Chinese Sea Wing (Haiyi) ocean glider UUV. The Chinese Sea Wing glider is very similar to the US Navy's Littoral Battlespace Sensing-Glider

by H I Sutton

China has deployed a fleet of underwater drones in the Indian Ocean. According to Chinese government sources, the drones were launched in mid-December 2019 and recovered in February after making more than 3,400 observations. These Sea Wing gliders are a type of Uncrewed Underwater Vehicle (UUV) which can operate for months on end.

The gliders are similar to ones deployed by the U.S. Navy. When China seized a U.S. Navy ocean glider in 2016 the stated reason was to ensure “safe navigation of passing ships.” Taken at face value, it may be surprising that China is now deploying these types of UUV en masse in the Indian Ocean. China has also deployed the Sea Wing from an ice breaker in the Arctic.

Reports from December 2019 suggested that 14 would be employed in the Indian Ocean mission. But newer reports suggest that only 12 were used. Possibly there were technical issues with the other two. They were launched by the specialist survey ship Xiangyanghong 06 which has since returned to Rizhou in China. The mission was the winter survey for the Joint Ocean and Ecology Research Project run by the Ministry of Natural Resources.

The Sea Wing (Haiyi) bear a striking resemblance to the Littoral Battlespace Sensing-Glider (LBS-G) used by the U.S. Navy. On December 15, 2016, China obtained a U.S. Navy LBS-G in international waters in the South China Sea. The glider was in the process of being recovered by USNS Bowditch when a small boat from a Chinese vessel which had been shadowing the Navy vessel plucked it from the water. After a diplomatic spat the glider was returned to a U.S. Navy warship.

The Sea Wing isn’t a case of reverse engineering however. It was reported in Chinese sources in September 2016, months before the U.S. Navy incident. But the American type is a clear influence and they are generally equivalent.

These gliders are unpowered. Instead they employ variable-buoyancy propulsion which makes them sink and then rise to the surface again. This is done by inflating and deflating a balloon-like device filled with pressurized oil. At the same time they have large wings so they can glide forward as they go. This allows them to run for extremely long periods of time, travelling vast distances. They are not fast or agile however, so a generally employed for long range missions where they can be left alone until they need to be picked up.

The Chinese gliders were reportedly gathering oceanography data. Sensors measured seawater temperature, salinity, turbidity, chlorophyll and oxygen levels. This information was transmitted back to the mother ship via the aerial in the tail. Although the aerial points directly backwards, it swings up above the surface as the glider noses down for another dive.

This is the sort of information which sounds innocuous but is commonly gathered for naval intelligence purposes. In particular it is relevant to submarine warfare. For example salinity levels can affect the distance that a submarine can be heard from. And it may be possible to detect submarines if they disturb chlorophyll.

For its part, China continues to report finding foreign UUVs off its coast. If Chinese fishing vessel catches a glider they are to hand it over to the government. Presumably the same fate did not befall any of the Chinese gliders.