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Quick Explainer: Don't underestimate the Polish PT-91 [1]

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Date: 2023-04-26  

So quite understandably, big headlines on tank deliveries to Ukraine focus on the Leopard 2 and Challenger 2 tanks. As first line Western Tanks, they are some of the most powerful tanks in the world (particularly the Leopard 2A6), and they deserve the attention of anybody who cares about Ukraine.

But Ukraine received a shipment of another advanced tank that has gotten far less attention from the media: at least 60 Polish PT-91 tanks that many analysts believe are an approximate equal to the Leopard 2A4 tank.

PT-91’s Strengths

The PT-91 is a Polish manufactured heavily upgraded Soviet T-72 tank. The Poles started with a very basic T-72M1 tank. The T-72M1 is the downgraded export variant of the T-72 manufactured by the Soviet Union in the early 80s.

Poland then added armor, improved the fire control system, stabilized the gun better, added armor, added modern military communication systems, and swapped in a more powerful engine for good measure.

The T-72 had two major weaknesses: a poor stabilization of the main gun and weak armor.

Gun stabilization is a process by which the main gun of the tank is “stabilized” against the movements of the tank—that is, if the gun is aimed at a target as the tank moves up and down or side to side, a gun stabilizer will compensate for the movements of the tank to keep the gun aimed at the same target.

The first gun stabilizers were introduced around the time of WW2, but had limited utility. They had to be frequently calibrated to work properly. They were single-axis stabilizers, meaning they only compensated for changes in up and down motions of the tank, not side to side. They only worked at slow speeds of around 10mph (15kmh) or less.

However, for the first time, a tank could continue moving and still fire accurately—earlier tanks could only fire while coming to a complete stop with any sort of accuracy.

For example, the US army went all-in on gun stabilization during WW2, becoming the first nation to equip it on all newly manufactured tanks by 1944, but tankers had mixed opinions of it. Many tank crews were not properly trained on keeping the stabilization calibrated, and many had been trained to bring the tank to a stop before firing, and did not make use of stabilization. Some tank crews went so far as to modify their tanks and remove the stabilization to reduce the weight load on the tank.

Gun stabilization steadily improved during the Cold War, and the introduction of dual-axis stabilization (where both up and down vs side to side motions are compensated for) allowing tanks to fire more accurately. Modern western tanks tend to have advanced dual axis stabilizers that allow gunners to be accurate even when the tank is moving over rough terrain at high speeds.

Today, nobody doubts the value of high quality dual axis gun stabilizers.

One of the weaknesses of the original T-72 design was that it had a single axis stabilizer that had calibration issues. The calibration would go awry easily, requiring frequent adjustments in the field to remain accurate. It could only compensate for up and down movements.

The PT-91 replaces this with a high quality dual-axis stabilizer comparable to those used on modern Western tanks, allowing it to traverse any kind of terrain at high speeds without impacting its firing accuracy.

The PT-91 also replaces the fire control system (FCS). Every tank has a “gunner’s sight’ that contains a range finder, that will tell the gunner how far away the target is, so they can obtain a fire solution. That is, the gunner needs to know how high to elevate the gun to hit his target.

Older FCS are optical, meaning you look through a lens which allows you to estimate the distance of the target, which you can then punch into a computer that spits out the necessary elevation.

Newer laser FCS integrated systems automate much of the process, using a laser range finder to get a precise distance instantly, and the integrated FCS connects to a computer which automatically adjust the firing angle for the gunner for an accurate shot, allowing the gunner to make only minor adjustments.

The Polish T-72M1s originally came equipped with the 1PN96MT-02 Optical range finder. Under optimal conditions, it could obtain an accurate fire solution up to 3000m. In practice, the original T-72M1s struggled to hit anything accurately beyond 1500-2000m. Later mid-80s T-72M1s and T-72B2 tanks came with an integrated laser sighted 1A40-1FCS, that was a major improvement to the 1PN96MT-02, but was rarely accurate beyond similar ranges.

Russia currently suffers from a lack of modern range finders. This is owing to the lack of electronic parts caused by western sanctions, that makes production of anything requiring advanced electronics extremely difficult.

Since around November 2022, Russian Army has resorted to equipping most T-72s and T-80 tanks with 50 year old 1PN96MT-02 Optical range finders. Many, if not most Russian tanks in the field will be using this technology (if not older for the T-55s and T-62s that Russia pulled from storage).

By contrast, the PT-91 replaces the Soviet era optical range finders with a modern integrated FCS system, called the Drawa 1T FCS system—a fully digital, laser range finding, fully integrated fire control system.

The Drawa 1T FCS is accurate up to 6500m, over double that of older FCS ranges. It can fire to the visible horizon (usually around 5000m at ground level) in most cases. It also features defensive measures like a laser warning receiver system—if the PT-91 is targeted by a laser range finder, it can detect that laser and be prompted to rapidly train the main gun at the source of the laser within seconds. It also integrates the smoke cannister deployment system, so if a laser range finder is pointed at the PT-91, it warns the crew and automatically deploys smoke to disrupt the enemy FCS.

The armor protection on the PT-91 is also dramatically upgraded compared to the basic T-72. The PT-91 frontal and frontal turret armor were strengthened using ERAWA-2 reactive armor blocks.

Testing on ERAWA-2 increased frontal armor protection by 60-70%, and could resist penetration by German Panzerfaust 3 ATGMs (antitank guided missile) that can penetrate 900mm of steel armor (the standard measure of tank armor protection). It’s estimated the PT-91 offers frontal armor protection in the equivalence of 1200mm to 1400mm range, a fairly robust frontal armor protection.

In practical terms, the PT-91 can survive direct hits to its frontal armor from almost any ATGM, and likely resist some hits from antitank guns, but the most powerful Russian armor penetrating munitions can likely destroy the PT-91 with a few direct hits.

Furthermore, the Polish engineers worked hard replacing various steel parts with lighter aluminum alloy parts where possible to reduce the weight of the tank despite all the added equipment and armor. The basic T-72M1 tank weighed in at 46 tons, and the PT-91 manages to reduce the weight to 45.2 tons—combined with the increase in engine power from 750hp to 830hp, the PT-91 has an excellent weight to power ratio.

This makes the PT-91 resilient in poor and muddy terrain. As an added benefit, being comparable in weight to most Ukrainian tanks in service since before the War, the PT-91 can be easily transported by Ukraine’s existing tank transportation infrastructure. It can cross most Ukrainian bridges safely. It also shares many of the same parts as Ukrainian T-72s, thus easing the logistical burden. It’s operation is similar to a T-72 as well, allowing T-72 trained tankers to quickly grasp how it operates.

The PT-91 comes with many highly modern features and strengths, but it does have some glaring weaknesses.

Drawbacks

The biggest weakness of the PT-91 is its side and rear armor. These have been left completely without any upgrades from the poorly armored basic T-72, making it vastly underprotected compared to the Tungsten fortified Chobham armor on the Challenger 2 or Leopard 2A6 tanks. It is underprotected on the flanks compared to even the Leopard 2A4 tanks, which I noted were vulnerable from the flanks based on their combat experience in Syria.

Some other weaknesses of the PT-91 include the lack of a more advanced active protection system featured on the most modern Western tanks, like the Leopard 2A6 or the Challenger 2, or the most advanced Russian tanks like the T-90.

For example, the Leopard 2A6 and Challenger 2 use the MUSS (Multifunctional Self-protection System) Active Protection System, that features laser jamming, radar jamming, infrared jamming and other electronic countermeasure systems. It is designed to help the tank against a wide range of threats, from laser range finders , laser guided munitions, and anti-tank missiles of all types.

The small number of T-90 and the most advanced T-80 tanks Russia has feature a Shtora APS system, that offers similar suite of electronic countermeasure systems against laser based FCS systems or ATGMs.

Conclusion

The PT-91 is a very good tank. Whereas older Russian tanks like older variants of the T-72, T-64, T-62 or T-55 tanks will struggle to fire accurately on the move in rough terrain, the PT-91 can maintain maximum mobility without sacrificing its firepower.

The advanced FCS system, comparable in quality to the best Western tanks, gives the PT-91 strong accuracy at long ranges. The PT-91 should have little problem operating alongside Leopard 2s and Challenger 2s, firing at similar ranges and achieving hits at comparable rates.

This allows the PT-91 to engage in out-ranging tactics, where tanks maneuver to keep their distance and fire at ranges where they are themselves accurate, but the enemy cannot return fire effectively.

As the PT-91’s strong frontal armor can protect it against almost any ATGM, Russian infantry should be ineffective when returning fire using even the most advanced infantry based antitank weapons, so long as it strikes only the frontal armor.

However, the weak side and rear armor of the PT-91 makes it highly vulnerable to flank attacks, and the lack of an advanced active protection system makes it even more vulnerable to flank attacks by ATGM armed Russian infantry.

In many respects, the PT-91 is very similar to the Leopard 2A4—extremely powerful when engaging from long ranges, but weak when flanked, particularly in close range combat. Avoiding urban combat, or areas with highly reduced visibility ranges will help maximize the PT-91’s strengths while minimizing its weaknesses.

it should be considered an “ideal” tank for a flat, featureless plain with far visibility. Like Southern Ukraine around Melitopol.

Thanks as always to BarbeCul for excellent editing work

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[1] Url: https://www.dailykos.com/stories/2023/4/26/2166052/-Quick-Explainer-Don-t-underestimate-the-Polish-PT-91

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