ClassNK issues world’s first approval in principle (AiP) for LNG carrier installed with Wind-Assisted Propulsion System August 3, 2024 International Shipping, Maritime, Shipping Line, Technology, Trending News TOKYO : ClassNK has issued an Approval in Principle (AiP) for the membrane-type LNG carrier installed with the ‘Wind Challenger’, a hard sail wind propulsion system. The ship is jointly developed by Mitsui O.S.K.