To get a rough estimate of run time till fuel exhaustion on the AS 355 F1, I add the percentages of the front tank and rear tank, then double again for total time. For instance, if I have 25% in the front tank, and 40% in the rear, I add for 65%, then double for 130 minutes run time. My question involves the inability to transfer fuel. If my fuel transfer system fails, and i have 25% in the front tank, when will exhaust the fuel? In 50 min. or 100 min.? thank you