Originally Posted by
bellblade2014
I assume you are talking about the 407 old style single FADEC. The sloppiness of the governing when the primary channel reverts is dangerous. It’s already a bad day if you get there, but it’s not something you want to fly with for long. Comparatively Easy to over torque or under speed. There was a period of FADEC issues on 407GX’s during the early years with the G1000 that put a number of pilots into manual mode due to corrosion on the FADEC connectors.... wasn’t good. A dual channel is simple to do if you plan it from the beginning... harder to add later in the life of an engine.
So what happens when you get corrosion with a both FADECs? If both are subject to the same conditions its possible they could fail at the same time due to a power issue etc etc.
In a previous life I did a lot of work with redundant systems... dissimilar redundancy is far more reliable with aging parts i.e. a mechanical backup to an electronic primary. When the electronics are operating you have the benefits of ease of use and efficiency, when you revert to mechanical its inefficient and difficult to use.. BUT keeps you in the air.
The issue is its a hard sell because its not a great marketing feature "if it fails... etc etc." and it cost more (upfront).