GPS Stand Alone Approaches

T-34C INSTRUMENTS

CHAPTER SEVEN

The GPS always displays distance to the active waypoint,

which is different than the DME distance from the NAVAID on the

instrument approach procedure. Pilots must exercise extreme

caution to preclude either a dangerously early or late descent on

final.

GPS STAND-ALONE APPROACHES

The GPS stand-alone approach is commonly known as the terminal arrival area (TAA) or "Basic

T" approach (Figure 7-16). The objective of the TAA is to provide a seamless transition from the

enroute structure to the terminal environment for arriving aircraft equipped with GPS. GPS TAA

approaches make use of both Fly-Over and Fly-By waypoints. Fly-By waypoints are used when

an aircraft should begin a turn to the next course prior to reaching the waypoint separating the two

route segments. This is known as turn anticipation and is compensated for in the airspace and

terrain clearance. Approach waypoints, except for the missed approach waypoint (MAWP) are

normally Fly-By waypoints. Fly-Over waypoints are used when the aircraft must fly over the

waypoint prior to executing a turn. Approach charts depict Fly-Over waypoints with a circle

around the waypoint.

The "T" design incorporates from one to three IAF's; an intermediate fix (IF) that serves as a dual

purpose IF (IAF); a FAF, and a MAP usually located at the runway threshold. The three IAF's are

normally aligned in a straight line perpendicular to the intermediate course, which is an extension

of the final course leading to the runway, forming a "T." The standard TAA consists of three

areas defined by the extension of the IAF legs and the intermediate segment course. These areas

are called the straight-in, left-base, and right-base areas. TAA area lateral boundaries are

identified by magnetic courses TO the IF (IAF).

The Terminal Arrival Approach procedure is a portion of the new and rapidly evolving GPS

arrival procedure program. For the most current and in-depth information on the TAA approach,

consult the AIM section 5-4-5.

INSTRUMENT NAVIGATION 7-29