Automatic/manual fuel tank supply balance system

In combination with a helicopter having first, second, and third main engines, a fuel supply balance system comprising:

• first, second, third and fourth fuel tanks, said first and fourth fuel tanks each being smaller in volume than either of said second and third fuel tanks and being connected to deliver fuel directly to said first and said third engines, respectively, and said second and third tanks being connected to deliver fuel directly to said second engine;
• a common fuel line for delivery of fuel to each of said tanks;
• first, second, third and fourth electrically operated valves connected between said common fuel line and respective ones of said first, second, third, and fourth tanks;
• first and second constant delivery pumps;
• fifth and sixth electrically operated valves connecting said first and second tanks to said first constant delivery pump, and seventh and eighth electrically operated valves connecting said third and fourth tanks to said second constant delivery pump;
• first, second, third and fourth level sensing means associated with said first, second, third, and fourth tanks, respectively, for providing electrical signals corresponding to the quantities of fuel in said tanks;
• control means having manual and automatic modes of initiation and responsive in said automatic mode to said electrical signals corresponding to a fuel decrease to a predetermined minimum quantity of fuel in either of said first and fourth tanks to initiate operation of a corresponding one of said pumps and actuation of appropriate ones of said valves so as to automatically effect transfer of a predetermined incremental quantity of fuel from one of said second and third tanks to the tank having said fuel decrease to said predetermined minimum quantity;
• and
• said control means further comprising interlock means for preventing operation of both of said pumps simultaneously, manually operated means, operable in said manual mode, for selectively ordering an incremental transfer of fuel from any one of said tanks to any other one of said tanks, and timing means, operative in said manual mode, for automatically terminating said incremental transfer upon transfer of fuel by running of one of said pumps for a predetermined time period corresponding to transfer of a predetermined weight of fuel.