4/20/23 

Pilot/Controller Glossary 

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OBSTACLE

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 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)

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 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 recommended 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

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 The OFZ is a three

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dimensional volume of airspace which protects  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

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5

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Vehicles/Equipment/Personnel Near/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 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 runways. 

(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. 

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 the beginning. 

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 airport elevation. 

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

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5, Vehicles/Equipment/Personnel Near/On Runways.) 

OBSTRUCTION

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 Any object/obstacle exceeding the obstruction standards specified by 14 CFR Part 77, 

Subpart C. 
OBSTRUCTION LIGHT

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 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. 

PCG O

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