TECHNICAL FIELD

The present application relates generally to fuel systems and, more particularly, to an aircraft fuel system and method for controlling a pump of an aircraft fuel system.

BACKGROUND INFORMATION

Aircraft fuel systems can be designed in many ways. In larger aircraft the fuel is stored in tanks located both in the wings and in the center fuselage. Each wing typically includes two electric motor driven fuel pumps that supply fuel to the engine on the same side of the plane. Depending upon the operating condition, one or both wing fuel tank pumps can be operational at the same time. The center fuel tank usually has two electric motor driven fuel pumps that also supply fuel to the engines; one pump for each engine. The center fuel tank pumps are connected by a cross feed valve in the event one center fuel tank pump fails and the remaining center fuel tank pump needs to feed fuel to both engines.

Normal aircraft operating procedures require fuel from the center fuel tank to be used before the fuel in the wing fuel tanks. After the center fuel tank is depleted, the center fuel tank pumps are turned off and the fuel from the wing tanks is delivered to the engines. The wing fuel tank and center fuel tank pumps are both operational during most phases of flight (unless they are turned off per operating procedure), so a key issue is how to deplete fuel from the center fuel tank before the wing fuel tanks. Conventionally, this is accomplished by using pumps having different performance characteristics. For example, the discharge pressure of the center fuel tank pump may be greater than the discharge pressure of the wing fuel tank pumps. Thereby, the center fuel tank pump overrides the wing fuel tank pump.

To maintain override when the center fuel tank pumps are operating at points where the flow is large, and the pressure is low, a Pressure Regulating Valve (PRV) is added on the discharge side of the wing fuel tank pump. This valve opens at a pressure lower than the discharge pressure of the center fuel tank pump and recirculates the fuel from the wing fuel tank back into the tank, instead of delivering it to the engine. When the center fuel tank is depleted of fuel and the pump is turned off, the regulating valve closes and allows fuel from the wing fuel tank to be delivered to the engine.

SUMMARY OF THE INVENTION

Recent fuel systems have adopted the idea of using identical pumps for the wing tank and center tank positions. This approach allows a single pump part number to be purchased and requires less inventory of spare parts. However, this approach presents a unique problem for maintaining fuel delivery from the center fuel tank pump as the primary path, with delivery of fuel from the wing fuel tank pumps occurring only after the center tank is empty. With similar discharge pressure versus flow curves for both pumps, the tendency will be for fuel to be delivered from both tanks simultaneously.

A device and method in accordance with the present invention simplify aircraft fuel system architecture, resulting in fewer components and thus reducing weight and system cost. In accordance with the invention, the speed of the wing fuel tank pumps and the speed of the center fuel tank pumps are controlled such that, under certain operating conditions, the pressure supplied from the center fuel tank pumps is higher than the pressure supplied from the wing fuel tank pumps. In this manner, the center fuel tank pump will override the wing fuel tank pumps and fuel delivery will be from the center tank until the center tank is depleted, without the need for a PRV.

According to one aspect of the invention, a method of controlling a fuel system on an aircraft, includes: selectively supplying fuel from either a center fuel tank or at least one wing fuel tank to a fuel consumer by varying a speed of at least one main fuel tank pump associated with the main fuel tank relative to a speed of at least one wing fuel tank pump associated with the at least one wing fuel tank.

Optionally, the at least one main fuel tank pump and the at least one wing tank fuel pump are fluidically coupled to the same fuel consumer through a common fuel line, and selection of fuel from the main fuel tank or the at least one wing fuel tank is based on a fluid pressure created by the respective fuel tank pumps, the pressure created by each fuel tank pump corresponding to a speed of the respective fuel tank pump.

Optionally, selectively supplying fuel comprises operating the at least one main fuel tank pump at a speed that is less than a speed of the at least one wing fuel tank pump while the aircraft is below a threshold altitude.

Optionally, selectively supplying fuel comprises operating the at least one main fuel tank pump at a speed that is greater than a speed of the at least one wing fuel tank pump while the aircraft is above a threshold altitude.

Optionally, selectively supplying fuel comprises operating the at least one main fuel tank pump at a speed that is greater than a speed of the at least one wing fuel tank pump, thereby providing fuel from the main fuel tank to the fuel consumer until the fuel in the main fuel tank is depleted.

Optionally, the method includes stopping the at least one main fuel tank pump upon the fuel in the main tank being depleted.

Optionally, selectively supplying fuel comprises operating the at least one main fuel tank pump at a speed that is less than a speed of the at least one wing fuel tank pump, thereby providing fuel from the at least one wing fuel tank to the fuel consumer.

According to another aspect of the invention, an aircraft fuel system includes: a main fuel tank including at least one main fuel tank pump; a first wing fuel tank including at least one first wing fuel tank pump; and a controller operably coupled to the at least one main fuel tank pump and the at least one first fuel tank pump, the controller configured to vary a speed of the at least one main fuel tank pump relative to a speed of the at least one first wing fuel tank pump to selectively supply fuel from either the main fuel tank or the first wing fuel tank to at least one fuel consumer.

Optionally, the at least one main fuel tank pump and the at least one first wing fuel tank pump are fluidically coupled to the same fuel consumer through a common fuel line, wherein selection of fuel from the main fuel tank or the at least one wing fuel tank is based on a fluid pressure created by the respective fuel tank pumps, the pressure created by each fuel tank pump corresponding to a speed of the respective fuel tank pump.

Optionally, the at least one main fuel tank pump and the at least one first wing fuel tank pump are fluidically coupled to the same fuel consumer through a common fuel line, and fuel is supplied from the main tank to the fuel consumer when the speed of the at least one main fuel tank pump is greater than a speed of the at least one first wing fuel tank pump, and fuel is supplied from the first wing fuel tank to the fuel consumer when the speed of the at least one first wing fuel tank pump is greater than a speed of the at least one main wing fuel tank pump.

Optionally, the at least one main fuel tank pump and the at least one first wing fuel tank pump comprise a pump having the same specifications.

Optionally, the at least one main fuel tank pump and the first wing fuel tank pump each have the same physical dimensions and the same performance characteristics.

Optionally, the at least one fuel consumer comprises a first fuel consumer and a second fuel consumer, further comprising a first fuel line coupling the at least one main fuel tank pump and the at least one first wing fuel tank pump to the first fuel consumer, and a second fuel line coupling the at least one main fuel tank pump and the at least one second wing fuel tank pump to the second fuel consumer.

Optionally, the at least one main fuel tank pump comprises a first main fuel tank pump and a second main fuel tank pump, further comprising a cross-feed valve fluidically coupling the first main fuel tank pump to the second main fuel tank pump.

Optionally, the fuel consumer comprises a jet engine.

Optionally, the fuel consumer comprises an auxiliary power unit.

Optionally, the controller is configured to selectively provide fuel by operating the at least one main fuel tank pump at a speed that is less than a speed of the at least one first wing fuel tank pump while the aircraft is below a threshold altitude.

Optionally, the controller is configured to selectively supply fuel by operating the at least one main fuel tank pump at a speed that is greater than a speed of the at least one first wing fuel tank pump while the aircraft is above a threshold altitude.

Optionally, the controller is configured to selectively supply fuel by operating the at least one main fuel tank pump at a speed that is greater than a speed of the at least one first wing fuel tank pump, thereby providing fuel from the main fuel tank to the fuel consumer until the fuel in the main fuel tank is depleted.

Optionally, the controller is configured to stop the at least one main fuel tank pump upon the fuel in the main fuel tank being depleted.

Optionally, the controller is configured to selectively supply fuel by operating the at least one main fuel tank pump at a speed that is less than a speed of the at least one first wing fuel tank pump, thereby providing fuel from the wing fuel tanks to aircraft engines.

The foregoing and other features of the invention are hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail one or more illustrative embodiments of the invention. These embodiments, however, are but a few of the various ways in which the principles of the invention can be employed. Other objects, advantages and features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

