OBSTACLE -- OVERLYING CENTER
OBSTACLE- An existing object, object of natural
growth, or terrain at a fixed geographical location
or which may be expected at a fixed location within
a prescribed area with reference to which vertical
clearance is or must be provided during flight
OBSTACLE FREE ZONE- The OFZ is a three dimensional
volume of airspace which protects for the transition
of aircraft to and from the runway. The OFZ clearing
standard precludes taxiing and parked airplanes
and object penetrations, except for frangible
NAVAID locations that are fixed by function. Additionally,
vehicles, equipment, and personnel may be authorized
by air traffic control to enter the area using
the provisions of FAA Order 7110.65, paragraph
VEHICLES/EQUIPMENT/PERSONNEL ON RUNWAYS. The runway
OFZ and when applicable, the inner-approach OFZ,
and the inner-transitional OFZ, comprise the OFZ.
a. Runway OFZ. The runway OFZ is a defined volume
of airspace centered above the runway. The runway
OFZ is the airspace above a surface whose elevation
at any point is the same as the elevation of
the nearest point on the runway centerline.
The runway OFZ extends 200 feet beyond each
end of the runway. The width is as follows:
1. For runways serving large airplanes, the
(a) 400 feet, or
(b) 180 feet, plus the wingspan of the most
demanding airplane, plus 20 feet per 1,000
feet of airport elevation.
2. For runways serving only small airplanes:
(a) 300 feet for precision instrument runways.
(b) 250 feet for other runways serving small
airplanes with approach speeds of 50 knots,
(c) 120 feet for other runways serving small
airplanes with approach speeds of less than
b. Inner-approach OFZ. The inner-approach OFZ
is a defined volume of airspace centered on
the approach area. The inner-approach OFZ applies
only to runways with an approach lighting system.
The inner-approach OFZ begins 200 feet from
the runway threshold at the same elevation as
the runway threshold and extends 200 feet beyond
the last light unit in the approach lighting
system. The width of the inner-approach OFZ
is the same as the runway OFZ and rises at a
slope of 50 (horizontal) to 1 (vertical) from
c. Inner-transitional OFZ. The inner transitional
surface OFZ is a defined volume of airspace
along the sides of the runway and inner-approach
OFZ and applies only to precision instrument
runways. The inner-transitional surface OFZ
slopes 3 (horizontal) to 1 (vertical) out from
the edges of the runway OFZ and inner-approach
OFZ to a height of 150 feet above the established
(Refer to AC 150/5300-13, Chapter 3 and
FAA Order 7110.65, paragraph 3-1-5, VEHICLES/EQUIPMENT/PERSONNEL
OBSTRUCTION- Any object/obstacle exceeding the
obstruction standards specified by FAR Part 77,
OBSTRUCTION LIGHT- A light or one of a group of
lights, usually red or white, frequently mounted
on a surface structure or natural terrain to warn
pilots of the presence of an obstruction.
OCEANIC AIRSPACE- Airspace over the oceans of
the world, considered international airspace,
where oceanic separation and procedures per the
International Civil Aviation Organization are
applied. Responsibility for the provisions of
air traffic control service in this airspace is
delegated to various countries, based generally
upon geographic proximity and the availability
of the required resources.
OCEANIC DISPLAY AND PLANNING SYSTEM- An automated
digital display system which provides flight data
processing, conflict probe, and situation display
for oceanic air traffic control.
OCEANIC NAVIGATIONAL ERROR REPORT- A report filed
when an aircraft exiting oceanic airspace has
been observed by radar to be off course. ONER
reporting parameters and procedures are contained
in FAA Order 7110.82, Monitoring of Navigational
Performance In Oceanic Areas.
OCEANIC PUBLISHED ROUTE- A route established in
international airspace and charted or described
in flight information publications, such as Route
Charts, DOD Enroute Charts, Chart Supplements,
NOTAM's, and Track Messages.
OCEANIC TRANSITION ROUTE- An ATS route established
for the purpose of transitioning aircraft to/from
an organized track system.
ODAPS- (See OCEANIC DISPLAY AND PLANNING SYSTEM.)
OFF COURSE- A term used to describe a situation
where an aircraft has reported a position fix
or is observed on radar at a point not on the
ATC-approved route of flight.
OFFSHORE CONTROL AREA- That portion of airspace
between the U.S. 12-mile limit and the oceanic
CTA/FIR boundary within which air traffic control
is exercised. These areas are established to permit
the application of domestic procedures in the
provision of air traffic control services. Offshore
control area is generally synonymous with Federal
Aviation Regulations, FAR Part 71, Subpart E,
"Control Areas and Control Area Extensions."
OFF-ROUTE VECTOR- A vector by ATC which takes
an aircraft off a previously assigned route. Altitudes
assigned by ATC during such vectors provide required
OFFSET PARALLEL RUNWAYS- Staggered runways having
centerlines which are parallel.
OFT- (See OUTER FIX TIME.)
OM- (See OUTER MARKER.)
OMEGA- An RNAV system designed for long-range
navigation based upon ground-based electronic
navigational aid signals.
ONE-MINUTE WEATHER- The most recent one minute
updated weather broadcast received by a pilot
from an uncontrolled airport ASOS/AWOS.
ONER- (See OCEANIC NAVIGATIONAL ERROR REPORT.)
OPERATIONAL- (See DUE REGARD.)
a. Used to indicate that an aircraft is established
on the route centerline.
b. Used by ATC to advise a pilot making a radar
approach that his aircraft is lined up on the
final approach course.
(See ON-COURSE INDICATION-COURSE INDICATION.)
ON-COURSE INDICATION- An indication on an instrument,
which provides the pilot a visual means of determining
that the aircraft is located on the centerline
of a given navigational track, or an indication
on a radar scope that an aircraft is on a given
OPPOSITE DIRECTION AIRCRAFT- Aircraft are operating
in opposite directions when:
a. They are following the same track in reciprocal
b. Their tracks are parallel and the aircraft
are flying in reciprocal directions; or
c. Their tracks intersect at an angle of more
OPTION APPROACH- An approach requested and conducted
by a pilot which will result in either a touch-and-go,
missed approach, low approach, stop-and-go, or
full stop landing.
(See CLEARED FOR THE OPTION.)
(Refer to AIM.)
ORGANIZED TRACK SYSTEM- A movable system of oceanic
tracks that traverses the North Atlantic between
Europe and North America the physical position
of which is determined twice daily taking the
best advantage of the winds aloft.
ORGANIZED TRACK SYSTEM- A series of ATS routes
which are fixed and charted; i.e., CEP, NOPAC,
or flexible and described by NOTAM; i.e., NAT
OROCA- An off-route altitude whic h provides obstruction
clearance with a 1,000 foot buffer in nonmountainous
terrain areas and a 2,000 foot buffer in designated
mountainous areas within the United States. This
altitude may not provide signal coverage from
ground-based navigational aids, air traffic control
radar, or communications coverage.
OTR- (See OCEANIC TRANSITION ROUTE.)
OTS- (See ORGANIZED TRACK SYSTEM.)
OUT- The conversation is ended and no response
OUTER AREA (associated with Class C airspace)-
Nonregulatory airspace surrounding designated
Class C airspace airports wherein ATC provides
radar vectoring and sequencing on a full-time
basis for all IFR and participating VFR aircraft.
The service provided in the outer area is called
Class C service which includes: IFR/IFR-standard
IFR separation; IFR/VFR-traffic advisories and
conflict resolution; and VFR/VFR-traffic advisories
and, as appropriate, safety alerts. The normal
radius will be 20 nautical miles with some variations
based on site-specific requirements. The outer
area extends outward from the primary Class C
airspace airport and extends from the lower limits
of radar/radio coverage up to the ceiling of the
approach control's delegated airspace excluding
the Class C charted area and other airspace as
(See CONTROLLED AIRSPACE.)
(See CONFLICT RESOLUTION.)
OUTER COMPASS LOCATOR- (See COMPASS LOCATOR.)
OUTER FIX- A general term used within ATC to describe
fixes in the terminal area, other than the final
approach fix. Aircraft are normally cleared to
these fixes by an Air Route Traffic Control Center
or an Approach Control Facility. Aircraft are
normally cleared from these fixes to the final
approach fix or final approach course.
OUTER FIX- An adapted fix along the converted
route of flight, prior to the meter fix, for which
crossing times are calculated and displayed in
the metering position list.
OUTER FIX TIME- A calculated time to depart the
outer fix in order to cross the vertex at the
ACLT. The time reflects descent speed adjustments
and any applicable delay time that must be absorbed
prior to crossing the meter fix.
OUTER MARKER- A marker beacon at or near the glideslope
intercept altitude of an ILS approach. It is keyed
to transmit two dashes per second on a 400 Hz
tone, which is received aurally and visually by
compatible airborne equipment. The OM is normally
located four to seven miles from the runway threshold
on the extended centerline of the runway.
(See MARKER BEACON.)
(See INSTRUMENT LANDING SYSTEM.)
(Refer to AIM.)
OVER- My transmission is ended; I expect a response.
OVERHEAD MANEUVER- A series of predetermined maneuvers
prescribed for aircraft (often in formation) for
entry into the visual flight rules (VFR) traffic
pattern and to proceed to a landing. An overhead
maneuver is not an instrument flight rules (IFR)
approach procedure. An aircraft executing an overhead
maneuver is considered VFR and the IFR flight
plan is cancelled when the aircraft reaches the
"initial point" on the initial approach
portion of the maneuver. The pattern usually specifies
a. The radio contact required of the pilot.
b. The speed to be maintained.
c. An initial approach 3 to 5 miles in length.
d. An elliptical pattern consisting of two 180
e. A break point at which the first 180 degree
turn is started.
f. The direction of turns.
g. Altitude (at least 500 feet above the conventional
h. A "Roll-out" on final approach
not less than 1/4 mile from the landing threshold
and not less than 300 feet above the ground.
OVERLYING CENTER- The ARTCC facility that is responsible
for arrival/departure operations at a specific