The People’s Republic of China has made grandiose claims for the performance of its JY-27A ground-based air surveillance radar. They should be treated with caution.
An article published in the Global Times, an offshoot of the People’s Daily, itself a mouthpiece for the People’s Republic of China’s ruling Communist Party, claimed on 28 May that the country’s new CETC JY-27A Very High Frequency (VHF: 30 megahertz/MHz to 300MHz) can detect aircraft with a low Radar Cross Section (RCS). The article said that, not only can the radar detect such aircraft, but can “guide missiles to destroy them.”
Low frequency radars detecting low RCS aircraft is not a new claim. This principle has been known for decades and has already been exploited in radars like Russia’s NNIIRT 1L119 Nebo-SVU VHF system. The long wavelength signals transmitted by VHF radars have meant that while low-RCS aircraft maybe detectable, they may not be detectable with the sharp precision required to guide an Air-to-Air Missile (AAM) or Surface-to-Air Missile (SAM) to its target. Put simply, this is why many fighter radars, ground- and ship-based fire control radars and missile radar seekers transmit in frequencies from X-band (8.5 gigahertz/GHz to 10.68GHz) and above. What these radars lose in detection range, compared to lower frequency radars, they make up for in precision. The Global Times article claimed that Chinese radar engineers have solved this precision deficit by networking together several radars positioned a known distance from one another, looking at the same patch of sky in different directions to determine an aircraft’s location. Once detected it could be possible to guide “long-range anti-aircraft missiles” to perform precision strikes on these targets.
Distributed, networked radars to counter stealth is an established concept. The electronic warfare and radar expert Dr. Carlo Kopp discussed this approach in his seminal 2012 article in Defence Today entitled ‘Advancing Counter-Stealth Radar Technology’. He asserted that “Defeating stealth targets using networking and data fusion presupposes that some radars can see the target some of the time, also that the target’s stealth is considerably poorer in some directions compared to others, and finally that the target is visible to radars from varying aspects.” Basically, a low RCS aircraft may have a low radar signature when viewed from head on, of from a particular angle but not an equally low signature in all directions. By scattering and networking several antennas across a wide area, one of the antennas may get a lucky glimpse of part of the aircraft which is not so stealthy and thus detect it. Dr. Kopp adds that for this to be effective, the non-stealthy part of the aircraft needs to be visible to that particular radar for some time. An aircraft flying into hostile airspace is unlikely to hang around and may be travelling at very high speeds, thus only exposing itself to the radar for a very short time. To further complicate matters, aircraft such as the US Air Force’s Northrop Grumman B-2A Spirit strategic bomber and Lockheed Martin F/A-22A Raptor air superiority fighter use ‘all-aspect’ RCS reduction techniques. This means that they are stealthy regardless of the angle from which they are viewed by radar. Future US aircraft, such as the forthcoming Northrop Grumman B-21 Raider strategic bomber are likely to have even better RCS reduction design configurations.
Dr. Kopp concedes that “a networked data fusion system (fusing data from several distributed radars) is thus not a panacea, but is potentially quite effective against stealth designs that do not have genuine ‘all aspect’ stealth capability.” There is an additional problem. Airframe limitations mean that low-RCS aircraft cannot be designed to defeat all radar transmission wavelengths. Instead, airframes are optimised to defeat the radar systems most likely to be used for the precision detection of such a target and for fire control. This typically includes radars transmitting in S-band (2.3GHz to 2.5GHz/2.7GHz to 3.7GHz) and above. To summarise, a network of VHF radars maybe capable of detecting an aircraft with a low RCS but lacking all-aspect stealth, yet weapons still have to be guided with precision to the target. This is where a fighter aircraft’s X-band radar would come into play, or the guidance radars and radar seekers used by AAMs or SAMs transmitting in X-band and above. These are precisely the frequencies that low-RCS aircraft are designed to defeat. Networked VHF radars may give you a good fix on where the aircraft is in the sky, but the missile’s end game still depends on higher frequency radars which stealth aircraft are designed to outfox.
Arguably this could be overcome by a salvo launch of SAMs and AAMs into the area of sky where the aircraft is thought to be. This might not be done with too much precision, but a load of missiles could be launched ballistically with the hope of scoring a lucky hit. It could prove an expensive tactic as it would potentially waste missiles at an early stage of a conflict, the moment when low-RCS aircraft are most likely to be used.
Moreover, these VHF radars, and fire control radars operating in higher wavebands would almost certainly be subjected to heavy electronic attack at the outset of a conflict. Aircraft such as the F/A-22A, B-2A, B-21 or Lockheed Martin’s F-35A/B/C Lightning-II fighters would be accompanied by jamming platforms like the US Navy’s E/A-18G Growler aircraft as they fly into contested airspace. The Block-2 Low Band Jammer (LBJ) segment of the latter aircraft’s Next Generation Jammer, which replaces its current Harris AN/ALQ-99 tactical jamming system, is thought to cover a waveband of 100 megahertz to two gigahertz. The US Navy is currently selecting a vendor for the Block-2 LBJ with a team comprising Northrop Grumman and Harris, and L3 vying for selection. While VHF radars like the JY-27A maybe trying to detect low RCS aircraft, they will be a prime target for both escort and stand-off jamming for aircraft like the E/A-18G. They will also be high priority targets for kinetic weapons. Given the frequencies they use, VHF radars tend to be big. In the case of the JY-27A PRC officials have hinted that several radars are required to detect low RCS aircraft. Such targets could show up well on aerial reconnaissance imagery. They also need to transmit, and once transmitting, will reveal their position to ELINT (Electronic Intelligence) gathering assets such as the US Air Force’s Boeing RC-135U Combat Sent aircraft. Once their position is betrayed, electronic and kinetic attack can be brought to bear.
The PRC maybe feeling emboldened by the development of the JY-27A and its touted capabilities. The death of low RCS airframe design has been predicted umpteen times since the B-2A and Lockheed Martin F-117A Nighthawk ground attack aircraft debuted in service in 1997 and 1983 respectively. The possible shortcomings of such radars are no excuse to be complacent, and such systems should be high priority electronic and kinetic targets at the start of any conflict. The JY-27A’s attributes may be accompanied with a healthy serving of hyperbole, but that is no excuse for complacency.