In 1631, he was appointed a commissioner of the King for making "a general survey of the whole navy at Chatham." For this and other works Pett was promoted by Charles to be a principal officer of the Navy, receiving £200 per annum. His patent was sealed on 16 January 1631. In the same year the King, Charles I of England, visited Woolwich to view the launch of the "Vanguard", which Pett had built. The king honoured Phineas by participating in a banquet at his lodgings. Pett was later the First Commissioner at Chatham and held this same post from 1631 until his death in 1647.