Chapter 3 Stabilized Glide Slope Indicator System

CHAPTER 3

STABILIZED GLIDE SLOPE INDICATOR SYSTEM

CHAPTER LEARNING OBJECTIVES

Upon completion of this chapter, you should be able to do the following:

Describe the procedures to follow when

Describe the stabilized glide slope indicator

troubleshooting the SGSI system

(SGSI) system and its associated components.

Describe the procedures to follow when

Identify the purpose and principles of operation

performing maintenance on the SGSI system

of the components of the SGSI system.

The stabilized glide slope indicator (SGSI) system

indicates to the pilot of the approaching aircraft whether

consists of a GSI cell mounted on top of an electro-

the aircraft is above (green), below (red), or on (amber)

hydraulic stabilized platform. The GSI cell is an optical

the correct glide slope. By varying the aircraft altitude

viewing system used to indicate to a pilot the aircraft

to keep the amber light bar visible, the pilot maintains

approach angle to a landing platform or ship. The GSI

the correct glide path to the ship's landing pad. The bar

system is an electrohydraulic optical landing aid de-

of light is formed by the combined actions of source

signed for use on ships equipped for helicopter opera-

light, Fresnel lens, and lenticular lens.

tions. By use of the SGSI, a helicopter pilot may visually

To steady the GSI with respect to the pitching and

establish and maintain the proper glide slope for a safe

rolling motions of the ship, the light cell is mounted on

landing. The system is self-contained, relying on the

an electrohydraulic stabilized platform. This equipment

ship for 115 volts ac 400-Hz and 440 volts ac 60-Hz

uses a local gyro for reference and develops electronic

power.

error signals that, in turn, control hydraulic cylinders

The GSI, which is mounted on a stable platform,

that move the platform in the opposite direction to the

provides a single bar of light either green, amber, or red

ship's pitch and roll axis. The system incorporates a

(fig. 3-1). The cell face acts as a window through which

failure detection circuit that turns off the lights in the

the pilot views the light. The color of the light bar

event of stabilization failure.

F'igure 3-1.--Glide slope indicator and light beam.

3-1