During the Lunar New Year holiday, an unidentified aircraft flew into the airspace of Lienchiang County’s Dongyin Island (東引), a small militarized island in the Matsu archipelago.
The military later said that the plane was a Chinese Harbin Y-12 light civilian aircraft. Although the incident occurred on Feb. 5, the reason for the intrusion and controversy surrounding the incident continue to reverberate.
On the first day of Russia’s invasion of Ukraine, uncrewed aerial vehicles (UAVs) and cruise missiles attacked administrative centers and military bases. It was a demonstration of the importance of early-warning systems and raises several questions for Taiwan.
How should the military respond to the incursion by the Chinese aircraft into Dongyin’s airspace, and how should it assess the threat posed by civilian Chinese aircraft to the nation’s other outlying islands? Are there similar problems with radar equipment installed on other islands? Answering these questions is far more important than reprimanding military personnel.
Opinions differ over how the plane was able to evade Dongyin’s three-dimensional air search radar, an AN/FPS-117 L-band active electronically scanned array produced by Lockheed Martin. On the day of the incident, atmospheric effects and the “human factor” might have played a part. Nevertheless, the military must thoroughly examine how it can effectively eliminate any vulnerability.
The AN/FPS-117 radar operates in short-range and long-range search modes. In short-range mode, it has a pulsewidth of 100 microseconds and a blind spot (its smallest measurement distance) of 15km. In long-range search mode, it has a pulsewidth of 800 microseconds and a blind spot of 120km.
Several Chinese People’s Liberation Army (PLA) air bases in China’s Fujian Province are within range of Dongyin, including Shuimen, Fuzhou Yixu and Longtian air bases, as well as the military-civilian dual-use Fuzhou Changle International Airport.
PLA jets and UAVs taking off from one of these facilities, flying at a low altitude toward Dongyin, might appear as nothing more than a flickering dot on a radar screen.
The North American Aerospace Defense Command — which stretches across the Arctic from the Bering Sea in Alaska to Canada’s Atlantic coast, and incorporates the North Warning System radar array — demonstrates a potential solution to the problem faced by Dongyin.
The North Warning System radar array is deployed in North America’s polar region. It provides early warning for airborne threats from the Eurasian landmass, passing through the Arctic. In addition to an array of 25 AN/FPS-117 radars, the system also consists of 36 short-range AN/FPS-124 “gap filler” Doppler radars.
The AN/FPS-124 has a blind spot of only 3.2km, while its 112km search range exactly complements the AN/FPS-117’s 120km blind spot. It is therefore effective in identifying low-flying UAVs, cruise missiles and fighter aircraft that could use topographic features or the curvature of the Earth to evade detection and penetrate air defenses.
The combined AN/FPS-124 and AN/FPS-117 radars provide the US and Canadian militaries with high and low altitude atmospheric defense of their airspace.
The problem for Taiwan is not limited to Dongyin. Kinmen County faces the threat of PLA aircraft taking off from nearby Huian, Longxi and Zhangpu air bases, as well as the military-civilian dual-use Quanzhou Jinjiang International Airport and Xiamen Gaoqi International Airport. The facilities are within the 120km blind spot of the AN/FPS-117 radar.
Xiamen Xiangan International Airport, which is being built to replace Xiamen Gaoqi and is to open next year, poses another threat.
Constructed on reclaimed land and situated between Xiamen’s Dadeng and Xiaodeng islands, it is only 12km from the radar installation on Kinmen’s Taiwu Mountain. This means that the problem for Kinmen would be even greater than for Dongyin.
Dongyin and Kinmen are on the front line of the Taiwan Strait’s air defenses. Therefore, the AN/FPS-117 radar problem must urgently be resolved. The short-range AN/FPS-124 “gap filler” radars integrated into the North Warning System possess the advantage of operating autonomously.
The Legislative Yuan in January passed a NT$236.96 billion (US$8.43 billion) special budget to enhance the nation’s defenses.
Taiwan’s outlying islands are the eyes and ears that protect the nation’s other military installations. The government must properly invest in them.
Lu Li-shih is a former instructor at the Republic of China Naval Academy and a former captain of the ROCS Hsin Chiang.
Translated by Edward Jones
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