Dash 8-300 prop de-icing
A silly question, but I have flown hugely and on a domestic flight this evening in poor weather Nelson-Auckland New Zealand the flight, scheduled for 60 minutes, took nearly twice as long. We climbed to 18,000 feet and then seemed to wallow for ages and then descended, at which point there was the kind of vibrations you'd worry about on a tractor: then there was a bit of prop whizzing and the pilot explained that there was nothing to worry about and that the props were being de-iced and we had descended altitude to achieve that. Two things occurred to me: doesn't a Dash 8 have electric de-icing, so why the need? And second, if the same thing happened in a really cold place like a Canadian winter, descent wouldn't help in that warming up from minus 40 to minus 30 degrees: what options would a pilot have in severe cold conditions when faced with icing?