Awwww - I'll never understand this fuel system
Does anyone have a complete engineering threeview drawing?
Not me, but given
http://www.airbushelicopters.com/sit...uel_system.pdf Page 2
I'd guess from my hip as follows:
- both main fuel tank pumps must have some kind of valve that prevents flow back through the pump. If the front one "runs dry" and the rear one still pumps fuel the long red line in the diagram will be filled with fuel from the rear pump but it will not circle back into the main tank through the not operating front pump.
- both rear tanks a fed fuel via the single hose conneting both main tanks' pump(s), until both rear tanks are full. Should the XFR pumps still be running, they'd work against the full rear tanks, nicely lubed by Jet-A1 (which is more or less diesel _OIL_)
- front and rear tanks seem to be separate containers as are the rear tanks. Fuel that ends up in one of the rear tanks stays there and will not "slosh back"
- from there the engine's internal pump will suck the fuel from its rear tank upwards, w/o the prime pump's help.
Actually a nice setup, highly redundand: with any one of the XFR pumps unservicable and additionally one of the rear tanks leaking heavily you can still fly (OEI) w/o necessity to have any working prime pump (rear tank to engine), as long as the internal fuel pump of the engine still works.
Personally I do like the SASless mode of operation: have both XFER pumps constanly on, till main tank is empty (and pump warning light come on), then switch them off and land on suitable spot. No constant pump switching necessary.
All under the assumption the SASless mode is compatible with the AFM and OPM.
