Page 132 - Planning and Design of Airports

Air Traf fic Management 101

course and altitude changes, as well as actively notifying pilots of
nearby aircraft. Pilots flying under VFR conditions are required to fly
under flight following in the busiest of airspace.
Aircraft flying in IMC or at altitudes over 18,000 ft above sea level
(AMSL) fly under instrument flight rules (IFR). Aircraft flying under
IFR navigate using ground-based and satellite-based navigation aides
and are fully controlled along planned routes by air traffic control per-
sonnel. Often times, flights operating under IFR will fly defined depar-
ture and approach procedures to and from airports which depend on
flying precise courses and altitudes to and from waypoints as defined
by ground- and satellite-based navigation systems. These published
instrument procedures provide for aircraft to safely and efficiently
depart from and arrive to airport runways while avoiding collisions
with terrain and other aircraft during poor visibility conditions. In many
ways, IFR rules, routes, and departure and approach procedures have
significant influence on the planning, design, and operation of airports.

Airspace Classifications and Airways
In the United States, domestic airspace is defined into six classes, plus
areas with special operating restrictions, and a designated series
routes between airports and waypoints. Aircraft are subject to differ-
ent levels of air traffic control depending on which airspace classifica-
tion they are currently operating in, the type of defined route they are
on, and whether they are flying under VFR or IFR flight rules.
Classes of airspace in the United States are identified alphabeti-
cally, as Class A, B, C, D, E, or G airspace, as illustrated in Fig. 3-2.
Class A airspace, also known as positive control airspace, is the
airspace between 18,000 ft above mean sea level (AMSL) (known as FL
180) and 60,000 ft (FL 600) AMSL over the 48 contiguous United States
and Alaska, extending out to 12 nm off the coast of the United States.

FL 600 CLASS A
18,000 MSL
14,500 MSL

CLASS E
CLASS B
CLASS C
CLASS D
Nontowered
Airport 700 AGL 1200 AGL
CLASS G CLASS G CLASS G
AGL-above ground level FL-flight level MSL-mean sea level
Effective September 16, 1993
FIGURE 3-2 Illustration of airspace classes.