TACAN Characteristics

CHAPTER ONE

INSTRUMENT FLIGHT RULES WORKBOOK

between like frequencies is inadequate. DME, azimuth, or identification from either

ground station may be received. This is not a malfunction of either air or ground

equipment, but a result of interfering signals of two ground facilities.

False or incorrect lock-on. False or incorrect lock-on indications in the aircraft can be

caused by misalignment or excessive wear of the airborne crystal selector assembly.

Selection of a numbered TACAN channel activates a drum and wiper arrangement

which rotates until the wiper contacts the proper crystal on the drum. These crystal

contact points are very small and close together. Wear or misalignment can cause the

wiper to miss the proper crystal and contact the wrong one. This can result in no

station being tuned in or the wrong station. When this occurs, rechanneling of the

receiver may result in the correct channel being selected.

5. Precautionary actions. The following precautionary actions should be taken to guard

against in-flight use or erroneous navigational signals:

ALWAYS check the identification of any NAVAID station and monitor it during

flight.

ALWAYS use all suitable navigational equipment aboard the aircraft and cross-check

heading and bearing information.

NEVER overfly preplanned estimated time of arrivals without careful cross-check of

NAVAIDs and ground checkpoints.

CHECK notices to airmen (NOTAMs) and FLIP before flight for possible

malfunctions or limitations on NAVAIDs to be used.

DISCONTINUE USE of any suspected NAVAID and confirm aircraft position with

radar or other equipment.

1-22 INTRODUCTION TO AIRBORNE NAVIGATION AND COMMUNICATIONS

EQUIPMENT AND PRINCIPLES OF OPERATION