April 23, 2018:
The new Chinese Z-19 helicopter gunships are apparently being equipped with a mast mounted radar, as in the American AH-64D, as standard equipment. Actually, the Z-19 is a heavily armed scout helicopter, a 4.5 ton, two seater armed with a 23mm autocannon and up to half a ton of munitions (missiles, usually). The AH-64D weighs twice as much. Cruising speed is 245 kilometers an hour for the A-19and range is 700 kilometers. Z-19 is basically an upgraded Z-9W (armed transport helicopter, a license-built version of the French AS365). The Z-19 proved a more successful and reliable design than the Z-10 gunship which was based on a lot of Russian helicopter technology and appeared in 2003. It was a seven ton gunship that never seemed able to work right. By 2012 it was clear that the slightly smaller, but much more capable Z-19 would replace it.
The Z-19 entered service in 2012 and by 2014 there were 80 of them being used in a variety of climates and types of terrain to see what modifications were needed. The version with the mast mounted radar appeared in late 2013. More of these were built and this version was officially revealed (for export sale) in 2017. There are now about 120 Z-19s and all the new ones appear to have the mast. Older models are being upgraded with the mast mounted radar system.
The AH-64D features the Longbow radar-based fire control system. This enables the crew to spot armored vehicles or stationary targets, in any weather, up to ten kilometers away. Once a target is spotted it can be destroyed with Hellfire laser guided missiles (max range, eight kilometers). Introduced in the late 1990s, Longbow was a late Cold War development, the perfect weapon for destroying enemy tanks at long range.
The AH-64D got some use during the 2003 Iraq invasion, but after that, the Longbow radar proved to be more of a liability. The radar system has not been much use for firing Hellfires at targets in residential areas, where you usually want to get a visual, not radar, a picture of the target. Moreover, the radar system weighs 227 kg (500 pounds, about three percent of the weight of a fully loaded AH-64D). Such a system would be seven percent of the Z-19s weight meaning if the Z-19 used a similar radar it would probably have to drop the 23mm cannon and carry no more than six Hellfire type missiles. So the Z-19 radar is apparently lighter and less capable, but capable enough to spot distant vehicles that can be taken out with the Chinese version of Hellfire.
In Afghanistan, where the AH-64s fly at high altitudes, where the thin air means less lift, the Longbow system was often removed. Losing three percent of your weight made a difference in performance. In Iraq, the high heat, and abundant dust makes the Longbow electronics more prone to break down. So after 2003 AH-64s were often seen without the radar mast.
Meanwhile, Longbow tech did not stand still and in 2005 the improved Arrowhead system appeared. The Arrowhead system proved itself during combat in Afghanistan and Iraq. The U.S. Army began installing Arrowhead in its AH-64s in 2005 after two years of development and testing. Arrowhead uses the latest night vision devices (light enhancement and thermal, or heat, based) and fire control electronics to enable AH-64 crews to operate more safely, and effectively, at lower altitudes and in any weather. This is particularly critical in urban areas. Work on Arrowhead got a boost after the Iraq invasion in 2003, which was followed by a growing amount of urban fighting. This created the need for an AH-64 that could hover at 800 meters (2,500 feet) altitude (safe from most small arms fire) and use its high resolution sensors to see who was doing what for out to eight kilometers (five miles) away. Arrowhead could do that, and now most American AH-64s have Arrowhead and many transport helicopters as well (to make night flying safer). Whatever an AH-64 can see (or detect via Arrowhead) it can hit with a Hellfire missile. The Z-19 radar tech seems to be moving towards an Arrowhead type design but the Chinese are deliberate about these upgrades and take the time to get right before producing a lot of them.