Its smaller , slower , and has lower range , it has its own radar more suitable to engage ballistic missile that don't do evasive maneuver yes it can be used against aircraft and no its not providing superior interception against aircrafts compared to PAC-2 , every change they made to the missile made it more suitable for engaging ballistic missiles
Smaller?
Due to improvements in design (technology miniaturization); higher number of missiles would fit in single TEL (~16 PAC-3 class versus ~4 PAC-2 class).
Being lightweight is also an important consideration for maneuverability.
Slower?
PAC-3 class interceptors are all MACH 4+
PAC-2 class interceptors are MACH 2+ on average*
*PAC-2 GEM-t is a new design optimized for BMD role and MACH 4+
Lower range?
Depends upon the variant/model, and there are additional considerations.
PAC-3 CRI = 70 KM maximum (Apogee = 30 KM)
PAC-2 GEM-t = 120 KM maximum (Apogee = 25 KM)
PAC-3 MSE = 160 KM maximum (Apogee = 35 KM)
Maximum advertised range is normally correct for engaging air-breathing targets such as aircrafts and drones, but true intercept possibilities vary in accordance to the speed and maneuvering capabilities of the target.
PAC-3 class interceptors, by virtue of their superior speed, maneuverability and onboard sensor systems, provide a larger window of intercept possibilities against increasingly challenging targets (defeating a more challenging target at a better range and/or higher altitude than an older generation interceptor). These matters aren't black and white.
PAC-3 class interceptors also address the issue of formerly distinct intercept specializations for ballistic missiles (PAC-2 GEM-t) and cruise missiles (PAC-2 GEM-c) by virtue of being multi-role capable.
engage ballistic missile that don't do evasive maneuver?
US is the
first country to develop maneuverable warheads (MaRV) such as Pershing II, back in the days when Iraq and Iran were using primitive Scuds. US is a master of rocket sciences [in case you forgot] and have developed and fielded the world's most advanced and reliable ICBM in Trident II D5 in large numbers. Majority of countries have yet to produce something on the level of even Minuteman II, mind you.
We are
NOT talking about 1970s era Soviet ABM technologies, featuring large and heavy interceptors lacking in maneuverability and onboard tracking mechanisms, and depending upon 'command guidance' of a pre-PESA radar system on the surface, to intercept incoming ballistic missiles. These interceptors were armed with nuclear warheads to score kills because their hit probability was almost non-existent.
We are talking about an interceptor class here, lightweight designs equipped with an advanced motor and several side thrustors to achieve extreme levels of maneuverability and sophisticated onboard target-acquisition capabilities in addition to receiving 'command guidance' from a 3rd generation AESA radar system (AN/MPQ-65) which can develop fire solutions for very complex set of targets in one go. These smart robotic kill vehicles are designed to defeat (maneuvering) targets in the nutshell.
No point in investing billions in the development of a SAM system which cannot produce a fire solution for (maneuvering) targets. Don't be naive.
Not surprisingly, PAC-3 class interceptors have defeated Pershing II MaRV, and different types of cruise missiles, in a complex series of trials. There is a lot about American testing regime, that is not public knowledge.
In fact, the kind of maneuvers PAC-3 class interceptors can pull, beyond your limited inmagination about possibilities with rocketry. This isn't to say that the interceptor class in question is virtually infallible (nothing really is) but one must be aware.
An RV does not have the luxury to play GTA with smart robotic kill vehicles mid-flight, it will follow its programming and try to destroy its intended target instead. The best course of evasion is its extreme speed (MACH 10+) which in turn imposes a significant cap on the maneuverability aspect although an MaRV can execute a curved terminal flight path to approach its target, but these qualities are no longer sufficient. This is to say that you are trying to knock out a high value target shielded by a Patriot defense system armed with PAC-3 class interceptors of-course.
