Pakistan’s Hangor-class submarines, derived from China’s Type 039A/B Yuan design and powered by four CHD620 diesel engines instead of German MTU 396 units, are drawing scrutiny over their acoustic performance as they move toward induction from 2026 under an eight-boat, 2015 deal worth about US$5 billion. The first PNS Hangor was launched in Wuhan on 26 April 2024, followed by subsequent boats Shushuk and Mangro in 2025, after delays linked partly to engine supply and integration issues. Analysts note that the CHD620, viewed as an unproven MTU 396 copy with inconsistent quality control, could be noisier and less reliable, potentially increasing detectability in the northern Arabian Sea, where India deploys P-8I aircraft, MH-60R helicopters and advanced surface sonars. Pakistan and China assert the engines meet required performance standards, but regional navies are expected to monitor the class closely once the first submarine enters service around 2026.