Juan Carlos I is a multi-purpose amphibious assault ship-aircraft carrier in the Spanish Navy (Armada Española). Similar in role to many aircraft carriers, the ship has a ski jump for STOVL operations, and is equipped with the AV-8B Harrier II attack aircraft. Her NATO denomination is LHD (Landing Helicopter Dock) and is named after His Majesty King Juan Carlos I (the former King of Spain), following a long tradition in the Spanish Navy to christen ships with the name of the reigning monarch. The new vessel plays an important role in the fleet, as a platform that not only replaces the Newport-class LSTs Hernán Cortés and Pizarro for supporting the mobility of the Marines and the strategic transport of ground forces, but also acts as a platform for carrier-based aviation replacing the now withdrawn aircraft carrier Príncipe de Asturias.
The design for the Buque de Proyección Estratégica (Strategic Projection Vessel), as it was initially known, was approved in September 2003. For the first time in the Spanish Navy, the ship uses diesel-electric propulsion, simultaneously connecting both diesels and the new technology gas turbine powerplant to a pair of azimuthal pods. The vessel has a flight deck of 202 metres (663 ft), with a ski-jump ramp. The ship’s flight deck has eight landing spots for Harrier, F-35 Lightning II or medium-sized helicopters, four spots for heavy helicopters of the CH-47 Chinook or V-22 Osprey size. The ship can carry either 30 helicopters or 10/12 McDonnell Douglas AV-8B Harrier II or Lockheed Martin F-35 Lightning II and 10/12 helicopters, using the light vehicles bay as an additional storage zone.
The complement of the ship is around 900 naval personnel, with equipment and support elements for 1,200 soldiers. Multi-functional garage and hangar space on two levels covers 6,000 m2 (65,000 sq ft), with capacity for 6,000 tonnes load on each level. The hangar can accommodate 12 aircraft, while six aircraft can be parked on the flight deck. The ship has two elevators, with a capacity to carry bigger aircraft in the future. A stern well deck measuring 69.3 by 16.8 m (227 by 55 ft) can accommodate four LCM-1E landing craft which can beach-deliver non-swimming ground vehicles like tanks and four RHIBs, or one Landing Craft Air Cushion plus Assault Amphibious Vehicles. The Spanish Navy will deploy the vessel jointly with the Army. The LHD has a 1,400m² heavy vehicle garage for M-60 or Leopard type tanks. The light vehicles garage is next to the aircraft hangar, in an area of up to 2,046m².
The LHD runs on a combined diesel-eLectric and gas turbine (CODLAG) propulsion system. The electric engines are powered by one gas turbine and two diesel generators. It has an endurance of 9,000NM at 15kt. An electric propulsion system means a reduction in fuel consumption, gas emissions and noise and vibrations; lower maintenance costs; reduction of necessary space and high manoeuvrability. Two POD-type propellers of 11MW each support the system. Similar propellers are in use in aircraft-carrier Príncipe de Asturias and the FFG frigates. Incidentally, Príncipe de Asturias is the first Spanish ship with gas turbine propulsion.