Airspace, ATC, and Communications


Understand the US airspace and how to communicate with Air Traffic Controllers.


This is the required reading for this lesson. Numbers in [brackets] indicate the starting and ending page in the referenced reading material. Read all the pages and sections referenced.


The notes below highlight the important parts in the referenced material. Reading the notes without having read the actual referenced material is generally not sufficient to pass the written exam!

PHAK - Chapter 14

  • HF Radio used for VFR flights
    • VHF118.0 - 136.975 MHz
    • Limited to line of sight
  • ATC radar
    • Primary
    • Radar Beacon System
  • Transponder
    • 4 codes, 0 to 7 (4,096 total)
    • Ident
    • 7500 - Hijack (must not be used!)
    • 7600 - Radio Failure
    • 7700 - Emergency

Radio alphabet

PHAK - Chapter 15

  • US Categories of Airspace
    • Class A - 18,000 to 60,000 feet. IFR only
    • Class B - Surrounding the largest airports. ATC clearance is required for all aircraft to enter
    • Class C - Surrounding large airports. Two-way communication with ATC is required to enter
    • Class D - Surrounding smaller airports with control tower. Two-way communication with ATC is required to enter
    • Class E - Controlled airspace not classified as Class A, B, C or D.
      • Sectional charts depict areas with Class E bellow 14,500 feet MSL.
      • In areas where not depicted, class E extends from 14,500 to 18,000 feet.
      • Base of Class E is usually 1,200 feet AGL
    • Class G - Uncontrolled airspace. ATC has no authority or responsibility to control air traffic.
  • Special Use Airspace
    • Prohibited areas
    • Restricted areas
    • Warning areas
    • Military operation areas (MOAs)
    • Alert areas
    • Controlled firing areas (CFAs)

AIM - Chapter 4

  • Before transmitting on frequency
    • Listen - make sure the frequency is clear
    • Think - know what you want to say before keying the transmitter
  • Initial contact with ATC should include:
    • Name of facility being called
      • Seattle Tower
    • Your full aircraft identification
      • Cessna 172 Three Six Five Tango Hotel, or
      • Skyhawk Three Six Five Tango Hotel
    • Position
      • South ramp, or
      • 15 miles south of airport at 3,500 feet
    • Request
      • Ready to taxi VFR departure to the south - no Flight Following, or
      • Inbound for full stop
  • VFR traffic en-route can request Flight Following services
    • Provided on a "workload permitting" bases
    • Can assist with weather and traffic avoidance
    • Pilot is still responsible for traffic separation and staying clear of controlled airspace until establishing communication with the appropriate controller

Sim Pilot Notes

These notes highlight the differences between simulator and real-world flying. These differences are most often due to simulator limitations or specific VATSIM rules.

PHAK - Chapter 14

  • VATSIM ATC clients simulate limited transponder functionality:
    • Standby
    • Altitude (Mode C)
    • Ident
  • All aircraft on VATSIM have an installed transponder in the pilot client and must squawk mode C on taxiways and in the air - unless otherwise advised by ATC
  • Common VATSIM squawk codes
    • 1200 - VFR
    • 2000 - IFR with ATC but without radar coverage (Oceanic)
    • 2200 - IFR without ATC

PHAK - Chapter 15

  • With no ATC on-line airports and surrounding Class B, C and D airspace reverts to Class G (uncontrolled)
    • VFR and IFR has the same priority when in uncontrolled airspace
  • Simulation of real-life tower closures is subject to local rules and varies between ARTCCs

AIM - Chapter 4

  • Although VATSIM frequencies often match charted frequencies, the actual radio frequency for each controller is provided by the pilot client
    • Some controllers provide services on more than one frequency. Secondary frequencies do not show up in the client
  • The universal UNICOM frequency on VATSIM is 122.800
    • Voice is the preferred voice of communication on UNICOM
    • Range of voice UNICOM is 30 nautical miles

Tomas Hansson (This email address is being protected from spambots. You need JavaScript enabled to view it.)
Chief Flight Instructor, VATSTAR
DISCLAIMER: all information contained herein is for flight simulation purposes only.
March 2021

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