A Transponder Landing System
Content
TLS-TRANSPONDER LANDING
SYSTEM
A transponder landing system (TLS) is an all-weather, precision landing system that
uses existing airborne transponder and instrument landing system (ILS) equipment
to create a precision approach at a location where an ILS would normally not be
available.
DESCRIPTION
Conventional ILS systems broadcast using a number of "single purpose" antennas.
One, located just off the end of the runway, provides a fan-shaped signal for
azimuth direction (side to side) and another located beside the runway provides
elevation to indicate a standard glideslope. ILS installations also include one or
more "marker beacons" located off the end of the runway to provide distance
indications as the aircraft approaches the runway. This complex set of antennas is
expensive to install and maintain, and are often difficult to site in built-up areas
WORKING
The TLS facility interrogates the transponders of all aircraft within 60 nautical miles
(110 km). After receiving a response, TLS determines the aircraft's location using
three sets of antenna arrays: one for horizontal position using monopulse
techniques, the other for vertical monopulse and a third for trilateration. TLS then
calculates the position of all aircraft using the transponder responses. Any aircraft
conducting a Precision Approach Radar PAR-type approach can be viewed on the
TLS PAR format console displaying azimuth and elevation. Up to five different
aircraft may be viewed independently on five different consoles to assist a PAR
controller with a conventional PAR talk-down approach. For one aircraft conducting
an ILS approach, the TLS produces a signal that the aircraft would "see" if they were
located at that location and approaching a conventional ILS system, and then
broadcasts that signal to the aircraft. The aircraft's ILS receivers receive a signal
that is indistinguishable from a normal ILS signal, and displays this information on
standard ILS glideslope and localizer displays. TLS can also produce marker beaconlike audio to indicate distance at appropriate times during the approach. All the pilot
has to do is tune in the TLS system as if it were an ILS.
SYSTEM
A transponder landing system (TLS) is an all-weather, precision landing system that
uses existing airborne transponder and instrument landing system (ILS) equipment
to create a precision approach at a location where an ILS would normally not be
available.
DESCRIPTION
Conventional ILS systems broadcast using a number of "single purpose" antennas.
One, located just off the end of the runway, provides a fan-shaped signal for
azimuth direction (side to side) and another located beside the runway provides
elevation to indicate a standard glideslope. ILS installations also include one or
more "marker beacons" located off the end of the runway to provide distance
indications as the aircraft approaches the runway. This complex set of antennas is
expensive to install and maintain, and are often difficult to site in built-up areas
WORKING
The TLS facility interrogates the transponders of all aircraft within 60 nautical miles
(110 km). After receiving a response, TLS determines the aircraft's location using
three sets of antenna arrays: one for horizontal position using monopulse
techniques, the other for vertical monopulse and a third for trilateration. TLS then
calculates the position of all aircraft using the transponder responses. Any aircraft
conducting a Precision Approach Radar PAR-type approach can be viewed on the
TLS PAR format console displaying azimuth and elevation. Up to five different
aircraft may be viewed independently on five different consoles to assist a PAR
controller with a conventional PAR talk-down approach. For one aircraft conducting
an ILS approach, the TLS produces a signal that the aircraft would "see" if they were
located at that location and approaching a conventional ILS system, and then
broadcasts that signal to the aircraft. The aircraft's ILS receivers receive a signal
that is indistinguishable from a normal ILS signal, and displays this information on
standard ILS glideslope and localizer displays. TLS can also produce marker beaconlike audio to indicate distance at appropriate times during the approach. All the pilot
has to do is tune in the TLS system as if it were an ILS.
