Hydraulic system failures represent a pinnacle of systems integration challenges in Airbus A320 operations. In the high-fidelity environment of a simulator—whether a Level D full-flight sim or an advanced desktop setup like ProSim or X-Plane—these scenarios strip away the comfort of underlying automation and demand a precise, coordinated response from the flight deck crew.

This guide provides an authoritative, step-by-step framework for managing hydraulic failures in A320 simulations. It moves beyond basic ECAM recall to explore the physical architecture of the systems, the logic of the QRH, and the cognitive strategies that separate a smooth recovery from a cascading emergency. Whether you are a professional pilot undergoing recurrent training or an enthusiast managing a complex simulation, mastering these procedures builds a deeper understanding of the aircraft's redundant safeguards.

The objective is not merely to pass a simulator check, but to internalize the interplay between the Green, Blue, and Yellow systems so that the correct actions become second nature under pressure.

Deconstructing the A320 Hydraulic Architecture

To handle a failure effectively, you must first understand the normal architecture. The A320 uses three independent hydraulic systems, each pressurized to 3,000 psi. This triple-redundancy ensures that no single failure leads to a complete loss of flight control. However, the specific combination of failed systems dictates the severity of the situation.

The Green, Blue, and Yellow Systems

  • Green System: Primarily pressurized by an Engine-Driven Pump (EDP) on Engine 1. It powers the landing gear normal extension and retraction, normal brakes, nose wheel steering, and parts of the flight controls (elevator, aileron, yaw damper). Loss of the Green system significantly impacts landing gear and braking capabilities.
  • Blue System: Pressurized by an EDP on Engine 2 and an Electric Motor Pump (EMP). Critically, the Ram Air Turbine (RAT) also powers the Blue system if both engines fail. Blue powers the alternate brakes, the landing gear normal extension, and essential flight controls. It is often the last line of defense in a dual hydraulic failure.
  • Yellow System: Pressurized by an EDP on Engine 2 and an EMP. Yellow powers the parking brake, nose wheel steering, engine 2 thrust reverser, and serves as a backup for the landing gear and brakes. The Power Transfer Unit (PTU) connects the Yellow and Green systems.

Each system has its own reservoir located in the landing gear wheel well area. Fluid quantity and temperature are critical parameters to monitor on the System Display (SD) Hydraulic page. Skybrary provides an excellent reference on the standard A320 hydraulic system layout.

Ancillary Components: PTU and RAT

Power Transfer Unit (PTU): The PTU is a hydraulic motor-pump that transfers power from the Yellow system to the Green system (or vice-versa) without transferring fluid. It automatically activates when the Green system pressure is low and Engine 1 is running. A common training reality is the loud, distinctive "growling" noise the PTU makes. Do not mistake this for a component failure—it is the PTU performing its intended function.

Ram Air Turbine (RAT): The RAT is the ultimate backup. It is a small propeller that deploys into the airstream to drive a hydraulic pump, exclusively pressurizing the Blue system. The RAT deploys automatically if both engines fail, or it can be deployed manually via a guarded switch on the overhead panel. Once deployed, it provides enough hydraulic power to control the aircraft via the Blue system and run the emergency generator.

Identifying Failures and Interpreting ECAM

The Electronic Centralized Aircraft Monitor (ECAM) is your primary diagnostic tool. When a hydraulic failure occurs, a single chime sounds, and a red or amber message appears in the Engine/Warning Display (E/WD). The corresponding System Display (SD) page automatically appears.

The messages you will typically encounter include:

  • HYD G SYS LO PR (Green system low pressure)
  • HYD B SYS LO PR (Blue system low pressure)
  • HYD Y SYS LO PR (Yellow system low pressure)
  • HYD G(B)(Y) SYS LEAK (System leak detected)

The SD page shows real-time reservoir quantities and pump status. A rapidly dropping quantity indicates a significant leak. It is essential to distinguish between a "LEAK" and a "LO PR" scenario because the QRH actions differ substantially. Boldmethod offers a practical breakdown of the A320 hydraulic system that helps visualize these pump connections.

Primary vs. Secondary Effects

When the failure occurs, identify the immediate "primary effect" (e.g., low pressure in the Green system) and then anticipate the "secondary effects" (e.g., landing gear will not retract or extend normally, nose wheel steering is lost, normal brakes are lost). Anticipating secondary effects is a hallmark of good airmanship and reduces workload during the critical approach and landing phase.

Executing the QRH: A Step-by-Step Walkthrough

The Quick Reference Handbook (QRH) provides the approved procedure. The golden rule remains: Aviate, Navigate, Communicate. The Pilot Flying (PF) should maintain control of the aircraft while the Pilot Monitoring (PM) runs the ECAR actions and retrieves the QRH.

Step 1: Immediate Actions (ECAM)

  1. PF: "I have control." Maintain a safe flight path. Consider leveling off if the failure occurs during a high-workload phase like climb or descent.
  2. PM: "I have the ECAM." Press the ECAR (Electronic Centralized Aircraft Reminder) clear button to acknowledge the failure and proceed to the STATUS page if multiple messages exist.
  3. Both: Verify the HYD SD page. Confirm which system is lost and check reservoir quantities.

Step 2: Addressing Low Pressure (LO PR)

If the ECAM shows "HYD X SYS LO PR" without a leak message:

  1. Refer to the QRH checklist for "HYD G/Y/B SYS LO PR."
  2. The procedure may allow one attempt to reset the associated pump switch (EDP or EMP).
  3. If pressure is not restored, leave the pump off. Check if the PTU has automatically activated (relevant for Green or Yellow system loss). Monitor the PTU caution timeout—prolonged operation can overheat the Yellow system fluid.
  4. If the Blue system is lost, verify the RAT is not deployed unless required. Manual RAT deployment is considered a separate, deliberate procedure.

Step 3: Addressing a LEAK

A LEAK message is more serious. The system has automatically isolated itself by stopping the relevant pump.

  1. Do NOT attempt to reset the pump. Doing so will only pump more fluid overboard and potentially drain the reservoir, leading to a complete loss of that system.
  2. Check the interconnected systems. For example, a leak in the Green system might affect the landing gear circuit.
  3. Proceed to the LANDING DISTANCE assessment in the QRH, as braking and flight control configuration will be affected.

Step 4: When to Deploy the RAT

The RAT deploys automatically when both engines fail. However, there are situations where manual RAT deployment is appropriate in the simulation:

  • Dual engine failure: RAT deploys automatically.
  • Total Blue system failure: If the EMP and EDP on the Blue system both fail, and you cannot restore pressure, consider manual RAT deployment to regain essential flight controls and backup electrical power.
  • Low hydraulic quantity: If you suspect a massive leak that will soon drain all systems, deploying the RAT early can save the Blue system pressure for landing.

Procedure: The PF calls "Deploy RAT." The PM pulls the guarded RAT control handle. A loud noise and slight drag will be felt. The Blue system pressure is restored. Confirm on the HYD SD page.

Step 5: Gravity Gear Extension

If the Green and Blue systems are unavailable, the landing gear will not extend normally. The PM must perform the gravity extension procedure, typically accomplished by pulling the GRAVITY GEAR EXTENSION handle on the center pedestal.

  1. Check: Verify airspeed is within limits (typically below 250 knots and slowing).
  2. Action: Pull the handle fully. This mechanically unlocks the gear doors and uplocks, allowing the main gear to free-fall and lock into place. The nose gear is driven down by the airstream.
  3. Confirmation: The landing gear control panel lights will show "UNLK" (unlocked) before changing to "DN" (down) with three green lights.
  4. Handle Reset: Once the gear is locked, the handle may need to be reset (pushed back in) to allow the doors to be closed or to permit future normal retraction.

This scenario is dramatically highlighted in real-world incidents. The Air Transat Flight 961 investigation report (TSB Canada) provides an authoritative case study of a gravity gear extension following a dual hydraulic failure. Studying such reports reinforces the critical nature of procedural discipline.

Step 6: Landing with Reduced Braking

Landing without normal brakes requires thorough preparation. The QRH provides landing distance factors that must be applied. Understand the remaining braking capability:

  • Alternate Brakes: If the Blue system is still available, alternate brakes with anti-skid are active. A dual brake pedal input is required.
  • Accumulator Brakes: If all hydraulic pressure is lost, the brake accumulator provides a limited number of brake applications (typically 5-7 full brake presses).
  • Parking Brake: The Yellow system accumulator provides parking brake pressure. The parking brake can be used as a backup braking method, but it applies full braking force, which can lead to a locked wheel and tire burst.
  • Reverse Thrust: Max reverse is an absolute necessity. Awareness of which engine drives which reverser (Engine 1 = Green, Engine 2 = Yellow) is essential.

Simulation-Specific Training Strategies

Desktop and professional simulators offer unparalleled opportunities to practice these worst-case scenarios. The key to effective training is designing sequences that build deep procedural memory rather than just "rote" button pushing.

Programming Realistic Failure Scenarios

When setting up a session for yourself or using an instructor station, avoid simply flipping a single hydraulic pump failure. Instead, create cascading failures:

  • Engine Fail + Hydraulic Leak: Combine an engine failure on one side with a hydraulic leak on the opposite system. This forces the PTU to act and complicates the electrical generation logic.
  • PTU Timeout: Set up a scenario where the PTU runs for an extended period, leading to a Yellow system overheat and subsequent failure. This teaches the importance of managing the PTU.
  • No Bleed Air: Simulate a dual bleed failure which can impact engine-driven pump efficiency, leading to intermittent low-pressure warnings.

For desktop sim users, Airbus Safety First articles provide outstanding technical depth that can be translated into realistic failure parameters for ProSim, A32NX, or X-Plane.

Common Trainee Pitfalls to Avoid

Being aware of common mistakes allows you to actively avoid them during your sim session:

  • Forgetting the Landing Distance Factor: Many pilots execute the procedure perfectly but forget to use the QRH landing distance factor, resulting in a runway overrun in the simulator (and a failed checkride). Always check the "LDG DIST" section of the QRH.
  • Rushing PTU Actions: The PTU is loud. Attempting to reset pumps repeatedly while the PTU is growling creates confusion. Pause, analyze the SD page, and methodically apply the checklist.
  • Poor Task Management: The PF becomes fixated on the PM's actions or vice-versa. The PF must fly the aircraft. If the PM is busy with the QRH, the PF must focus solely on the flight path, speed control, and configuration.
  • Incorrect Bus Power Setup: After a dual engine failure where the RAT provides the emergency generator, remember that the electrical system is on "EMER ELEC" configuration. Some galley and non-essential buses are shed.

Optimizing Recurrent Training

To truly master hydraulic failures, schedule dedicated "systems review" sessions. Do not just practice the failure itself; practice the systems knowledge that underpins the procedure. Spend 20 minutes reviewing the HYD SD page with the aircraft powered up. Trace the fluid paths. Note the reservoir quantities at different stages (gear up, gear down).

Key Focus Areas for Your Next Session:

  1. ECAM Recall: Practice recalling the ECACM procedure for "HYD G/Y/B SYS LO PR" without looking at the QRH.
  2. Manual RAT Deployment: Simulate a dual engine failure and time how long it takes you to confirm the RAT is deployed and the Blue system is pressurized.
  3. Non-Normal Landing Checklist: The landing preparation phase is where most errors occur. Brief the final flap setting (often Flaps 3 with a hydraulic failure to reduce drag and maintain go-around capability), the VAPP speed, and the landing distance factor.

Conclusion

Hydraulic failures in A320 simulations are demanding precisely because they strip away the layers of automation and redundancy we rely on daily. They force the crew back to basics: system knowledge, strict adherence to the QRH, and flawless Crew Resource Management. By understanding the underlying architecture of the Green, Blue, and Yellow systems, and by practicing purposefully designed failure scenarios, you build the cognitive muscle memory needed to handle these events with confidence and precision. Treat every simulated failure as a genuine learning opportunity, and your proficiency—and your command of the aircraft—will benefit immediately.