Hmmmm. Well, if you just need a new airframe, with proven engines and props, to fit kit you've already designed inside, looks like there's a new alternative to second hand P-3s........
Ares:
China's Maritime Patroller
China's AVIC-Shanxii Y-8F-600, a modernized version of a reverse-engineered Antonov An-12, is spawning a growing family of special-use variants without having apparently entered service as a transport. Two AEW versions (one with a rotodome and another with an AESA similar to Saab's EriEye) have been sighted. Now, the latest version is a weapons carrier -- an antisubmarine warfare aircraft.
The extensively modified airframe has a weapons bay, surface-search radar, EO/IR sensor turret (ahead of the weapons bay) and a magnetic anomaly detector boom at the end of a redesigned, ramp-less rear fuselage. It will presumably have an acoustics system and sonobuoy tubes.
It's the first ASW aircraft of this scale and capability for the Chinese armed forces, and the only such active program outside the USA (following the demise of the Nimrod MRA4 in last year's UK defense review). It's not hard to guess its intended targets.
Aircraft of this type are not usually found searching large tracts of ocean for submarines. Norman Friedman's book Network-Centric Warfare describes the P-3 as an interceptor, launched to prosecute targets detected by SOSUS (sound surveillance system). An isolated report in 2008 suggested that China was deploying its equivalent of SOSUS.
Other missions for oceanic-range ASW aircraft include providing cover for ballistic missile submarines, making it possible to detect and track hostile subs that might be trailing the SSBN as it leaves on a patrol.
The appearance of the new Y-8 platform indicates that China is expanding its ASW ambitions. Building an aircraft is only a small part of the ASW battle. It also requires sensor and processing technology -- systems like the P-8A Poseidon draw on decades of experience with acoustic systems, using passive and active sonobuoys to detect and pin down the target -- and human expertise. So what is important is that the PLA-N is setting off down that long and difficult road.
By the way, the engines on the Y-8F600 are Pratt & Whitney PW150s and the propellers are from GE's Dowty unit. The program was launched in 2001-03 as a commercial venture.