Aaaaah! Punkah Louvres,
We had them on BOAC VC10s too. I always had this image in my mind of a turbaned Indian down in the cargo bay with a string tied around his big toe, gently wafting, via a suitable system of knotted strings and pulleys, a large feathered contraption above my head wafting cool air to sooth my fevered brow while I flew a complicated approach!!
But it never seemed to work quite that way.