Fuel pumps for engines are generally which types?

Fuel pumps for engines are typically classified as positive displacement gear, piston, or rotary vane types because these designs are effective in maintaining a consistent flow of fuel at the required pressure within the engine's fuel system.

Positive displacement pumps work by forcing fuel through the system using mechanical means, which ensures that a specific volume of fuel is delivered regardless of the system pressure. Gear pumps utilize rotating gears to move the fuel, while piston pumps use a reciprocating mechanism to create pressure and flow. Rotary vane pumps function similarly by utilizing vanes that slide in and out of slots, effectively creating chambers that trap and move the fuel.

Understanding the specific mechanisms and applications of these types of pumps is crucial for maintaining optimal engine performance and efficiency. The option highlighting electric and mechanical types, while relevant in some contexts, does not specify the types of pumps best suited for the high-pressure, constant flow demands of aircraft engine fuel systems. Diaphragm and volumetric types also do not typically categorize fuel pumps used in aviation engines, further positioning positive displacement gear, piston, or rotary vane as the most correct response.