It's a personal choice! Had this argument a long time ago when we were re-writing an RAF helicopter checklist and someone wanted to mandate "Position Lights - ON" in the the pre-start items. He thought it was a compulsory thing, even by day! I produced the relevant document and we settled on "Position lights - As required".
However, it is of course a legal requirement in UK for helicopters to display the anti-collision light by day whenever the rotors are turning.
Edit: With the exception given for helicopters on an offshore platform, for signalling that it is safe to board pax.
Last edited by ShyTorque; 14th June 2006 at 18:48.