Pete,
Since the rudder scares, 737’s are now fitted with an RPR (Rudder Pressure Reducer) to reduce the rudder authority by about 30%. It is clever enough to give you back full rudder pressure at certain critical times ie:
a) During take-off below 1000’ Rad.alt.
b) During approach below 700’ Rad.alt.
c) If a difference of >45% N1 exists between power units.
d) If B-system hydraulic pressure is lost.
Unfortunately it cannot give you back full rudder pressure if system-A is lost because it is powered by system A!
A good article on the 737 rudder system can be found at:
www.b737.org.uk\theruddersystem.htm
S & L