657 

Federal Aviation Administration, DOT 

§ 77.19 

as landing and takeoff pathways. Those 
determined pathways must be consid-
ered runways, and an appropriate pri-
mary surface as defined in § 77.19 will 
be considered as longitudinally cen-
tered on each such runway. Each end of 
that primary surface must coincide 
with the corresponding end of that run-
way. 

(e) The standards in this subpart 

apply to construction or alteration 
proposals on an airport (including heli-
ports and seaplane bases with marked 
lanes) if that airport is one of the fol-
lowing before the issuance of the final 
determination: 

(1) Available for public use and is 

listed in the Airport/Facility Direc-
tory, Supplement Alaska, or Supple-
ment Pacific of the U.S. Government 
Flight Information Publications; or 

(2) A planned or proposed airport or 

an airport under construction of which 
the FAA has received actual notice, ex-
cept DOD airports, where there is a 
clear indication the airport will be 
available for public use; or, 

(3) An airport operated by a Federal 

agency or the DOD; or, 

(4) An airport that has at least one 

FAA-approved instrument approach. 

§ 77.17

Obstruction standards. 

(a) An existing object, including a 

mobile object, is, and a future object 
would be an obstruction to air naviga-
tion if it is of greater height than any 
of the following heights or surfaces: 

(1) A height of 499 feet AGL at the 

site of the object. 

(2) A height that is 200 feet AGL, or 

above the established airport ele-
vation, whichever is higher, within 3 
nautical miles of the established ref-
erence point of an airport, excluding 
heliports, with its longest runway 
more than 3,200 feet in actual length, 
and that height increases in the pro-
portion of 100 feet for each additional 
nautical mile from the airport up to a 
maximum of 499 feet. 

(3) A height within a terminal obsta-

cle clearance area, including an initial 
approach segment, a departure area, 
and a circling approach area, which 
would result in the vertical distance 
between any point on the object and an 
established minimum instrument 
flight altitude within that area or seg-

ment to be less than the required ob-
stacle clearance. 

(4) A height within an en route obsta-

cle clearance area, including turn and 
termination areas, of a Federal Airway 
or approved off-airway route, that 
would increase the minimum obstacle 
clearance altitude. 

(5) The surface of a takeoff and land-

ing area of an airport or any imaginary 
surface established under § 77.19, 77.21, 
or 77.23. However, no part of the take-
off or landing area itself will be consid-
ered an obstruction. 

(b) Except for traverse ways on or 

near an airport with an operative 
ground traffic control service furnished 
by an airport traffic control tower or 
by the airport management and coordi-
nated with the air traffic control serv-
ice, the standards of paragraph (a) of 
this section apply to traverse ways 
used or to be used for the passage of 
mobile objects only after the heights of 
these traverse ways are increased by: 

(1) 17 feet for an Interstate Highway 

that is part of the National System of 
Military and Interstate Highways 
where overcrossings are designed for a 
minimum of 17 feet vertical distance. 

(2) 15 feet for any other public road-

way. 

(3) 10 feet or the height of the highest 

mobile object that would normally tra-
verse the road, whichever is greater, 
for a private road. 

(4) 23 feet for a railroad. 
(5) For a waterway or any other tra-

verse way not previously mentioned, 
an amount equal to the height of the 
highest mobile object that would nor-
mally traverse it. 

§ 77.19

Civil airport imaginary sur-

faces. 

The following civil airport imaginary 

surfaces are established with relation 
to the airport and to each runway. The 
size of each such imaginary surface is 
based on the category of each runway 
according to the type of approach 
available or planned for that runway. 
The slope and dimensions of the ap-
proach surface applied to each end of a 
runway are determined by the most 
precise approach procedure existing or 
planned for that runway end. 

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