What hydraulic system normally operates the landing gear, and which serves as backup?

• A. 3; 2
• B. 2; 3
• C. 1; 2
• D. 4; 3

Answer: (A)

The idea tested is how landing gear stays operable even if one hydraulic path fails—the system uses redundancy so you can still extend or retract the gear.

Normally, the landing gear is powered by the third hydraulic system. This is the primary source that provides the pressure and flow needed to operate the gear through its actuators during normal operations. If that system loses pressure or cannot power the gear for any reason, a separate hydraulic system—the second one—acts as the backup. It has its own pump and lines so it can take over and allow the gear to be extended or retracted, ensuring a safe landing even with a failure in the primary system.

Other hydraulics on the airplane handle different functions (like flight controls or flaps), but they aren’t used as the primary gear power. The backup path is deliberately independent to maintain gear operability under failure conditions.