Interesting excerpts from a now defunct blog - Trishul, regarding the T-90.
''In hunter-killer fire-control systems as those on board the Merkava-4, Challenger 2, M-1A2 Abrams, Leopard 2A6 and the Leclerc, it is the commander's panoramic sight that is responsoble for target acquisition, target tracking and target designation. Only after the MBT commander completes these three tasks is the engagement phase undertaken by the gunner. In other words, while the commander's sight does three separate but sequential functions, the gunner's sight performs only one function. While all four processes are smoothly conducted by the Arjun Mk1 MBT's hunter-killer fire-control system, this is not the case with the upgraded T-72M1 CIA and T-90S MBTs for the simple reason that neither of these two MBTs have a panoramic commander's sight (they have a 'semi-panoramic' sight). This in turn prevents the MBT commander from looking around the MBT's periphery searching for targets. Instead, the entire turret has to be traversed (moved around) to look for targets and once they're acquired, the turret stays fixated in the direct of the target so that the fixed gunner's sight can complete the target engagement process.''
''Kindly allow me to be more specific. The T-90S brochure from Uralvagonzavod states that the commander's sight offers a "semi-panoramic view of the terrain through sight by the commander". In addition, a quick glance of the T-90S MBT's photo clearly shows the limited independent traverse of the commander's sight (burdened as it is by the anti-aircraft gun. Consequently, the sight cannnot be rotated 360 degrees, unlike a panoramic sight that can be. Secondly, to say that a replacement commander's panoramic sight be retrofitted within the T-90S as a simple 'drop-in installation' without any kind of structural/electrical modifications is, to say the least, oversimplifying the challenges involved in carry out such retrofits. Had you taken a first-hand look inside the turret and spoken to personnel from the Russian Army's Armoured Warfare Directorate (who usually accompany Uralvagonzavod JSC marketing officials in defence expos around the world), you would not have undulged in such oversimplifications. ''
''FYI I've come across several technical documentations on the T-80, T-84 and T-90 MBTs brought out since the 1990s by Oboronexport, Promexport, Rosvoorouzhenie and now Rosoboronexport, and NOT ONE of them has ever used terms like 'hunter-killer fire-control system' or 'hit-survivable' MBT design features when describing the design/performance characteristics of MBTs of Soviet/Russian origin. I wonder why, since such terms are explained in great detail when it comes to similar literature emanating from MBT manufacturers of non-Soviet/Russian origin. ''
''There are a number of reasons why the radical modification of the T-90S (mind you, not the latest T-90M which the Army is also acquiring), especially the turret interior, could well be impossible. The foremost challenge lies in having adequate space for accommodating a panoramic commander's sight (with its built-in thermal imager) along with the battlespace management system, and then doing the impossible: catering to the extra battery power reqmts (by figuring out how exactly to accommodate such batteries and where) andinstalling the related wiring and harnesses. In fact, this was the most difficult issue to solve when it came to fitting the THALES-supplied Catherine-FC thermal imagers as part of the gunner's sight. Therefore, unless the turret volume of the T-90S is increased (like what has been done with the T-90M), the installation of a functional commander's panoramic sight in an existing T-90S is a VERY BAD & UNACHIEVABLE IDEA.''
''India's refusal to acquire the Shtora was primarily due to the system's demonstrated ineffectiveness under Indian operating conditions, however, in its place the IDAS is being acquired as the integrated defensive aids suite.
Lastly, regarding the issue of hit-survivability, I'm of the firm belief that post-World War-II MBT designs emanating from the Soviet Union (and now Russia) have been fundamentally flawed. The sheer numbers of T-72Ms, T-80s and T-90s destroyed in combat since the late 1960s in the Middle East and the Caucasus is testimony to the ineffectiveness of the hit-survivability features of Soviet/Russian MBTs. I'm afraid I can't agree with the MBT writeoff figures (suffered in combat) that have been exhaustively documented globally. I totally agree with you that even more can be done, and I am sure the right lessons will be applied to the FMBT that will in future emerge from Uralvagonzavod JSC''