For CAT II approach, the decision height is below 200ft but not lower than 100ft with RVR of 300m. In this case, if the aircraft is at 100ft above the ground, should the captain of that aircraft be able to see the runway threshold lights (green) at that moment? Or seeing the approach lights is considered sufficient to continue?

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    $\begingroup$ You can always edit your question... $\endgroup$ – mike Dec 24 '17 at 6:57

Short answer: for CAT II, seeing the approach lights (minimum 3 segments) is sufficient given a lateral element is also acquired.

Visual acquisition definition may vary between FAA, EASA, ICAO, etc. What follows is for EASA (as tagged).

For CAT II, you may descend below the DH if you can see:

  • 3 consecutive approach lights,
  • or touchdown zone (TDZ) lights,
  • or runway centerline lights,
  • or runway edge lights,
  • or a combination of the above,
  • and must include a lateral element, i.e., crossbar, threshold, or TDZ pattern lights.

enter image description here
(Source: Airbus) A crossbar plus 3 segments.

For CAT IIIa and CAT IIIb (fail-passive; no roll-out mode):

  • The same as above, minus the lateral element.

For CAT IIIb (fail operational; roll-out mode):

  • At least one centerline light is attained and can be maintained.

Do not use for flight.

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