 Coaxial rotor helicopters in flight are highly resistant to side-winds, which makes them suitable for shipboard use, even without a rope-pulley landing system.Marine and offshore helicopter decks on board offshore oil platforms and ships are typically regulated by the rules defined within CAP 437, which defines standards for the design, marking, and lighting of marine/offshore helicopter decks, and is produced by the Civil Aviation Authority.The largest marine helicopter decks will accommodate the Boeing CH-47 Chinook, which requires a D value of , and has a weight of 21.3 tons.