Good picture Nutty, I wish I was clever enough to insert graphics (or extracts from my Dads 1950s trade training notes!) Now then is that one or two threads poking though? I rest my case M'laud.
Tuc, yes three Olympic type rings (I'd be guessing at Def Stan 05-40 I could probably have written chapter 400 of 00-970!) now there was no standard for identifying metric threads on English aircraft so they were labelled "Metric" This was in the extreme only where proprietary items had to be used.
I was dead worried about the unified fixings on the Gazelle as some were blind threaded holes in potted inserts into the nomex honeycomb structures. There may have been a couple on the Lynx and Puma as well.
Now you will know the Nimrod had mostly BA/BSF on the airframe, all our racks were unified. the later avionics were Metric post about 1980. can't remember if the Starwindow stuff from America was metric. I would probably have had discussions on the topic. the problem was metric hardware to aircraft standard with metallic locking elements was as rare as rocking horse droppings back then. Getting hold of stuff from the Jaguar, Tonka or even Sea Eagle Missile was an issue.
I certainly remember the Argentine CH47 at Wroughton. I thought it only got used for BDR training. We had the pylon at JATE for a spell when we were devising transport dollies. I wonder how they went on with the A109s
Apologies for the tread drift. just expanding on a few points and illustrating scope for Mr Murphy coming home to roost.