The document discusses airport obstructions and imaginary surfaces. It defines obstructions as objects that interfere with aircraft movement and lists different types of imaginary surfaces like approach surfaces, takeoff climb surfaces, and horizontal surfaces that establish height limits for objects near airports. It also describes land use and height zoning laws that regulate development around airports based on distances from runways to maintain safety.

2.  Airport obstructions
 Imaginary surfaces
 Height of objects in approach zone
 Turning zone
 Zonal laws

3.  Obstructions are the objects or entities which
are present in the path of air craft or on the
facilities provided for the aircraft that cause
hindrance to the safe and easy movement of
the aircraft.
 Obstructions are mainly related to type of
development and height of development in
case of buildings

4.  Obstructions divided into 2 types
 Imaginary surfaces
 Objects with actual heights
 Assumed surfaces on any airport by which
the aircrafts should move above of that
particular surface only
 Different types of the development in the
vertical direction and its height.

5.  These imaginary surfaces are basically
established surfaces in relation to airport and
to each runway above which no obstruction
should project.
 Size of imaginary surface depends upon
 The category of each runway
 Type of approach planned for that runway

6.  Imaginary surfaces
 Approach surface
 Conical surface
 Horizontal surface
 Takeoff climb surface
 Transitional surface

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9.  Approach Surface
 Provided at the end of landing side of runway
 Trapezoidal in shape
 Diverging away with upgrade
 Longitudinally centered on the extended center-
line of runway

12. ILS = Instrumental Landing System
Non ILS – Non Instrumental Landing System

15.  Take off climb surface
 Similar to approach surface
 Provided at the takeoff end of runway
 Trapezoidal in shape

17.  Horizontal Surface
 Extends from upper edge of transition surface and
ends at lower or inner circular edge of conical
surface
 The height of outer horizontal surface extends
from 150 m (above the ARP elevation) to 9900 m
(for airports with length of runway b/w 900 m and
1500 m) or to 15000 m (for airports having
runways length more than 1500 m)above
elevation of airport reference point.

18.  The shape of HIS may or may not be circular .
 The radius of outer limit measured from the
ARP.
 Not provided for the airports having runway
length < 900 m.
 Structures having height above IHS are not
permitted.

19.  Transition Surface
 Trapezoidal in shape
 Extends along the landing strip
 Slopes upward and outward to the IHS (Inner
Horizontal Surface)

21.  Conical Surface
 Extends upwards and outwards from inner HS to
a point which is at some height above the
horizontal surface
 Circular in shape

24.  any object which is located beyond a distance
of 4.5 km from the runway end is considered
as an obstruction if its height above 30 meter
increases by more than 7.5 meter for each
additional 1.5 km distance from the runway.
 When we reach 15km from runway end it
should not exceed 75m

25.  Any object which projects above the
minimum approach flight altitude or whose
height exceeds 150 meter above the ground
is also to be considered as an obstruction.

27.  Runway Clear zone
 Provided after runway end starting at 60m from
the end within approach area
 Length determined by approach surface attaining
a height of 30m
 It is dependant on the rate at which approach
surface is going up

28. W1 is at the beginning of clear zone that is after moving 60m at the end of strip and
W2 is after L distance

30.  It is used in the case of emergencies for
turning of aircraft
 any object which is located within a distance
of 4.5 km from the ARP is considered as an
obstruction if its height exceeds 51 meter
above the ground or the established airport
elevation whichever is more

31.  any object which is located beyond a distance
of 4.5 km from the ARP is considered as an
obstruction if its height exceeds 51 meters
plus 30 meters for each additional 1.5 km
from ARP.
 If the value exceeds 150m with in 15km it
remains same

33.  Height Zoning
 Given w.r.t. to 4.5km distance from runway and
further w.r.t. every 1.5km upto a distance of 15km
from airport
 This area should remain with low profile of
development

34.  Land Use Zoning
 Governs the type of development which is taking
place at the adjoining areas of airport
 These are classified as
Closely related like terminal buildings, parking etc.,
Non-Aviation use like commercial, industrial,
residential or recreational

35.  Following factors must be considered w.r.t. the
zoning laws
 Zoning laws or legal rules should not hamper the
somebody rights
 Nature of ordinance or law should have the qualities
like
▪ not unreasonable, not arbitrary, not compulsive
 Zoning map has to be provided
▪ Defines what type of activity can take place at what distance
▪ Helps people to decide their activities
▪ It should land use pattern, permissible heights, limits of zoning
laws etc.