The Horizon Reference Set provides a stable, external visual, Horizon Reference to enhance the pilot's capability to operate LAMPS MK III helicopters in adverse weather conditions on the small flight decks of LAMPS MK III ships experiencing extreme roll motions.

A requirement exists to provide the capability to operate helicopters in all weather conditions, up to and including upper Sea State 5, from the decks of Air Capable ships operating within the LAMPS mission profile.

LAMPS MK III helicopters will be recovered aboard LAMPS ships first by approaching from astern, flying to arrive in a hover position at a safe position above the flight deck. Assisted recoveries will employ the Recovery Assist, Securing and Traversing (RAST) System in which a messenger cable from the helicopter is lowered to the ship's flight deck where it is attached to a fitting on the free end of a recovery assist cable. When the helicopter crew retrieves the messenger cable the recovery assist cable and its end fitting is drawn into and locked within the main probe of the helicopter. Below deck RAST machinery, under the control of the RAST control officer, reels in the slack recovery assist cable until taut whereupon the control system automatically maintains a constant hover tension on the cable to provide a steadying effect on relative helicopter to ship motion. The Horizon Reference Set to be installed in the LAMPS MK III ships with the Stabilization Data Indicator mounted on, or near, the top of the hangar at the centerline and in the same plane of vision as seen by the helicopter pilot conducting his normal obstruction clearance scan during the landing approach and recovery operation. The Electronic Components Assembly is to be mounted in a protected area in the hangar or the flight control station. Where required, the Control-Indicator will be mounted in the flight control station to provide remote control of the set. Vertical reference signals will be obtained from the ship's central reference system.