caa.co.uk, as data

(1) a segment of at least three consecutive lights being the centreline of the approach lights, or touchdown zone lights, or runway centreline lights, or runway edge lights, or a combination of them;(2) this visual reference should include a lateral element of the ground pattern, such as an approach light crossbar or the landing threshold or a barrette of the touchdown zone light unless the operation is conducted utilising an approved HUDLS to touchdown.(1) For CAT IIIA operations and for CAT IIIB operations conducted either with fail-passive flight control systems or with the use of an approved HUDLS: at DH, a segment of at least three consecutive lights being the centreline of the approach lights, or touchdown zone lights, or runway centreline lights, or runway edge lights, or a combination of these is attained and can be maintained by the pilot.(2) For CAT IIIB operations conducted either with fail-operational flight control systems or with a fail-operational hybrid landing system using a DH: at DH, at least one centreline light is attained and can be maintained by the pilot.(3) For CAT IIIB operations with no DH, there is no specification for visual reference with the runway prior to touchdown.(e) Approach operations utilising EVS — CAT I operations(1) At DH, the following visual references should be displayed and identifiable to the pilot on the EVS image:(i) elements of the approach light; or(ii) the runway threshold, identified by at least one of the following:(A) the beginning of the runway landing surface,(B) the threshold lights, the threshold identification lights; or(C) the touchdown zone, identified by at least one of the following: the runway touchdown zone landing surface, the touchdown zone lights, the touchdown zone markings or the runway lights.