How does the Airbus A320 hydraulic system work?
The Airbus A320 hydraulic system uses three separate 3,000 psi circuits, called Green, Blue and Yellow, to power the flight controls, landing gear, brakes and other actuators. In real-world aviation and in good flight simulators, the pumps create pressure, the fluid carries that force, and losing one circuit only affects the equipment assigned to it.
What are the Green, Blue and Yellow hydraulic systems?
They are three independent hydraulic circuits kept separate so one failure does not take out the whole aeroplane.
Each system has its own fluid supply and pressure source, and the A320 spreads important services across them for redundancy. Exact actuator mapping varies a little by A320 family member and by how deeply a simulator models the aircraft, but the basic architecture stays the same.
| System | Typical pressure source | Examples of what it powers |
|---|---|---|
| Green | Engine 1-driven pump, with PTU assistance available | Landing gear, normal brakes, nose-wheel steering and some flight-control actuators |
| Blue | Electric pump in normal use, RAT in emergency | Many flight-control actuators and essential backup hydraulic power |
| Yellow | Engine 2-driven pump, plus an electric pump for ground and backup use | Some flight controls, parking or alternate braking functions, cargo doors and other ground services |
A mistake we see constantly is assuming the PTU moves fluid from one side to the other. It does not. It transfers hydraulic power between Green and Yellow, which is why one system can help the other while the fluid remains separate. Blue stays independent and has its own emergency backup logic.
What do the pumps, pressure and fluid actually do?
The pumps do not move the control surfaces by themselves; they supply pressurised fluid to the actuators that do the work.
- Engine-driven pumps are the main in-flight source. Once the engines are running, they normally bring the Green and Yellow systems up to around 3,000 psi.
- Electric pumps let a system pressurise without relying on engine power. On the A320, the Blue system normally depends on an electric pump, and the Yellow electric pump is especially useful on the ground.
- Pressure is the usable force in the system. A switch can be on, but if pressure is low, the components tied to that circuit may be slow, limited or unavailable.
- Hydraulic fluid is the medium carrying that force. In advanced add-ons it can also be lost through leaks, which reduces quantity first and eventually affects pressure; in simpler aircraft it may be little more than a gauge reading.
The RAT, or ram air turbine, is the emergency backup. If the aircraft suffers a major electrical or hydraulic upset, the RAT can pressurise the Blue system so the crew still has essential control authority. Many basic A320 models show the idea of this system without fully modelling its consequences.
If you need help finding these indications, our guide to the main A320 cockpit controls and displays shows where the hydraulic information appears, and our explanation of how the A320 ECAM presents system pages and cautions makes the HYD page much easier to read.
How do you check A320 hydraulic pressure in a flight simulator?
The quickest A320 hydraulic check is on the ECAM HYD page backed up by the overhead pump panel.
- Call up the HYD page and confirm Green, Blue and Yellow are shown without abnormal low-pressure warnings for the phase of flight you are in.
- After engine start, verify the engine-driven pumps have brought Green and Yellow to normal operating pressure.
- Check Blue and make sure the electric pump logic in your aircraft model has pressurised that system as expected.
- Watch the PTU during one-engine taxi, turnaround states and unusual ground setups. If one of Green or Yellow is pressurised and the other is not, PTU action can be completely normal.
- Before taxi, make sure the aircraft has the braking, steering and hydraulic status your add-on expects, not just that the switches look correct.
Do not chase every amber hydraulic indication during a cold-and-dark start. Low pressure is normal until the pumps have a valid power source.
Why do hydraulic switches sometimes seem to do nothing?
Because many Airbus A320 simulator models display hydraulic systems more convincingly than they actually simulate them.
| Model depth | What usually works | What is often missing |
|---|---|---|
| Basic or default aircraft | Pump switches, ECAM pages, some cautions and generic system labels | Real knock-on effects on brakes, steering, PTU behaviour, RAT logic, leaks and flight-control degradation |
| Study-level add-on | Pressure logic, PTU operation, emergency backup behaviour and meaningful ECAM consequences | Little tolerance for wrong setup; you must follow the Airbus flow properly |
If your landing gear still operates normally with obviously wrong hydraulic settings, or the brakes feel unchanged with a failed system, that is usually a limitation of the aircraft model rather than a misunderstanding of Airbus procedure. This is common across simpler aircraft in MSFS, FSX, Prepar3D and X-Plane.
For the wider Airbus flow around startup and taxi, our step-by-step A320 guide for Microsoft Flight Simulator shows where hydraulic checks fit into a normal cockpit scan.
What hydraulic problems do simmers hit most often?
Most A320 hydraulic problems in a simulator come from setup errors or simplified modelling, not from an obscure Airbus failure.
- No Green or Yellow pressure after start: the engine-driven pumps are off, the engines are not actually stabilised, or the add-on has loaded in an abnormal state.
- Low Blue pressure on the ground: the Blue electric pump is off, or the aircraft model does not simulate its automatic behaviour properly.
- Unexpected PTU operation: one of the Green or Yellow systems is pressurised and the other is not. That often means the aeroplane is behaving normally.
- Amber HYD indications during startup: normal until at least one valid pressure source is online.
- Switches animate but nothing changes: the add-on is using simplified hydraulics, so the cockpit looks Airbus-like but the underlying system logic is generic.
For practical sim flying, remember the chain: pumps create pressure, pressure moves fluid, and fluid powers the actuators. Once you understand which colour system feeds which part of the aeroplane, A320 hydraulic pages stop looking mysterious and start becoming a quick fault-finding tool.