Electric Hydraulic Pump

[MSFS 2020] Questions & Community Discussions
1

Hello all. How have others modeled a single hydraulic system that has 2 pumps,
one driven by the engine and another, a backup electric pump. This is what I
have in Systems.cfg [HYDRAULIC_SYSTEM] normal_pressure = 1550 electric_pumps
= 1 engine_map = 1,0,0,0 ailerons_require_hydraulics = 0
rudder_require_hydraulics = 0 elevator_require_hydraulics = 0
spoilers_require_hydraulics = 1 I quickly learned that the key event of
HYDRAULIC_SWITCH_TOGGLE only cuts hydraulic pressure that the engine pump is
already providing. If, I turn the engine off, the pressure drops to zero, with
or without, the above key event triggering on or off. But with the engine on,
the pressure is as expected, but triggering the key event, would bring the
pressure down to zero. Below is the code I thought would turn an electric pump
on or off: (A:HYDRAULIC SWITCH:1, Bool) ! IF{ 1 ( > K:HYDRAULIC_SWITCH_TOGGLE)
} (A:HYDRAULIC SWITCH:1, Bool) IF{ 1 ( > K:HYDRAULIC_SWITCH_TOGGLE) }
Ultimately, what I need is to be able to pressurize the hydraulic system if
the engines are not running and while the engines are running, the pressure
would be the higher value of either the pressure from the engine pump or the
pressure from the electric pump. Any ideas would be welcome. Thanks

2

This is a wild guess, but I think you should be able to turn on/off just the
electric pump by going through the electric circuit to turn the hydraulic pump
circuit on/off via something like ELECTRICAL_CIRCUIT_TOGGLE.
HYDRAULIC_SWITCH_TOGGLE probably switches on/off all hydraulics.

3

Unfortunately that will not work because I would still have no way of
pressurizing the hydraulic system without the engines running. There must be a
way of doing this, I just do not see it.

4

Did you also wire up the electric pump in the electrical system?
Something like

circuit.x = Type:CIRCUIT_HYDRAULIC_PUMP:1#Connections:bus.1#Power:2, 5, 26.0#Name:Electrical_Hydraulic_Pump_1

(replace x)

6

Aircraft that use electric pumps still need the battery charging bus. So this means the engines must be running because a battery charging bus get it’s electricity from the alternators.

So I assume your backup pump is incase of low pressure coming from the engine driven pumps. The engine driven hydraulic pressure changes based on rpm. Our planes user manual (PTM) states the auxiliary pump has a maximum duty cycle of 3 minutes on, then 20 minutes off, to cool the pump. So it’s not a full time backup pump either.

8

Hi @FlyingRaccoon,

I want to express that what I posted above is wrong about how the pumps need the alternators. In fact our plane the L35A uses the battery for the backup hydraulic pump.

Right now the sim if forcing the circuit type CIRCUIT_HYDRAULIC_PUMP to fail when the alternators are off. This needs to be fixed. Should use the battery bus. And even if we remove the tag then we can’t produce hydraulic pressure at all. So we are stuck until this gets fixed.

Looking forward to a major overall so all the engine driven and electric hydraulic pump index’s are fed into a single master index. Because some backup pumps needs to cycle on and off to top off the pressure when low.

We also need relays to run systems that use the hydraulics as well. So if no electrical when you have pressure will fail to operate.
Need Power Topic

Looking forward to a response.

9

Update:
I was wrong about the sim forcing the CIRCUIT_HYDRAULIC_PUMP to fail when the alternators are off. When I had copied the circuit entry code from a default plane the minimum volts required was 26 and our batteries are 24.6 so this is why It lost power without the alternators. So excellent I can now simulate the electrical hydraulics and the engine driven.

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