In May 2020, a U.S. Navy P-8A maritime surveillance aircraft was spotted flying near the new Chinese naval base on Hainan Island. This large island, 30 kilometers off the southern coast of China, is where China has built several new naval bases.
Foreign reconnaissance aircraft can operate close (22 kilometers off the coast), but most stay out a little further because China is hostile to foreign intelligence aircraft or ships anywhere near their coast.
What made this P-8A mission special was the aircraft was carrying, under its fuselage, a long box-like sensor known as the APS-154 AAS (Advanced Airborne Sensor). This is a solid-state, wide-aperture, AESA (active electronically scanned array) radar with numerous capabilities, most of them classified. The APS-154 also contains a SAR (Synthetic Aperture Radar) and ISAR (Inverse Synthetic Aperture Radar) that captures photo-like images. All these sensors operate simultaneously against whatever is present in a nearly 360-degree area around the aircraft. This further aids in real-time identification of what is below. All this data is shared in real-time with encrypted digital communications. The 154 is also believed to collect electronic emissions from whatever is down there and link those emissions with specific vessels or land-based facilities and moving objects, especially ships. The APS-154 not only detects and tracks ships below, but uses a digital library to identify them in real-time. This provides target information for long-range weapons launched from distant ships or aircraft.
All this data can then be used by a missile fired from another aircraft or ship at a moving target. The AN-154 can do this at a distant target, often one outside the range of most anti-aircraft weapons. These sensors work at night and in bad (overcast) weather for tracking land-based moving targets as well as ships. The AESA can also carry out jamming or radar deception tasks. This justifies all the secrecy because if potential enemies knew the details, they would be better able to degrade the effectiveness of the AN-154 system.
The APS-154 replaces or supplements the older APS-149 LSRS (Littoral Surveillance Radar System) and apparently has a lot of added or improved features. The APS-149 was also attached underneath the fuselage of the P-8 or older P-3C via three attachment points. The APS-154 was seen being flight tested on a P-8 in 2015 and is believed to have entered service by 2018.
The APS-154 is used mainly on P-8s that have additional electronics installed to handle all the APS-154 capabilities. The navy does not reveal which of its hundred or so P-8s in service can handle the APS-154 or when P-8s fly missions equipped with the APS-154. This way the nation about to be scanned cannot take special measures to conceal what is down there and which of its electronic devices are normally operating. APS-154 equipped P-8s are known to have made two recent flights near the Hainan Yulin naval base. This is the major base for the Chinese Southern Fleet and its Type 94 SSBNs (nuclear powered ballistic missile carrying submarines) as well as many naval aircraft. The APS-154 equipped P-8s are also believed to have visited Chinese naval facilities throughout the South China Sea as well as major Chinese naval training exercises on the high seas. The APS-154 can spot ships and detect electronic signals more than a hundred kilometers distant, but the closer the APS-154 is to something the more detail is obtained.
There are currently 124 P-8s in service or on order and the U.S. Navy expects to eventually have 122 of them. Using the APS-154, the P-8 can fly higher and faster than the older P-3C. While the P-3C often carried the APS-149, that aircraft was also equipped with more and more electronic sensors and had its maritime surveillance capabilities modified so the aircraft was also very useful patrolling over land areas. The P-8 has built on that experience.
Until recently many NATO countries felt little need to upgrade their ASW (anti-submarine warfare) aircraft, which were usually P-3s. But since 2014 Russia has revived the Cold War and a growing number of NATO nations are responding by purchasing P-8As rather than refurbishing their P-3Cs so those could serve another ten or twenty years. With Russia a growing threat, the more expensive option (P-8As) became more attractive, in part because the P-8A can also handle ELINT (intelligence collection) work thus replacing smaller dedicated ELINT aircraft.
The P-8 Poseidon is based on the widely used Boeing 737 airliner. Although the Boeing 737 based P-8A is a two-engine jet, compared to the four-engine turboprop P-3, it is a far more capable aircraft. The P-8A has 23 percent more floor space than the P-3, is larger (38 meter/118 foot wingspan versus 32.25 meter/100 foot), and heavier (83 tons versus 61). Most other characteristics are the same. Both can stay in the air for about 10 hours per sortie. Speed is different. Cruise speed for the 737 is 910 kilometers an hour, versus 590 for the P-3. This makes it possible for the P-8A to get to a patrol area faster, which is a major advantage when chasing down subs first spotted by distant sonar arrays or satellites. However, the P-3 can carry more weapons (9 tons versus 5.6). This is less of a factor as the weapons, torpedoes, missiles, mines, and up to 129 sonobuoys) are lighter and more effective today, and that trend continues. Both carry the same size crew of 10-11 pilots and equipment operators. Both aircraft carry search radar and various other sensors. The P-8A will be the first 737 designed with a bomb bay and four wing racks for weapons.
The 737 has, like the P-3, been equipped with hardpoints on the wings for torpedoes or missiles. The B-737 is a more modern design and has been used successfully since the 1960s by commercial aviation. Navy aviators are confident that it will be as reliable as the P-3 and so far P-8s have over 255,000 flight hours and demonstrated that the new maritime reconnaissance aircraft is reliable.
The P-3 was based on the Electra civilian airliner that first flew in 1954, although only 170 were built, plus 600 P-3s. Some Electras are still in service. The Boeing 737 first flew in 1965, and over 5,000 have been built.
The P-8 entered service in 2013. The U.S. is buying 122 P-8s and already has most of its planned P-8s in service. The P-8A got good reviews from its American crews as well as those of export customers. That is important because export customers for the P-3 are still operating about 200 of those aircraft and the P-8A is looking more attractive as a replacement. Some nations are using business jets equipped for maritime reconnaissance but without the P-8’s ASW capabilities.