I’m currently authoring a native 2024 aircraft and using the HYDRAULICS_SYSTEM_EX1 section in my system.cfg file.
The aircraft in question is extremely simple in terms of hydraulics - it has an engine driven pump with a small reservoir and no accumulator, that drives a set of continuous flaps as well as the landing gear.
The primary issue I’ve noted is that when the actuators contain fluid (as shown in the debug window), the simulator ignores the calculated ‘stop working pressure’ and allows slow movement of the actuator anyway.
In my basic system, I’ve added two shutoff valves so that I can experiment and affect the pressure and flow of fluid to test. In the below steps, I’m using the hydraulically powered flaps to test.
When the aircraft is first loaded, the shutoff valves are preventing fluid from entering the system, as designed. The hydraulic flaps should not, and do not, function.
After the engine is started and the first shutoff valve is opened to allow fluid to the engine pump, we have pressure generated, but since the valve to the actuators is closed, the actuators have no fluid and thus remain at their initial pressure. The hydraulic flaps still should not, and do not, function.
Once the second shutoff valve is opened, the actuators fill with fluid and are pressurized. The hydraulic flaps now should be able to function, and they do.
Now… when the actuators lose pressure, which I can cause by shutting off the engine, the actuators (according to the SDK, as well as the mouseover indication of the calculated ‘stop working pressure’) should not function. In the below image, all components have now returned to the standard ‘14.5 psi’ pressure that the system started with.
However, in this situation, the hydraulic flaps will continue to slowly operate, in either selected direction. While the flaps actuator is active, the fluid will slowly transfer from the actuators back into the reservoir.
If, via the debug window, I close the second shutoff valve and manually empty the actuators, the flaps will then cease to work.
All of this raises the question as to why are the actuators continuing to function, even though the system pressure is far below the minimum required pressure?