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6/17/21 

Pilot/Controller Glossary 

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 
operation. 

OBSTACLE DEPARTURE PROCEDURE (ODP)

 

A preplanned instrument flight rule (IFR) departure 
procedure printed for pilot use in textual or graphic 
form to provide obstruction clearance via the least 
onerous route from the terminal area to the 
appropriate en route structure. ODPs are recom­
mended for obstruction clearance and may be flown 
without ATC clearance unless an alternate departure 
procedure (SID or radar vector) has been specifically 
assigned by ATC. 

(See IFR TAKEOFF MINIMUMS AND 

DEPARTURE PROCEDURES.) 

(See STANDARD INSTRUMENT 

DEPARTURES.) 

(Refer to AIM.) 

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 
JO 7110.65, paragraph 3

1

5

Vehicles/Equipment/ 

Personnal Near/On Runways. The runway OFZ and 
when applicable, the inner­approach OFZ, and the 
inner­transitional 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 

greater of: 

(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 run­

ways. 

(b) 

250 feet for other runways serving small 

airplanes with approach speeds of 50 knots, or more. 

(c) 

120 feet for other runways serving small 

airplanes with approach speeds of less than 50 knots. 

b. 

Inner­approach OFZ. The inner­approach OFZ 

is a defined volume of airspace centered on the 
approach area. The inner­approach OFZ applies only 
to runways with an approach lighting system. The 
inner­approach 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 
inner­approach OFZ is the same as the runway OFZ 
and rises at a slope of 50 (horizontal) to 1 (vertical) 
from the beginning. 

c. 

Inner­transitional OFZ. The inner transitional 

surface OFZ is a defined volume of airspace along the 
sides of the runway and inner­approach OFZ and 
applies only to precision instrument runways. The 
inner­transitional surface OFZ slopes 3 (horizontal) 
to 1 (vertical) out from the edges of the runway OFZ 
and inner­approach OFZ to a height of 150 feet above 
the established airport elevation. 

(Refer to AC 150/5300-13, Chapter 3.) 
(Refer to FAA Order JO 7110.65, Para 3

1

5, 

Vehicles/Equipment/Personnel Near/On 
Runways.) 

OBSTRUCTION

 Any object/obstacle exceeding 

the obstruction standards specified by 14 CFR 
Part 77, Subpart C. 

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 Interna­
tional Civil Aviation Organization are applied. 
Responsibility for the provisions of air traffic control 

PCG O