Haven't there been problems with the EC135 suffering from fuel gauge issues recently? I understood there to have been a number of complaints to EC about this. I appreciate tech logs should show correct uplift/consumption, but it wouldn't be the first time a helicopter had less fuel in it than the PIC thought and if the gauge wasn't reading correctly, it would hide the issue until too late. I believe both engines flamed out when they ran out of fuel before the Low Fuel warning lamp came on.