The emergency hydraulic system operates which of the following?

• A. Landing gear, flaps, speed brake
• B. Landing gear, main inboard gear doors, flaps
• C. Landing gear, flaps, and speed brake
• D. Landing gear, main inboard doors, flaps, and nose wheel steering

Answer: (D)

When hydraulic power fails, the airplane relies on a dedicated emergency hydraulic system to keep the most critical functions available. This backup system uses an accumulator to provide limited hydraulic pressure for a set period, allowing essential operations to continue.

These essential functions include extending and retracting the landing gear, operating the main inboard gear doors, adjusting the flaps for a safe approach and landing, and supplying nose wheel steering for ground control. Extending the gear and opening the doors are fundamental to a safe landing, while flap movement helps manage lift and approach speed, and nose wheel steering keeps the aircraft controllable on the ground.

Other options miss one or more of these crucial capabilities. For example, omitting nose wheel steering would leave you with poor ground maneuverability, or missing the main inboard doors or flaps would prevent proper gear operation or approach control.