Hydraulic System Question

[Guest Eagle2006]

Hello,I am new to this forum and fairly new to the Panel Design and have a question to a hydraulic system issue.I would like to simulate a hydraulic pressure fluctuation on the pressure indicator due to large control inputs. Lets say you pull on the stick and the elevator is deflected to it's maximum value, there should be a quick pressure drop (from 3100 psi to 2900) and if the control surface remains in that position it should come back to 3100.How could I set it up if I read in the control surface positions?I am looking forward to your answers.Thank you.

[Guest Patrick_Waugh]

What do you mean by "how do I set it up"? Are you trying to program it in C, or XML?What have you tried? Where are you stuck? It is info like this that helps better define your question, and how we can help.

[Guest Eagle2006]

Sorry, you are right. I should have been a little bit more specific.I want to code it in C. Well, I thought about reading in the control surface positions. Let's take the rudder for example. It could have a deflection of +30, -30 deg. If the pilot will step into the rudder and gets immediately 30 deg deflection, I will let the pressure drop to a certain level and if the control surface stays in the current position, the pressure will build up again. I have to find a way to determine the deflection rate. Well, I could do it by calculating the difference between the current and the previous time step and devide it by the time step time, in order to get the rate. However, the rate could be high, but the deflection might be only 5 degrees in the end, which wouldn't cause a pressure drop. Only large deflections in a small period of time.I am currently stuck searching for a method evaluating if there is a large deflection in a small amount of time.

[marcom 139]

Eagle,I know this isn't what you asked for but if you want to simulate something big then here are a few tips:-hydraulic pressure is always fluctuating a few psi. Many modern aircraft have demand pumps that kick in randomly (especially if there is something "big" being extended/retracted).-primary flight control surfaces don't really have an impact on the hyd. system. Maybe you could focus on the heavy duty stuff like gear and/or flaps.

[Bob Scott 7,721]

Generally speaking, most transport category jets use a variable-volume constant pressure pump that reacts very quickly to demand. Something like the gear actuators, which cycle quickly and use fairly large displacement piston cylinders, might produce a momentary drop in pressure, but hydraulic motors (i.e. flaps) aren't likely going to put such a hig volume demand on the system that the pump will fail to hold pressure. UNLESS...the engine isn't running and you're looking at windmilling pressure, which is a whole different animal, and one that I have never seen simulated in FS before.CheersBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

[kanogek 0]

Came across this post while searching for some hydraulic system simulation tips.Thanks to all of the input given here on this forum i am on the roll with XML increasingly better. This is just one big library of knowledge, searchable and all...Anyway, thought i'd share this gauge i made with you, maybe someday someone will find use for it.It simulates a hydraulic system which operates the flaps (other systems will follow of course, but the principle is the same so one can add that for himself).xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx(L:Hydraulic_switch_1, number) 1 == (A:Turb eng1 N1, percent) 25 > (L:Hydraulic_press_1, number) 3200 < && && if{ (L:Hydraulic_Press_1, number) 40 + (>L:Hydraulic_Press_1,number) } els{ (L:Hydraulic_switch_1, number) 0 == (A:Turb eng1 N1, percent) 25 < || (L:Hydraulic_press_1, number) 40 > && if{ (L:Hydraulic_Press_1, number) 45 - (>L:Hydraulic_Press_1,number) } }(G:Var1) 0 == if{ (A:FLAPS HANDLE INDEX, number) (>L:FLap_Handle, number) 0 (>L:Flap_Delta, number) }(A:FLAPS HANDLE INDEX, number) (L:FLap_Handle, number) == ! (G:Var3) 0 == && if{ 600 (>L:Flap_Delta, number) 0 (>G:Var1) } els{ (G:Var1) ++ (>G:Var1) }(G:Var1) 17 > if{ 0 (>G:Var1) }(G:Var2) 0 == if{ (A:TRAILING EDGE FLAPS RIGHT PERCENT, percent) (>L:Flap_pos, number) 1 (>G:Var2) } els{ (G:Var2) 1 == (A:Trailing edge flaps right percent, percent) (L:Flap_Pos, number) == && if{ 0 (>G:Var3) 0 (>G:Var2) } els{ 1 (>G:Var3) 0 (>G:Var2) } }(L:Hydraulic_Press_1, number) 600 > if{ (L:Hydraulic_Press_1, number) (L:Flap_Delta, number) - (>L:Hydraulic_Press_1, number) }(L:Hydraulic_Press_1, number) 1500 < (G:Var4) 0 == if{ (A:Trailing Edge Flaps Right Percent, percent) 163.83 * (>L:Freeze_Flaps, number) 1 (>G:Var4) } (L:Hydraulic_Press_1, number) 1500 > (G:Var4) 1 == && if{ 0 (>G:Var4) }(G:Var4) 1 == if{ (L:Freeze_Flaps, number) (>K:FLAPS_SET) }(L:Hydraulic_Press_1, number)%Hydraulic pressure% %((L:Hydraulic_Press_1, number))%!4d! %psi%xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxThe system is controlled by a switch (not included) which toggles L:Hydraulic_switch_1, number. (my plan is to introduce 2 systems in my aircraft, hence the _1 suffix).Also a small dip in pressure can be observed when selecting the flaps to a new position and the flaps are not in travel already. This prevents incremental decrease of pressure when sequential flap selections are made. In real life this dip might not be visible, but hey i find this a nice touch. Just think of it as if the pump is at the end of its life, struggling to keep up.The pump needs to adapt to the required flow and once it has, there is no need for another pressure dip as long as the flow remains constant, so to speak.Should the pressure drop below 1500 psi, the flaps stop at the nearest position.Maybe not the most elegant of XML codes around, but it works...And once i figure out how to make the code "indented" and still keep it functioning, i will do so lol.grtWillem.