Alternate air is an alternate source of air, it can for example be used during ice, when the normal filter is blocked to have a backup source available.
Alternate air is unfiltered air and should not be used during ground operation because the unfiltered air may contain dust and other contamination.
Only hydraulic gear.
Easier for the company in regards to training, maintenance and spare parts as you only use one type of aircraft.
Live side to oppose the yawing moment.
17KTS
Yes, feathering locks engage at 800 RPM on the Seneca.
We feather to stop windmilling and reduce drag.
Hydraulically driven by 2 electric pumps with a 7 second transit.
No, you mechanically change a valve that changes the air intake to air that runs past the exhaust manifold and is therefore heated.