Final answer:
While it is possible to fly an aircraft without hydraulic systems through exceptional piloting skills, as demonstrated by the Gimli Glider incident, modern aircraft like the Boeing 777 rely on fly-by-wire systems that require electrical power and functioning computer technology for control.
Step-by-step explanation:
An aircraft can potentially be flown without hydraulic systems, but it presents significant challenges. A famous instance illustrating this is the story of the Gimli Glider, a Boeing 767 that ran out of fuel mid-flight due to a unit conversion error during refueling. In this incident, experienced pilot Captain Robert Pearson glided the plane to a safe landing, though the normal operation of the aircraft was severely compromised without its hydraulic systems. The 767 effectively became a glider, with limited control over the aircraft.
Moreover, engineering advances in aircraft, such as those evident in the design of the Boeing 777, have introduced fly-by-wire systems that use computer technology and electrical signals rather than hydraulics for controlling the aircraft. These systems are computer-based and allow the aircraft to be operated by a minimal crew, but they also require reliable computer systems and power to function appropriately.