Can anyone explain the purpose for the large horizontally mounted cylinder on the back of the T-80BV turret (highlighted in the attached image)? It has two square boxes fitted on top. Again, what are these exactly? My guess is that the cylinder is used for storage (but for what exactly?)
The tube is part of the Schnorkel system for the vehicle; the 2 boxes - the 3rd appears to be visible just forward (towards the bottom left of your red rectangle) - contain the crew’s protective NBC kit (ie one each- the crew consisting of 3, as I’m sure you know).
Pretty much every Soviet designed tank since at least the T-54A has had a snorkel tube system for river crossings. Usually stowed on the engine deck rear or rear quarters of the turret. The T-80 used a larger snorkel tube due to its turbine engine.
That’s exactly what I thought … at least the cylinder; the boxes, I wasn’t sure.