Complex sentence: A tethered landing system was developed to land and take off in up to Force-6 seas, this system consisted of steel rails which were screwed to the flight deck and a cable system to pull the helicopter out of the hangar bay.
Split into simpler sentences: A tethered landing system was developed to land and take off in up to Force-6 seas. This system consisted of steel rails which were screwed to the flight deck and a cable system to pull the helicopter out of the hangar bay.