Aviation communications can be thought of short, mundane transmissions
that doesn't make a lot of sense to the lay person. However, these
communications are part of an integrated air traffic control system
that is important to the safety of aircraft pilots and passengers.
The many facets of ATC
There is a lot of misconception about
ATC communications. First, an aircraft is not guided by the 'control
tower' from point-to-point, rather there are a series of ATC controllers
working in all aspects which make up the entire "system."
Honolulu International Airport on the
island of Oahu is the only controlled airport in Hawaii manned
24 hours a day, seven days a week. While certain services like
clearance delivery and ground control can be consolidated during
the late evening/early morning hours, Honolulu Tower and the Honolulu
Control Facility (HCF) is always manned, due to the nature and
scope of operations at the Honolulu International Airport.
Other major commercial airports in Hawaii, Hilo
(ITO), Kona (KOA), Kahului (OGG), Lihue (LIH), and Molokai (MKK)
have "part-time" towers, usually operating from 0600
local time to early to late evening, depending on the airport.
When the local tower is not in operation, all pilots will tune
to the tower frequency to activate airfield lightning, and advise
other aircraft in the area of their intentions.
Airfields with no control tower facilities
are considered non-controlled airports. At these airports, pilots
tune to a Common Traffic Advisory Frequency (CTAF), usually 122.9
in which pilots declare their intentions and activate airfield
lighting, if necessary. Local tower frequency is often used as
a CTAF when the control tower is not in operation.
Air Traffic Control Divisions
ATIS - Automated Terminal Information Service is a coded
message regarding the airport in question. The current weather,
runways/approaches in use, and any pertinent NOTAMs, AIRMETs,
and SIGMETs are continuously broadcast.
An example ATIS broadcast for Honolulu Airport would be;
Honolulu International Airport information Echo, 1253 zulu.
Wind 060 at 10 visibility 10. Few clouds 2,500 scattered, 3,500
scattered, 5,000 broken, 8,000 overcast. Temperature 23, dew
point 17, altimeter 2995. Landing and departing runways 4 and
8, expect ILS or Visual Approach. Notices to Airmen: Taxiway
Bravo closed between Taxiway Romeo-Bravo and Taxiway Golf. Advise
on initial contact you have information Echo.
Clearance Delivery - The responsibility for this controller
is the safe and expedited flow for all IFR departures using standard
IFR routing out of the terminal control area (local tower). In
Hawaii, unlike other places, has standard abbreviated routings,
so there would be limited need to make mention of specific jet
or victor routes in the clearance message:
An example of an enroute clearance message for Northwest 808
to Minneapolis Airport:
HNL Clearance: Northwest 808 heavy is cleared to the Minneapolis
Airport via the Molokai Four Departure, Cluts transition as
filed. After departure, turn right heading 155, climb and maintain
5,000 and expect flight level 350 after departure. Departure
frequency 124.8, squawk 1732.
Ground Control - The primary responsibility of the ground
controller is to coordinate the safe movement of aircraft on the
ramp and taxiways.
An example of a ground control message for United 879 to Narita
HNL Ground: United 879, taxi to Runway 8R via Taxiway Zulu,
Alpha and Romeo-Bravo. Hold-short of Runway 8 Left and monitor
tower on 118.1. (Runway crossing restrictions are common
at HNL as Runway 8 Left is the main arrival runway for heavy
Tower - Local controller coordinates the movement of aircraft
landing and departing the active runways. Local control assumes
responsibility for airspace out to 5 miles from the airport.
Departure Control - Separates departing traffic from arrivals
and other traffic by way of altitude and/or speed restrictions,
and clears aircraft to their initial enroute waypoint.
Approach Control - Separates arriving traffic from departures
and other traffic by way of altitude and/or speed restrictions;
their main job is to space traffic to minimize traffic conflicts,
and to line them up onto the final approach course before handing
the control of the aircraft to the tower.
Center - The Air Route Traffic Control Center handles
the enroute portion of the flight. The center consists of several
sectors defining a specific control area (horizontally), and then
separated vertically into two sectors: the low-altitude sector
(up to 18,000 feet), and the high-altitude sector (between 18,000
and 60,000 feet). This is where commercial jets fly, and air traffic
controllers will use the term "Flight Levels" instead
of the actual altitude: FL190 for 19,000 feet.
NOTE: Honolulu Approach/Departure,
Honolulu Center, and Maui Approach/Departure merged into a single
control facility in 2002. All frequencies remain the same, except
that the radio callsign for these sectors are now addressed as