JL

G1000 System Overview, LRUs, and Instrument Flight Concepts

System Overview and Instrumentation Notes

  • Purpose of the session: overview of the G1000-equipped aircraft systems, with emphasis on the instrument rating material and upcoming quizzes on the schematic/layout.
  • The last half of the instrument rating covers the G1000, and the system overview is foundational for the rest of the course.
  • Memorize the schematic/layout to identify what instruments operate off each system; a quiz will test you on EFT, MSD, GIA #1, GIA #2, ADC, etc. (You don’t have to take notes on the schematic itself, but you should understand its relationships.)
  • Autopilot note: this aircraft has one autopilot; some others may have more. The autopilot servos are shown on the schematic as the moving parts for the ailerons, rudder, and elevator (two-axis autopilot in this airframe).

Equipment Overview (What’s in the cockpit)

  • PFD (Primary Flight Display) and MFD (Multi-function Display) pair are the core displays; both are line replaceable units (LRUs). They come in different sizes.
  • Audio panel: handles navigation, communications, digital data (digital voice), intercom, and marker beacons.
  • Integrated Avionics Units (IAUs): act as the brains and hub that link all LRUs. They are the main communication hub.
  • Air Data Computer (ADC): processes pitot-static data to provide pressure altitude, airspeed, vertical speed, and outside air temperature. Data comes from the pitot-static system and is integrated into the IAUs.
  • Engine Airframe Units (EAUs) or engine/airframe sensors: provide engine and airframe data and communicate with IAUs via a digital interface.
  • Transponder: supports modes Alpha (A), Charlie (C), and Sierra (S). It communicates with both IAUs.
  • AHARS (Attitude, Heading and Reference System) / ARs: attitude and heading information; magnetometer provides magnetic heading data.
  • Magnetometer: located in the right wing on the DA-40; detects magnetic north and provides heading data to the AHRS and ultimately to the HSI.
  • Data Link Receiver: integrates with the avionics network for updates and communications.
  • GPS receivers: the VA-40 houses two GPS receivers; you have two GPS units in the VA-40 and one in the “nose” location (total of at least two in the main unit and one elsewhere, depending on configuration). Each IAU contains a GPS receiver.
  • Marker beacons: linked to ILS; the marker beacons provide position information for approach procedures.
  • Intercom: enables front-seat and back-seat crew to communicate.

Core Interfaces and Concepts

  • The IAU (Integrated Avionics Unit) connects all LRUs and provides the central data flow between the displays, the ADC, sensors, GPS, and other subsystems.
  • The GPS receivers in each IAU feed the navigation data that flows to the PFD and MFD.
  • The ADC provides pitot-static data (airspeed, altitude, vertical speed) and outside air temperature (OAT) to the IAUs.
  • The AHRS/ARs system uses the magnetometer, accelerometers, and rate sensors, synchronized with GPS data to compute attitude and heading.
  • The magnetometer data helps correct heading information on the HSI by providing a stable reference to magnetic north; this improves heading accuracy when ARs are working normally.
  • The data path: sensors (air data, attitude sensors, magnetometer) → EAU/IAU → PFD/MFD and other displays; transponder and data link also participate in the data path.

Turn Anticipation (TA) and Flight Guidance

  • Turn anticipation is a function of the air data computer via the avionics, which uses computed airspeed and ground speed to anticipate when to start a turn to the next waypoint.
  • How TA works: for a given route, if the next leg requires a turn, the system countdowns and initiates the turn before you reach the next fix, allowing a smooth intercept of the outbound course.
  • During turn anticipation, the HSI/needle stays centered as the system leads the turn for you.
  • Important caveats:
    • On instrument approaches, TA typically does not occur at the final approach segment, and misses are treated differently.
    • At the missed approach point (MAP), the waypoint circle indicates a flyover waypoint (you must fly over it) rather than a fly-by turn.
    • If you load an instrument approach, TA may be active outside the initial segment but at the MAP you need to fly the published action (flyover for MAP).
  • Practical note: TA relies on ground speed and airspeed calculations; it helps maintain turns within the boundaries of the published procedure but should not replace your situational awareness or required pilot actions.

Missed Approach Point and Flyover Waypoints

  • When an instrument approach is loaded, the MAP is typically a flyover waypoint (circled) on the leg to be flown; this requires you to fly the aircraft over the point before initiating the missed approach.
  • The distinction between flyover and fly-by waypoints influences how the autopilot and the FMS/AHRS manage the transition at decision altitude/point.

Engine and Airframe Interfaces

  • Engine Airframe Unit (EAU/EAU): communicates with IAUs to provide engine and airframe sensor data; handles signal processing from engine and airframe sensors.
  • EAU data is used to drive engine indicators in the engine indication system and to feed the reversionary display logic when a primary display fails.
  • The EAU can trigger a reversionary display switch to ensure critical engine data remains visible if one display fails.
  • A small red button exists to test or demonstrate automatic switching behavior in case of a detected issue; in normal operation, the system automatically reconfigures to maintain information on the remaining displays.
  • If the integrated avionics (IAU) detects a fault, the system may auto-switch to the other screen (reversionary mode) to keep essential information accessible.

Reversionary Display Operation

  • Reversionary display: if a display or IAU fails, the system automatically switches to a backup display so that all critical information remains available.
  • On the remaining display, you still see the primary flight data (PFD) and engine indication information; any data that cannot be read may show as an “X” (indicating loss of that parameter).
  • Example: if oil temperature exceeds maximum tolerances and the engine indication cannot read the temperature, the corresponding indicator may show an X on the display.
  • This is a key safety feature to maintain situational awareness even during component failures.

The Engine Indication System (EIS) and Availability of Data

  • The engine indication system (EIS) presents engine data such as:
    • Manifold pressure, RPM, fuel flow (in gallons per hour), and fuel pressure.
    • Cylinder head temperature, oil temperature, oil pressure, amperage, voltage, and fuel quantity.
  • If a parameter becomes unreadable or is out of tolerance, that parameter can show as an X on the display, and the system may switch to reversionary mode to keep other critical data visible.

System Status and Tests

  • The system has a dedicated System Status page to run tests on all subsystems (e.g., AHRS, ARs, GPS, data link, etc.).
  • The System Status page also shows the SafeTaxi database status, including the current validity window and cycle information.
  • SafeTaxi: a database feature that provides taxi routing inside airports; the database includes:
    • Valid operating date (date when the data is valid)
    • Cycle number
    • Database time (timestamp for the current data)
  • It is common to update the database a few days prior to the actual use window; in practice, updates are done to ensure currency.
  • Example scenario discussed: IFR currency can be valid even if the validity date is only a couple of days ahead, as long as the database is within its valid window and the date is logged. FAA guidance may consider this valid if the logs show the update date and coupon of currency.
  • In our aircraft, each G1000 installation has one SD card in the GIA; there is a separate SD card for each airplane (one master card per airplane).
  • Software manipulation is typically performed by a commercial repair station; the avionics shop handles checks like autopilot and glide slopes to ensure compatibility with your particular aircraft configuration.

Data Management and Updates

  • The GIA #2 (GIA-2) holds an SD card used to download subscriptions every 28 days. In normal flight operations you should not remove the card; updates are kept to a minimum.
  • A bundled update package previously included SafeTaxi for all DA40s, improving taxi routing at the airport.
  • The database validity period can be queried to determine current validity; updates are scheduled a few days before the expiry to ensure continued IFR currency.
  • When maintaining currency, the logs provide a record indicating the date of updates; this is important if questioned by authorities about IFR currency.
  • A key operation: updating the database three to four days prior to expiry helps maintain a current validity window.

Display Operation and Redundancy

  • Normal display layout (PFD left, MFD right) shows engine and system data; there is an engine page on the MFD that can illuminate the entire engine cluster for easier engine monitoring, especially during takeoff.
  • Reversionary display operation means that if the primary display fails, the engine cluster and vital information will be shown on the remaining display, ensuring continued situational awareness.
  • In the event of an instrument or display failure, you will see a corresponding “X” if a parameter cannot be read. This is a visual cue to avoid operating on uncertain data.

Advisories, Cautions, and Warnings (Enunciations)

  • The G1000 provides multiple enunciations across systems; common categories include advisories, cautions, and warnings.
  • Important operating note: never take off with a live (active) annunciation displayed on the panel because it can be distracting and may indicate an actual issue.
  • If you see a warning or caution, assess the situation and, if necessary, contact ATC or request extra time, especially if you’re still on the runway.
  • Specific areas of concern include:
    • Alternator issues (engine electrical system) can cause an advisory to appear if the alternator is not supplying power adequately; ensure the engine is producing enough RPM to keep the alternator online.
    • If you pull throttle back to idle frequently, the alternator can go offline and trigger an advisory.
  • It is standard practice to manage these advisories and not fly with them active during departure until you address the underlying issue.

WAAS/WAAS-Related Content (Upcoming Video)

  • The instructor mentions a forthcoming video on WAS (likely WAAS) and the ability to disable WAAS for certain checks. If WAAS is disabled, you may be required to perform a rain check or additional verification, depending on the procedure.
  • Plan to review WAAS functionality and how its presence or absence affects approach paths and navigation integrity in future sessions.

Practical Reminders from Experience

  • The instructor shares personal notes: in 13 years there have been two runaway trim incidents on the DA40s; runaway trim occurs when a dive or climb trim command continues in one direction due to a faulty switch or solenoid.
  • If a runaway trim occurs, you must manually counteract the trim using throttle adjustments or other control inputs to maintain flight; the cockpit has limited mechanical trim authority in some configurations, so you might need to manage the aircraft with thrust until you reach a safe level.
  • Green or red collar markings around circuit breakers for electric trim help remind students of critical safety components and indicate the potential risk of carbon-trim runaway events.

Quick Reference Summary

  • Equipment and data flow: PFD/MFD (LRUs) ← IAUs ← ADC/EAUs ← GPS/marker beacons/ARs/磁as appropriate → Transponder/Data Link → AHRS/HSI.
  • TA and approach data rely on ADS/bearing to turn anticipation; MAPs may be flyover waypoints.
  • Reversionary display ensures continued visibility of critical data when a display or subsystem fails.
  • Data updates and SafeTaxi database currency require ongoing maintenance; keep logs of update dates for IFR currency verification.
  • Maintain discipline about annunciations and understand the consequences of system advisories and warnings during flight operations.
  • WAAS considerations will be covered in the next session; be prepared to discuss how disabling WAAS affects IFR procedures.