737 Stab Out Of Trim

[mrmaster]

Hi all,

I am into writing the program for my arduino and have a question. When exactly is the Stabilizer out of trim?

Cheers, Marc

[will1911]

This only applies when the A/P is engaged. When the 'STAB OUT OF TRIM' light illuminates, the A/P isn't trimming the stabilizer properly.

It indicates that there's a problem with either the A/P or the stabilizer trim (electric trim for example might be inoperative).

[mrmaster]

Yep that is what I found as well in my manual, BUT: I have to work with datarefs from XPLANE and how can I calculate or define when the autopilot is not trimming properly?

[will1911]

I think that's quite hard to define. In an out of trim situation, the A/P would have to apply a greater amount of force to keep flying the airplane the way you want it to. So I can imagine that if the A/P has to apply more than a certain amount of force, it knows it's flying out of trim. The A/P might also have predefined trim ranges within which it should fly at certain speeds. If the stab trim setting is out of that range, it might indicate out of trim.

Whatever it is, you won't find out by checking any of the manuals. I've actually flown the 737 and I don't know. Try contacting a mechanic or perhaps Boeing.