South Korea has had to seek a different supplier for electronics to upgrade its older P-3s to the current P-3C standard. That’s because of a reluctance by the United States to allow the export of a key electronic warfare components for new weapons or upgrades. This is especially true with gear that detects and classifies radar signals or interprets acoustic signals from sonar. The U.S. believed that these items (or parts of them) might be stolen (by China and a number of other usual suspects) and thus degrade the effectiveness of the technology for the United States. For example, P-3Cs operated by the U.S. Navy and some of the most trusted allies use the AN/USQ-78B acoustic processor system. South Korea had to use a non-military one that is largely open source software (Vpx ENhanced Open architecture, Multi-static, or VENOM). Many other P-3 operators who cannot get the AN/USQ-78B use VENOM instead. According to users, the P-3Cs with VENOM seem as effective as those with the AN/USQ-78B.
Three years ago South Korea finally received the eight American P-3C maritime reconnaissance aircraft it had ordered. But when the South Koreans sought to upgrade them to the latest standard they ran into an 18 month delay because the U.S. refused to upgrade the South Korea P-3Cs with the AN/USQ-78B. This caused a problem with South Korea, which did not like being excluded from the “most trusted” club. The South Koreans eventually accepted the U.S. fears (there are a lot of Chinese, Russian and North Korean spies operating in South Korea) and went for alternatives like VENOM. South Korea has 24 P-3s in service, eight of them P-3Cs and ten of the older ones being upgraded to the P-3C standard with a recent order for ten VENOM systems.
South Korea is eager to obtain more, and better, anti-submarine capabilities. North Korea has a growing fleet of small coastal subs that are a real threat to South Korean warships. To prove the point, a North Korean sub sank a South Korean corvette in 2010. The upgraded P-3Cs are part of the solution. Despite the cutting edge electronics, the American built P-3C airframe is getting old. The average age of the U.S. P-3Cs is 28 years. The P-3 entered service in 1962. The current version has a cruise speed of 610 kilometers per hour, endurance of up to 13 hours, and a crew of eleven. The 37.4 meter (116 foot) long, propeller driven aircraft has a wingspan of 30 meters (nearly 100 feet). The P-3C can carry about ten tons of weapons (torpedoes, mines, or missiles like Harpoon and Maverick).
The 63 ton P-3 is based on the 1950s era Lockheed Electra airliner. The last P-3 was built in 1990. A more likely replacement for these elderly search planes are UAVs (Unmanned Aerial Vehicles), like Global Hawk or smaller aircraft like Predator and Reaper. These UAVs typically stay in the air for 24 hours, or more, at a time. What maritime reconnaissance aircraft need, more than anything else, is endurance or, as the professionals like to put it, "persistence." A fully equipped, for maritime patrol, Reaper costs over $20 million each. Such a Reaper can spot ships both night and day and has cameras that can zoom in on any ship or speedboat for a detailed video close up. A P-3 aircraft can only stay in the air for half as long as a Reaper but carries more sensors and weapons. A P-3 also requires a larger ground crew and more maintenance after each flight.
Nevertheless, the demand for Reapers for land operations and the skill and experience of the P-3 crews makes the P-3 the most effective, and available, maritime recon aircraft for just about any kind of reconnaissance. In the event of a war in Korea, the P-3s would be essential for patrolling coastal waters and even land areas. In the meantime, South Korea wants more P-3s to keep track of the growing number of North Korean and Chinese subs in the area.