Posted directly from wikipedia:
RS rockets suffered from poor accuracy. Early testing demonstrated that, when fired from 500 m, a mere 1.1% of 186 fired RS-82 hit a single tank and only 3.7% hit a column of tanks. RS-132 accuracy was even worse with no hits scored in 134 firings during one test. Combat accuracy was even worse since the rockets were typically fired from even greater distances. To further complicate the matters, RS-82 required a direct hit to disable light German armor with near-misses causing no damage. RS-132 could defeat medium German armor with a direct hit but caused almost no damage to light or medium armor with a near-miss.
Aware of their ground attack ineffectiveness, Soviets began to experiment two new tactics in order to destroy tanks with airplanes at the battle of Kursk:
Modified Il-2 based on two seat Il-2, armed with Nudelman-Suranov NS-37 instead of 20/23 mm cannons, this version is a very similar concept to the german Ju87G. However, combat effectiveness was quite low, may be because of the IL-2 relative low maneuverability or because of the level of training such weapon needed to attack the thin top of tanks. Moreover, bomb load decreased from 600 kg to 200 kg and even with 48mm of penetration, this gun didn't have enough punch for heavy tanks.
Conventional Il-2 with 220 PTAB anti-tank bomblets in the internal weapon bays or 192 PTAB in four external dispensers. The PTAB-2.5-1.5 has 1.5kg of explosive and could penetrate from 60mm to 70mm, which was enough to destroy any tank of the WWII even the heavier ones because it falls generally straight to the top of tanks. The amount of bombs dropped ensured high probability of hits against enemy tanks even when they were in open formation. The usual maneuver needed to use the PTAB was a dive bombing from 70 to 100m altitude and the footprint of bombs dropped by a single aircraft could cover 2 or 3 tanks spaced 60-75m apart.
First used on July 2 1943, group of eight Il-2 (Captain M.I.Smilskij, 1st Guard Assault Division) performed five runs over about 70 German tanks poised for attack, dropping no less than 1200 PTABs. Fifteen machines were set afire.
Pilots of 266th ShAD, 1st ShAK destroyed or damaged 10 panzers and 10 vehicles during an attack (led by Matikov of the 673rd ShAP) of stationary tanks near Yakovlevo and Pogorelovo. 491 PTABs were used.
The claims by pilots using the bombs were so extensive that they were often doubted by superior officers. Staffs officer and commanders started flying combat missions to monitor the result of air strikes in person, and finally stated : "the enemy losses statistics cited were correct"
"the encrypted message sent by Col Gen Vorozheykin to Stalin on 11 July 1943 says that Soviet ground troops deployed on Hill 255.1 saw six IL-2 attack 15 Tiger tanks, settings six of them on fire. A large panzer force was detected on a hill cast of Kashary on 10 July. Soviet attack aircraft delivered a pin-point air strike, killing 30 enemy tanks and settings 14 on fire, while the rest of the panzer group dispersed and started a chaotic retreat northwards"
The PTAB had indeed made an impressive debut, as a result the Soviet command chose to employ the PTAB on large scale. In other hand, production of the NS-37 variant of the IL2 stopped. Recovering from the initial shock of the PTAB, Germans tanks soon adopted open formations as a reaction, undermining their morale, speed of deployment, command and control efficiency but reducing the effectiveness of IL2 strikes.
