SUBCHAPTER J - NAVIGATIONAL FACILITIES
PART 170 - ESTABLISHMENT AND
DISCONTINUANCE CRITERIA FOR
AIR TRAFFIC CONTROL SERVICES
AND NAVIGATIONAL FACILITIES
Subpart A - General
Sec.
170.1
170.3

Scope.
Definitions.

Subpart B - Airport Traffic Control Towers
170.11 Scope.
170.13 Airport Traffic Control Tower (ATCT)
establishment criteria.
170.15 ATCT discontinuance criteria.

Subpart C [Reserved]
AUTHORITY: 49 U.S.C. 106(g), 40103-40107,
40113, 44502, 44701-44702, 44708-44709, 44719,
44721-44722, 46308.
SOURCE: 56 FR 341, Jan. 3, 1991, unless otherwise noted.

Subpart A - General
Section 170.1 Scope.
This subpart sets forth establishment
and discontinuance criteria for navigation aids operated and maintained by
the United States.
Section 170.3 Definitions.
For purposes of this subpart - 
Air navigation facility (NAVAID)
means any facility used, available for
use, or designated for use in the aid of
air navigation. Included are landing
areas; lights; signaling, radio directionfinding, or radio or other electronic
communication; and any other structure or mechanism having a similar
purpose of guiding or controlling flight
or the landing or takeoff of aircraft.
Air traffic clearance means an authorization by air traffic control for an aircraft to proceed under specified traffic
conditions within controlled airspace
for the purpose of preventing collision
between known aircraft.
Air traffic control (ATC) means a service that promotes the safe, orderly, and
expeditious flow of air traffic, including airport, approach, departure, and
en route air traffic control.

Air traffic controller means a person
authorized to provide air traffic service, specifically en route and terminal
control personnel.
Aircraft operations means the airborne
movement of aircraft in controlled or
noncontrolled airport terminal areas,
and counts at en route fixes or other
points where counts can be made.
There are two types of operations:
local and itinerant.
(1) Local operations mean operations
performed by aircraft which:
(i) Operate in the local traffic pattern or within sight of the airport;
(ii) Are known to be departing for, or
arriving from flight in local practice
areas located within a 20-mile radius of
the airport; or
(iii) Execute simulated instrument
approaches or low passes at the airport.
(2) Itinerant operations mean all aircraft operations other than local operations.
Airport traffic control tower means a
terminal facility, which through the
use of air/ground communications, visual signaling, and other devices, provides ATC services to airborne aircraft
operating in the vicinity of an airport
and to aircraft operating on the airport
area.
Alternate airport means an airport,
specified on a flight plan, to which a
flight may proceed when a landing at
the point of first intended landing becomes inadvisable.
Approach means the flight path established by the FAA to be used by aircraft landing on a runway.
Approach control facility means a terminal air traffic control facility providing approach control service.
Arrival means any aircraft arriving at
an airport.
Benefit-cost ratio means the quotient
of the discounted life cycle benefits of
an air traffic control service or navigation aid facility (i.e., ATCT) divided by
the discounted life cycle costs.
Ceiling means the vertical distance
between the ground or water and the
lowest layer of clouds or obscuring phenomena that is reported as  - broken, - 
 - overcast, -  or  - obstruction. - 

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