Fuel pumps play an important role in aviation. With the exception of small, gravity-fed airplanes, most modern airplanes use them to deliver fuel to their engines. Airplanes typically feature an electric boost pump for takeoffs and landings, and they feature a main engine-driven pump for normal flight operations. In addition to a boost pump and engine-driven pump, however, many airplanes also feature a fuel scavenge pump.
What Is a Fuel Scavenge Pump?
A fuel scavenge pump is a special type of fuel pump that’s designed to collect and move fuel from the bottom of a tank. They prevent usable fuel from becoming trapped.
Depending on their size, airplanes can carry a lot of fuel. Small airplanes typically carry about 100 gallons, whereas large airplanes may carry up to 50,000 gallons. Even with traditional boost pumps and engine-driven pumps, though, some of this fuel may remain untouched.
Fuel tanks are often integrated into the wings, tail or fuselage. As a result, they have complex shapes that mirror the space in which they are integrated. Ribs, baffles and other intricate shapes can create low points that collect fuel. Scavenge fuel pumps are designed to “scavenge” fuel from these hard-to-reach areas so that it can be used for combustion.
Benefits of fuel scavenge pumps include the following:
- Prevents moisture accumulation
- Helps to balance aircraft weight
- Prevents fuel starvation warnings
- Ensures proper fuel utilization
How a Fuel Scavenge Pump Works
Fuel scavenge pumps typically work automatically. The pilot doesn’t have to press any switches or pull any levers. Instead, fuel scavenge pumps will automatically collect and move fuel when fuel levels drop to a certain point.
Some fuel scavenge pumps are electrically driven. They feature mechanical parts that are powered by electricity. Other fuel scavenge pumps leverage pressurized fuel to create suction. They essentially use pressure created by an engine-driven pump to create a suction force. This suction force pulls fuel from hard-to-reach areas.
Fuel Scavenge Pump vs Oil Scavenge Pump
There are also oil scavenge pumps. As you may have guessed, they are designed to collect and move oil from hard-to-reach areas. Oil scavenge pumps pull oil out of ridges and crevasses in an airplane’s engines so that it can be recirculated.
Fuel scavenge pumps work in a similar way, but they are designed exclusively for fuel. Oil scavenge pumps, in comparison, only collect and move oil.
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