Due to limited information provided in the AIM, and by popular demand, I'm expanding on information provided in the AIM concerning radar approaches.................
There are two basic types of radar approaches (or GCAs, Ground Controlled Approaches); Airport Surveillance Radar (ASR) and Precision Approach Radar (PAR). The surveillance approach provides course and range information and is classified as a non-precision approach, while the PAR additionally provides glidepath information, thus giving it precision capability. On ASR approaches, the final controller will, on request, provide recommended altitudes on final to the last whole mile that is at-or-above the published MDA. Recommended altitudes are computed from the start descent point to the threshold of the runway. ASRs have an accuacy of bringing the pilot within 500 feet of either runway edge, while PARs are accurate to within 25 feet either side of runway centerline. For this reason, pilots flying an ASR to parallel runways should take caution for assuring that they're lined up with the correct runway upon breakout. ATC uses the normal controller's scope to perform ASR approaches, whereas PAR approaches utilize an entirely separate radar system from the normal ATC radar.
If available, prior to flying a GCA, select a back-up approach (compatible with existing WX and aircraft capabilities) to use if the controller's radar goes down, or if the aircraft goes NORDO during the approach final segment. It is important to have a back-up plan since radar approaches are so comm-dependant. In the event of lost comm, the pilot is automatically cleared to fly any published approach unless ATC previously issued a specific IAP to fly in the event of lost comm. To insure lost comm hasn't occurred, the pilot should attempt contact with ATC if no transmissions are heard for:
-1 minute while being vectored in the radar pattern
-15 seconds while on ASR final
-5 seconds while on PAR final
If the pilot goes NORDO, or the ATC radar fails and you're unable to maintain VFR, transition to your back-up approach. Intercept the approach at the nearest point that will allow for a normal descent rate and not compromise safety. Maintain the last assigned altitude or MSA/ESA, whichever is higher, until established on a segment of the published approach. If no back-up approach is available that's compatible with your aircraft or with the exisiting WX, advise ATC upon initial contact of your intentions in the event of lost comm. If local conditions dictate, ATC may specify which approach to fly in the event of lost comm. Either way, it's the pilot's responsibility to determine the adequacy of any NORDO procedures issued by ATC.
Since the radar approach relies entirely upon voice comm instructions issued by ATC, it is imperative that the pilot repeat all headings, altitudes (departing and assigned), and altimeter settings, like you'd normally do, until the final controller advises "do not acknowlege further transmissions". After this point, the final controller will query you if he needs a reply on anything, such as acknowleging landing clearance. And the standard still applies of keeping radio comm clear/concise/correct, especially during high-density radar traffic operations.
During both types of radar approaches, ATC will vector you to the final segment prior to handoff to the final controller. Each radar approach is on it's own discreet frequency so as not to be interfered with by other transmissions; you'll only hear you and the final controller once handed off to his frequency. The vector to dogleg final (transition to final) encompasses all maneuvering up to a point where the aircraft is approximately 8 NM from touchdown and inbound. ATC will, at a minimum, provide the pilot with position information at least once prior to handoff to the final controller. Prior to this time, have your appropriate approach/landing checks accomplished (per your ops), and have a descent rate predetermined. For example on the PAR, if the glidepath is known to be 3 degrees, and your final approach groundspeed is 160 kts, then your initial descent rate would be 800 fpm.
(groundspeed x 10)/2 ; or (160 x 10)/2= 800 fpm for a 3 degree GP.
Final segment ASR: The ATC final controller will inform the pilot of the runway to which the approach will be made, the straight-in MDA (if a straight-in), the MAP location, and advanced notice of where the descent to MDA will begin. If terminating an ASR to a circling approach, the pilot must furnish the aircraft's approach category to the final controller, the final controller will then issue the circling MDA appropriate to the runway the pilot is circling to and the aircraft's category, as applicable. On final, upon reaching the descent point, the final controller will advise the pilot to "begin descent," advising the pilot of any descent restrictions if any exist. Use normal non-precision descent rates in order to arrive at MDA with time to acquire the runway environment and make a normal descent to landing. The final controller will issue course guidance when required and will give you range information each mile while on final. This guidance will be provided until the aircraft is over the MAP, unless the pilot requests discontinuation of guidance. The final controller will advise when you're at the MAP. At that point, the pilot must advise that he either 1. "Runway in sight, landing assured"; or 2. "Executing missed approach" with reason, at which point ATC will issue missed approach instructions (as before, in the event of any lost comm at this time, follow your lost comm instructions issued by ATC.) The final controller will also, during the descent on final, issue the landing clearance to the pilot that he's pre-coordinated with tower. Radar approaches do not utilize frequency changes after switching to the final controller, since the final controller will also initially work your missed approach, were you to do one. On landing rollout, switch to tower and advise them you're on frequency. Ex: "Tower, Harlot 41, GCA rollout..." Upon request, the final controller will provide the pilot with recommended altitudes on final at each mile to the last whole mile that is at or above the published MDA. Due to possible different locations of the MAP, recommend altitudes may place you at or slightly prior to, the MAP. This should be considered in relation to the normal VDP for your particular aircraft, since depending on the MAP location, descent from the MDA, once runway is in sight, often will have to be initiated prior to reaching the MAP in order to allow for a normal descent to landing.
Comm will sound like this:
"8 miles from touchdown, slightly left of course, turn right heading 140, begin descent."
"7 miles from touchdown, turn left heading 130, recommended altitude 6,500" (assuming recommended altitudes requested)
"on course"
"6 miles from touchdown, on course, recommended altitude 5,700"
and so on.....
Final Segment: PAR: PAR final approach starts when the aircraft is within the range of the PAR radar, which is separate from the normal ATC radar. This is normally at the same 8 NM from touchdown point as with the ASR approach. Upon switching to the final controller, and approximately 10-30 seconds prior to reaching the descent point, the final controller will usually ask what the aircraft's heading is reading so he can use this as a baseline for corrections compared to what he sees on his scope. Additionally, the final controller will advise the pilot that he's approaching the glidepath and additionally that "wheels should be down" (for military). Upon reaching the descent point, the final controller will advise "begin descent" then begin the azimuth and elevation corrections about every 5 seconds. Establish the predetermined rate of descent, and utilize power or drag devices as required to maintain desired airspeed or AOA. When the airspeed or AOA and and glidepath are stabilized, take quick note of the power, attitude and VVI, and utilize these indications as a baseline for corrections for the remainder of the approach. ATC will issue course and glidepath guidance and will provide corrections along with trend information. Examples: (note: no callsigns used since you're on a discreet frequency)
"7 miles from touchdown, on glidepath, on course."
"Slightly below glidepath, on course, 6 miles from touchdown"
"slightly below glidepath going further below, 5 miles from touchdown"
"slightly below glidepath coming up, slightly left of course, turn right heading 135, 4 miles from touchdown.."
Position information for course will be noted as slightly/well left/right; and for glidepath will slightly/well above, slightly/well/dangerously below. Trend information will be given as "going further below", etc. As with an ILS approach, make all turns within the "heading bars" on the HSI. In any event, course corrections from ATC won't be much more than 3-5 degrees. Follow corrections as soon as ATC gives them. For glidepath corrections, pitch changes of no more than 1 degree are normally sufficient. Heading corrections should also not be made with an angle of bank more than the correction to be made, otherwise an overshoot could result. Do not exceed 1/2 standard rate turn when makiing heading corrections once the descent has been made on the final segment. After a new heading is issued by the final controller, he assumes that heading is being maintained. Additional corrections are being made based on the last heading given.
The final controller will advise the pilot when he's reached the published DH. DH is determined in the cockpit as read on the altimeter, or when advised by the final controller, whichever occurs first. The final controller will continue to provide advisory course and glidepath guidance until the aircraft passes over the approach landing threshold at which time the controller will advise "over the landing threshold". At DH, if proceeding missed, advise the final controller and the procedures are the same as with the ASR. If landing, advise the final controller when you have the runway in sight with landing assured, and upon rollout, contact/switch to tower and advise them. Ex: "Tower, Harlot 11, PAR rollout". Like the ILS, the PAR is a straight-in procedure only, with no circling minima existant. PAR are certified down to 100' and 1/4 mile, more accurate than the ILS (Cat 1) 200' and 1/2.
No-Gyro Final Segment: If your heading indicator or HSI should become inoperative during the approach or prior, advise ATC and request a No-Gyro approach. The final segment for this approach can be either ASR or PAR. Perform turns during transition to final by establishing an angle of bank that will approximate a standard rate turn, not to exceed 30 degrees. Perform turns on the final segment by establishing an angle of bank on the attitude indicator that will approximate a 1/2 standard rate turn. If unable to comply with this, advise the final controller so he can manually determine lead-points for turn and heading corrections. Initiate turns immediately upon hearing "turn left/right". Stop turns when hearing "stop turn". Acknowlege these commands until advised by the final controller to no longer acknowlege further transmissions. Do not begin using half-standard rate turns until advised to do so by ATC. ATC may want to continue standard rate turns even on final if abnormal conditions exist such as strong crosswinds or turbulance.
MD
There are two basic types of radar approaches (or GCAs, Ground Controlled Approaches); Airport Surveillance Radar (ASR) and Precision Approach Radar (PAR). The surveillance approach provides course and range information and is classified as a non-precision approach, while the PAR additionally provides glidepath information, thus giving it precision capability. On ASR approaches, the final controller will, on request, provide recommended altitudes on final to the last whole mile that is at-or-above the published MDA. Recommended altitudes are computed from the start descent point to the threshold of the runway. ASRs have an accuacy of bringing the pilot within 500 feet of either runway edge, while PARs are accurate to within 25 feet either side of runway centerline. For this reason, pilots flying an ASR to parallel runways should take caution for assuring that they're lined up with the correct runway upon breakout. ATC uses the normal controller's scope to perform ASR approaches, whereas PAR approaches utilize an entirely separate radar system from the normal ATC radar.
If available, prior to flying a GCA, select a back-up approach (compatible with existing WX and aircraft capabilities) to use if the controller's radar goes down, or if the aircraft goes NORDO during the approach final segment. It is important to have a back-up plan since radar approaches are so comm-dependant. In the event of lost comm, the pilot is automatically cleared to fly any published approach unless ATC previously issued a specific IAP to fly in the event of lost comm. To insure lost comm hasn't occurred, the pilot should attempt contact with ATC if no transmissions are heard for:
-1 minute while being vectored in the radar pattern
-15 seconds while on ASR final
-5 seconds while on PAR final
If the pilot goes NORDO, or the ATC radar fails and you're unable to maintain VFR, transition to your back-up approach. Intercept the approach at the nearest point that will allow for a normal descent rate and not compromise safety. Maintain the last assigned altitude or MSA/ESA, whichever is higher, until established on a segment of the published approach. If no back-up approach is available that's compatible with your aircraft or with the exisiting WX, advise ATC upon initial contact of your intentions in the event of lost comm. If local conditions dictate, ATC may specify which approach to fly in the event of lost comm. Either way, it's the pilot's responsibility to determine the adequacy of any NORDO procedures issued by ATC.
Since the radar approach relies entirely upon voice comm instructions issued by ATC, it is imperative that the pilot repeat all headings, altitudes (departing and assigned), and altimeter settings, like you'd normally do, until the final controller advises "do not acknowlege further transmissions". After this point, the final controller will query you if he needs a reply on anything, such as acknowleging landing clearance. And the standard still applies of keeping radio comm clear/concise/correct, especially during high-density radar traffic operations.
During both types of radar approaches, ATC will vector you to the final segment prior to handoff to the final controller. Each radar approach is on it's own discreet frequency so as not to be interfered with by other transmissions; you'll only hear you and the final controller once handed off to his frequency. The vector to dogleg final (transition to final) encompasses all maneuvering up to a point where the aircraft is approximately 8 NM from touchdown and inbound. ATC will, at a minimum, provide the pilot with position information at least once prior to handoff to the final controller. Prior to this time, have your appropriate approach/landing checks accomplished (per your ops), and have a descent rate predetermined. For example on the PAR, if the glidepath is known to be 3 degrees, and your final approach groundspeed is 160 kts, then your initial descent rate would be 800 fpm.
(groundspeed x 10)/2 ; or (160 x 10)/2= 800 fpm for a 3 degree GP.
Final segment ASR: The ATC final controller will inform the pilot of the runway to which the approach will be made, the straight-in MDA (if a straight-in), the MAP location, and advanced notice of where the descent to MDA will begin. If terminating an ASR to a circling approach, the pilot must furnish the aircraft's approach category to the final controller, the final controller will then issue the circling MDA appropriate to the runway the pilot is circling to and the aircraft's category, as applicable. On final, upon reaching the descent point, the final controller will advise the pilot to "begin descent," advising the pilot of any descent restrictions if any exist. Use normal non-precision descent rates in order to arrive at MDA with time to acquire the runway environment and make a normal descent to landing. The final controller will issue course guidance when required and will give you range information each mile while on final. This guidance will be provided until the aircraft is over the MAP, unless the pilot requests discontinuation of guidance. The final controller will advise when you're at the MAP. At that point, the pilot must advise that he either 1. "Runway in sight, landing assured"; or 2. "Executing missed approach" with reason, at which point ATC will issue missed approach instructions (as before, in the event of any lost comm at this time, follow your lost comm instructions issued by ATC.) The final controller will also, during the descent on final, issue the landing clearance to the pilot that he's pre-coordinated with tower. Radar approaches do not utilize frequency changes after switching to the final controller, since the final controller will also initially work your missed approach, were you to do one. On landing rollout, switch to tower and advise them you're on frequency. Ex: "Tower, Harlot 41, GCA rollout..." Upon request, the final controller will provide the pilot with recommended altitudes on final at each mile to the last whole mile that is at or above the published MDA. Due to possible different locations of the MAP, recommend altitudes may place you at or slightly prior to, the MAP. This should be considered in relation to the normal VDP for your particular aircraft, since depending on the MAP location, descent from the MDA, once runway is in sight, often will have to be initiated prior to reaching the MAP in order to allow for a normal descent to landing.
Comm will sound like this:
"8 miles from touchdown, slightly left of course, turn right heading 140, begin descent."
"7 miles from touchdown, turn left heading 130, recommended altitude 6,500" (assuming recommended altitudes requested)
"on course"
"6 miles from touchdown, on course, recommended altitude 5,700"
and so on.....
Final Segment: PAR: PAR final approach starts when the aircraft is within the range of the PAR radar, which is separate from the normal ATC radar. This is normally at the same 8 NM from touchdown point as with the ASR approach. Upon switching to the final controller, and approximately 10-30 seconds prior to reaching the descent point, the final controller will usually ask what the aircraft's heading is reading so he can use this as a baseline for corrections compared to what he sees on his scope. Additionally, the final controller will advise the pilot that he's approaching the glidepath and additionally that "wheels should be down" (for military). Upon reaching the descent point, the final controller will advise "begin descent" then begin the azimuth and elevation corrections about every 5 seconds. Establish the predetermined rate of descent, and utilize power or drag devices as required to maintain desired airspeed or AOA. When the airspeed or AOA and and glidepath are stabilized, take quick note of the power, attitude and VVI, and utilize these indications as a baseline for corrections for the remainder of the approach. ATC will issue course and glidepath guidance and will provide corrections along with trend information. Examples: (note: no callsigns used since you're on a discreet frequency)
"7 miles from touchdown, on glidepath, on course."
"Slightly below glidepath, on course, 6 miles from touchdown"
"slightly below glidepath going further below, 5 miles from touchdown"
"slightly below glidepath coming up, slightly left of course, turn right heading 135, 4 miles from touchdown.."
Position information for course will be noted as slightly/well left/right; and for glidepath will slightly/well above, slightly/well/dangerously below. Trend information will be given as "going further below", etc. As with an ILS approach, make all turns within the "heading bars" on the HSI. In any event, course corrections from ATC won't be much more than 3-5 degrees. Follow corrections as soon as ATC gives them. For glidepath corrections, pitch changes of no more than 1 degree are normally sufficient. Heading corrections should also not be made with an angle of bank more than the correction to be made, otherwise an overshoot could result. Do not exceed 1/2 standard rate turn when makiing heading corrections once the descent has been made on the final segment. After a new heading is issued by the final controller, he assumes that heading is being maintained. Additional corrections are being made based on the last heading given.
The final controller will advise the pilot when he's reached the published DH. DH is determined in the cockpit as read on the altimeter, or when advised by the final controller, whichever occurs first. The final controller will continue to provide advisory course and glidepath guidance until the aircraft passes over the approach landing threshold at which time the controller will advise "over the landing threshold". At DH, if proceeding missed, advise the final controller and the procedures are the same as with the ASR. If landing, advise the final controller when you have the runway in sight with landing assured, and upon rollout, contact/switch to tower and advise them. Ex: "Tower, Harlot 11, PAR rollout". Like the ILS, the PAR is a straight-in procedure only, with no circling minima existant. PAR are certified down to 100' and 1/4 mile, more accurate than the ILS (Cat 1) 200' and 1/2.
No-Gyro Final Segment: If your heading indicator or HSI should become inoperative during the approach or prior, advise ATC and request a No-Gyro approach. The final segment for this approach can be either ASR or PAR. Perform turns during transition to final by establishing an angle of bank that will approximate a standard rate turn, not to exceed 30 degrees. Perform turns on the final segment by establishing an angle of bank on the attitude indicator that will approximate a 1/2 standard rate turn. If unable to comply with this, advise the final controller so he can manually determine lead-points for turn and heading corrections. Initiate turns immediately upon hearing "turn left/right". Stop turns when hearing "stop turn". Acknowlege these commands until advised by the final controller to no longer acknowlege further transmissions. Do not begin using half-standard rate turns until advised to do so by ATC. ATC may want to continue standard rate turns even on final if abnormal conditions exist such as strong crosswinds or turbulance.
MD
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