What is the general procedure for bleeding an aircraft hydraulic system after a gear maintenance event?

• A. Follow manufacturer bleed sequence, purge air from lines, ensure no contamination, check reservoir level, and verify system pressure and function.
• B. Empty reservoir and refill with any hydraulic fluid.
• C. Bleed only until color is clear.
• D. Bleed by opening all valves and cranking interfaces randomly.

Answer: (A)

The key idea is that you must restore a clean, air-free hydraulic circuit by following the prescribed bleed procedure, then confirm the system is full, uncontaminated, and functioning at the proper pressure. After gear work, air can hide in lines and components, and if not purged in the correct sequence you end up with air pockets that compress and cause sluggish or incomplete gear operation. Following the manufacturer’s bleed sequence ensures air is removed from each segment in the intended order and prevents trapped pockets. Purging air from the lines also reduces the chance of hydraulic shock or inconsistent movements when the gear cycles. Keeping the system free of contamination is crucial, so you use the proper fluid and maintain cleanliness throughout the process, avoiding introducing dirt or moisture that could damage pumps, valves, or actuators. Checking the reservoir level ensures there’s enough fluid to feed the pump during cycling and prevents cavitation. Finally, verifying system pressure and function by cycling the gear and observing pressures and indicators confirms the bleed was successful and that the system operates smoothly without leaks. As for other approaches, emptying the reservoir and refilling with any fluid won’t purge air properly and risks introducing the wrong fluid or contaminants; relying on color alone isn’t a reliable indicator of air removal; and randomly cranking valves and interfaces can damage components and fail to remove air, leaving the system unsafe to operate.