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Reading through a TBM 930 avionics handbook, I came across the integrated avionics unit. What does this do and how does it work? Also, why does the auto pilot only follow one flight director as seen on the text? enter image description here

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    $\begingroup$ What do you expect to happen if an autopilot were to attempt to "follow" two flight directors that were giving something besides the same commands? $\endgroup$
    – Ralph J
    Apr 23, 2023 at 23:15
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    $\begingroup$ Not terribly familiar with the G3000 integrated flight deck components, but, at a guess, an Integrated Avionics Unit (IAU) is most likely the “brains” of the system, taking in air data, magnetometers and user inputs from the touchscreen controllers and AFCS unit. It has its own AHARS and contains all of the operating components, radios, GPS, transponder, etc. and operates the two PFDs and MFD accordingly. $\endgroup$ Apr 24, 2023 at 4:14

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The Integrated Avionics Unit (IAU) is the core component of the Garmin G3000 setup used in the TBM 930. For redundancy, there are two IAUs. They contain various radio and GPS receivers and interface with several inputs (like ADC, AHRS) and outputs (like PFD, autopilot servos):

GIA 63W (2) – The Integrated Avionics Units (IAU) function as the main communications hub, linking several LRUs with each on-side GDU 1200W. Each IAU contains a GPS Satellite-Based Augmentation System (SBAS) receiver, a very high frequency (VHF) communication/navigation/glideslope (COM/NAV/GS) receiver, a Flight Director (FD) and system integration microprocessors. The IAUs communicate with each other through using usign HSDB and additional backup paths.

G3000

(Garmin G3000 Integrated Flight Deck Pilot’s Guide for the TBM 930 - 1.1 SYSTEM DESCRIPTION)

The two flight directors (one in each IAU) also exist for redundancy. Each pilot will see the flight director command bars of their respective side IAU on their PFD. Usually, they should agree with each other. In case of differences, the pilots need to determine which unit functions correctly and can select the active flight director using the XFR button. The autopilot servos can only be connected to one flight director input at a time because these inputs might differ and the servos wouldn't know which one to follow.

This is different from an autoland system on larger aircraft, which allows multiple autopilots to be connected at the same time. The TBM 930 does not have autoland capability and therefore does not need such a complex setup.

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  • $\begingroup$ Thanks for all the information! $\endgroup$
    – Boeing787
    Apr 24, 2023 at 14:42

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