Not forgetting that when switchable HISLS are operated on the white setting on a helicopter, in UK the red anti-collision light must also remain switched on.
Edit:
Having just gone through my latest downloaded copy of CAP393 with a fine toothed comb, it appears that a helicopter may now also use a white anti-collision light; my original copy differentiated between aeroplanes (could be red or white) and helicopters (must be red). The newer copy now simply refers to "flying machines" with no separate reference to helicopters, so I presume the rule no longer applies.
