smartt1982
Topic Author
Posts: 226
Joined: Sat Nov 24, 2007 11:17 pm

737 Stab Trim Setting Indicator

Tue Oct 09, 2012 7:23 pm

On the stab trim indicator on the 737. Is there one side which is going to be more accurate than the other. Should there be a difference between them and if so, how much of a difference? On our procedures we set the stab trim according to the captains side because it is he or she who will check it as part of their take off/departure brief to check it is set correctly. Other than that, I cannot think of a reason why we set it according to one side over another, I thought they should be the same both sides?
 
yeelep
Posts: 727
Joined: Mon Apr 04, 2011 7:53 pm

RE: 737 Stab Trim Setting Indicator

Tue Oct 09, 2012 8:14 pm

On the NG's (classic's are probably the same) when the indicators are checked against the physical location of the jackscrew/stab, each indicator must be +-0.5 unit from the target and within 0.5 unit from each other. Neither target is considered the master, so either one could be the most accurate.

[Edited 2012-10-09 13:16:34]
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: 737 Stab Trim Setting Indicator

Wed Oct 10, 2012 12:57 am

Quoting smartt1982 (Thread starter):
I thought they should be the same both sides?

They're on a common shaft so the offset should be constant but, thanks to tolerance stackup in both the shaft and the indicators, you're never going to get perfect agreement between the two sides.

Tom.
 
mandala499
Posts: 6459
Joined: Wed Aug 29, 2001 8:47 pm

RE: 737 Stab Trim Setting Indicator

Wed Oct 10, 2012 6:06 am

Do the cheat... select the Stab-Trim according to the FMC readout first... (forgot which page)... then cross check with whichever StabTrim indicator your SOP tells you to!   
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
yeelep
Posts: 727
Joined: Mon Apr 04, 2011 7:53 pm

RE: 737 Stab Trim Setting Indicator

Wed Oct 10, 2012 3:40 pm

Quoting yeelep (Reply 1):
Neither target is considered the master, so either one could be the most accurate.

Whoops, target should have read indicator.

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