byJOY N. HERMOSILLA, PECE # 00203

Air Navigation System SpecialistManila Approach Radar

Civil Aviation Authority of the Philippines

Air Navigational Tools

Objectives:To learn the basics of electronic Air Navigational tools.To learn its purpose.To learn on the future of electronic Navigational tools.

Air Navigational Tools

Introduction Electronic navigational tools were used to determine

the position of an aircraft relative to a fixed position onthe ground.

Pilots can navigate by using rate and time relationship.

Air Navigational Tools Three Methods of Navigation

1. Rho Theta – measuring distance and bearing information.

North

θρ

Air Navigational Tools2. Rho Rho Rho – measuring 3 distance information.

ρ1

ρ3ρ2

Air Navigational Tools3. Theta Theta Navigation – measuring bearings to two

or more ground stations.

θ1

θ2θ3

North

Instrument Landing System (ILS) Assist the pilot in positioning the aircraft for landing

under low visibility conditions. A VHF/UHF radio navigational aid that provide two

radio beams which can be used as an ideal flight path. Two transmitters are located at the runway:

Localizer – Provides azimuth. Glide Slope – Provides elevation information.

Both transmitters radiates two electromagnetic energypatterns that overlaps one another.

Instrument Landing System (ILS)•The emission patterns of the localizer and glide slope signals

The narrow area of overlapdefines the ideal flightpath by providing: Azimuth Approximate range Elevation reference

Localizer frequency range: 108-112MHz

Spaced at 50KHz with fc of odd frequencies.

Instrument Landing System (ILS)

Glide Slope frequency range: 328 – 336MHz Localizer and Glide Slope frequencies are paired. At the cockpit, the pilot sets the Localizer frequency

and the system will automatically set the Glide Slope. Front Course Approach – the combination of Localizer

and Glide Slope. Fly to the needle.

At the back course, Glide slope is absent. Fly away from the needle.

MARKER BEACON Outer Marker- a transmitter antenna located about

6miles from the end of the runway that gives distanceinformation. Transmits vertical cone (elliptical) signal at 75MHz. The modulation is repeated Morse-style dashes of a

400 Hz tone. The cockpit indicator is a blue lamp that flashes in

unison with the received audio code.

MARKER BEACON Middle Marker – located 3500ft away from the

threshold. It is modulated with a 1.3 kHz tone as alternating Morse-

style dots and dashes at the rate of two per second. The cockpit indicator is an amber lamp that flashes in

unison with the received audio code. Inner Marker - Ideally at a distance of approximately

1,000 ft (300 m) from the threshold. The modulation is Morse-style dots at 3 kHz. The cockpit indicator is a white lamp that flashes in

unison with the received audio code.

MARKER BEACON

Instrument Landing System (ILS)

Instrument Landing System (ILS)

Loc.OSC

IF Audio Det.

RFMixer 90Hz

Filter150Hz Filter

Flag

Deviation

MICROWAVE LANDING SYSTEM MLS employs 5GHz transmitters at the landing place

which use passive electronically scanned arrays to sendscanning beams towards approaching aircraft. Anaircraft that enters the scanned volume uses a specialreceiver that calculates its position by measuring thearrival times of the beams.

Is an all-weather, precision landing system originallyintended to replace or supplement the InstrumentLanding System (ILS). A wide selection of channels to avoid interference with

other nearby airports (200 channels). Excellent performance in all weather. A small "footprint" at the airports.

MICROWAVE LANDING SYSTEM

• MLS used a singlefrequency, broadcastingthe azimuth and altitudeinformation one after theother.

MICROWAVE LANDING SYSTEM The system may be divided into five functions:

Approach azimuth Back azimuth Approach elevation Range Data communications

Approach azimuth guidance - The azimuth stationtransmits MLS angle and data on one of 200 channelswithin the frequency range of 5031 to 5091 MHz and isnormally located about 1,000 feet (300 m) beyond the stopend of the runway.

MICROWAVE LANDING SYSTEM The azimuth coverage:

Laterally, at least 40degrees on either side of therunway centerline in astandard configuration.

In elevation, up to an angleof 15 degrees and to at least20,000 feet (6 km), and inrange, to at least 20 nauticalmiles (37 km).

MICROWAVE LANDING SYSTEM Elevation guidance

The elevation stationtransmits signals on thesame frequency as theazimuth station.

Located about 400 feetfrom the side of therunway between runwaythreshold and thetouchdown zone.

MICROWAVE LANDING SYSTEM Range guidance

The MLS Precision Distance Measuring Equipment(DME/P) functions the same as the navigation DME, butthere are some technical differences.

The beacon transponder operates in the frequency band962 to 1105 MHz and responds to an aircraft interrogator.

The MLS DME/P accuracy is improved to be consistentwith the accuracy provided by the MLS azimuth andelevation stations.

A DME/P channel is paired with the azimuth andelevation channel.

MICROWAVE LANDING SYSTEM Data communications

The data transmission can include both the basic andauxiliary data words.

All MLS facilities transmit basic data. Where needed, auxiliary data can be transmitted. MLS data are transmitted throughout the azimuth (and

back azimuth when provided) coverage sectors. Representative data include:

Station identification, Exact locations of azimuth,elevation and DME/P stations, Ground equipmentperformance level, DME/P channel and status.

MICROWAVE LANDING SYSTEM Auxiliary data content:

3-D locations of MLSequipment.

Waypoint coordinates. Runway conditions and

Weather etc.

VHF OMNIDIRECTIONAL RANGE Is a type of radio navigation system for aircraft. A VOR ground station broadcasts a VHF radio

composite signal including the station's identifier inMorse code (and sometimes a voice identifier).

The data allows the airborne receiving equipment toderive a magnetic bearing from the station to theaircraft.

The intersection of two radials from different VORstations on a chart allows for a "fix" or approximateposition of the aircraft.

VHF OMNIDIRECTIONAL RANGE

VHF OMNIDIRECTIONAL RANGE

VHF OMNIDIRECTIONAL RANGE An aircraft could follow a specific path from station to

station by tuning the successive stations on the VORreceiver.

Then either following the desired course on a RadioMagnetic Indicator, or setting it on a Course DeviationIndicator (CDI) or a Horizontal Situation Indicator(HSI, a more sophisticated version of the VORindicator) and keeping a course pointer centered onthe display.

VHF OMNIDIRECTIONAL RANGE VORs are assigned radio channels between 108.0 MHz

and 117.95 MHz (with 50 kHz spacing); this is in theVHF range.

The VOR uses the phase relationship between areference-phase and a rotating-phase signal to encodedirection.

The carrier signal is Omni-directional and contains anamplitude modulated (AM) station Morse code orvoice identifier.

The reference 30 Hz signal is frequency modulated ona 9960 Hz sub-carrier.

VHF OMNIDIRECTIONAL RANGE

VHF OMNIDIRECTIONAL RANGE A second, amplitude modulated (AM) 30 Hz signal is

derived from the rotation of a directional antennaarray 30 times per second.

Although older antennas were mechanically rotated,current installations scan electronically to achieve anequivalent result with no moving parts.

When the signal is received in the aircraft, the two30 Hz signals are detected and then compared todetermine the phase angle between them.

The phase angle is equal to the direction from thestation to the aircraft, in degrees from local magneticnorth, and is called the "radial."

VHF OMNIDIRECTIONAL RANGE OBS – Omni Bearing

Selector. In the illustration on the

right, notice that theheading ring is set with 360degrees (North) at theprimary index.

The needle is centered andthe To/From indicator isshowing "TO".

VHF OMNIDIRECTIONAL RANGE In many cases the VOR stations have co-located DME

(Distance Measuring Equipment) or military TACAN(TACtical Air Navigation).

A VOR radial with DME distance allows a one-stationposition fix.

VORTACs and VOR-DMEs use a standardized schemeof VOR frequency.

DISTANCE MEASURING EQUIPMENT Distance measuring equipment (DME) is a

transponder-based radio navigation technology thatmeasures distance by timing the propagation delay ofVHF or UHF radio signals (Int:1025 to 1150 MHz,Xponder: Tx,962 to 1150 MHz; Rx, 962 to 1213 MHz).

Aircraft use DME to determine their distance from aland-based transponder by sending and receivingpulse pairs - two pulses of fixed duration andseparation.

DME is similar to Secondary Surveillance Radar (SSR),except in reverse.

DME can be co-located with VOR, ILS, or MLS.

DISTANCE MEASURING EQUIPMENT The DME system is composed of a UHF

transmitter/receiver (interrogator) in the aircraft and aUHF receiver/transmitter (transponder) on theground.

The aircraft interrogates the ground transponder witha series of pulse-pairs (interrogations).

The ground station replies with an identical sequenceof reply pulse-pairs with a precise time delay (typically50 microseconds).

The DME receiver in the aircraft searches for pulse-pairs (X-mode= 12 microsecond spacing) with thecorrect time interval between them.

The correct time between pulse pairs is determined byeach individual aircraft's particular interrogationpattern.

The aircraft interrogator locks on to the DME groundstation once it understands that the particular pulsesequence is the interrogation sequence it sent outoriginally.

Once the receiver is locked on, it has a narrowerwindow in which to look for the echoes and can retainlock.

DISTANCE MEASURING EQUIPMENT

DISTANCE MEASURING EQUIPMENT

Slant Distance – is the measured distance between DME transponder station and aircraft interrogator.

Slant Distance = (Ttot-50μsec)/2(12.36), NM

Accuracy : ±0.1NM, about ± 185m.

Surveillance System Primary Surveillance Radar (PSR)

The radar transmitter sends out a pulse of radio energy,of which a very small proportion is reflected from thetarget aircraft back to the radar receiver.

The orientation of the radar antenna provides thebearing of the aircraft from the ground station.

The time taken for the pulse to reach the target andreturn provides a measure of the distance of the targetfrom the ground station.

The bearing and distance of the target then displayed tothe Air Traffic Controller.

Surveillance System

Surveillance System

Surveillance System Secondary Surveillance Radar (SSR)

The purpose of this system is to improve the ability todetect and identify aircraft while it additionally providesautomatically the Flight Level (pressure altitude) of aflight.

An SSR continuously transmits interrogation pulses asits antenna rotates, or is electronically scanned in space.

A transponder on an aircraft that is within line-of-sight'listens' for the SSR interrogation signal and sends backa reply that provides aircraft information.

The reply sent depends on the mode that wasinterrogated.

Surveillance System Secondary Surveillance Radar (SSR)

The aircraft is then displayed as a tagged icon on the controller's radar screen at the calculated bearing and range.

An aircraft without an operating transponder still may be observed by primary radar, but would be displayed to the controller without the benefit of SSR derived data.

A cross-band beacon is used, which simply means that the interrogation pulses are at one frequency (1030 MHz) and the reply pulses are at a different frequency (1090 MHz).

Surveillance System Secondary Surveillance Radar (SSR) The SSR interrogation format (sometimes called

uplink format) is very simple. Consisting of two pulses (P1 and P3) of 0.8 µs width

which are separated by a certain time – thatdetermines the mode of interrogation.

P2 is used for side lobe suppression.

Surveillance System

P1 P3

P2

T

Surveillance System Military Mode 1: T=3(±0.2)μsec.

used to support 32 military identification codes (although 4096 ‘mode 1’ codes could also be used).

Normally, the 32 codes could be used to indicate role / mission / type.

However, this mode itself is not in common use in a normal peacetime environment.

Military Mode 2: T=5(±0.2)μsec. provides 4096 ID codes for military use (as for mode A). Normally used to identify an individual aircraft airframe.

Surveillance System Military Mode 3/ Civil Mode A: T=8(±0.2)μsec.

Provides 4096 ID codes for civil / military use. Normally,the 32 codes could be used to indicate role / mission /type.

The commonly used mode. Civil Mode B: T=17(±0.2)μsec.

Originally defined but never been used. Civil Mode C: T=21(±0.2)μsec.

Pressure Altitude Extraction.

Surveillance System Civil Mode D: T=25(±0.2)μsec.

Not Used. Mode S: Selective Unique Interrogation.

providing an individual address capability (24-bit addresses are allocated to every airframe by their registering authority).

Increase in data integrity by the use of a parity check mechanism.

Surveillance System

Surveillance System

Side Lobe Suppression P2 comparison

Future of Air Navigation System

Communication Improvements This involved a transition from voice communications to

digital communications. Aircraft Communications Addressing and Reporting

System (ACARS) is the medium used. An application was hosted on the airplane known as

Controller Pilot Data Link Communication (CPDLC).

Future of Air Navigation System

Navigation Improvements This involves a transition from Inertial Navigation to

Satellite Navigation using the GPS satellites and WAAS. Surveillance Improvements

This involves the transition from voice reports (based oninertial position) to automatic digital reports.

FANS procedural control The improvements to CNS allow new procedures which

reduce the separation standards for FANS controlledairspace.