Third HDX Display Wiring

[maartenversteeg]

It very much depends on what functionality you want to have available, I would consider to have the 3rd display added in a way so that it enhances the redundancies within the system to the maximum extend possible. There are a number of groups of shared signals all on the 37-pin D-connector, just from memory I would think (the the installation manual would provide the full list):

• serial interfaces: the up-to five serial interfaces: radio, GPS transponder, ADSB etc should all be tied together to make these functions available on all 3 displays
• the 3rd display would presumably have it's own backup battery
• digital inputs: go-around, level etc, could just be wired together, but I think the preferred solution is to diode or these together to the switches so that an inactive display doesn't prevent this function to be used
• the 3rd display should have it's own WiFi adapter and it's own USB data connector (the latter certainly if you want to be able to use the external maps stored on the USB drive
• and Ethernet adapter connecting the 3 units would make life easier in that there is no need to install the aviation and obstacle databases separately (also to prevent issues when only a partial update of the 3 units are done where you could have different aviation databases on the 3 systems)

 

[Rhino]

The level and go around signals are just ground, but yes, you need the diodes. But the most important part of that is the first sentence. It depends on what functionality you want to have available. Individual priorities and flying style will also play a role. If you've had two displays fail in a three display system, you're most likely looking to land immediately. So, while more features are always nice, you may not really need all the bells and whistles available in such a scenario.

 

[maartenversteeg]

I agree, but in case of two displays failing having still flight instrumentation and GPS data would ease the search for a suitable landing space preferrably at an (unplanned) airport much less of an emergency, so I would at least want to connect that 3rd display to the GPS and give it map information (assuming we are only carrying outdated paper maps and green book). The full connection of the third display although a hassle doesn't seem to much of an issue, it's just work that needs to be completed.

 

[Rhino]

Exactly. Each pilot chooses what suits them best.