The Parthenavia was one of the hotter "lighties" I can remember. But come the end of my G.A. days (back in the late '70's), I figured my days of sitting in sweat boxes (C310's, Navajo's, Twin Commanches, etc) were over.
WRONG!!
My first airline aircraft was the "Mouse" the F27 (200 & 500) - named because of its long nose. Now while today's modern airline transport aircraft have APU's and GPU's, the Mouse had ZILCH, NADA, NIL! Except for a "ground blower" - in other words, a fan that inducted air at ambient temp. and blew it into the cockpit/cabin.
Moree, Coonabarrabran, Gunnedah, Wee Waa, Dubbo and Broken Hill.
Alice Springs, Rockhampton, Gladstone, and Isa!
Real crutch-rot territory in Summer.
But the Mouse had an added bonus for the sauna afficionados - window heat :o
That delightful innovation that had to be turned on (in those days) at least 10 minutes prior to take-off.
Light aircraft on a HOT Summer's Day....
sheer bloody luxury!!