Facing great difficulty in finding North Korean submarines, the South Korean navy is pushing for a big increase in its maritime aviation force. Competition with Japan, although not mentioned, may also be a factor.

The country will have a force of 16 upgraded Lockheed Martin P-3 Orion maritime aircraft by 2018 under an L-3 Communications and Korean Air program to refit eight aircraft that have yet to be modernized. Separately, the South Korean navy is seeking 20 more maritime aircraft, which would considerably augment its anti-submarine capability.

Work began in April on P-3Cs that South Korea has operated since 1995, says Ernie Lock, L-3's program manager. The U.S. company is due to deliver components for the first aircraft within 22 months; the last unit should be upgraded within 60 months. The defense ministry values the program at $400 million, including manuals and training.

The aim is to bring the aircraft to the same specification as eight P-3Bs that Korea Aerospace Industries and L-3 upgraded to the P-3CK standard last decade. The P-3Cs are newer but still lack the advanced equipment retrofitted to the P-3Bs. The P-3Cs will gain all new electronics, including a new magnetic anomaly detector, electro-optical sensor, electronic surveillance gear, radar, self-protection suite and data link. The system is built around a data management system with seven operator stations plus a tactical display in the cockpit. L-3 declines to discuss weapons.

L-3 is building the equipment at its Greenville, Texas, facility. Installation will be done at Korean Air's Gimhae works. Korean Air and L-3 are not working on the structure of the P-3Cs, except as needed to install the new equipment. Electrical and cooling requirements are no greater, and possibly less, than those of the old electronics.

L-3 is offering the same maritime warfare suite for installation in a maritime version of the Bombardier Q400 turboprop airliner, the Q400 MPA, but that is not mentioned as a candidate for the navy's requirement for 20 more maritime aircraft. The South Korean joint chiefs of staff has approved the navy's request for the aircraft, which would serve alongside the Orions, says the Yonhap news agency, quoting a military source.

The Defense Acquisition Program Agency sees prospective aircraft as the Boeing P-8 Poseidon, Lockheed Martin SC-130J Sea Hercules and Airbus Military C295. Listing the C295 and Poseidon as mutual alternatives is unusual, given the vast differences in flight characteristics, system performance and cost between the 86-metric-ton (189,000-lb.) jet and 23-ton turboprop.

While the program seems not yet to have approved funding, the military is proposing it as a response to North Korea's submarine force. A North Korean submarine torpedoed and sank the South Korean corvette Cheonan in March 2010; 46 sailors died. North Korea has about 70 submarines, according to a South Korean board of inquiry report. Although mostly small and all rudimentary, as diesel-electric submarines they are hard to find when submerged.

South Korean warships detected only 28% of North Korean submarines that exercised in the first quarter of 2010, Shin Hak-yong, a Democratic member of the National Assembly's Defense Committee, told the Chosen Ilbo newspaper in 2011. The performance of the P-3CKs in detecting North Korean submarines was not discussed. South Korea is reportedly installing a fixed underwater acoustic-detection chain, similar in principle to the U.S. Navy's Cold War Sosus. Aircraft like P-3s are used as interceptors, prosecuting contacts from the fixed sensors.

The estimated budget for new maritime aircraft is 1 trillion won ($900 million), which will certainly not cover 20 Poseidons nor even SC-130Js, whose design is offered by Lockheed Martin as a maritime development of the C-130J Hercules transport. So if more money is unavailable, the C295 will be a strong candidate.

If the South Korean navy is serious about the Poseidon, then it is probably raising concerns about Japan as well as North Korea. “Japan's defense posture is a consideration in South Korean defense planning that outside observers often greatly underestimate,” says Tim Huxley of the International Institute for Strategic Studies in Singapore. Japan revealed in 2010 that it would increase its submarine force to 24 vessels from 18, including two assigned to training, apparently in response to growing Chinese assertiveness and naval strength.

China's fleet of full-size submarines is by far the largest in Asia, but Huxley doubts that the giant neighbor features significantly in South Korea's threat perceptions.

With Bill Sweetman in Washington.