AlphaOneSix

That's in the general vicinity (if I'm remembering correctly) of where the Romeos did their FTX around the tail end of their AIT. Of course, that was a long time ago for me, so no clue if they even still do that, but I suspect it may have been part of that. When I went through AIT, we actually towed one of the hangar trainers from Felker to the field site. Would have been much easier to just leave one out there. So maybe that's part of the story.

With the crossfeed valve closed:
 
The Rear tank feeds the right engine.
The Forward tank feeds the left engine.
 
Opening the crossfeed allows both tanks to feed both engines.
 
If damage occurs to one fuel tank and you suspect that one of the fuel tanks is leaking, your best course of action is to OPEN the crossfeed and turn OFF the tank pump for the GOOD tank. This will burn more fuel faster out of the bad tank, instead of just losing it overboard. Once the bad tank nears empty, simply turn ON the tank pump for the good tank.
 
There are check valves that prevent fuel being pumped from the forward tank into the rear tank, and vice versa.

Sorry, I've been away from the forums for a long time.
 
The batteries are always turned on, even when starting with ground power. It is true that they do not need to be turned on if you have a DC ground power source, since the APU generator and eventually the rectifiers will power all of the DC electrical buses. However, the batteries are just a backup/emergency power source in case of a problem in-flight that causes both rectifiers to go offline, to give you power to start the APU in flight so that you can use the APU generator for DC power. And of course, the batteries are also to start the APU on the ground when DC external power is not available. My understanding is that most "Russian-like" operators of the Mi-8 use external power as much as possible for the APU start, just to go easy on the batteries. My organization has replaced all of the default NiCad batteries with Concorde SLABs (Sealed Lead-Acid Batteries), and we never use external power unless we're testing something on the ground for a prolonged period of time.