3. Pakistan Civil Aviation Authority is a regulatory authority who is responsible to regulate
all aspects of civil aviation in Pakistan.CAA head quarter is situated in terminal 1 of Jinnah
International Airport in Karachi.
Pakistan Civil Aviation Authority is a Public sector autonomous body working under the
Federal Government of Pakistan through the Ministry of Defence. It was established on
7th December, 1982 as an autonomous body. Prior to its creation, a Civil Aviation
Department in the Ministry of Defence used to manage the civil aviation related
activities.
ELECTRONIC Engineering Department(EED)
It holds following major functions at CAA:
· Procurement of all new aviation equipments (Radars, Voice logging systems,ILS
etc) and thorough testing of each equipment after purchase.
· Providing on field repair and maintenance facilities all over Pakistan through its
trained personnel.
· Workshops for extensive repair facilities at EED in case the equipment could not
be repaired at site.
It subdivided into following sections also:
∙ Navigational Aids
· HF(High Frequency ) Section
· VHF/UHF Section
· Radar Central Workshop
Our INTERNSHIP at EED was designed in such a way so that that we could understand the
functionality of each section. We spent the allocated time in each section and got familiar
with the functioning of equipments. Following is the short detail of each section‘s
4. equipment and operation.
Navigational aid section
The department of navigational aid deals with en route navigation and terminal
navigation.
En Route Navigation:
When airplane is successfully in air after takeoff then navigational aid guide aircraft to
its destination known as En route Navigation. It has following equipments:
❏ N.D.B(Non directional beacons)
❏ VOR(VHF Omni directional Range)
❏ DME(Distance measuring equipment)
N.D.B(Non directional beacons):
It is a radio transmitter at a known location and used as an aviation and marine
navigational aid. It send Morse code of desired landing city at some frequency to pilot.It
is operating at a frequency between 190 KHz to 1750 KHz. It operated in all direction.It
uses AM modulation and has maximum output power 25 watt to 5k watt.
At MULTAN, It is operated at frequency of 387khz and
transmitted Morse Code MICE TANGO ( ) at every 8 seconds and it is
normally utilized by low flying aircrafts and it has 0.2k watt maximum
output power. It has 200 to 300 NM coverage and maximum forward
power is maximum and has zero reflection and 90% modulation depth.
NDB signal follow curvature of earth and it can be received at
maximum distance at low altitude (major advantage over VOR).
NDB signal are affected by many thing:
5. ❏ Night affect
❏ Interference
❏ Mountain affect
❏ Coastal affect
Night affect:
Radio waves reflected back from Ionosphere at night can cause signal strength
fluctuated 30 to 60 NM (54 to 108 km) from from transmitted, especially just
before and after sunset.
ADF(Automatic Direction Finder):
It is installed at aircraft and determines direction of NDB station.
It also determined distance of aircraft from NDB station:
Distance=Speed*time
*time=60*(number of minutes flown/degree of bearing
change)
Example:
Germany Rorberg airport has two runways (Runway
18&36).Runway 18(approach from North) has 2 NDB’s with ILS.These are called
“Romeo” and “Oscar Golf”. Runway ‘36’ (approach from South)has only one NDB
called “Golf Sierra” and no ILS.
❏ Romeo operated at 414 kHz AM and has Morse Code “.-. “
❏ Oscar Golf operated at 328 kHz AM and has Morse code “--- --.”
6. Models of NDBs. used by CAA are:
Aerocom 5401, 5034 ,Nautel ND-500, ND-2000 Southern Avionics SS – 1000
VOR(VHF Omni directional Range)
It is used as a navigation system, a pilot can navigate from point A to point B. VOR station
is identified by Morse Code.
VOR is actually a radio aid that provide info about:
❏ Azimuth
❏ Course
❏ To-from to the VOR station
Azimuth:
It is clockwise angle between magnetic north and line connecting the VOR and aircraft.
In aircraft, indication is displayed on “Omni bearing Indicator”
Course:
VOR provide center line to pilot.
To-from to the VOR station:
It tells whether an aircrafts is approach to or moving away from VOR station.
Operating Frequency:
It operates in VHF band range from 112 to 118 MHz
In CAA, its 116 MHz
Basic Principle of Operation:
VOR facility transmitted two 30Hz signals at the same time.
7. ❏ Reference Signal
❏ One 30Hz signal in all direction (constant phase)
❏ Variable Signal
❏ One 30Hz signal is rotated about the station.
Airborne equipment receives both signal at phase difference b/w two signals & interpret
the result as the “radial” from the station.
VOR has two types:
❏ CVOR(Conventional VOR)
❏ DVOR(Doppler VOR)
Comparison between D- VOR & C-VOR:
Doppler VOR beacons are inherently more accurate than Conventional VORs because they
are more immune to reflections from hills and buildings. The variable signal, in a DVOR,
is the 30Hz FM signal. In a CVOR it is the 30Hz AM signal. If the AM signal from a CVOR
beacon, bounces off a building or hill, the aircraft will see a phase that appears to be at
the phase centre of the main signal and the reflected signal, and this phase centre will
move as the beam rotates. In a DVOR beacon, the variable signal will, if reflected, seem to
be two FM signals of unequal strengths and different phases. Twice per 30Hz cycle, the
instantaneous deviation of the two signals will be the same, and the phase locked loop
will get (briefly) confused. As the two instantaneous deviations drift apart again, the
phase locked loop will follow the signal with the greatest strength, which should be that
due to the line-of-sight signal. This will depend on the bandwidth of the output of the
phase comparator in the aircraft. Hence some reflections can cause minor problems, but
these are usually about an order of magnitude less than in a CVOR beacon.
CVOR
DVOR
8. DME(Distance Measuring Equipment):
It is transponder based radio navigation technology. It measures Distance from
aircraft to ground beacons. It provides indication of slant range(in NM) of an
aircraft from a ground DME facility. It is identified by Morse Code.
It has two components:
❏ One is installed in aircraft and it is Interrogator
❏ Second is ground based Transponder
Operation Frequency:
It is operated at frequency between 926 to 1213 MHz.Interrogation and Reply
frequency are associated frequency with at least 1 MHz separation.It has
coverage of about 200NM and ground based transponder capable of handling at
least 100 aircrafts. It measures distance by timing the propagation delay of VHF
or UHF radio signals. Aircraft use DME to determine their distance from a
land-based transponder by sending and receiving pulse pairs - two pulses of fixed
duration and separation. The ground stations are typically co-located with VORs.
A typical DME ground transponder system for en-route or terminal navigation
will have a 1 kW peak pulse output on the assigned UHF channel.
Terminal Navigation:
The navigation techniques used to help the aircraft in landing is known as terminal
navigation. The whole set of equipment used in the process is known as Instrument
Landing System (ILS).
It consists of Localizer, Glide Scope, TDME and Marker Beacons.
Guidance Info: Localizer, Glide scope
9. Range info: Marker beacons, PAPI approach lights, touchdown lights, centerline lights,
runway lights.
Localizer:
It provides center line info to pilot and it consists of 14-log periodic
dipole antennas and installed at the stop end of runway. It can cover 25or 10 NM and
have transmitting frequency in VHF band (108 to 112 MHz). It is identified by its Morse
code like for Multan is IMT and fro Karachi is IKC.
Principle of Operation of Localizer:
A localizer antenna array is normally located beyond the departure end of the runway
and generally consists of several pairs of directional antennas. Two signals are
transmitted on one out of 40 ILS channels between the carrier frequency range 108.10
MHz and 111.95 MHz (with the 100 kHz digit always odd). One is modulated at 90 Hz,
the other at 150 Hz and these are transmitted from separate but co-located antennas.
Each the left of the runway centerline, the other to the right antenna transmits a narrow
beam, one slightly to the left of the runway centerline, the other to the right.
10. Glide Scope:
It is installed at the approach end of the runway and provide “Glide Path Angle” info to
pilot. The glide path angle is adjusted to project an angle of 2’ or 4’ above horizon. For
Multan, it is 3’.
Its transmitting frequency in UHF band ranging b/w 328 to 332 MHz. Glide scope
frequency is paired with specific localizer frequency.
Upper side of the course is modulated at 90Hz and lower side modulated at 150Hz.
Marker beacons:
They operated at frequency of 75 MHz.
It consists of:
1. Outer marker beacons
2. Middle marker beacons
11. 3. Inner marker beacons
Outer Middle Inner
Mod tone 400HZ 1300HZ 3000HZ
Keying - - O-O- OOOOOO
Id PURPLE/BLUE AMBER WHITE
Coverage 600m 300m 150m
TDME:
Terminal Distance Measuring Equipment (TDME) gives the information of distance
from touch down point. Terminal DME, referred to as a TDME in navigational
charts, is a DME that is designed to provide a 0 reading at the threshold point of
the runway, regardless of the physical location of the equipment. It is typically
associated with Glide Slope.
Visit to Navigational Aid Section and Control Tower:
During our Internship, we have visited Navigational Aid Section of CAA at Multan
International Airport and also see the ongoing up gradation work progress at Multan
airport. We have seen the installation of Rotunda at domestic arrivals and visited CIP
lounge while our lectures have held at OCC center. We have visited CCR room and get
brief info about PAPI lights current regulator. We have also visited ECR(Equipment
Control Room) and got familiar with aeronautical message handling system(AMHS) and
have visited ATC control room.
12. HF Section
High frequency (HF) radio provides aircraft with an effective means of communication
over long distance oceanic and trans-polar routes. In addition, global data communication
has recently been made possible using strategically located HF data link (HFDL) ground
stations. An aircraft HF radio system operates on spot frequencies within the HF
spectrum. In the HF range (3 MHz to 30 MHz) radio waves propagate over long distances
due to reflection from the ionized layers in the upper atmosphere.
HF section deals with the equipment of direct communication in Long Range, providing
maintenance repairing and upgrading of HF communication equipments, for four
purposes:
• Ground to Air Domestic
• Ground to Ground Domestic
• Ground to Air International
• Ground to Ground International
VHF/UHF Section
This section deals with all the equipments of VHF/UHF used for the communication
between Air traffic Control to the plane or in other words ground to air
communication. The maintenance of all the VHF/UHF equipments from all over Pakistan
comes under this department. There are various types of antenna used in Communication
of VHF/UHF, like whip antenna, long wire antenna, umbrella antenna, half and full dipole
antenna, VHF extended antenna etc. Whereas, the general range of Frequencies used in
CAA is from 118MHZ to 136 MHz.
Radar(Radio detection and ranging)
Radar is termed as “radio detection and ranging”. It is an equipment which is used to
determine range, altitude, direction and speed of an objects like aircrafts, missiles etc
The radar dish/antenna transmits pulses of radio waves or microwaves which bounce
back from any object in their path. The object returns tiny part of the wave’s energy to a
dish/antenna which is usually located at the same site as transmitter.
Radar functions:
• Normal radar functions:
13. 1. Range (from pulse delay)
2. Velocity (from Doppler frequency shift)
3. Angular direction (from antenna pointing)
• Signature analysis and inverse scattering:
4. Target size (from magnitude of return)
5. Target shape and components (return as a function of
Direction)
6. Moving parts (modulation of the return)
7. Material composition
Radar classification:
In Pakistan, we used two types of Surveillance radars.
❏ Primary surveillance radar
❏ Secondary surveillance radar
Primary Surveillance Radar:
It can detect any object in its operating frequency area by transmitting EM waves to the
object, after striking an object EM waves bounce back to the ground transmitter and
object can be detected.
14. Secondary Surveillance Radar:
It is used for identification and detecting altitude of an object in its path by using
interrogator and transponder, the interrogator has carrier frequency of 1030MHz and
has 1090MHz frequency of reply transmission.
Pakistan has 3 PSR and 6 SSR. They cover whole Pakistan.
15. RUSSIAN S-300 PMU-1 SURFACE TO AIR MISSILE
❏ The long range surveillance radar tracks object over a
range of 185 miles and relays info to the command
vehicle which can assess potential target.
❏ A target is identified and command vehicle orders the
engagement radar to launch missiles
❏ Launch data is sent to best placed of battalion’s six
launch vehicles and it releases two surface to air missiles
❏ Engagement radar helps guide missiles towards target
