Flight control shutoff valves

[tl1975]

Hardy:

indeed some switches have four peanut lights. What I see most of the time are switches with randomly 1, 2 or 3 bulbs U/S. So the switch is badly illuminated.

When you  have spare time, you can try simulating this!  :mrgreen:

[tl1975]

Simulating valve-transit-time is really what we talk about here.

Hardy, I have noticed that in some 744(F)'s the fuel crossfeed valves (2 and 3) take a long time in transit. (thus amber VALVE light on).
These crossfeed valves are in one particular situation automatically switched to CLOSED. Forgot but I think it's during certain flap position transits.

This would be really great to see simulated. Of course this really pops up on an aging valve that is sticky or slow in closing. But I have seen a few crews astonished by the valve lights briefly coming on and off.

[Hardy Heinlin]

When you  have spare time, you can try simulating this!  :mrgreen:

I had spare time two years ago and therefore, indeed, put four bulbs into the fire handle :-)

http://aerowinx.com/forum/topic.php?post=6652#post6652

...

I will model the motion of the fuel tank valves. But I'm not at the fuel system yet. So far, I've implemented valve motion in the hydraulics model and engine start stuff.


Cheers,

|-|ardy

[tl1975]

Fantastic! (I should have read you post better!)

Right now manufacturers are upgrading FD with LED lights. Our current A/C will get them this summer.
Another classic item gone out of the cockpit...

[Jeroen D]

Some years ago a few forum members and myself organised a PS1 day in the Netherlands. Star of the day was a KLM pilot who talked to us for hours. I remember him telling us that the valve lights in the cockpit don't really represent the actual valve position at all. According to him there is/was no actual feedback from the valves. The valve-transit-time was not due to the valve actual needing some time to change position, but it was pure electronic trickery! So essentially an electronic timer, no real indication!

I've tried to search for my post on the old forum, but can't find it anymore.

So are we sure that there are actual sensors on the valves that indicate the position?

If what he told us is/was true the phrase "Simulating valve-transit-time" becomes really that Hardy needs to simulate the simulating valve transit time!

Jeroen

[Hardy Heinlin]

Some years ago a few forum members and myself organised a PS1 day in the Netherlands. Star of the day was a KLM pilot who talked to us for hours. I remember him telling us that the valve lights in the cockpit don't really represent the actual valve position at all. According to him there is/was no actual feedback from the valves. The valve-transit-time was not due to the valve actual needing some time to change position, but it was pure electronic trickery! So essentially an electronic timer, no real indication!

I've tried to search for my post on the old forum, but can't find it anymore.

So are we sure that there are actual sensors on the valves that indicate the position?

If what he told us is/was true the phrase "Simulating valve-transit-time" becomes really that Hardy needs to simulate the simulating valve transit time!

Jeroen

I think this cannot be generalized. In many areas there are time delays between the sensor and the indication. But there are also valves that really take 1 to 3 seconds between fully open and closed. And if there's only one sensor switch at one end, it may take a few seconds till that end.

The valve light and EICAS symbol, however, does not indicate if there's really something flowing through the valve. The valve may be open (no yellow indication), but there may be no bleed air, no fuel, no hydraulic fluid ... or no current through a closed electrical switch. Perhaps that's what he talked about?


Cheers,

|-|ardy

[John H Watson]

According to him there is/was no actual feedback from the valves. The valve-transit-time was not due to the valve actual needing some time to change position, but it was pure electronic trickery!

It would be wrong to say that there is absolutely no valve feedback on the 747-400. Not all valves will have fully open and fully closed position sensing, but all have position sensing for, at least, the most important position.

The electrically driven valves should have sensors on both fully open and fully closed positions. Some valves even have full monitoring between open and closed (e.g. pack trim air valves).

Having said that, if valve position sensors are faulty, flow bars on EICAS system synoptics may not necessarily show actual flow.

Perhaps this is what you were thinking of?

There are no timing circuits, other than for fault annunciation (a message will be generated if the valve fails to reach its commanded position.

Rgds
JHW.


edit by JH:  maybe you meant: "(... if the valve fails to reach its commanded position in a predetermined time)"?

[dutch57]

Hardy & Jhon,

Just looked in my SSM the valve has a position, open and not-open.

The not-open position switch is activated as soon as the valve body moves from the open position towards close. The switches are mounted inside the gearbox between actual valve and electric motor

Sincerly
Bob