Indian Navy Talwar class frigate F43 INS Trishul, berthed at Mumbai naval base, April 14th, 2012. The 4000gt Talwar class guided missile class frigates are a modified Russian Krivak 111 class and use stealth technology and a special hull design to ensure a reduced radar cross section. This waqs brought to light in Dec 05, when INS Trishul collided with a merchant ship,AMBUJA LAXMI, outside Mumbai port.The radar installations, both in the port and on the merchant ship, failed to pick up the warship and a side on collision ensued.