Curtiss-Wright supplies a Horizon Reference System (HRS) that extends ship borne helicopter operations during periods of reduced visibility, high sea states and at night. The Indal HRS provides a steady reference with the horizon while the ship rolls during heavy seas or maneuvering. The HRS provides a true horizon reference by driving the roll bar in the direction opposite to the ship's roll.

The HRS position, when compared to the fixed lights on the ship's hangar or deck, provides the pilot with the degree and periodicity of the ship's roll. Curtiss-Wright incorporates two fixed one foot lighted panels that are mounted at the end of and parallel to the roll bar. The HRS can also be installed as part of a more comprehensive lighting or landing aid package to further enhance the visual cues to the pilot, thus reducing his workload and enhancing safety. The HRS remains the key element in providing the pilot the "true horizon" when preparing to land.

The HRS system is in use with almost every Indal RAST system worldwide, as a stand-alone product, and is modified to incorporate additional pilot cue light boxes when sold with Indal ASIST.