Atc unit 1

ATC
1-BASIC CONCEPTS
DINESHBABU V/AP/NIET

Air traffic control (ATC) is a service provided by
ground-based controllers who direct aircraft on the ground and
in the air.
The primary purpose of ATC systems is:
 to separate aircraft to prevent collisions
 to organize the air traffic process
 To process the air traffic flow fast and efficiently
 to provide information and other support for pilots when
able.
Air traffic controllers are the people who operate
the air traffic control systems to expedite and maintain a safe
and orderly flow of air traffic and help prevent mid-air
collisions.
Air Traffic Control

Development of ATC
• 1919-International Commission for ATC Started
• 1920-Used radio direction finder
• 1928-1932 Crossed loop type radio stations are installed
• Then they used vertical tower were used
• Air traffic rules were introduced -1936
• 1938 Federal regulation of ATC controls all the activities of
ATC
• 1944-Federal Airways system is developed
• They developed modernization of system which includes
VHF(fan markers and radio ranges ) ,ILS were used for
communication

Development of ATC
• Flagmen
• Radio equipped air traffic control tower –cleveland airport
• Standard of proficiency for instrument flying by pilot were
prescribed.
• Airway traffic control centers was about 80kms from the
airport reference point.
• Communication is made between party line telephone
circuit with local airline radio stations
• Positions of a/cs plotted with marker and flight data were
posted with chalk
• Pilot to be qualified -1936

Purpose of ATC
• General
– Protection and property –avoiding collision
– Well trained ,certified pilot is appointed
• Safety and Requirement
– Proper guidance to pilot –landing ,departure
– Maintaining separation
• Efficiency
– Expeditions –sequencing the a/c operation
– Maintaining time table
• Economy
– Avoiding delays-less usage of fuel –short runway

Types of Airport
• Based on Function
– Heliports
– STOL ports
– Conventional
– Sea plane bases
• Based on Usage or Ownership
– Public
– Private
– Military
– Joint use (Civil and military aviation)
• Based on Facility available
– NO. And type of runway
– Navigation aids
• Based on type of aircraft designed to serve

Airport Area
• Land side
– Passenger ,cargo ,mail arrive and depart
– Holding facilities (buses ),parking (car)
– Terminal buildings ,commercial services
• Airside
– Landing ,take off
– Maintenance and servicing ,baggage loading and
unloading
– Emergency rescue automotive traffic control

Divisions of Air-traffic Services
Area Control Service:
The provision of air traffic control service for controlled flights, except
for those parts of such flights which are under the jurisdiction of Approach Control
or Aerodrome Control to accomplish following objectives:
a) prevent collisions between aircraft
b) expedite and maintain an orderly flow of air traffic
Approach control service:
The provision of air traffic control service for those parts of controlled
flights associated with arrival or departure.
Aerodrome control service:
The provision of air traffic control service for aerodrome traffic,
except for those parts of flights which are under the jurisdiction Approach Control

Flight information service:
Provide advice and information useful for
the safe and efficient conduct of flights.
Alerting service:
Notify appropriate organizations regarding
aircraft in need of search and rescue aid and
assist such organizations as required.

Control areas and
Controlled aerodrome
• The areas where the Air traffic Control
services will be provided to IFR flights called
control areas
• The areas where the Air traffic control services
will be provided to aerodrome traffic is called
controlled Aerodromes.

• Visual flight rules (VFR) are a set of regulations which allow a pilot to
operate an aircraft in weather conditions generally clear enough to allow
the pilot to see where the aircraft is going.
• Specifically, the weather must be better than Basic VFR Weather
Minimums, as specified in the rules of the relevant aviation authority.
• If the weather is worse than VFR minimums, pilots are required to
use Instrument Flight Rules.
• Meteorological conditions that meet the minimum requirements for VFR
flight are termed visual meteorological conditions (VMC).
• If they are not met, the conditions are considered instrument
meteorological conditions(IMC), and a flight may only operate under
IFR.
• VFR rules require a pilot to be able to see outside the cockpit, to control
the aircraft's attitude, navigate, and avoid obstacles and other aircraft.
• A VFR flight is "conducted in accordance with the visual flight rules
Visual flight rules(VFR Flights)

• An aircraft operated in accordance with the visual flight rules which wishes to
change to compliance with the instrument flight rules shall-
– Communicate the necessary changes to be effected to its current flight plan or
– Submit a flight plan to the appropriate air traffic services unit and obtain a clearance prior to
proceeding IFR when in controlled airspace.

• Except when a clearance is obtained from an air traffic control unit, VFR
flights shall not take-off or land at an aerodrome within a control zone or
enter the aerodrome traffic zone or traffic pattern:
– When the ceiling is less than 450M(1550 Ft) or
– When the ground visibility is less than 5KM.
• VFR flights shall not be operated between sunset and sunrise, except
when exempted by air traffic control for local flights and such training
flights of flying club aircraft as may be cleared by air traffic control.
• VFR flights can not be operated-
– Above FL50
– At transonic and supersonic speeds
– More than 100 NM seaward from the shoreline within controlled airspace.
• Expect when necessary for take-off or landing or except by permission
from appropriate authority, a VFR flight shall not be flown-
– Over congested area of city, town or settlements or over an open-air assembly of
persons at a height less than 300M above the highest obstacle within a radius of 600M
from the aircraft.
VFR Rules

 Instrument flight rules (IFR) are regulations and procedures for
flying aircraft by referring only to the aircraft instrument panel for navigation.
 Even if nothing can be seen outside the cockpit windows, an IFR-rated pilot can
fly while looking only at the instrument panel.
 An IFR-rated pilot can also be authorized to fly through clouds, using Air
Traffic Control procedures designed to maintain separation from other aircraft.
 Training is normally done in simulated IFR conditions with training aids such as
block alls to help a pilot concentrate only on the instrument panel.
 Most scheduled airline flights operate under IFR.
 Visual Flight Rules (VFR) are often used for sight-seeing flights, aerial
photography, or lift services for parachute jumping.
 Pilots flying under VFR are not permitted to fly through clouds. Many non-
commercial, private recreational aircraft also operate under VFR whenever the
sky is clear.
 Under VFR, the pilot is primarily responsible for navigation, obstacle clearance
and maintaining separation from other aircraft using the see-and-avoid concept.
INSTRUMENT FLIGHT RULES (IFR FLIGHTS)

 All aircraft shall be equipped with suitable instruments and navigation
equipment appropriate to the route to be flown.
 Except when necessary for take-off or landing or when specifically
authorized by the appropriate authority, an IFR flight shall be flown at a
level that is not below the established minimum flight altitude or where no
such minimum flight altitude had been established-
 Over high terrain or in mountainous areas, at a level which is at least 600M
above the highest obstacle located within 8KM of the estimated position of the
aircraft.
 Elsewhere at a level at least 300M above.
 An aircraft electing to change the conduct of flight from IFR to VFR shall
notify the app. Air traffic services unit specifically that the IFR flight is
cancelled and communicate the changes to be made to its current flight plan.
 When an a/c operating under IFR is flown in or encounters visual
meteorological conditions, it shall not cancel its IFR flight rules unless it is
anticipated and intended that the flight will be continued for a reasonable
period of time in interrupted visual meteorological conditions
IFR Rules

Instrument Flight
panel and Enroute
Guidance

• Based on ATC usage:
– Controlled Airspace:
• ATC services are provided throughout the majority of airspace, and
its services are available to all users (private, military, and
commercial).
• When controllers are responsible for separating some or all aircraft,
such airspace is called "controlled airspace“.
– Uncontrolled Airspace:
• In contrast to "uncontrolled airspace“ is the airspace, where aircraft
may fly without the use of the air traffic control system.
Types of Airspace

Types of Air spaces
• Class A
Airspace in which only IFR operation are permitted
.Pilot must be instrument rated and have ATC clearance
to enter in airspace. Airspace between 6000m(18000ft )
above mean sea level to flight level 20000m (60000ft)
• Class B
IFR and VFR flights are permitted but ATC clearance is
required. The Aircraft must be equipped with
frequencies and VHF omni range radio receiver for
IFR .VFR must remains clear clouds .Each are
subjected to ATC separation.

Class D:
 Airspace established around airports with operating ATC towers .
 Near by airports are included
 Radio contact is need for entering this airspace.
 830m(2500ft) above ground level
 Airspaces in terminal areas, control areas, control zones and aerodrome
traffic zones have been classified and designated as class D airspace.
Class E:
 Airspace above 4830 m(14500ft) above MSL and 400m(1200ft ) above ground level for
Instrument approach.
 IFR and VFR flights are permitted, IFR flights are provided with air traffic control
service and are separated from other IFR flights.
 IFR flights receive traffic information in respect of VFR flights, VFR flights receive
traffic information in respect of all other flights, as far as is practical.
 VFR minima 1 km visibility ,150m below clouds ,300 m above clouds and 600m
horizontal from clouds .Above 3000m MSL
 VFR minima 1.6 km visibility 300m ,300 and 1.6 km Airspaces in designated ATS routes
outside terminal areas, control areas and control zones, where air traffic control service is
provided, have been classified and designated as class E airspace.
 Airspace under not controlled of any ATC facility ,IFR is required –flight plan
Based on ATC Services(India):

Class F:
• IFR and VFR flights are permitted. All IFR flights receive an air traffic
advisory service and all flights receive flight information service, if
requested.
• Airspaces in designated ATS route segments outside terminal areas, control
areas and control zones, where air traffic advisory service is provided, have
been classified and designated as class F airspace.
Class G:
• IFR and VFR flights are permitted and receive flight information service if
requested.
• Airspaces other than those in Class D, E and F have been classified and
designated as class G airspace.

SEPARATION
• In air traffic control, separation is the concept of
keeping an aircraft outside a minimum distance
from another aircraft to prevent from collision
• To prevent accidents due to wake turbulence.
• The rule used to control collision between aircraft
is called as separation minima
• When an aircraft passes behind or follows another
aircraft, wake turbulence minima are applied due
to the effect of the wingtip vortices of the
preceding aircraft on the following aircraft.

SEPARATION
Separation
Vertical
separation
RVSM
CVSM (climb
/decent)
Horizontal
separation
Lateral Longitudinal
Radar

• Vertical separation :
Between the surface and an altitude of 29,000 feet
(8,800 m), no aircraft should come closer vertically
than 300 metres, unless some form of horizontal
separation is provided
• RVSM :
In certain airspace, between 29,000 and 41,000 feet
(12,500 m), pairs of aircraft equipped with more
modern altimeter and autopilot systems can be
vertically separated by minimum of 1,000 feet (300 m)
rather than the standard 2,000 feet (600 m).

• Longitudinal separation
If two aircraft are not laterally separated, and
are following tracks within 45 degrees of each
other (or the reciprocal), then they are said to
be following the same route and some form of
longitudinal separation must exist.

• Horizontal separation
If any two aircraft are separated by less than the vertical separation
minimum, then some form of horizontal separation must exist.
The golden rule is the 10-minute rule: no two aircraft following the
same route must come within 15 minutes flying time of each other. In
areas with good navigation aid cover this reduces to 10 minutes; If the
preceding aircraft is faster than the following one then this can be
reduced further depending of the difference in speed.
• Radar separation
Radar separation is applied by a controller observing that the radar
returns from the two aircraft are a certain minimum horizontal
distance away from each other, as observed on a suitably calibrated
radar system. The actual distance used varies: 5 nmi (9 km) is common
in en route airspace, 3 NM is common in terminal airspace at lower
levels.

• Procedural separation
Procedural separation is separation based upon the position
of the aircraft, based upon reports made by the pilots over
the radio. It therefore does not necessarily require the use of
radar to provide air traffic control using procedural
separation minima.
In procedural control, any period during which two aircraft
are not vertically separated is said to be "level change". In
some cases, procedural separation minima are provided for
use with radar assistance, however it is important not to get
this mixed up with radar separation as in the former case the
radar need not necessarily be certified for use for radar
separation purposes, the separation is still procedural.

ALTIMETER SETTING
PROCEDURE
• Altimeter setting is essential to know the
correct altitude /height from a reference
surface.
• This enables the pilot from providing adequate
vertical separation between aircraft and
provide adequate terrain clearance during all
phases of flight .

Transition altitude
• The altitude at or below which the vertical
position of an aircraft is controlled by
reference to altitude
• Every country sets a transition altitude below
which the aircraft are not allowed fro crusing
flight performance.
• Transition layer – Airspace b/w TA
• Transition level –lowest flight level available

Atc unit 1

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Atc unit 1