It only needs to move 15 degrees. The issue is the complexity of adding yet another system for certification along with the gearbox. I doubt the variable pitch makes it to the 2025 target date, but comes later, ~2030 time frame.

I am really pessimistic about that kind of technology. I agree, I have a hard time imagining it being out in less than 10 years.

I'm not sure what you mean about 15 degrees though, are you talking about for an effective braking movement from the blades?

Moving fan blades sounds terrifying!

It creates massive amounts of drag, the thrust does not reverse out of the engine. The extreme bypass ratio, and the size of the fan blades, because they are composite, make this possible.

That is going to have some rudder.

Or MCAS 2.0

They’ll have to add blue line and red line back to the A/S gauge.

Look into variable geometry turbos

You would almost certainly crash if that system activated in flight, that's why there must be some kind of mechanical shear pin that separates the main fan from the rest of the engine. At what point do they say enough is enough on engine reliability vs fuel savings. The 737Max is certainly a causality of this process.

Never. Maybe we should have stopped here.

Animated Engines - Gnome Rotary