As a committed fan of staircases (I was looking at stairporn.org yet again on my lunch break yesterday) and a pedant, I would be much happier if they were called "helical staircases", unless the radius does actually increase or decrease as one climbs.
Apparently it is limerick day . . . well, unless in it no longer May 12 where you live . . . But it is here, so, hmmm . . . I shall create a limerick A woman who knew she was blue Said, " 'ello, how do you do?" The children all ran As fast as a van Making her cry, "Oh, boo hoo." I know, it's not great. But, it was quick and fun.