A helicopter is maintained at a base in Tianjin, north China, on Sept. 9, 2017. China's Fenglei aerobatic team will attend the 4th China International Helicopter Expo, which will be held in Tianjin on Sept. 14-17.(Xinhua/Bai Yu)
A helicopter is maintained at a base in Tianjin, north China, on Sept. 9, 2017. China's Fenglei aerobatic team will attend the 4th China International Helicopter Expo, which will be held in Tianjin on Sept. 14-17.(Xinhua/Bai Yu)