In order to ensure a fast and safe landing when helicopter pilots approach the ship, a stable sliding and rolling indicator (GSI & HRB) system becomes a basic visual aids.
When the helicopter is homing, it should gradually reduce altitude and decelerate. At about 1.5 nautical miles (or 3 nautical miles) from the stern, the helicopter glides down at a pitch of 4 degrees relative to the ground. At night or during the day when visibility is low, the helicopter hovers at 3-5 meters above the deck guided by the GSI slide indicator. The helicopter pilot then watches the motion of the ship's deck through the HRB horizontal reference light. After knowing this information, choose the opportune moment to land.
GSI –GLIDE SLOPE INDICATOR
The GSI contains a light projector, which is mounted on a 3 degree of freedom platform in thewatertight enclosure. The optical guidance consists of a motion stabilized light beam composed by three sectors eachone indicating an approaching cone: over, centered, below the glide path.
The light beam can be oriented in azimuth (around the vertical axis) and elevationangles. In addition it is dynamically stabilized with respect to the pitch and roll ship motions.
HORIZON REFERENCE BAR
The HRB consists the servo system,the luminousbar is aluminium made,the Line Reference Lightsand the de-icing system.The HRB provides a luminous line stabilized with respect to the horizon movement by means of aservo driver system.The Line Reference Lights on the contrary are fixed to the ship hangar face and it can be eventually increasedto extend the visual perception of the roll movements.