The hydraulic actuator is near the same as the hydraulic actuator. The difference is that you cannot free the oil like the air. So the oil will flow in a circle. Also air will not be compressed, so the hydraulic is very accurate and should be combined with a differential valve to avoid the hard start movement. The hydraulic system is only be usable in rooms with good air condition and rooms that can get dirty. Nearby you will find a simple hydraulic system. Oil pressure is a high pressure system which will need much power. Because the power will be converted to energy, the hydraulic system becomes hot very fast. A good oil cooling and compressor is needed for a correct usage in a simulator system. Oil is one of the best cooling fluids you can get, so it will also transport the valve throughput energy to the tank. Normally there are only short used hydraulic systems on the market for fast actions. The simulator needs continues work.

1. Open hydraulic circuit
First a gear pump will suck some oil out of a oil tank. Because oil can get dirty there is normally a filter installed. The pump will generate pressure only if needed and switches itself of if there is no need. The valve block will fully control the hydraulic cylinder. The not needed oil will be returned in the catch tank. If there is a analogue valve installed, you are able to change the speed, else this is like the 5/3 valve block of the pneumatic system.
You should control the pump with a interface relay to avoid overheating the system. You are able to cool the oil in the catch tank.

2. Closed hydraulic circuit
This is the advanced version of the first circuit but do not need a catch tank. Because temperature will expand the fluid there must be some pressure balance installed. You should control the pump with a interface relay to avoid overheating the system. This circuit is not designed for long time usage.