Cat 3A Visual Requirements
A segment of at least 3 consecutive lights being the centreline of the approach lights, or TDZ lights, or runway centreline lights , or runway edge lights, or a combination of these is maintained and can be maintained.
Descent below DH without adequate visual reference is prohibited.
in the trusty 737 any AP disconect/Nav set failure/ 2 or more deviation flashes or Stab out of Trim below 500R is a mandatory Go Around