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Comment by repiret | Hacker News Reader

The RAT is backup power for the hydrolics. Do you have a citation that there's no backup battery for the electronics, because I don't believe it. Even for the crappy 25 year old not-approved-for-IFR GPS I had in my Cessna needed the engine/alternator to fail plus two separate batteries to drain before it would turn off. I can't believe the electronics on a fly-by-wire airliner are less redundant.

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RAT provides electrical generation too. Its all layers of protection, there are batteries for limited duration and limited equipment. RAT provides more (duration and functionality).

There are some components that are considered like that GPS that have small enough power requirements and are critical enough that they can have significant battery and others that are powered by the RAT, and yet others that just don't work with a main engine failure.

Highly suggest watching some of the Mayday episodes about the power failure incidents like Gimli, its very educational.

Yes - the electrical generators are generally powered off the hydraulic system.

I was trying to paint a picture of why the RAT is needed, in order to share my admiration about the people who build it.

I don't know exactly which systems it powers, but have been told that in the case of engine failure, the plane cannot fly without it. You may be correct about the specifics.

Apparently also for electronics: https://en.wikipedia.org/wiki/Ram_air_turbine

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