It’s not the iPads themselves, it’s the addition of Bluetooth and/or wifi to support them. I agree that they can alleviate a lot in terms of paperwork reduction etc. My issue is the additional exposed surface.
Wireless isn’t a requirement and connectivity seems slow to be adopted anyhow according to this source.
https://www.aircraftit.com/articles/data-connectivity-for-efbs-part-2/
If we agree that connectivity is a good thing, why has the adoption rate been so slow?
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The first required piece is an actual connection between the device and the airplane. This connection can be wired or wireless. It’s now possible to have a wireless access point that’s dedicated to the crew. A wireless connection will need to include security capabilities so users can prove their identity to the wireless network. Let’s not forget that security must also be practical for in-service use. A wired connection is generally seen as more secure, since there has to be physical access from the flight deck, which is considered a secure domain.