Thanks Shwan, just bringing it into the discussion because for now at least, the Glasgow crash also 'was not caused by any problem with the helicopter'.
To put a theory on Potomac like some are doing here with Glasgow, The Potomac ac lifted at 2304, crashed at 2311 (7 mins). The Low Fuel warning (if it illuminates) on a 680 litre tank requires you to land within 8 mins! How accurate is that 8 mins?
Perhaps they are closer than at first look!