I'm studying for my first twin job in an EC135. With the fuel system if you go to zero fuel in the main tank, do you turn off the XFER PUMPS?

This is just a therotical question and i'm not saying I would fly with less than zero fuel in the main tank, even though it looks like the numbers on the supply tanks would cover the 20 minute VFR reserve.

Yes, at least on the 145 (Similar fuel system). You'll get an FUEL PUMP AFT and then a FUEL PUMP FWD caution on the CAD when they run low respectively. Both of those have a procedure to check the amount of fuel and then turn them off.

The xfer pumps take the fuel from main to supply tanks.  In normal forward flight the aft pump will go dry first with the appropriate CAD msg followed by the fwd pump. They are then just sucking air so you turn them off.  Remember to always verify what switch before moving. If you left running I'm not sure anything would happen, but the rfm calls for turn off.  I'm not sure be check with the newest models 135 to see if that procedure is still valid.  Airbus may have changed due to too many inadvertent xfer pumps being turned off causing premature engine shut down

Study your fuel system alerts, cautions, and warnings like the Bible......everything else is EASY !!!!! 2k hours in 135's......

The EC135 fuel system is designed so that the fuel above the baffles in the supply tank is also counted as Main Tank fuel.  You'll need to shut off your transfer pumps prior to the CAD actually showing 0 in the Main.

do that. it used to say turn them off when running on supply tanks. once the mains are empty: 30 minutes 

Different subject----But when you top off a 135 with fuel, is it really full or not.  Seems like it registers full for 20 minutes of flight; gives a false reading of being full.  Hard to determine if it's full or 20 gallons short. 

If your fuel system seems to be erroneous in readings, ask your mech to check calibration.  One way is to add x amount of fuel fuel from a known amount and check if fuel indicator increases accordingly.  Otherwise I believe there is a calibration component.   One thing to have more fuel than you think, but something totally different to have less than indicated.  One thing for sure is the fwd xfer pump light.  When it comes on, usually after the aft forward flight, and you suspect faulty fuel display, be looking at LZ

Yes, if the tank level is such that you determine the pump in question is running dry, turn it off. However, should the second fuel transfer pump illuminate, you turn them both on regardless of quantity. Read the EP.

Under no circumstance, regardless of main tank leve, ignor the low fuel 1/2 warning lights! Without going into a long post, it is possible to flame out with fuel in the main tanks!

Its not uncommon for me to land, for me to land with the Aft transfer pump off. Generally, I dont turn it back on for landing even the the aircraft attitude is nose up. Depends on circumstances.

but some jack a  s  s would come on right after I did it and tell me I was all wrong, and then you would just end up more confused than you already are. So, sorry.

when the light come on, turn off the pumps. no ambiguity. 

They seem worse in Airbus products than any other brand...

The EC130 was horribly inaccurate (the % bar is technically what you're supposed to use and there's a supplemental fuel chart for what your actual gallons are because the indicator on the VMD is always wrong).  

The EC145 was consistently off and required you to be in similar flight profile when taking first and second reading to compare.  I agree about seeing the 20 minutes it sits full and then starts moving like the EC135 comment above.  

OH-58/UH-1/OH-6 didn't have lots of tick marks to see exactly where you were at but they were always very accurate.  

UH-60 probably the most accurate.  Would guess the AH-64 and CH-47 were similar.  Bigger airframes using pricier capacitance fuel probes is probably why.  

Bounce high and low 50-100 pounds. I suppose you could say it was accurate if you visually split the difference. As I recall, it was only the A model guage that would vary constantly like that.

first twin job was 45 years ago.  It's all in the RFM.