How many hydraulic pumps are typically present on the aircraft?

The correct answer reflects the typical configuration of hydraulic systems in many aircraft, specifically those used in naval aviation, such as the HSC-3. Generally, these aircraft are equipped with four hydraulic pumps to ensure redundancy and reliability in flight operations. The presence of multiple pumps is critical for managing systems that require hydraulic pressure, including landing gear, brakes, and flight control surfaces.

Having four pumps allows for operational flexibility and safety, as if one pump were to fail, the remaining pumps can still provide adequate hydraulic pressure for essential functions. This redundancy is particularly important in military operations where aircraft may be exposed to harsh conditions and high-stress scenarios.

In terms of the other answer choices, having only two or three pumps would limit the aircraft's operational capability and safety features, while five pumps might suggest unnecessary complexity for most operational requirements. Thus, four hydraulic pumps represent a balanced design that meets both performance and safety standards commonly found in this class of aircraft.