Apr/May 2010

PART B

1. (i) Enumerate various ATC aids.

Ans: The following are the various ATC aids:

1. Radio and Navigation Aids

2. Airport Lighting Aids (ALS)

3. Airport Visual Aids

4. Air Navigation and Obstruction Lighting Aids

5. Airport Marking Aids and Signs

6. Fitness for Flight

7. Flight Safety

8. Emergency services

(ii) Briefly discuss the various parts of ATC services

Ans: Air Traffic Control services: A generic term meaning area control service, approach

control service or aerodrome control service. The air traffic services comprise of three services

identified as follows:

1. Air traffic control service

□ Area control service

□ Approach control service

□ Aerodrome control service

2. Flight information service

3. Alerting service

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.

Provision of air traffic control service:

The parts of air traffic control service, shall be provided by the various units as follows:

Area control service

Area control service shall be provided: a) By an area control centre (ACC); or

b) By the unit providing approach control service in a control zone or in a control

area of limited extent which is designated primarily for the provision of approach control

service, when no ACC is established

Approach control service

Approach control service shall be provided: a) By an aerodrome control tower or an ACC, when it is necessary or desirable to

combine under the responsibility of one unit the functions of the approach control service and

those of the aerodrome control service or the area control Service.

b) By an approach control unit, when it is established as a separate unit.

Aerodrome control service

- Aerodrome control service shall be provided by an aerodrome control tower.

Operation of air traffic control service:

In order to provide air traffic control service, an air traffic control unit shall: a) Be provided with information on the intended movement of each aircraft, or

variations there from, and with current information on the actual progress of each aircraft

b) Determine from the information received, the relative positions of known aircraft

to each other

c) Issue clearances and information for the purpose of preventing collision between

aircraft under its control and of expediting and maintaining an orderly flow of traffic;

d) Coordinate clearances as necessary with other units:

1) Whenever an aircraft might otherwise conflict with traffic operated under

the control of such other units

2) Before transferring control of an aircraft to such other units.

e) Information on aircraft movements, together with a record of air Traffic control

clearances issued to such aircraft, shall be so displayed as to permit ready analysis in order to

maintain an efficient flow of air traffic with adequate separation between aircraft.

Explanation:

Area Control Service: En-route air traffic controllers work in facilities called Area Control Centers, each of which

is commonly referred to as a "Center". The United States uses the equivalent term Air Route Traffic

Control Center (ARTCC). Each center is responsible for many thousands of square miles of

airspace (known as a Flight Information Region) and for the airports within that airspace. Centers

control IFR aircraft from the time they depart from an airport or terminal area's airspace to the time

they arrive at another airport or terminal area's airspace. Centers may also "pick up" VFR aircraft

that are already airborne and integrate them into the IFR system. These aircraft must, however,

remain VFR until the Center provides a clearance.

Center controllers are responsible for climbing the aircraft to their requested altitude while,

at the same time, ensuring that the aircraft is properly separated from all other aircraft in the

immediate area. Additionally, the aircraft must be placed in a flow consistent with the aircraft's

route of flight.

As an aircraft reaches the boundary of a Center's control area it is "handed off" or "handed

over" to the next Area Control Center. In some cases this "hand-off" process involves a transfer of

identification and details between controllers so that air traffic control services can be provided in a

seamless manner; in other cases local agreements may allow "silent handovers" such that the

receiving center does not require any co-ordination if traffic is presented in an agreed manner. After

the hand-off, the aircraft is given a frequency change and begins talking to the next controller. This

process continues until the aircraft is handed off to a terminal controller ("approach").

Approach and terminal control: Many airports have a radar control facility that is associated with the airport. In most

countries, this is referred to as Terminal Control; in the U.S., it is referred to as a TRACON

(Terminal Radar Approach Control.) While every airport varies, terminal controllers usually handle

traffic in a 30-to-50-nautical-mile (56 to 93 km) radius from the airport. Where there are many busy

airports close together, one consolidated Terminal Control Center may service all the airports. The

airspace boundaries and altitudes assigned to a Terminal Control Center, which vary widely from

airport to airport, are based on factors such as traffic flows, neighboring airports and terrain.

Terminal controllers are responsible for providing all ATC services within their airspace.

Traffic flow is broadly divided into departures, arrivals, and over flights. As aircraft move in and

out of the terminal airspace, they are handed off to the next appropriate control facility (a control

tower, an en-route control facility, or a bordering terminal or approach control). Terminal control is

responsible for ensuring that aircraft are at an appropriate altitude when they are handed off, and

that aircraft arrive at a suitable rate for landing.

Not all airports have a radar approach or terminal control available. In this case, the en-route

center or a neighboring terminal or approach control may co-ordinate directly with the tower on the

airport and vector inbound aircraft to a position from where they can land visually. At some of

these airports, the tower may provide a non-radar procedural approach service to arriving aircraft

handed over from a radar unit before they are visual to land. Some units also have a dedicated

approach unit which can provide the procedural approach service either all the time or for any

periods of radar outage for any reason

2. Write short notes on:

(i) Area control service (6)

Ans: Area control service: Air Traffic Control service for controlled flights in control areas. In air traffic control, an Area Control Center (ACC), also known as a Center, is a facility

responsible for controlling instrument flight rules aircraft en route in a particular volume of

airspace (a Flight Information Region) at high altitudes between airport approaches and departures.

- A Center typically accepts traffic from, and ultimately passes traffic to, the

control of a Terminal Control Center or of another Center.

- Most Centers are operated by the national governments of the countries in

which they are located.

- The general operations of Centers worldwide, and the boundaries of the

airspace each Center controls, are governed by the ICAO

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;

Area control service shall be provided:

a) By an area control centre (ACC); or

b) By the unit providing approach control service in a control zone or in a control area of

limited extent which is designated primarily for the provision of approach control service, when no

ACC is established.

En-route air traffic controllers work in facilities called Area Control Centers, each of which

is commonly referred to as a "Center". The United States uses the equivalent term Air Route Traffic

Control Center (ARTCC). Each center is responsible for many thousands of square miles of

airspace (known as a Flight Information Region) and for the airports within that airspace. Centers

control IFR aircraft from the time they depart from an airport or terminal area's airspace to the time

they arrive at another airport or terminal area's airspace. Centers may also "pick up" VFR aircraft

that are already airborne and integrate them into the IFR system. These aircraft must, however,

remain VFR until the Center provides a clearance.

Center controllers are responsible for climbing the aircraft to their requested altitude while,

at the same time, ensuring that the aircraft is properly separated from all other aircraft in the

immediate area. Additionally, the aircraft must be placed in a flow consistent with the aircraft's

route of flight.

As an aircraft reaches the boundary of a Center's control area it is "handed off" or "handed

over" to the next Area Control Center. In some cases this "hand-off" process involves a transfer of

identification and details between controllers so that air traffic control services can be provided in a

seamless manner; in other cases local agreements may allow "silent handovers" such that the

receiving center does not require any co-ordination if traffic is presented in an agreed manner. After

the hand-off, the aircraft is given a frequency change and begins talking to the next controller. This

process continues until the aircraft is handed off to a terminal controller ("approach").

(ii) Runway lighting (4)

Ans: Runway lighting includes such lights as edge, threshold, centre line, end, touchdown zone

and wing bar lights. Runway lighting shall not be operated if the runway is not in use for landing,

take-off or taxiing purposes. If the runway lighting is not operated continuously, lighting following

a take-off shall be provided as specified below:

1. At aerodromes where ATC service is provided and where lights are centrally controlled, the

lights of one runway shall remain lighted after take-off as long as is considered necessary

for the return of the aircraft due to an emergency occurring during or immediately after

take-off.

2. At aerodromes without ATC service or without centrally controlled lights, the lights of one

runway shall remain lighted until such time as would be required to reactivate the lights in

the likelihood of the departing aircraft returning for an emergency landing, and in any case

not less than fifteen minutes after take-off.

3. Where obstacle lighting is operated simultaneously with runway lighting, particular care

should be taken to ensure that it is not turned off until no longer required by the aircraft.

(iii) Flight plans (6)

Ans: Flight plan: Specified information provided to air traffic services units, relative to an

intended flight or portion of a flight of an aircraft.

Flight plans are documents filed by pilots or a Flight Dispatcher with the local Civil

Aviation Authority prior to departure. Flight plan format is specified in the ICAO Doc 4444. They

generally include basic information such as departure and arrival points, estimated time en route,

alternate airports in case of bad weather, type of flight (whether instrument flight rules or visual

flight rules), the pilot's information, number of people on board and information about the aircraft

itself. In most countries, flight plans are required for flights under IFR, but may be optional for

flying VFR unless crossing international borders.

Flight plans are highly recommended, especially when flying over inhospitable areas, such

as water, as they provide a way of alerting rescuers if the flight is overdue. In the United States and

Canada, when an aircraft is crossing the Air Defense Identification Zone (ADIZ), either an IFR or a

special type of VFR flight plan called a DVFR flight plan must be filed (the "D" is for Defense).

For IFR flights, flight plans are used by air traffic control to initiate tracking and routing

services. For VFR flights, their only purpose is to provide needed information should search and

rescue operations be required, or for use by air traffic control when flying in a "Special Flight Rules

Area".

Contents of a Flight Plan: The ICAO FPL form shall be used for the purpose of completing a flight plan prior to

departure or, in case the flight plan is submitted by telephone or tele-fax, the sequence of items in

the flight plan form shall be strictly followed.

The following information shall be included in the flight plan:

Aircraft Identification

Flight rules and type of the flight

Number of aircraft, type of aircraft and wake turbulence category

Equipment

Departure aerodrome

Estimated off-block time

Cruising speed

Level

Route

Destination aerodrome and total estimated elapsed time

Alternate aerodrome(s)

Endurance

Persons on board

Survival equipment

Pilot in command

Other information

If a flight is to cross a Finish state border, details of the entire flight to the destination

aerodrome shall be submitted in the flight plan.

3. (i) Describe the procedure for the design of aerodrome. (8)

Ans: Instrument approach procedures are designed to enable pilots to operate under Instrument

Flight Rules (IFR) in Instrument Meteorological Conditions (IMC). The instrument approach

procedures may direct aircraft to either descend down to circling minima and conduct a visual

circling approach, or to a runway aligned position down to the runway landing minima and conduct

a straight-in approach.

Where the instrument approach procedure does not provide a straight-in approach, the

runway is still classified as a non-instrument runway. Where the instrument procedure provides for

a straight-in approach, the runway is classified as an instrument non-precision approach (NPA)

runway.

CASA strongly recommends that, where terrain permits, NPA procedures be provided as

they enhance the safety and efficiency of aircraft operations. NPA procedures may use ground-

based navigation aids, such as VOR, DME, NDB, etc. Increasingly, NPA procedures may also be

designed using GPS. The use of GPS allows NPA procedures to be provided to aerodromes which

have no access to ground-based navigation aids.

Before a GPS NPA procedure is designed and published for a particular runway, the runway

must meet the standards of a NPA runway. At some aerodromes there may be a cost involved in

meeting these aerodrome standards. Whilst it is the prerogative of an aerodrome operator to

determine whether his or her aerodrome should be upgraded, CASA strongly recommends that

aerodrome operators avail themselves of the benefit of GPS technology.

Request for NPA procedures may come from the Regional Airspace Planning and Advisory

Committee (RAPAC), airline operators, aviation organizations, or aerodrome operators.

Any proposal for, and design of, instrument approach procedures to a runway should only

be made with the knowledge that the runway meets the appropriate aerodrome standards for NPA.

Use of a runway which does not meet the appropriate aerodrome standards for NPA procedures

could result in unsafe situations.

Aerodrome standards: The standards for a NPA runway are different to the standards

applicable to a non instrument runway in several aspects. These include:

· Runway strip width

` · Approach OLS area and gradient

· Availability of wind direction indicator near the threshold

· Runway edge light spacing

RUNWAY STRIP WIDTH: Many existing aerodromes have runways of 30 metres width contained within runway strips

90m to 150m wide. NPA procedures may be designed for runways with strip widths down to 90m

provided the landing minima is adjusted in accordance with design requirements. The 90m strip

width for NPA procedures are limited only to runways used by code 1, code 2 and up to code 3C

aero planes. (Runways accommodating aero planes above code 3C (eg. B737) require a minimum

graded runway strip width of 150m).

APPROACH OLS AREA AND GRADIENT The standard approach obstacle limitation surface (OLS) area for a NPA runway is

considerably larger than a non-instrument runway. For code 1 and code 2 runways, the increases

are not extensive. For a code 3 runway, the differences in the approach OLS area are:

· Length - increases from 3000m to 15000m

· Length of the inner edge - 150m.

· Side splay - increases from 10% to 15%

· Approach gradient - down from 3.3% to 2% in the first section, 2.5% in the second

section and horizontal for the third section.

It should be noted that a code 3 runway also requires a 180m inner edge for the take-off

surface, unless the runway is used only by aircraft with MTOW of less than 22700 kg and operating

only in Visual Meteorological Conditions (VMC) during the day.

To facilitate the introduction of NPA procedures without compromising aircraft safety, the

following procedures may be used in dealing with obstacles within the approach OLS area:

· Obstacles within 3000m of the inner edge of the approach surface (2500m for code

1 and 2 runways) are to be identified based on the applicable standard.

· Objects previously not identified as obstacles, but which are classified as obstacles

under the applicable standards, are to be referred to the relevant CASA Office for assessment of

their impact upon aircraft operations and the need for marking and/or lighting of such obstacles.

The obstacle data should also be provided directly to the procedure designer concerned

· For areas beyond the 3000m, the procedure designer will obtain obstacle

information from the national tall structure data bank and topographical maps.

· Before a new or revised procedure is cleared by CASA for publication, the

procedure will be flight validated to ensure that the required obstacle clearances are provided in the

design.

· The procedure designer will advise the aerodrome operator of the critical obstacles

which govern the procedure minima, including allowances provided for the height of vegetation.

· After the NPA straight-in procedure is published, the aerodrome operator will be

required to monitor the approach OLS area and report any new obstacles or potential obstacles to

the relevant CASA Office and to the Air services Procedure Design Section.

AVAILABILITY OF A WIND DIRECTION INDICATOR NEAR THE

THRESHOLD Because the primary wind direction indicator (WDI) may not be visible from the approach

minima, NPA runways require WDI near the threshold to provide surface wind information to

pilots of landing aircraft. However, if another acceptable means of providing surface wind

information is available, such as through an aerodrome weather information broadcast (AWIB), or

an approved observer with a suitable communication link, the WDI requirement may be waived.

Alternative arrangements for provision of surface wind information should be made with the

relevant CASA Office if there is no WDI near the threshold. In addition, if a WDI is located near

the threshold for NPA procedures purposes, and the NPA procedures are conducted at night,

appropriate illumination of the WDI will have to be provided.

RUNWAY EDGE LIGHT SPACING Existing runway edge lights for a non-instrument runway are normally spaced 90-100m

apart. For a NPA runway, the lights should be spaced not more than 60m apart. However, NPA

procedures may be provided for a runway with runway edge lights spaced at 90-100m apart, subject

to the visibility minima being not less than 1.5 km and provided there are no extraneous lights

around the aerodrome which may affect visual acquisition of the runway.

Before NPA procedures are made available for night use, the lighting system will need to be

checked. This hecking will generally be done as part of the NPA flight validation process, or by the

relevant CASA Office. The aerodrome operator concerned will be consulted if there is a problem

with the aerodrome lighting.

At aerodromes where NPA operations are conducted, aerodrome operators should ensure

that time limited works are co-ordinated with arrival schedules to avoid risk to aircraft and persons

on the ground.

Currently, development works are being done in the global navigation satellite system

(GNSS) with local or wide area augmentation to enhance the accuracy of the system. It is likely

that in the near future Cat I precision approaches will be able to be conducted to runways with no

Instrument Landing System (ILS).

The aerodrome standards will need to be met to support these operations are more stringent,

particularly in regard to runway and approach lighting. Aerodrome operators should bear this in

mind if they are considering upgrading their aerodrome lighting systems.

GPS NPA procedures may also be provided for helicopter landing sites (HLS), either on or

off aerodromes. Currently, Australian standards do not specify NPA standards for HLS. In the

interim, HLS meeting the NPA standards specified in ICAO Annex 14 Volume II are acceptable.

(ii) How are aerodrome classified in India. (8)

Ans:

Airports Classification: In order to provide guide to airport designers for a reasonable amount of uniformity in

airport landing facilities, design criteria have been prepared by ICAO and FAA through airport

classifications.

Aerodrome in India: With so many airports in India, traveling has become really convenient and easy. Over all

these years, the Indian air industry has grown several folds and contributed in a big way to the

tourism industry in India. Today there are a large number of airlines in India which have made it

convenient for the travelers to reach their destinations easily. Most of the airports in India connect

the Indian cities with the International cities. These are the international airports in India. The

domestic airports in India link all the major corners of the country.

Airports Authority of India (AAI) This Airports Authority of India which is under the control of Ministry of Civil Aviation is

in charge of managing all the airports in India. The AAI is involved in the management and

operation of 126 airports in India which include:

11 international airports

89 domestic airports

26 civil enclaves

Classification of Airports in India India has a total of 449 airports, out of which 92 airports and 28 civil enclaves in Defence

airports offer flight services over the entire airspace of India and the neighboring oceanic areas.

However, only 61 airports out of the total are permitted to be utilized by the airlines.

The Indian airports are categorized into following classifications:

Indian airports are divided into 3 broad categories

* Domestic

* International and

*Civil enclave

There are two more categories in India

* Customs Airport

* Model Airport

International Airports in India: These are declared as international airports and are

available for scheduled international operations by Indian and foreign carriers. Presently,

Mumbai, Delhi, Chennai, Calcutta and Thiruvananthapuram are in this category.

The following airports link the major Indian cities to the international cities:

Amritsar International Airport , Indira Gandhi International Airport, New Delhi, Lokpriya

Gopinath Bordolio International Airport, Guwahati, Sardar Vallabhbhai Patel International

Airport, Ahmedabad, etc.,

Domestic Airports in India: All the Indian airports come under this category.

Custom Airports in India: Custom Airports provide immigration and customs facilities for

the international tourists. They also operate cargo charter flights. The custom airports in India

are located at: Bangalore, Hyderabad, Ahmedabad, Calicut, Cochin, Goa, Varanasi, Patna,

Agra, Jaipur, Amritsar, Tiruchirapally

Model Airports in India: Indian Model Airports are the domestic airports with following

features:

Minimum 7500 feet length of runway

Sufficient terminal capacity for handling aircraft of Airbus 320 type

If required, can also handle limited international traffic

The model airports in India are located in: Lucknow, Bhubaneshwar, Guwahati, Nagpur,

Vadodara, Coimbatore, Imphal, Indore

Civil Enclaves in Indian Defence Airports: 28 civil enclaves are included in the Defence

airfields of India.

4. Briefly discuss the various requirements of an airport lighting systems and airport

marking systems.

Ans: Refer Question No. 14 and 16 in Part B Ques and Ans.

5. Draw the typical layout of a small domestic’s terminal building and typical airport layout.

Explain any two.

Ans: The layout of an airport is determined by five basic factors:

- The direction of prevailing winds (the major runways being oriented to the

prevailing wind with a back up runway on a cross wind alignment)

- The size and number of terminal buildings

- The ground transport system, especially the position of major access roads and

railways

- Mandatory clearance dimensions between aircraft and buildings

- Topography and geology

Small airports are usually a direct reflection of these spatial and organizational

characteristics but as airports become larger a number of secondary factors come into play such as

environmental controls, the geography of the surrounding region, and the capacity of the local road

system. International airports, though their site layout is shaped primarily by wind direction, are

increasingly constrained by such factors as community disturbance. As a consequence their growth

and configuration rarely permit simple planning solution but are compromised by influences of a

regional nature.

Airport Types:

There are three main types of airport: - International airports serving over 20 million passengers a year

- National airports serving between 2 and 20 million passengers a year

- Regional airports serving up to 2 million passengers a year

Such a classification, based upon the level of traffic flow is a useful guide but by no means

infallible. In countries such as Germany, which have a strong hub network of airports, some of the

larger regional airports have passenger movements that approach international dimensions.

Conversely in smaller countries with single national airports passenger movement below the norm

for the classification may justify the inclusion of the airport in the top rank. If the level of

passengers is a good is good general guide, other factors relevant to typological classification

include:

- The split between domestic, national and international movements

- The role of the airport as an international centre for aviation or as a distribution

hub

- The scale of non airport facilities such as other transportation modes, hotels,

business and conference centres.

Airport types are also a clue to security risks: International terrorism tends to target

major international, not minor regional airports. The development of airport is more than the

satisfying of aviation needs. No matter how lucrative or demanding these may be. Airports, whether

international or regional in nature, need to develop the total business and this consists of aviation,

retailing, land ownership and integrated transport opportunities. There are specific facilities for the

business community: executives can jet in from different locations, have a meeting in one of the

conference suites, and fly home. Business conferencing is an area of growth for regional airports,

particularly those away from congested airspace locations.

Or (use any one diagram)

Fig: Typical Airport Layout

Fig: Typical design of a terminal building: showing the Departures (upper half of

page) and Arrivals levels. 1. Departures Lounge. 2. Gates and jet bridges. 3. Security Clearance Gates. 4 Baggage Check-in. 5. Baggage Carousels

Terminal Building: An airport terminal is a building at an airport where passengers transfer between ground

transportation and the facilities that allow them to board and disembark from aircraft.

Within the terminal, passengers purchase tickets, transfer their luggage, and go through

security. The buildings that provide access to the airplanes (via gates) are typically called

concourses. However, the terms "terminal" and "concourse" are sometimes used interchangeably,

depending on the configuration of the airport.

Smaller airports have one terminal while larger airports have several terminals and/or

concourses. At small airports, the single terminal building typically serves all of the functions of a

terminal and a concourse.

Some larger airports have one terminal that is connected to multiple concourses via

walkways, sky-bridges, or underground tunnels. Some larger airports have more than one terminal,

each with one or more concourses. Still other larger airports have multiple terminals each of which

incorporates the functions of a concourse.

Airport Terminal Concept: The terminals at small airports have mostly been designed as centralized building that is

where the processing of the passengers is done in one location rather than being distributed through

several points in the terminal. The concept of the centralized terminal in combination wither piers,

fingers or satellites is also used at larger airports. It provides easy orientation for the passengers

through check in and security, optimum utilization of space and concentration of services in the

terminal building. However, as the number of stands increases, the distance to the outlying stands

exceeds the recommended walking distances and therefore it is necessary to provide transportation

for the passengers from the central processing building to the gates together with an effective

information system. A central building with a system of several parallel satellite piers

interconnected by a transportation system makes an almost ideal solution for large airports if the

space is available midfield ie., between parallel runways. It has a large capacity of both stands and

peak hour passengers. It enables transfer of passengers to and from common travel areas without

using the central building which then not required to handle these passengers. Therefore this design

is convenient for the hub and spoke type of operation. It seems that it is possible to use central

processing terminals up to about 30 mppa and 50or so gates, whether they have piers and moving

walkways or have satellites and people movers.

6. (i) What are the ATC clearance requirements for airport (8)

Ans: ATC clearance is an authorization for an aircraft to proceed under conditions specified by

an air traffic control unit. Clearance may be prefixed by the words “taxi”, “take off”, “departure”,

“en-route”, “approach” or “landing” to indicate the particular portion of flight to which the air

traffic control clearance relates.

ATC clearances normally required to contain the following: a. Clearance Limit: The traffic clearance issued prior to departure will normally authorize

flight to the airport of intended landing. Many airports and associated NAVAIDs are collocated

with the same name and/or identifier, so care should be exercised to ensure a clear

understanding of the clearance limit. When the clearance limit is the airport of intended landing,

the clearance should contain the airport name followed by the word “airport.” Under certain

conditions, a clearance limit may be a NAVAID or other fix. When the clearance limit is a

NAVAID, intersection, or waypoint and the type is known, the clearance should contain type.

Under certain conditions, at some locations a short-range clearance procedure is utilized

whereby a clearance is issued to a fix within or just outside of the terminal area and pilots is

advised of the frequency on which they will receive the long-range clearance direct from the

center controller.

b. Departure Procedure: Headings to fly and altitude restrictions may be issued to

separate a departure from other air traffic in the terminal area. Where the volume of traffic

warrants, DPs have been developed.

c. Route of Flight: 1. Clearances are normally issued for the altitude or flight level and route filed by

the pilot. However, due to traffic conditions, it is frequently necessary for ATC to specify an

altitude or flight level or route different from that requested by the pilot. In addition, flow

patterns have been established in certain congested areas or between congested areas whereby

traffic capacity is increased by routing all traffic on preferred routes. Information on these flow

patterns is available in offices where preflight briefing is furnished or where flight plans are

accepted.

2. When required, air traffic clearances include data to assist pilots in identifying

radio reporting points. It is the responsibility of pilots to notify ATC immediately if their radio

equipment cannot receive the type of signals they must utilize to comply with their clearance.

d. Altitude Data:

1. The altitude or flight level instructions in an ATC clearance normally require that

a pilot “MAINTAIN” the altitude or flight level at which the flight will operate when in

controlled airspace. Altitude or flight level changes while en route should be requested prior to

the time the change is desired.

2. When possible, if the altitude assigned is different from the altitude requested by

the pilot, ATC will inform the pilot when to expect climb or descent clearance or to request

altitude change from another facility. If this has not been received prior to crossing the

boundary of the ATC facility's area and assignment at a different altitude is still desired, the

pilot should reinitiate the request with the next facility.

3. The term “cruise” may be used instead of “MAINTAIN” to assign a block of

airspace to a pilot from the minimum IFR altitude up to and including the altitude specified in

the cruise clearance. The pilot may level off at any intermediate altitude within this block of

airspace. Climb/descent within the block is to be made at the discretion of the pilot. However,

once the pilot starts descent and verbally reports leaving an altitude in the block, the pilot may

not return to that altitude without additional ATC clearance.

e. Holding Instructions: 1. Whenever an aircraft has been cleared to a fix other than the destination airport

and delay is expected, it is the responsibility of the ATC controller to issue complete holding

instructions (unless the pattern is charted), an EFC time, and a best estimate of any additional

en route/terminal delay.

2. If the holding pattern is charted and the controller doesn't issue complete holding

instructions, the pilot is expected to hold as depicted on the appropriate chart. When the pattern

is charted, the controller may omit all holding instructions except the charted holding direction

and the statements AS PUBLISHED, e.g., “HOLD EAST AS PUBLISHED.” Controllers must

always issue complete holding instructions when pilots request them.

3. If no holding pattern is charted and holding instructions have not been issued, the

pilot should ask ATC for holding instructions prior to reaching the fix. This procedure will

eliminate the possibility of an aircraft entering a holding pattern other than that desired by ATC.

If unable to obtain holding instructions prior to reaching the fix (due to frequency congestion,

stuck microphone, etc.), hold in a standard pattern on the course on which you approached the

fix and request further clearance as soon as possible. In this event, the altitude/flight level of the

aircraft at the clearance limit will be protected so that separation will be provided as required.

4. When an aircraft is 3 minutes or less from a clearance limit and a clearance

beyond the fix has not been received, the pilot is expected to start a speed reduction so that the

aircraft will cross the fix, initially, at or below the maximum holding airspeed.

5. When no delay is expected, the controller should issue a clearance beyond the fix

as soon as possible and, whenever possible, at least 5 minutes before the aircraft reaches the

clearance limit.

6. Pilots should report to ATC the time and altitude/flight level at which the aircraft

reaches the clearance limit and report leaving the clearance limit.

(ii) Mention the approximate obstruction clearances requirements of the current airports.

(8)

Ans:

Air traffic is responsible for obstacle clearance when issuing a “descend via” instruction to

the pilot. The descend via is used in conjunction with STARs/RNAV STARs/FMSPs to reduce

phraseology by not requiring the controller to restate the altitude at the next waypoint/fix to

which the pilot has been cleared.

The ILS glide slope is intended to be intercepted at the published glide slope intercept

altitude. This point marks the PFAF and is depicted by the ”lightning bolt” symbol on U.S.

Government charts. Intercepting the glide slope at this altitude marks the beginning of the final

approach segment and ensures required obstacle clearance during descent from the glide slope

intercept altitude to the lowest published decision altitude for the approach.

Terminal Arrival Area (TAA): The TAA provides the pilot and air traffic controller with a

very efficient method for routing traffic into the terminal environment with little required air

traffic control interface, and with minimum altitudes depicted that provide standard obstacle

clearance compatible with the instrument procedure associated with it.

Minimum MSL altitudes are charted within each of these defined areas/subdivisions that

provide at least 1,000 feet of obstacle clearance, or more as necessary in mountainous areas.

Where lower minimum vectoring altitude (MVAs) are required in designated mountainous

areas to achieve compatibility with terminal routes or to permit vectoring to an IAP, 1,000 feet

of obstacle clearance may be authorized with the use of Airport Surveillance Radar (ASR).

The minimum vectoring altitude will provide at least 300 feet above the floor of controlled

airspace.

Visual Segment of a Published Instrument Approach Procedure: Instrument procedures

designers perform a visual area obstruction evaluation off the approach end of each runway

authorized for instrument landing, straight-in, or circling. Since missed approach obstacle

clearance is assured only if the missed approach is commenced at the published MAP or above

the DA/MDA, the pilot should have preplanned climb out options based on aircraft

performance and terrain features. Obstacle clearance is the sole responsibility of the pilot when

the approach is continued beyond the MAP.

Vertical Descent Angle (VDA) on Non-precision Approaches: The pilot must determine

how to best maneuver the aircraft within the circling obstacle clearance area in order to land.

Pilot Operational Considerations When Flying Non-precision Approaches: Pilots must be

especially vigilant when descending below the MDA at locations without VDPs. This does not

necessarily prevent flying the normal angle; it only means that obstacle clearance in the visual

segment could be less and greater care should be exercised in looking for obstacles in the visual

segment.

ILS or RNAV (GPS) charts: Some RNAV (GPS) charts will also contain an ILS line of

minima to make use of the ILS precision final in conjunction with the RNAV GPS capabilities

for the portions of the procedure prior to the final approach segment and for the missed

approach. Obstacle clearance for the portions of the procedure other than the final approach

segment is still based on GPS criteria.

Obstacle clearance is provided to allow a momentary descent below Decision Altitude

(DA) while transitioning from the final approach to the missed approach. The aircraft is

expected to follow the missed instructions while continuing along the published final approach

course to at least the published runway threshold waypoint or MAP (if not at the threshold)

before executing any turns.

Descent to the procedure turn (PT) completion altitude from the PT fix altitude (when

one has been published or assigned by ATC) must not begin until crossing over the PT fix or

abeam and proceeding outbound. Some procedures contain a note in the chart profile view that

says “Maintain (altitude) or above until established outbound for procedure turn”. Newer

procedures will simply depict an “at or above” altitude at the PT fix without a chart note. Both

are there to ensure required obstacle clearance is provided in the procedure turn entry zone.

Obstacle Clearance:

Final approach obstacle clearance is provided from the start of the final segment to the

runway or missed approach point, whichever occurs last. Side-step obstacle protection is

provided by increasing the width of the final approach obstacle clearance area.

Circling approach protected areas are defined by the tangential connection of arcs drawn

from each runway end. The arc radii distance differs by aircraft approach category (see FIG 5-

4-26). Because of obstacles near the airport, a portion of the circling area may be restricted by a

procedural note: e.g., “Circling NA E of RWY 17-35.” Obstacle clearance is provided at the

published minimums (MDA) for the pilot who makes a straight-in approach, side-steps, or

circles. Once below the MDA the pilot must see and avoid obstacles. Executing the missed

approach after starting to maneuver usually places the aircraft beyond the MAP. The aircraft is

clear of obstacles when at or above the MDA while inside the circling area, but simply joining

the missed approach ground track from the circling maneuver may not provide vertical obstacle

clearance once the aircraft exits the circling area. Additional climb inside the circling area may

be required before joining the missed approach track. Missed Approach, for additional

considerations when starting a missed approach at other than the MAP.

Precision Obstacle Free Zone (POFZ): A volume of airspace above an area beginning at

the runway threshold, at the threshold elevation, and centered on the extended runway

centerline. The POFZ is 200 feet (60m) long and 800 feet (240m) wide. The POFZ must be

clear when an aircraft on a vertically guided final approach is within 2 nautical miles of the

runway threshold and the reported ceiling is below 250 feet or visibility less than 3/4 statute

mile (SM) (or runway visual range below 4,000 feet). If the POFZ is not clear, the MINIMUM

authorized height above touchdown (HAT) and visibility is 250 feet and 3/4 SM. The POFZ is

considered clear even if the wing of the aircraft holding on a taxiway waiting for runway

clearance penetrates the POFZ; however, neither the fuselage nor the tail may infringe on the

POFZ. The POFZ is applicable at all runway ends including displaced thresholds.

Circling Minimums: In some busy terminal areas, ATC may not allow circling and circling

minimums will not be published. Published circling minimums provide obstacle clearance when

pilots remain within the appropriate area of protection. Pilots should remain at or above the

circling altitude until the aircraft is continuously in a position from which a descent to a landing

on the intended runway can be made at a normal rate of descent using normal maneuvers.

Circling may require maneuvers at low altitude, at low airspeed, and in marginal weather

conditions. Pilots must use sound judgment, have an in-depth knowledge of their capabilities,

and fully understand the aircraft performance to determine the exact circling maneuver since

weather, unique airport design, and the aircraft position, altitude, and airspeed must all be

considered.

The published missed approach procedure provides obstacle clearance only when the

missed approach is conducted on the missed approach segment from or above the missed

approach point, and assumes a climb rate of 200 feet/NM or higher, as published.

7. (i) Explain the four elements of the RADAR control and non RADAR control with the

help of a neat sketch. (8)

Ans: Refer Question No. 20 in Part B Ques and Ans.

(ii) An option is given either to improve an existing airport on to develop a new airport.

What will be the governing considerations? (8)

Ans:

Increase of airport and airspace capacity

Increase of airport and airspace

capacity ACI POLICY

ACI RECOMMENDED PRACTICE /

COMMENT

1. ACI believes that technical and

operational means should be

developed to improve airport and

airspace capacity at existing

facilities, as well as the building of

new capacity

ACI supports closer cooperation

with ANSPs to develop better

1. The capacity of a given airport and runway system

is determined by many factors, such as airfield

layout, the air traffic control system and its

management, the type and mix of aircraft, traffic

peaking, weather conditions, environmental

considerations, etc. Some of these factors can be

accurately assessed, while others are site specific,

very difficult to quantify and subject to rapid change.

models, tools and procedures to

determine capacity

ACI considers that a useful

measure of the performance of

airports or airspace management

can be derived from a careful

assessment of delay information.

In order to make realistic judgments and

comparisons with regard to capacity, there would

have to be universal agreement on the specific details

of each factor and, since there are so many variables,

it is doubtful whether any uniform operational

measurement of potential capacity could be

developed.

Measurement and analysis of runway occupancy and

pilot performance may also be appropriate. Runway

occupancy should be defined as in 5.11.4 below.

Improvements in system capacity cannot be achieved

by any one sector acting in isolation. The air

transport industry must work in close cooperation

with governments, regulatory agencies and air

navigation service providers to achieve the full

capacity potential of existing facilities and to

enhance them, where possible, through the adoption

of new technologies and enhancements to procedures

which permit higher movement rates in a safe

operational manner. In addition, major initiatives

will be necessary to develop new facilities required

for airports to meet growing demand. New

technologies and practices which provide the means

of increasing capacity should be assessed and

implemented whenever there is proven economic

benefit.

2. ACI supports the further

development and the introduction

of ICAO’s CNS/ATM

(Communications, Navigation

and Surveillance/Air Traffic

Management) systems concept, as

well as the continued use of the

Instrument Landing System

where essential, until its

replacement by new precision

approach and landing systems.

2. ACI strongly supports accelerated deployment of

the Global Navigation Satellite System (GNSS),

including related Augmentation Systems and

procedures to support precision approach and

landing capability, and thereby optimize system

capacity.

ACI supports equipage of aircraft with Multi-Mode

Receivers (MMR) to enable aircraft so equipped to

operate flexibly during the transition period from

existing precision approach and landing systems to

new systems, regardless of the system deployed at a

particular airport to support all-weather operations.

ACI supports the development of standard criteria for

certificating procedures using GNSS, as already

developed for RNP/ RNAV.

These may enable more flexibility in SIDS and

STARS, including curved approaches, which may

assist in noise mitigation

3. ACI supports further research programmes and activities aimed at mitigating the

effect of wake vortices, in order to reduce aircraft separations while maintaining safety.

4. To minimize runway

occupancy times by aircraft, the

runway and taxiway

infrastructure should be

optimized, including studies of

4. ACI encourages the appropriate location along

runways of rapid exit and access taxiways whose

design complies with ICAO specifications and whose

layout does not increase the risk of runway

incursions.

elements such as the optimal

location of rapid exit and access

taxiways and their lighting and

marking.

Runway occupancy time is an increasingly important

factor in determining airport capacity.

Another important factor in minimizing runway

occupancy time is the maintenance of adequate

runway surface friction characteristics

To improve airport and airspace capacity, simultaneous operations on parallel or near-

parallel instrument runways should be considered as a means of optimizing the use of new

or existing parallel runways. ACI POLICY

5. ACI supports all efforts to

achieve simultaneous operations

on parallel or near-parallel

instrument runways under visual

and instrument meteorological

conditions which are consistent

with operational safety and

efficiency.

5. ACI encourages the ICAO work programme to

evaluate the use of GNSS for the purpose of

supporting simultaneous operations on close-spaced

parallel instrument runways.

6. At airports with intersecting

runways, to enhance capacity

Simultaneous Intersecting

Runway Operations (SIRO) may

be allowed following appropriate

hazard analysis and risk

assessment

6. SIRO should be performed only when the

necessary safety measures are effective, for instance

as proposed in the ICAO European Air Navigation

Plan (EANP). SIRO may include both take-offs

(intersection take-offs, multiple line-ups) and

landings (Land and Hold Short – LAHSO)

8. Write in detail on air transportation in India with special references to the civil aviation

department

Ans: “Aerodrome Reference Code or Special References to Civil Aviation” means a code used for

planning purposes to classify an aerodrome with respect to the critical aircraft characteristics for

which the aerodrome is intended;

AERODROME FACILITY REFERENCE CODE: 1 – The aerodrome facility reference code, also to be known as the aerodrome reference

code, is a two-element, alpha-numeric notation (for example 1B, 3C) derived from the critical

aeroplane for that aerodrome facility. The code number is based on the aeroplane reference field

length and the code letter is based on the aeroplane wing span and the outer main gear wheel span.

As detailed below, a single element may sometimes suffice.

2 – The aerodrome reference code provides a method of grouping aeroplanes with different

characteristics (eg. wing span, outer main gear wheel span, approach speed and all-up mass) which

behave similarly when landing, taking-off or taxying. This, in turn, enables standards for aerodrome

facilities such as runways to be set in terms of a small number of aeroplane groups, rather than

individually for a large number of separate aeroplanes. The task of the standard setting authority

and of the aerodrome operator is thus simplified.

3 – As the aerodrome reference code notation is derived from aeroplane and not aerodrome

characteristics, it applies to the individual aerodrome facilities (eg, runways and taxiways) and

indicate their suitability for use by specific groups of aeroplanes. Thus at the same aerodrome there

may exist, for example, a code 4E runway, a code 1A runway, a code C taxiway and a code 2

runway strip ( a single element sufficing in the latter case).

4 – In many cases to determine the appropriate design standard for an aerodrome facility, it

is necessary first to identify the aeroplanes for which the facility is intended, and then to determine

the aerodrome reference code notation for the most critical of these aeroplanes. The particular

standard for the facility is then related to the more demanding of the two criteria (the number or the

letter) or to an appropriate combination of both.

5 – The code number for the critical aeroplane is to be determined from Table 7–1 by

entering the aeroplane reference field length and reading off the corresponding code number.

6 – The code letter for an aeroplane is to be obtained from Table 7–2 by deriving the code

letter applicable to the wing span, and separately deriving the code letter applicable to the outer

main gear wheel span. The code letter to be used is the more senior of these letters where A is the

junior.

7 – The general dimensions, of a typical aeroplane, are shown in the diagrams below.

8 – A list of representative aeroplanes operating in Australia and others, chosen to provide an

example of each possible aerodrome reference code number and letter combination, is shown in the

table below (sample only). For a particular aeroplane the table also provides data on the aeroplane

reference field length (ARFL), wing span and outer main gear wheel span used in determining the

aerodrome reference code. For aerodrome planning purposes, data is also provided on the overall

aeroplane length, maximum take-off weight and tyre pressure of main wheel tyres. It should be noted

that the data provided is indicative only, for instance, factors such as engine type or flap settings can

result in a different aeroplane reference field length. Exact values of a particular aeroplane’s

performance characteristics should be obtained from information published by the aeroplane

manufacturer

9. Write short notes on :

(i) Airway aids and terminal aids (8)

Ans: Airway aids: In the early days of flight, there were no navigation aids to help pilots find

their way. Pilots flew by looking out of their cockpit window for visual landmarks or by using

automobile road maps. These visual landmarks or maps were fine for daytime, but airmail operated

around the clock. In 1919 - bonfires and the first artificial beacons to help with night navigation. By

July 1923, Bruner's ideas for lighted airport boundaries, spot-lit windsocks, and rotating beacons on

towers had taken hold. Beginning in 1923, the Post Office worked to complete a transcontinental

airway of beacons on towers spaced 15 to 25 miles (24 to 40 kilometers) apart, each with enough

brightness, or candlepower, to be seen for 40 miles (64 kilometers) in clear weather. Each tower

had site numbers painted on it for daytime identification. At night, the beacons flashed in a certain

sequence so that pilots could match their location to the printed guide that they carried. Besides the

rotating beacon, one fixed tower light pointed to the next field and one to the previous tower,

forming an aerial roadway. Official and emergency fields were lit with green lights while

dangerous fields were marked with red.

Established minimum lighting requirements for all airmail stations: a 500-watt revolving

searchlight, projecting a beam parallel to the ground to guide pilots; another searchlight projecting

into the wind to show the proper approach;

The use of lighted airways allowed pilots to fly at night, but pilots still needed to maintain

visual contact with the ground. A really useful air system demanded two-way voice communication

and the ability to find out about changing weather conditions while in flight. Pilots could only

receive weather information and details about other planes in the air just before takeoff. If

conditions changed while flying, the ground had no way to warn them. A pilot, too, had no way of

communicating with the ground.

The Aeronautics Branch stepped up installation of four-course radio ranges, and this

technology became standard for civil air navigation through World War II.

Pilot to use only aircraft instrument guidance to take off, fly a set course, and land. He used

the four-course radio range and radio marker beacons to indicate his distance from the runway. An

altimeter displayed his altitude, and a directional gyroscope with artificial horizon helped him

control his aircraft's orientation, called attitude, without seeing the ground. These technologies

became the basis for many future developments in navigation.

First ultrahigh-frequency radio range system for scheduled airline navigation, eventually

expanding use of such equipment.

Advances in radio very high frequency (VHF) omni-directional radio range (VOR) that

allowed pilots to navigate by watching a dial on their instrument panel rather than by listening to

the radio signal.

The FAA began using distance-measuring equipment on its entire system. This equipment

allowed aircraft to determine their distance from known checkpoints in order to confirm their

position. The first Doppler radar version of the VOR system made it more accurate for longer

distances.

The FAA participated with the National Aeronautics and Space Administration in the first

public demonstration of a new system in March 1967 that would use orbiting satellites to transmit

navigation data from aircraft to ground stations. The test was followed by further development of

aircraft antennas to send and receive satellite messages.

In October 1969, 16 area navigation routes were developed. Previously, pilots had flown

directly toward or away from the ground-based radio navigation aid (a VOR or VORTAC). This

aid transmitted a course along invisible lines called radials. With area navigation, pilots could fly

any pre-selected flight path roughly within the boundaries of that local system while an onboard

computer tracked and reported the aircraft's position. Courses could be established along the

shortest path within these route segments.

Navigation aids, the computers supporting the system, and cockpit displays and instruments

to send and receive navigation data all improved steadily.

Additional navigation technologies are in partial use or development, including the Global

Positioning System both to locate and help control aircraft by satellite, the Future Air Navigation

System for remote and oceanic flights, and the Communication, Navigation and Surveillance for

Air Traffic Management system. These technologies combine the need for point-to-point

navigation and for higher quality voice and data communication with the need for air traffic

control--the safe separation of aircraft from hazards and other aircraft.

Terminal aids: an airfield equipped with control tower and hangars as well as

accommodations for passengers and cargo. An airport (terminal) is a location where aircraft such as

fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained

at an airport. An airport consists of at least one surface such as a runway for a plane to take off and

land, a helipad, or water for takeoffs and landings, and often includes buildings such as control

towers, hangars and terminal buildings.

Area Control Centres (ACCs): Area Control Centres provide air traffic control,

information services and alerting services for aircraft within a designated area. ACCs normally

divide their assigned airspace into sectors that are controlled by a controller or team of controllers.

Control services are provided through a combination of radar, information technology,

voice communication and highly skilled personel applying strict and proven separation criteria and

procedures; to ensure safe, consistent separation and orderly, efficient flow of traffic from origin to

destination. NAV CANADA operates 7 Area Control Centres in Gander, Moncton, Montreal,

Toronto, Winnipeg, Edmonton, and Vancouver.

Air Traffic Control Towers (ATCs) : Air Traffic Controllers working in Control Towers

provide pilots approaching and departing busy airports with clearances and instructions to ensure

their aircraft have sufficient separation (horizontal, lateral, and vertical distance from each other).

Tower controllers also provide flight information to aircraft operating within designated

airspace around their airports. At busier airports monitoring of ground movements is enhanced

through ground surveillance radar systems. NAV CANADA operates 41 control towers across the

country.

Flight Service Stations (FSSs): Flight Service Stations (FSS) provide resources for flight

planning, access to briefings on weather and other preflight information, aeronautical information,

enroute and airport advisory services, vehicle control services, monitoring of navaids, VHF/DF

assistance and alerting of Search and Rescue centres for overdue aircraft. NAV CANADA has 58

Flight Service Stations.

Flight Information Centres (FICs): FICs centralize the provision of those flight

information services that are not location dependent, providing pilots with efficient, seamless flight

planning, enroute services and better access to flight information services. They are a one-stop shop

for flight planning and in-depth interpretive weather briefings provided by qualified specialists,

using the latest computer and communications technology. Services are offered pre-flight and en

route.

Aerodrome Radio Stations (ARS): Aerodrome Radio Stations provide aviation weather and

communications services at designated sites. These facilities are equipped with meteorological

instruments for monitoring and recording aviation surface weather, and communications equipment

for providing operational information to pilots. They are operated by observers/communicators who

are usually recruited locally.

Remote Communications Outlets (RCOs) and Remote Aerodrome Advisory Services

(RAAS): Remote Communications Outlets are remote transmitters/receivers set up to extend the

communications capabilities of FSS stations. They allow Flight Service Specialists to provide some

flight information services to remote areas and aerodromes without a staffed NAV CANADA

facility. When an RCO is used to provide airport advisory services at a remote aerodrome, the

service is referred to as a Remote Aerodrome Advisory Service (RAAS).

Landing and Navigational Aids: Landing Aids and Related Facilities directly support

aircraft and assist during departure, en-route, and arrival. The Instrument Landing System (ILS) is

the primary international precision approach system approved by ICAO. It provides navigational

guidance signals and information on a cockpit display which guides pilots to the point of landing in

reduced visibility.

Radio Navigation Facilities: Radio Navigation Facilities are installed on defined flight

tracks for use in the enroute phase of flight, or at aerodromes where they can be used to perform

non-precision approaches under IFR conditions. Normally two or more types of Navigational Aids

(NAVAIDS) are co-located at a site to provide a combination of functions and to ensure reliability.

Non-directional radio beacons (NDB) transmit on a low frequency a non-directional radiation

pattern. Distance Measuring Equipment (DME) responds to aircraft queries to provide cockpit

display of the distance to the DME facility from a suitably equipped aircraft. VHF Omni-

Directional Range/Distance Measuring Equipment is a ground-based, short-distance radio aid

which provides continuous azimuth information in the form of 360 usable radials TO or FROM a

station. It serves as the basis for most of the civil airways structure. The Tactical Air Navigation

System is used to define the azimuth lines between the aircraft and the transmitter, and also the

distance from the aircraft to the transmitter. TACAN is supplied by the military and operated and

maintained.

RAMP Radar Site Equipment - The air navigation system uses radar surveillance for both

terminal and enroute control.

Airport Surface Detection Equipment (ASDE) – At six airports surface aircraft and

vehicle traffic is monitored during periods of reduced visibility through the use of Airport Surface

Detection Equipment (ASDE) radar.

(ii) External aids and internal aids (8)

Ans: ATC requires various types of navigational surveillance and communication equipment-

both in the cockpit and on the ground. The technologies involve while widely used are fairly

complex and training in their use, maintenance and repair is not trivial.

Aids to aerial navigation can be broadly classified into two groups: 1. those that are located

on the ground (external aids) and 2. Those installed in the cockpit (internal aids). Some aids are

designed primarily for flying over oceans: other aids are only applicable to fight over land masses:

and finally there are aids that can be used over either land or water. Some aids are used only during

en-route portion of the flight while other aids are necessary in terminal areas near airports.

The principal aids for ATC are voice communications and radar. The controller monitors

the separation between aircraft by means of radar and instructs the pilot by means of voice

communication. The following are some of the internal and external aids for aviation or aerodrome

operation.

External Aids:

Airport Lighting

The majority of airports have some type of lighting for night operations. The variety and

type of lighting systems depends on the volume and complexity of operations at a given airport.

Airport lighting is standardized so that airports use the same light colors for runways and taxiways.

Airport Beacon

Airport beacons help a pilot identify an airport at night. The beacons are operated from dusk till

dawn. Sometimes they are turned on if the ceiling is less than 1,000 feet and/or the ground visibility

is less than 3 statute miles (VFR minimums). However, there is no requirement for this, so a pilot

has the responsibility of determining if the weather meets VFR requirements. The beacon has a

vertical light distribution to make it most effective from 1–10° above the horizon, although it can

be seen well above or below this spread. The beacon may be an omni-directional capacitor-

discharge device, or it may rotate at a constant speed, which produces the visual effect of flashes at

regular intervals. The combination of light colors from an airport beacon indicates the type of

airport. Some of the most common beacons are:

• Flashing white and green for civilian land airports;

• Flashing white and yellow for a water airport;

• Flashing white, yellow, and green for a heliport; and

• Two quick white flashes alternating with a green flash identifying a military airport.

Approach Light Systems

Approach light systems are primarily intended to provide a means to transition from

instrument flight to visual flight for landing. The system configuration depends on whether the

runway is a precision or non-precision instrument runway. Some systems include sequenced

flashing lights, which appear to the pilot as a ball of light traveling toward the runway at high

speed. Approach lights can also aid pilots operating under VFR at night.

Visual Glide slope Indicators

Visual glide slope indicators provide the pilot with glide path information that can be used

for day or night approaches. By maintaining the proper glide path as provided by the system, a pilot

should have adequate obstacle clearance and should touch down within a specified portion of the

runway.

Visual Approach Slope Indicator (VASI)

VASI installations are the most common visual glide path systems in use. The VASI provides

obstruction clearance within 10° of the runway extended runway centerline, and to four nautical

miles (NM) from the runway threshold.

The VASI consists of light units arranged in bars. There are 2-bar and 3-bar VASIs. The 2-

bar VASI has near and far light bars and the 3-bar VASI has near, middle, and far light bars. Two-

bar VASI installations provide one visual glide path which is normally set at 3°. The 3-bar system

provides two glide paths; the lower glidepath normally set at 3° and the upper glidepath ¼ degree

above the lower glide path.

The basic principle of the VASI is that of color differentiation between red and white. Each

light unit projects a beam of light, a white segment in the upper part of the beam and a red segment

in the lower part of the beam. The lights are arranged so the pilot sees the combination of lights to

indicate below, on, or above the glide path.

Other Glide path Systems

A precision approach path indicator (PAPI) uses lights similar to the VASI system except

they are installed in a single row, normally on the left side of the runway. A tri-color system

consists of a single light unit projecting a three-color visual approach path. Below the glidepath is

indicated by red, on the glidepath is indicated by green, and above the glidepath is indicated by

amber. When descending below the glidepath, there is a small area of dark amber. Pilots should not

mistake this area for an “above the glidepath” indication.

Pulsating visual approach slope indicators normally consist of a single light unit projecting

a two-color visual approach path into the final approach area of the runway upon which the

indicator is installed. The on glidepath indication is a steady white light. The slightly below

glidepath indication is a steady red light. If the aircraft descends further below the glidepath, the red

light starts to pulsate. The above glidepath indication is a pulsating white light. The pulsating rate

increases as the aircraft gets further above or below the desired glide slope

Obstruction Lights

Obstructions are marked or lighted to warn pilots of their presence during daytime and

nighttime conditions. Obstruction lighting can be found both on and off an airport to identify

obstructions.

Wind Direction Indicators

It is important for a pilot to know the direction of the wind. At facilities with an operating

control tower, this information is provided by ATC. Information may also be provided by FSS

personnel located at a particular airport or by requesting information on a CTAF at airports that

have the capacity to receive and broadcast on this frequency.

Traffic Patterns

At those airports without an operating control tower, a segmented circle visual indicator

system if installed is designed to provide traffic pattern information. Usually located in a position

affording maximum visibility to pilots in the air and on the ground and providing a centralized

location for other elements of the system, the segmented circle consists of the following

components: wind direction indicators, landing direction indicators, landing strip indicators, and

traffic pattern indicators.

The use of one of the external aids (e.g., a kneepad) can reduce the demands of Air Traffic

Control (ATC) communication on pilots’ working memory during routine flight. The use of two

external aids that may vary in ease of coordination: a conventional knee pad and an electronic

notepad, or e-pad.

Internal Aids:

Radio Communications

Operating in and out of a towered airport, as well as in a good portion of the airspace

system, requires that an aircraft have two-way radio communication capability. For this reason, a

pilot should be knowledgeable of radio station license requirements and radio communications

equipment and procedures

ATC Radar Beacon System (ATCRBS)

The ATC radar beacon system (ATCRBS) is often referred to as “secondary surveillance

radar.” This system consists of three components and helps in alleviating some of the limitations

associated with primary radar. The three components are an interrogator, transponder, and

radarscope. The advantages of ATCRBS are the reinforcement of radar targets, rapid target

identification, and a unique display of selected codes.

Transponder

The transponder is the airborne portion of the secondary surveillance radar system and a system

with which a pilot should be familiar. The ATCRBS cannot display the secondary information

unless an aircraft is equipped with a transponder. A transponder is also required to operate in

certain controlled airspace as discussed in Chapter 14, Airspace.

10. Calculate the actual length of the runway from the following data:

Airport Elevation RL 100

Airport reference temperature 28 deg C

Basic length of runway 1600 m

Highest part along the length RL 98.2

Lowest part along the length RL 95.2

Ans: Refer the answer in Air Transportation and Planning by virendra kumar