737 rudder problems
As a 737-200 driver I've been trying to educate myself about the "hardover" problem for a number of years with varying degrees of success. I'd appreciate a little help from all you "sharp pencil" types.
The checklist for "uncommanded rudder" seems to be a typical process of elimination affair. First get rid of the autopilot, then the yaw damper, then switch system B flight control to STBY RUD.
I can see it up to there but I wonder why there aren't more steps. By switching system B to standby rudder you have the standby PCU on line in (I assume) an attempt to use it to position the rudder where you want it. OK but what if the main PCU was the problem in the first place and it is still trying to push the rudder the wrong way with A pressure? Will the standby PCU overpower the main PCU? They both operate at 3000psi so I don't see how. It seems that the next logical step would be to remove A pressure from the main PCU by selecting sys A flt control switch to STBY RUD or perhaps to OFF. I'm sure I'm missing something obvious here. Anyone care to point it out?