Surveillance radar approach
Encyclopedia
In aviation
, Approach Surveillance Radar (ASR or SRA) is a type of radar instrument approach
provided with active assistance from Air Traffic Control
. The only airborne radio equipment required for radar
approaches is a functioning radio transmitter and receiver
. The radar controller vectors the aircraft
to align it with the runway
centerline. The controller continues the vectors to keep the aircraft on course until the pilot can complete the approach
and landing by visual reference to the surface.
There are two types of radar approaches: Precision (PAR)
and Surveillance (ASR).
A radar approach may be given to any aircraft upon request and may be offered to pilots of aircraft in distress or to expedite traffic; however, an ASR might not be approved unless there is an ATC operational requirement, or in an unusual or emergency situation. Acceptance of a PAR or ASR by a pilot does not waive the prescribed weather minimums for the airport or for the particular aircraft operator concerned. The decision to make a radar approach when the reported weather is below the established minimums rests with the pilot. PAR and ASR minimums are published on separate pages in the FAA Terminal Procedures Publication.
1. A Precision Approach (PAR) is one in which a controller provides highly accurate navigational guidance in
azimuth and elevation to a pilot. Pilots are given headings to fly, to direct them to, and keep their aircraft aligned
with the extended centerline of the landing runway. They are told to anticipate glidepath interception
approximately 10 to 30 seconds before it occurs and when to start descent. The published decision height will be given
only if the pilot requests it. If the aircraft is observed to deviate above or below the glidepath, the pilot is given
the relative amount of deviation by use of terms “slightly” or “well” and is expected to adjust the aircraft rate
of descent/ascent to return to the glidepath. Trend information is also issued with respect to the elevation of
the aircraft and may be modified by the terms “rapidly” and “slowly” (e.g., “well above glidepath, coming
down rapidly”). Range from touchdown is given at least once each mile. If an aircraft is observed by the
controller to proceed outside of specified safety zone limits in azimuth and/or elevation and continue to operate
outside these prescribed limits, the pilot will be directed to execute a missed approach
or to fly a specified
course unless the pilot has the runway environment (runway, approach lights, etc.) in sight. Navigational
guidance in azimuth and elevation is provided the pilot until the aircraft reaches the published decision height. Advisory
course and glidepath information is furnished by the controller until the aircraft passes over the landing
threshold, at which point the pilot is advised of any deviation from the runway centerline. Radar service is
automatically terminated upon completion of the approach.
2. A Surveillance Approach (SRA) is one in which a controller provides navigational guidance in azimuth only.
The pilot is furnished headings to fly to align the aircraft with the extended centerline of the landing runway.
Since the radar information used for a surveillance
approach is considerably less precise than that used for a
precision approach, the accuracy of the approach will not be as great and higher minimums will apply.
Guidance in elevation is not possible but the pilot will be advised when to commence descent to the minimum decision altitude (MDA) or, if appropriate, to an intermediate stepdown fix Minimum Crossing Altitude (MCA) and subsequently to the prescribed MDA. In addition, the pilot will be advised of the location of the MAP prescribed for the procedure
and the aircraft position each mile on final from the runway, airport, heliport, or MAP, as appropriate. If
requested by the pilot, recommended altitudes will be issued at each mile, based on the descent gradient
established for the procedure, down to the last mile that is at or above the MDA. Normally, navigational
guidance will be provided until the aircraft reaches the MAP. Controllers will terminate guidance and instruct
the pilot to execute a missed approach unless at the MAP the pilot has the runway, airport, or heliport in sight
or, for a helicopter point-in-space approach, the prescribed visual reference with the surface is established.
Also, if, at any time during the approach the controller considers that safe guidance for the remainder of the
approach cannot be provided, the controller will terminate guidance and instruct the pilot to execute a missed
approach. Similarly, guidance termination and missed approach will be effected upon pilot request and, for
civil aircraft only, controllers may terminate guidance when the pilot reports the runway, airport, heliport or
visual surface route (point-in-space approach) in sight or otherwise indicates continued guidance is not
required. Radar service is automatically terminated at the completion of a radar approach.
Aviation
Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...
, Approach Surveillance Radar (ASR or SRA) is a type of radar instrument approach
Instrument approach
For aircraft operating under instrument flight rules , an instrument approach or instrument approach procedure is a series of predetermined maneuvers for the orderly transfer of an aircraft under instrument flight conditions from the beginning of the initial approach to a landing, or to a point...
provided with active assistance from Air Traffic Control
Air traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
. The only airborne radio equipment required for radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
approaches is a functioning radio transmitter and receiver
Transponder (aviation)
A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation...
. The radar controller vectors the aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
to align it with the runway
Runway
According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...
centerline. The controller continues the vectors to keep the aircraft on course until the pilot can complete the approach
Final approach (aviation)
A final approach is the last leg in an aircraft's approach to landing. In aviation radio terminology, it is often shortened to "final".In a standard airport landing pattern, which is usually used under visual meteorological conditions , aircraft turn from base leg to final within one to two miles...
and landing by visual reference to the surface.
There are two types of radar approaches: Precision (PAR)
Precision Approach Radar
Precision approach radar is a type of radar guidance system designed to provide lateral and vertical guidance to an aircraft pilot for landing, until the landing threshold is reached. After the aircraft reaches the decision height or decision altitude , guidance is advisory only...
and Surveillance (ASR).
A radar approach may be given to any aircraft upon request and may be offered to pilots of aircraft in distress or to expedite traffic; however, an ASR might not be approved unless there is an ATC operational requirement, or in an unusual or emergency situation. Acceptance of a PAR or ASR by a pilot does not waive the prescribed weather minimums for the airport or for the particular aircraft operator concerned. The decision to make a radar approach when the reported weather is below the established minimums rests with the pilot. PAR and ASR minimums are published on separate pages in the FAA Terminal Procedures Publication.
1. A Precision Approach (PAR) is one in which a controller provides highly accurate navigational guidance in
azimuth and elevation to a pilot. Pilots are given headings to fly, to direct them to, and keep their aircraft aligned
with the extended centerline of the landing runway. They are told to anticipate glidepath interception
approximately 10 to 30 seconds before it occurs and when to start descent. The published decision height will be given
only if the pilot requests it. If the aircraft is observed to deviate above or below the glidepath, the pilot is given
the relative amount of deviation by use of terms “slightly” or “well” and is expected to adjust the aircraft rate
of descent/ascent to return to the glidepath. Trend information is also issued with respect to the elevation of
the aircraft and may be modified by the terms “rapidly” and “slowly” (e.g., “well above glidepath, coming
down rapidly”). Range from touchdown is given at least once each mile. If an aircraft is observed by the
controller to proceed outside of specified safety zone limits in azimuth and/or elevation and continue to operate
outside these prescribed limits, the pilot will be directed to execute a missed approach
Missed approach
Missed approach is an instrument flight rules procedure which is a standard component segment of an instrument approach. Generally, if the pilot flying or the pilot in command determines by the time the aircraft is at the decision height or missed approach point , that the runway or its...
or to fly a specified
course unless the pilot has the runway environment (runway, approach lights, etc.) in sight. Navigational
guidance in azimuth and elevation is provided the pilot until the aircraft reaches the published decision height. Advisory
course and glidepath information is furnished by the controller until the aircraft passes over the landing
threshold, at which point the pilot is advised of any deviation from the runway centerline. Radar service is
automatically terminated upon completion of the approach.
2. A Surveillance Approach (SRA) is one in which a controller provides navigational guidance in azimuth only.
The pilot is furnished headings to fly to align the aircraft with the extended centerline of the landing runway.
Since the radar information used for a surveillance
Surveillance
Surveillance is the monitoring of the behavior, activities, or other changing information, usually of people. It is sometimes done in a surreptitious manner...
approach is considerably less precise than that used for a
precision approach, the accuracy of the approach will not be as great and higher minimums will apply.
Guidance in elevation is not possible but the pilot will be advised when to commence descent to the minimum decision altitude (MDA) or, if appropriate, to an intermediate stepdown fix Minimum Crossing Altitude (MCA) and subsequently to the prescribed MDA. In addition, the pilot will be advised of the location of the MAP prescribed for the procedure
and the aircraft position each mile on final from the runway, airport, heliport, or MAP, as appropriate. If
requested by the pilot, recommended altitudes will be issued at each mile, based on the descent gradient
established for the procedure, down to the last mile that is at or above the MDA. Normally, navigational
guidance will be provided until the aircraft reaches the MAP. Controllers will terminate guidance and instruct
the pilot to execute a missed approach unless at the MAP the pilot has the runway, airport, or heliport in sight
or, for a helicopter point-in-space approach, the prescribed visual reference with the surface is established.
Also, if, at any time during the approach the controller considers that safe guidance for the remainder of the
approach cannot be provided, the controller will terminate guidance and instruct the pilot to execute a missed
approach. Similarly, guidance termination and missed approach will be effected upon pilot request and, for
civil aircraft only, controllers may terminate guidance when the pilot reports the runway, airport, heliport or
visual surface route (point-in-space approach) in sight or otherwise indicates continued guidance is not
required. Radar service is automatically terminated at the completion of a radar approach.
- note to reader. Pilots should check Radar services at the airport they desire to land in order to determine if Radar Approaches are available. Radar Approaches are used a lot by many Navy/Marine Corps Pilots as a default to emergency situations, thus many Navy/Marine Pilots are proficient in Radar approaches.