Avionics Navigation Systems, 2nd Edition

13 Landing Systems

13.1 INTRODUCTION

Every successful flight culminates in a landing. Although the majority of landings are conducted solely with visual cues, aircraft must frequently land in weather that requires electronic assistance to the pilot or to the autopilot. This chapter describes the landing maneuver and the electronic systems that provide lateral and vertical guidance to the aircraft relative to the runway chosen for landing. The emphasis is on current systems proposed or in use; historical notes are added when needed for proper perspective.

On a normal flight, an aircraft takes off, climbs to cruising altitude, and flies to the vicinity of its destination. There it begins its descent and intercepts the projected runway center line, then makes a final approach and landing with position errors of a few feet in each axis at touchdown (Section 1.5). The approach and landing are the riskiest phases of flight; approximately one-half of the catastrophic accidents occur during these flight phases of which two-thirds are attributed to errors made by the flight crew (Table 13.1). Considering the “exposure times” in the approach and landing phases, the catastrophic-accident probability for any one operation is on the order of 10⁻⁸ [1],

13.2 LOW-VISIBILITY OPERATIONS

Considerable interference to civil and military operations results due to reduced visibility in terminal areas. For example, Figure 13.1 shows that the visibility at London's Gatwick Airport requires Category II ...