Hydraulic SYSTEM Pressure Offset

[High-Octane]

Offset 08D8 (engine1) 0970 (engine2) obviously its both engine hydraulic pressure.

But I am looking for Hydraulic System Pressure offset? Aren't there any of it listed in offset table? because I couldn't find one. My understanding, it has something to with entire aircraft hydraulic such as flaps, landing gears, brake, and etc.... And I am not sure if FS include that

Let me know

[Pete Dowson]

But I am looking for Hydraulic System Pressure offset? Aren't there any of it listed in offset table? because I couldn't find one.

In an airliner I am pretty sure there are always at least two hydraulic systems, powered by separate engine-driven pumps and/or electric pumps, with the latter powered by different electric subsystems / generators.

For example, in the 737's Hyd. Engine 2 pump and Hyd Elec 1 pump power Hyd. system B, and Hyd. Engine 1 pump and Hyd Elec 2 pump power Hyd. system A. This cross-over system allows two separate original sources for each system, as a failsafe.

In normal configuration the hydraulic needs in the 737NG series are shared as follows:

Alt Brakes, Left Flight Spoilers, Ground spoilers, Landing gear, Nose wheel steering, A/P A -- System A

Nml Brakes, Autoslats, Autobrake, Right flight spoilers, Flaps, Yaw damper, A/P B -- System B

Rudder, Ailerons, Elevator and "elevator feel" -- Both A and B.

There is also a standby hydraulic reservoir and associated system which I won't go into here. For 737 stuff see http://www.b737.org.uk/index.htm.

My understanding, it has something to with entire aircraft hydraulic such as flaps, landing gears, brake, and etc.... And I am not sure if FS include that

It doesn't really do a lot of the sub-system simulation -- I use pmSystems and program it there. But all this is, of course, very aircraft specific. I expect some of the more sophisticated models like the PMDG 737NG and the LDS 767 simulate this stuff very well.

But I think you are mistaken about the hydraulics -- where there are multiple systems you get multiple pressure readings. In the case where two or more systems are feeding the same actuators I expect you can add the pressures, but why would you want to?

Regards,

Pete

[High-Octane]

Pete, Very interesting.... Thanks for extra information on hydraulic stuffs

For example, in the 737's Hyd. Engine 2 pump and Hyd Elec 1 pump power Hyd. system B, and Hyd. Engine 1 pump and Hyd Elec 2 pump power Hyd. system A. This cross-over system allows two separate original sources for each system, as a failsafe.

737 fan aren't you? :D

But I think you are mistaken about the hydraulics -- where there are multiple systems you get multiple pressure readings. In the case where two or more systems are feeding the same actuators I expect you can add the pressures, but why would you want to?

Right, I wouldn't bother adding pressure...I didn't realize there are multiple hydraulic working separately in one aircraft. I always though one hydraulic for all parts such as engine, flap, landing gear and etc. And I realize it would be silly if they actually does that.

I guess it's something that I learned today, the new information for me. Actually, What I was going to do is adding hydraulic status in my application (VB) Nothing complicated, just adding label "Hyd sys press" stating the hydraulic system pressure is on. And whenever it needs to be off the label would simply disappear. And at this point I am not sure when hydraulic will ever stop running. Just one question... does engine hydraulic system constantly running when engine is on? How about does it keep running when pilot is starting up engines at subsequent procedure? "Apu, fuel flow and etc..."

[Pete Dowson]

737 fan aren't you? :D

Well, it's just the one I've been studying most and attempting to simulate thoroughly in my cockpit. A 737-700 to be specific. ;-)

Nothing complicated, just adding label "Hyd sys press" stating the hydraulic system pressure is on. And whenever it needs to be off the label would simply disappear.

Sounds okay, but you'd have to logically 'or' the multiple conditions. And of course the indication wouldn't necessarily tell you everything was okay because if one Hyd system is down some things wouldn't work.

And at this point I am not sure when hydraulic will ever stop running. Just one question... does engine hydraulic system constantly running when engine is on?

Well in the default FS aircraft it does because it doesn't simulate the subsystem very much -- the cockpits don't have the switches. In my cockpit I have the four switches -- Electric and Engine pumps for system A and system B. Certainly you get no pressure if no pumps are on. But there are no pumps or switches in FS itself, only in add-ons.

How about does it keep running when pilot is starting up engines at subsequent procedure? "Apu, fuel flow and etc..."

There's a reservoir for each system, including the standby, so you do still get some hydraulic pressure for a while after the engines are switched off, but I assume it will decrease quite rapidly if you actually try using anything. You have to take care not to switch on System A pumps even with engines off before pushback, because the nose wheel steering could become activated with remaining pressure, and that could be dangerous for both equipment and groundcrew -- pushback needs a "loose" nosewheel. Same goes for flaps and things moving when there are groundcrew around.

Regards,

Pete