Originally Posted by
Aluminium Mallard
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).
First, it doesn’t cost more. it costs less. The 505 is cheaper than the 206B ever was when adjusted for inflation. The dual FADEC also reduces maintenance costs (reducing start and shutdown issues for example) and improves performance by reducing inefficiencies inherent in manual control designs (tighter governing or NR reduces conservative design factors throughout the aircraft design and certification).
Also, talking to the Bell engineers has given me an appreciation for the redundancy of the newly designed generation of aircraft. Between the Garmin avionics and the engine controls, there are so many backup pathways and indications and fallbacks that I’m convinced it is similar to the video of the Chevy old bel air vs the 2009 Chevy Malibu in the link below. New helo crash requirements are much higher than old ones... seat and fuel system designs are much better protection than old but current production helicopters (current H125, H145, and Puma designs are all older standards for example).