Chapter Eight Global Positioning System

CHAPTER EIGHT

GLOBAL POSITIONING SYSTEM

800. INTRODUCTION

Specific GPS equipment capabilities vary widely from aircraft to aircraft; therefore, all pilots

must be thoroughly familiar with the GPS equipment installed in their aircraft, its authorized use,

and its limitations. Refer to the NATOPS manual for additional information on the GPS system

and its specific capabilities.

The T6A has a panel-mounted KLN 900 GPS system consisting of a sensor/navigation computer,

a database card, and an antenna. This system is used to conduct non-precision instrument

approaches based on satellite-transmitted positioning information.

While the GPS system does provide the capability to conduct GPS SID procedures and GPS

STAR procedures, they will not be studied in this phase of training. Student training will only be

conducted utilizing radar vectors to the final portion of a stand-alone or overlay GPS approach.

NOTE

Students should be familiar with the Turn-On and Self-Test Page

functions of the GPS at initial power up in order to verify correct

initialization and position data.

801. GENERAL REQUIREMENTS

There is important information to know when using the GPS for IFR navigation and instrument

approaches. As a part of the system integrity, the GPS receiver monitors and predicts satellite

orbital position and geometry. The process of monitoring and predicting satellite position is

known as RAIM. RAIM verifies the predicted orbital position of the satellite or satellites used

for a particular approach matches the actual orbital position(s). If the positions do not match, the

accuracy of the GPS position data may not meet non-precision approach requirements. In this

case, the GPS receiver will generate a message notifying the pilot that GPS data should not be

used for the approach. RAIM outages may occur due to an insufficient number of satellites,

unsuitable satellite position, terrain masking, aircraft dynamics (changes in pitch or bank angle),

or improper barometric altitude data input.

Prior to any IFR GPS operation, the pilot must check for planned GPS outages at the departure

and destination airports by either calling an FSS preflight briefer or checking online NOTAM

information using "KGPS" as the airfield identifier. The military provides airfield-specific GPS

RAIM (M-series) NOTAMs for non-precision approach procedures at military airfields. During

longer flights, predictive RAIM at the destination should be checked manually by using the

Status 5 (STA5) page of the KLN 900. This may provide early indications an unscheduled

satellite outage has occurred since takeoff. Predictive RAIM cannot account for terrain masking

problems associated with flights in the vicinity of mountainous terrain, for unplanned satellite

outages, or for internal equipment malfunctions. Since the relative positions of the satellites are

GLOBAL POSITIONING SYSTEM

8-1