Er, not so Notso Fantastic, I think you'll find the 747 doesn't actually have leading edge slats! As I recall, the wing anti-ice IS there to protect the leading edge - hot air is ported into the leading edge area via a 'spray tube' inside the leading edge of each wing. As a result it becomes ineffective when the leading edge flaps are extended, because the hot air simply gets dumped overboard. As you said though, it is rarely used and any icing on the inboard part of the wing is likely to be caused by condensation freezing on the wing surface because of cold fuel in the tank.
Last edited by BuzzBox; 4th October 2003 at 23:37.