INSTRUMENT FLIGHT RULES WORKBOOK
When an air traffic clearance has been obtained under instrument flight rules, the pilot in
command of the aircraft shall NOT deviate from the provisions thereof unless an amended
clearance is obtained. The most important and guiding principle to remember is the last ATC
clearance received has precedence over related portions of any previous ATC clearance. It is
possible to change your flight plan while enroute; however, you must request and receive an
amended clearance prior to deviating from your original clearance. Should a pilot, for any
reason, be incapable of complying with any provision of an amended ATC clearance or
restriction, the pilot is expected to immediately advise ATC. A brief reason, such as "unable due
to fuel," may be included if considered necessary.
Upon arriving in the vicinity of your destination airport, you will be handed off to the Approach
Control serving the terminal airport. Approach Control will issue a clearance for an instrument
approach to your destination, depending on your intentions and the existing traffic in the area.
They may let you use an approach of your own choosing or they may assign you a specific one.
Normally the Approach Control facility will have extensive radar coverage of the terminal area.
They may use this radar for traffic advisory information or they may use it for a radar approach
to the field. Approach Control will handle all Ground Controlled Approaches (GCA) serving the
airport in their area.
The Terminal Radar Approach Control (TRACON)facility controls aircraft approaching and
departing airports, generally out to about 50 miles from the airport. A TRACON "sees" aircraft
using radar. A TRACON has responsibility for controlling specifically defined and limited
sections of "airspace." That involves ensuring that all aircraft entering or departing the airspace
are kept separated at safe distances. When necessary TRACONs reroute aircraft to avoid
dangerous weather patterns. A TRACON's total airspace is subdivided into small sections called
sectors. Each sector is assigned to an individual air traffic controller who works in the TRACON
facility. That controller directs the movement of aircraft in and out of that space on an individual
radar screen and maintains voice contact with pilots. Although the controller's individual
responsibility is only for his or her own sector, all controllers within a TRACON have full radar
information on all the aircraft that are under control of the entire TRACON facility. Because
they are colocated, these controllers are able to communicate with one another instantaneously,
something that contributes significantly to assuring the safety of aircraft.
Approach/Departure Control at Navy airfields normally consists of a Radar Air Traffic Control
Center (RATCC). This same type of facility at an Air Force Base is called Radar/Approach
Control (RAPCON). The following diagram shows air traffic over the United States during a
peak period and provides a link to the FAA for additional information.
8-16 INTRODUCTION TO GROUND, AIRBORNE, LOST COMMUNICATION, AND
EMERGENCY VOICE PROCEDURES