CHAPTER 5: OBSTACLE LIMITATION SURFACES- RESTRICTION AND
REMOVAL
5.1
General
5.1.1
The Obstacle Limitation Surfaces (OLS) are a series of surfaces that
define the limits to which objects may project into the airspace.
5.2
The OLS comprises the following:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
.
5.3
Transitional surface;
Approach surface/ Take-off climb surface;
Inner horizontal surface;
Conical surface;
Outer horizontal surface;
Inner approach surface;
Inner transitional surface;
Balked landing surface;
Transitional surface
5.3.1
It is a complex surface sloping upwards and outwards upto the inner
horizontal surface from the edge of the approach surface and from a line originating at
the end of the inner edge of each approach area, drawn parallel to the runway centre line
in the direction of landing. Its slope shall be measured in a vertical plane perpendicular
to the centre line of each runway as given below:
5.3.2
The outer limit of the transitional surface is determined by its intersection
with the plane containing inner horizontal surface.
5.3.3
In case of instrument runway, its slope shall be 14.3% i.e. (1:7). In case of
non- instrument runway, the slope shall be 20% i.e. (1:5) for runway length less than 1200
m and 14.3% i.e. (1:7) for runway length 1200 m and above.
5.4
Approach surface/ take-off climb surface
5.4.1
The approach and take-off climb area shall be established from the smaller
ends of the runway strip for each runway direction intended to be used for the landing
and take-off of aeroplanes. The limits and slopes are given in the Table 5-1 below:
Table 5-1: DIMENSIONS AND SLOPES OF TAKE-OFF CLIMB/ APPROACH
SURFACES
RUNWAY
INSTRUMENT RUNWAY
(DIVERGENCE
15% ON EITHER SIDE
FIRST
SECOND
Code No.
SECTION
SECTION
Length
Length
Length
Slope
(M) Slope
(M)
(M)
1.
< 3000
3600
3%
800
2.5%
3600
3%
2.
800 < 3000
1200
2.5%
3600
2.5%
3.
1200 < 3000
2%
1800
3600
3000
2% 2.5%
4.
1800 &
above
NON-INSTRUMENT RWY
(DIVERGENCE 10% ON
EITHER SIDE)
Length
(M)
Slope
1600
5%
2500
4%
3000
3.33%
3000
2.5%
NOTE 1
Any existing obstacle penetrating in the take off climb surface that
cannot be removed will be notified.
NOTE 2
The permissible elevations shall be restricted to that of either
Approach or Inner Horizontal Surface/Conical Surface, whichever
is the lowest.
For Datum of Approach/Take-off climb surface refer Para 5.8.1.1
NOTE 3
At aerodromes where there are more than one runway with
overlapping take-off/climb approach areas and associated surface
the criteria shall be as prescribed for the main runway.
For determining the take-off climb/approach area, the physical
extremities
of the runway shall only be considered
irrespective of the fact that a
runway threshold is displaced
due to any reason. However, where
clearway
is
provided, take-off climb surface will commence at the end of
the clearway, if its length exceeds 60 m.
At Aerodromes, where the proposals for runways extension exist,
the
requisite surface will be determined from the proposed
extended runway
strip/associated clearway, as applicable.
5.5
Inner horizontal surface
5.5.1
The dimension and permissible height of Inner Horizontal Surface are
given in the Table 5-2 below:
Table 5-2: DIMENSIONS AND PERMISSIBLE HEIGHTS OF INNER HORIZONTAL
SURFACE
RUNWAY
CODE
NO.
LENGTH
(M)
INSTRUMENT RUNWAY
RADIUS
(M)
HEIGHT
(M)
NON-INSTRUMENT
RUNWAY
RADIUS
HEIGHT
(M)
(M)
1.
< 800
3500
45
2000
45
2.
800 < 1200
3500
45
2500
45
3.
1200 < 1800
4000
45
4000
45
4.
1800 & above
4000
45
4000
45
5.5.2
Where the runway length is 1525 m or more, the inner horizontal surface
will be a composite pattern, consisting of two circular areas centred at the two runway
ends with a radius of 4000 m. These areas will be joined tangentially to form an elliptical
shape.
5.5.3
Where it is required to protect two or more widely spaced long runways,
an even more complex pattern involving four or more circular arcs are formed. These
arcs would be joined tangentially by straight lines and the IHS will be defined by the
external limits of the resulting pattern.
5.5.4
Adjoining aerodromes with overlapping circuits
5.5.4.1
When two aerodromes are close to each other with overlapping circuits the
IHS will be drawn as prescribed in Para 5.5. The Inner Horizontal Surfaces of these two
aerodromes will be joined tangentially to form one common IHS.
5.5.5
Landing ground without paved runways
5.5.5.1
For the landing ground without paved runways a clearance of 4% (1:25)
from the Boundary of aerodrome in all direction shall be applied up to a distance of 460
m and beyond
that a uniform elevation of 45 m above ARP elevation be permitted up to a distance of
2600 m. A conical surface extending upwards and outwards from the edge of the area
ending at 2600 m would be provided up to a distance of another 1525 m. with a slope of
5% (1:20).
5.5.5.2
In case of common horizontal surface serving two aerodromes, the
elevation of the IHS will be the lower of the two aerodromes.
5.5.5.3
In case of complex IHS for two runways at the same aerodrome, a
common surface need not be worked out. However, when these surfaces overlap each
other, the lower surface be regarded as over-riding.
5.6
Conical surface
5.6.1
The conical surface shall be projected upwards and outwards from the
periphery of the Inner Horizontal Surface (IHS). The slope of the conical surface
measured above the IHS in a vertical plane will be 5% (1:20). The outer limits and
permissible heights of the conical surface are given in the Table 5-3 below:
Table 5-3: OUTER LIMITS AND PERMISSIBLE HEIGHTS OF CONICAL
SURFACE
RUNWAY
CODE
ENGTH
NO.
(M)
1.
< 800
INSTRUMENT RUNWAY
L HORIZONTAL
DISTANCE
OF
HEIGHT
CONICAL
ABOVE
SURFACE
IHS
BEYOND IHS
(M)
(M)
1200
60
NON-INSTRUMENT RUNWAY
HORIZONTAL
MAXIMUM
DISTANCE OF
HEIGHT
CONICAL
ABOVE
SURFACE
HIS
BEYOND IHS
(M)
(M)
700
35
2.
3.
800 < 1200 1200
1200 <
1500
60
1200
60
75
1500
75
2100
105
1800
2100
4.
1800 &
105
above
5.7
Outer horizontal surface
5.7.1
The Outer Horizontal Surface (OHS) will extend to 15240 m from the
Aerodrome Reference Point (ARP) for Aerodromes with runway code 3 and 4.
5.7.2
In case of Aerodromes with Runway code 2, the Outer Horizontal Surface
(OHS) will extend to 14740 m from Aerodrome Reference Point (ARP) for Instrument
runways and 13740 m for Non-Instrument of runways.
5.7.3
Where combined IHS is established for two aerodromes, the OHS will be
centred on the ARP of the more important aerodrome.
Note: Outer Horizontal Surface (OHS) is not established at aerodromes with runway
code 1.
5.7.4
The height of the OHS will be 150 m above the ARP elevation. The
constructions protruding above these surfaces will not be permitted. The existing
obstruction would be marked.
5.7.5
The tall structures will be considered to be of possible significance, if they
are 35 m or more above ground level within the obstacle limitation surfaces and 120 m or
more above ground level outside the obstacle limitation surfaces.
5.8
Datum for OLS
5.8.1
Approach/Take-off climb surfaces
5.8.1.1
The elevation of the associated runway end or the elevation of the runway
end after completion of the proposed extension will be the datum.
5.8.2
Inner horizontal surface, Conical surface and outer horizontal surface
5.8.2.1
In respect of Inner Horizontal Surface (IHS) and Conical Surface, the
elevation of the associated runway ends will be considered if the runway length is 1525
m or more. In case, the runway length is less than 1525 m, the ARP will be considered as
its datum. In case of OHS, the elevation will be determined with the ARP as its datum.
5.8.3
Transitional surface
5.8.3.1
For the transitional surface, the elevation of the point on the centre line of
the runway, which is the nearest to the proposed building/structure will be the datum.
5.8.3.2
For the areas in the transitional surface, which are located beyond the
length of the runway strip, the elevation of the runway end nearest to which the new
construction is proposed will be the datum for determining the permissible height.
5.9
Obstacle-free zone
5.9.1
The inner approach, inner transitional and balked landing surfaces together
define a volume of airspace in the immediate vicinity of a precision approach runway
Cat-II & III, which is known as the obstacle- free zone. This zone will be kept free from
fixed objects, other than lightweight frangibly mounted aids to air navigation which must
be near the runway to perform their function, and from transient objects such as aircraft
and vehicles when the runway is being used for precision approaches Cat II/III.
5.10
Inner approach surface
5.10.1
The inner approach surface is a rectangular portion of the approach
surface immediately preceding the threshold.
5.10.2
The inner approach surface originates from an inner edge of a specified
length, at the same location as the inner edge for the approach surface, and extends on
two sides parallel to the vertical plane containing the runway centerline, to an outer edge
which is located at a specified distance to the inner edge and parallel to the inner edge.
5.11
Inner transitional surface
5.11.1
The inner transitional surface is similar to the transitional sur face but
closer to the runway. The lower edge of this surface originates from the end of the inner
approach surface, extending down the side of the inner approach surface to the inner edge
of that surface, thence along the runway strip to the inner edge of the balked landing
surface and from there up the side of the balked landing surface to the point where the
side intersects the inner horizontal surface.
5.11.2
The elevation of a point on the lower edge is to be:
(i)
along the side of the inner approach and balked landing
surface, equal to the elevation of the particular surface at
that point.
(ii)
along the runway strip, equal to the elevation of the nearest
point on the center line of the runway.
5.11.3
The inner transitional surface slopes upwards and outwards at a specified
rate and is to be measured in a vertical plane at right angles to the centerline of the
runway.
5.11.4
The upper edge of the inner transitional surface is located in the plane of
the inner horizontal surface.
5.11.5
The inner transitional surface would be used as the controlling surface for
navigational aids, aircraft and vehicle holding positions which have to be located near the
runway. The transitional surface would be used for building height control.
5.12
Balked landing surface
5.12.1
The balked landing surface is an inclined plane originating at a specified
distance after the threshold and extending between the inner transitional surfaces.
5.12.2
The balked landing surface originates from an inner edge of a specified
length, located horizontally and perpendicularly to the centerline of the runway, with two
sides from the ends of the inner edge diverging uniformly at a specified rate from the
vertical plane containing the centerline of the runway, ending at an outer edge located in
the plane of the inner horizontal surface.
5.12.3
The elevation of the inner edge is to be equal to the elevation of the
runway center line at the location of the inner edge.
5.12.4
The specified slope of the balked landing surface is to be measured in the
vertical plane containing the centerline of the runway.
5.13
Shielding benefit from the existing structures
5.13.1
The following criteria will be applied to determine whether a structure is
shielded by an already existing obstruction or whether the benefit of shielding from an
already existing obstruction should be given to a newly proposed structure.
5.13.2
The principle of shielding will not be applied in the transition surface area.
5.13.3
The principle of shielding will not be applied in the approach/take-off
climb areas within 3000 m of the Inner edge of these areas
5.13.4
The principle of shielding will not be applied in the IHS up to radius of
2500 m from the runway end/ARP, as the case may be.
5.13.5
Beyond the radius of 2500 m from the runway end/ARP, the principle of
shielding will be applied in the inner, conical and outs horizontal surfaces. In the
approach/take-off climb areas, the principle of shielding will be applied beyond 3000 m
from the Inner edge in a negative slope of 10% from the top of the authorized existing
buildings/structures causing obstructions when projected towards the runway and on a
horizontal plane when projected away from the runway.
5.13.6
Tall and skeletal obstructions such as isolated towers, chimney, masts,
electric pylons, telephone and power lines and poles will not provide any shielding.
5.13.7
The benefit of shielding will not be given from a building which has not
been constructed lawfully.
5.14
Restrictions/prohibition of new constructions, the height of which
does not constitute obstruction but which is nevertheless considered hazardous to
the safety of aircraft operations:
5.14.1
New construction/installation which will adversely affect the performance
of radio/radar/navigational aids which will adversely affect the published instrument
approach to land procedures or which will necessitate a probable change in the published
procedures, shall be restricted/prohibited as deemed fit.
Overhead HT/LT lines or telephone/telegraph lines will not be permitted in
the approach/take-off climb areas within 3000 m of the Inner edge of these areas.
5.14.2
Construction of butcheries, tanneries and refuse dumps will not be
permitted within a radius of 10 kms from the Runway ends/ARP.
NOTE: Incinerators could be permitted clear of approach/take-off climb areas.
5.14.3
Factory chimneys proposed to be constructed within a radius of 8 km of
runway ends/ARP will not be permitted unless the owners give a written undertaking that
oil- fired or electric furnaces or any other fuel which will not cause smoke- hazard will
only be used.
5.14.4
A 3 m deduction will be made from the permissible elevation of the
proposed structure falling in approach/take-off climb surfaces and transition surfaces in
the close proximity of approach funnels. This provision is kept for super structures of
any kind, such as, Wireless/TV antennas, cooling towers, mumties, lift machine rooms,
overhead water tanks, etc.
5.14.5
For the buildings/structures to be constructed in the vicinity of an
aerodrome, the owner will have to give an undertaking in the prescribed performa to the
effect that he is aware of the fact that no complaints of claims against the noise, vibration,
nuisance or other damage to buildings/property/individuals, caused by the regular aircraft
operations from/to the aerodrome, shall be entertained by the Central
Government/Airports Authority of India.
5.14.6
considered:
For mobile obstructions, the following additional heights will be
Rail Track
Road
5.15
aids
:
:
7.62 m
5.0 m
Parameters to be taken into consideration from navigation/landing
5.15.1
In an aerodrome, no building or structure shall be constructed or erected or
no tree will be planted on any land within the limits specified as under:
a)
the land within 305 m radius of the VOR/TVOR/DVOR/DME/VHF DF;
b) the area up to 305 m on + 350 of the localizer beam and up to 60 m on
area beyond + 350 of the localizer antenna.
c) In the case of Glide Path, the area bounded by the following:(i)
A line 460 m in the direction of the approach from the glide path
facility and perpendicular to the runway.
(ii)
A line 120 m in the opposite direction and perpendicular to the
runway.
(iii)
Far edge of the runway from the glide path.
(iv)
A line 120 m in the directions away from the runway and parallel
to it.
d) the land within a radius of 30 m of the site of the markers and locator
beacons.
e) the area within a radius of 305 m of the ASR.
f) the area within a radius of 610 m of the ARSR/SSR site.
g) the area of 45 m width on either side of the direct line of slight in the
azimuth and 9 m from the line of sight in elevation in the vertical plane of
MICROWAVE link.
h)
up to a distance of 305 m in front of the antenna of the Extended range
VHF.
i) on a corridor of 90 m on either side of the direct line of azimuth and 30 m
in vertical from the line of sight in the elevation plane of UHF link;
j) within a radius of 180 m around the antenna of Beacon.
k) within a radius of 1525 m of the site of the remote receiver facilities.
5.15.2
In an aerodrome no building or structure or no tree shall be planted higher
than the heights as specified below:
a) VOR/TVOR/DVOR/DME/VHF DF:- Beyond 305 m radius of the facility,
an object should not protrude an angle of elevation of one degree from the
facility site.
b) ILS
Localizer:- Beyond the area specified in sub para (b) of para 5.15.1 above, an
object should not protrude an angle of elevation of 0.75 degrees.
Glide Path:- Beyond the area specified in sub para © of para 5.15.1 above, a
building/structure should not subtend an angle of elevation of 1 degree.
c) Markers/Locators:- Beyond the area specified in sub para (d) of para
5.15.1 above structure is allowed up to a height of 9 m to a distance of 110 m
from the facility and angle of elevation of 0.5 degree beyond 110 m.
d) ASR:- Beyond 305 m of the facility, the structure should not subtend an
angle of elevation more than 0.5 degree.
e) ASSR/SSR:- Beyond 610 m of the facility up to 1 NM, structure is
allowed up to radar antenna height. More than 1 NM, structure should not
form an angle of elevation more than 0.5 degree.
f) Extended Range VHF:- Beyond 305 m from the antenna front, the
elevation angle permitted is 0.5 degree in the line of shoot (10 degrees on
either side of the desired direction).
5.16
Operational criteria
5.16.1
The heights of structures will be restricted with reference to the Obstacle
Clearance Altitudes as published in Notices to Airmen and amended from time to time.
The vertical clearance between the structure and the aircraft making an instrument
approach to land shall be up to 150 m.
Note:
To have the effective control over the construction activities of the
Government or private agencies within the areas specified for obstacle
limitation surfaces, all in-charges of aerodromes are enjoined to exercise
continuous vigilance over such activities. They are to take immediate action
to bring any violation of the laid down criteria to the notice of Local
Administrative Authorities for stoppage of such construction activities and
also keep Headquarters informed in this regard.