The riggers that used to crawl into fuel tanks had my greatest respect.
On Valiant's the Instrument bods seemed to spend an inordinate amount of time in there, muttering about 'tank units'.
Me, I didn't want to know, no way was I going in there.
This whole thread is really not about 'hard jobs' but simple jobs made difficult, by various bit of kit being put in inaccessible places, and a/c being parked in 'ot and cold places.
