the current altitude profile.
  • STGT / TGT ALRT Pushbutton (Target Alert): Monitors for intense precipitation blocks located just beyond the current display range scale. If a severe convective cell is identified down track, a flashing amber hazard block appears on the ND map to warn the crew long before entering the cell area.

9. FLIGHT DECK DIGITAL CLOCK PANEL AND TIME SCHEDULING (Page 126)

An independent digital clock module is integrated into each pilot's primary instrument panel section to provide baseline timing vectors.

  • Primary Time Synchronization: The Master Avionics Clock continuously transmits GPS-synchronized universal coordinated time (UTC) codes over the ARINC data buses. This ensures that the flight crew displays, flight data recorders, and FMS computing clocks share a single time reference.
  • CHRONO Pushbutton Operation: Pressing the button initiates an independent count timer loop that displays elapsed minutes and seconds on the lower PFD screen bezel. This is used to track precision timing blocks during engine start sequencing, holding pattern legs, and instrument approach profiles.
  • ET (Elapsed Time) Switch Function: A three-position toggle switch used to track total block flight duration. Selecting ET to ON starts the timer at block-out. This value runs continuously until the switch is manually stopped at block-in.

10. RECORDER (RCDR) PANEL LAYOUT & OPERATION (Page 127)

Located on the overhead panel space. Manages power loops to the flight recorders.

  RCDR INTERFACE VALVE PANEL
  ┌────────────────────────────────────────────────────────┐
  │                         RCDR                           │
  │                                                        │
  │                     [ CTL FAULT ]                      │
  │                                                        │
  │                       GND WIRED                        │
  │                        [  ON  ]                        │
  └────────────────────────────────────────────────────────┘

10.1. System Activation Logic Rules

To conserve component runtime and protect data retention tracks, the solid-state Cockpit Voice Recorder (CVR) and Digital Flight Data Recorder (DFDR) activate based on specific system states:

  • AUTO Mode (Default State - Button Released): Power line relays feed current to the recorders automatically according to three scheduled triggers:
  • On the ground during the first 10 minutes following initial aircraft electrical power-up.
  • On the ground continuously once at least one engine is running ($N_H > 61\%$).

  • In flight continuously from the moment the main landing gear shock struts uncompress at liftoff until touchdown.

  • GND WIRED ON Mode (Button Depressed - White Bar visible): Overrides the automatic scheduling loops to force power directly to the recording fields on the ground. This allows maintenance crews to check microphone paths or download system fault logs prior to engine start.

11. INTEGRATED ELECTRONIC STANDBY INSTRUMENT (IESI) (Page 128)

The Integrated Electronic Standby Instrument (IESI) is a standalone emergency backup module mounted centrally on the main instrument panel. It functions completely independently of the primary glass cockpit networks.

  • Emergency Power Input: Wired directly to the HOT EMERGENCY BATTERY BUS. This bypasses all master generation contactors and load-shedding relays, ensuring the display remains active for a minimum of 30 minutes following a total aircraft electrical failure.
  • Internal Sensor Suites: The IESI housing contains its own solid-state micro-machined inertial sensors and internal pressure transducers. It bypasses the primary ADCs and AHRS computers to calculate its own independent backup telemetry lines:
  • Attitude data (Pitch, Roll, and slip indications derived from internal rate-gyros).
  • Indicated Airspeed (Computed via dedicated backup pitot-static line connections).
  • Barometric Altitude (Tracks absolute pressure height, managed via a dedicated manual baro setting knob on the bezel frame).

12. PFD AIRSPEED TAPE MARKINGS AND SPEEDS MATRIX (Page 129)

The vertical airspeed indicator tape on the primary flight display calculates real-time operating bounds based on the aircraft's current weight, flap setting, and icing environment configuration.

  PFD SPEED TAPE SYMBOLOGY PROFILE
  ┌────────────────────────────────────────────────────────┐
  │  [ ▇▇▇ ] ◄── Vmo Maximum Speed Limit Red Checkerboard  │
  │    │                                                   │
  │  [ 210 ] ◄── Current indicated speed pointer           │
  │    │ ─── ◄── Speed Trend Vector (6-Second Prediction)  │
  │    │                                                   │
  │  [ F15 ] ◄── Flap Retraction Speed Bug (White Label)  │
  │    │                                                   │
  │  [ Vapp] ◄── Target Approach Target Bug (Target Cyan) │
  │    │                                                   │
  │  [ ░░░ ] ◄── Vms Minimum Stable Amber Checkerboard    │
  └────────────────────────────────────────────────────────┘

12.1. Critical Target Bug Definitions:

  • Speed Trend Vector: A dynamic vertical line extending from the center speed pointer. It evaluates current acceleration parameters to project what the indicated airspeed will be exactly 6 seconds into the future.
  • Minimum Stable Speed ($V_{MS}$): Rendered as a solid amber checkerboard strip crawling up the bottom of the speed tape. This marks the absolute lower aerodynamic safety boundary for the current configuration before entering the stall buffet region.
  • Maximum Operating Limit Speed ($V_{MO}$): Rendered as a high-visibility red-and-white striped column running down from the top of the tape. This marks the structural limit speed. Exceeding this boundary triggers the master warning lights and activates the mechanical clacker audio alarm.

13. ALTIMETER VERTICAL TAPE DISPLAY AND BAROMETRIC REFS (Page 130)

The right-hand vertical scale on the PFD displays real-time barometric altitude data using a moving tape layout and a centralized readout window.

  • Altimeter Tape Scaling: Displays continuous altitude intervals marked every 100 feet, with primary numerical index lines stamped at every 1,000-foot level.
  • Barometric Target Entry Window: Located below the altimeter tape scale. Pilots adjust this setting using the baro knob on the EFCP to synchronize pressure tracking metrics:
  • QNH Mode: Displays local airfield barometric pressure settings (altimeter reads absolute altitude above mean sea level).

  • STD Mode: Pressing the center of the baro knob overrides manual entries and locks the altimeter code to standard pressure ($1013.2\text{ hPa} / 29.92\text{ inHg}$). This is used above the transition altitude to unify flight levels across cruise channels.

  • Metric Altitude Overlay Display: Actuating the metric selection toggle projects a duplicate altitude target window at the top of the primary tape scale. This displays the aircraft's current altitude in meters to satisfy regional air traffic control requirements.