This is an informative and concise video on primary/secondary radar and transponders
Important takeaways:
Primary Radar is only displays the radar return signature of aircraft on the scope. This return signature is often referred to as a 'Primary Target' and has no information associated with it.
Secondary Radar involves an aircraft's transponder, and correlates important information to the primary target such as altitude and squawk codes.
Why do we need Radar?
In a vast majority of cases, radar separation and other radar related procedures are more efficient than nonradar operations.
2−1−3. PROCEDURAL PREFERENCE
a. Use automation procedures in preference to nonautomation procedures when workload, communications, and equipment capabilities permit.
b. Use radar separation in preference to nonradar separation when it will be to an operational advantage and workload, communications, and equipment permit.
c. Use nonradar separation in preference to radar separation when the situation dictates that an operational advantage will be gained.
NOTE− One situation may be where vertical separation would preclude excessive vectoring.
5−3−2. PRIMARY RADAR IDENTIFICATION METHODS
Identify a primary, radar beacon, or ADS−B target by using one of the following methods:
a. Observing a departing aircraft target within 1 mile of the takeoff runway end at airports with an operating control tower, provided one of the following methods of coordination is accomplished:
1. A verbal rolling/boundary notification is issued for each departure, or
2. A nonverbal rolling/boundary notification is used for each departure aircraft.
NOTE− Nonverbal notification can be accomplished via the use of a manual or electronic “drop tube” or automation.
b. Observing a target whose position with respect to a fix (displayed on the video map) or a visual reporting point (whose range and azimuth from the radar antenna has been accurately determined and made available to the controller) corresponds with a direct position report received from an aircraft, and the observed track is consistent with the reported heading or route of flight.
c. Observing a target make an identifying turn or turns of 30 degrees or more, provided the following conditions are met:
1. Except in the case of a lost aircraft, a pilot position report is received which assures you that the aircraft is within radar coverage and within the area being displayed.
2. Only one aircraft is observed making these turns.
3. For aircraft operating in accordance with an IFR clearance, have the aircraft climb to the highest minimum altitude in your area of jurisdiction before you issue a heading.
5−3−3. BEACON/ADS−B IDENTIFICATION METHODS
When using only Mode 3/A radar beacon or ADS−B to identify a target, use one of the following methods:
a. Request the pilot to activate the “IDENT” feature of the transponder/ADS−B and then observe the identification display.
PHRASEOLOGY− IDENT.
SQUAWK (code) AND IDENT.
b. Request the pilot to change to a specific discrete or nondiscrete code, as appropriate, and then observe the target or code display change.
c. Request the pilot to change their transponder/ ADS−B to “standby.” After you observe the target disappear, request the pilot to return the transponder to normal operation and then observe the reappearance of the target.
PHRASEOLOGY− SQUAWK STANDBY,
then
SQUAWK NORMAL.
5−3−4. TERMINAL AUTOMATION SYSTEMS IDENTIFICATION METHODS
TERMINAL
a. Consider an auto-acquired aircraft as identified when the data block is displayed and is visible to you, and one of the following conditions exist:
1. The radar or beacon identification procedures have been used to confirm the identity of the tagged target.
2. The aircraft is being handed off using a NAS automated system and one of the following does not appear in the data block: “CST”, “NAT”, “NT”, “AMB”, “OLD”, or “TRK”.
5−3−7. IDENTIFICATION STATUS
a. Inform an aircraft of radar contact when:
1. Initial radar identification in the ATC system is established.
2. Subsequent to loss of radar contact or terminating radar service, radar identification is reestablished.
PHRASEOLOGY− RADAR CONTACT (position if required).
b. Inform an aircraft when radar contact is lost.
PHRASEOLOGY− RADAR CONTACT LOST (alternative instructions when required).
UND ATCast Video on Radar Identification Methods
5−3−6. POSITION INFORMATION
Inform an aircraft of its position whenever radar identification is established by means of identifying turns or by any of the beacon identification methods outlined in Paragraph 5−3−3, Beacon/ADS−B Identification Methods. Position information need not be given when identification is established by position correlation or when a departing aircraft is identified within 1 mile of the takeoff runway end.
5−2−18. VALIDATION OF MODE C READOUT
Ensure that Mode C altitude readouts are valid after accepting an interfacility handoff, initial track start, track start from coast/suspend tabular list, or during and after an unreliable Mode C readout, except as follows:
a. CTRD−equipped tower cabs are not required to validate Mode C altitude readouts after accepting interfacility handoffs from TRACONs according to the procedures in Paragraph 5−4−3, Methods, subparagraph a4.
b. ERAM facilities are not required to validate Mode C altitude readouts after accepting interfacility handoffs from other ERAM facilities, except:
1. After initial track start or track start from coast is required, or
2. During and after the display of a missing, unreasonable, exceptional, or otherwise unreliable Mode C readout indicator.
c. Consider an altitude readout valid when:
1. It varies less than 300 feet from the pilot reported altitude, or
PHRASEOLOGY−
(If aircraft is known to be operating below the lowest useable flight level),
SAY ALTITUDE.
or
(If aircraft is known to be operating at or above the lowest useable flight level),
SAY FLIGHT LEVEL.
2. You receive a continuous readout from an aircraft on the airport and the readout varies by less than 300 feet from the field elevation, or
3. You have correlated the altitude information in your data block with the validated information in a data block generated in another facility (by verbally coordinating with the
other controller) and your readout is exactly the same as the readout in the other data block.
d. When unable to validate the readout, do not use the Mode C altitude information for separation.
e. Whenever you observe an invalid Mode C readout below FL 180:
1. Issue the correct altimeter setting and confirm the pilot has accurately reported the altitude.
PHRASEOLOGY− (Location) ALTIMETER (appropriate altimeter), VERIFY ALTITUDE.
2. If the altitude readout continues to be invalid:
(a) Instruct the pilot to turn off the altitude reporting part of his/her transponder and include the reason.
PHRASEOLOGY− STOP ALTITUDE SQUAWK. ALTITUDE DIFFERS BY (number of feet) FEET.
f. Whenever you observe an invalid Mode C readout at or above FL 180, unless the aircraft is descending below Class A airspace:
1. Verify that the pilot is using 29.92 inches of mercury as the altimeter setting and has accurately reported the altitude.
PHRASEOLOGY− VERIFY USING TWO NINER NINER TWO AS YOUR ALTIMETER SETTING. VERIFY FLIGHT LEVEL.
2. If the Mode C readout continues to be invalid:
(a) Instruct the pilot to turn off the altitude reporting part of his/her transponder and include the reason.
PHRASEOLOGY− STOP ALTITUDE SQUAWK. ALTITUDE DIFFERS BY (number of feet) FEET.
5−2−21. AUTOMATIC ALTITUDE REPORTING
Inform an aircraft when you want it to turn on/off the automatic altitude reporting feature of its transponder.
PHRASEOLOGY− SQUAWK ALTITUDE, or STOP ALTITUDE SQUAWK.
5−2−15. FAILURE TO DISPLAY ASSIGNED BEACON CODE
a. Inform an aircraft with an operable transponder that the assigned beacon code is not being displayed.
PHRASEOLOGY− (Identification) RESET TRANSPONDER, SQUAWK (appropriate code).
4−7−10. APPROACH INFORMATION
a. Both en route and terminal approach control sectors must provide current approach information to aircraft destined to airports for which they provide approach control services. This information must be provided on initial contact or as soon as possible thereafter. Approach information contained in the ATIS broadcast may be omitted if the pilot states the appropriate ATIS code. For pilots destined to an airport without ATIS, items 3−5 below may be omitted after the pilot advises receipt of the automated weather; otherwise, issue approach information by including the following:
1. Approach clearance or type approach to be expected if two or more approaches are published and the clearance limit does not indicate which will be used.
2. Runway if different from that to which the instrument approach is made.
3. Surface wind.
4. Ceiling and visibility if the reported ceiling at the airport of intended landing is below 1,000 feet or below the highest circling minimum, whichever is greater, or the visibility is less than 3 miles.
5. Altimeter setting for the airport of intended landing.
e. TERMINAL: If multiple runway transitions are depicted on a STAR procedure, advise pilots of the runway assignment on initial contact or as soon as possible thereafter.
Scenario #1 - Aircraft has not already been assigned a squawk code
N123AB: "Waco Approach, N123AB 6,000"
Type F6 N123AB <Enter> and see that no squawk code has been assigned (0000). Click 'Assign Code' or type F9 N123AB <Enter>
ACT_APP: "N123AB, Waco approach, squawk 2232"
N123AB: "Squawk 2232, N123AB"
The data tag should either pop up or auto track the aircraft. If neither of these happen, have the aircraft ident. Once the aircraft has been correctly identified, ensure the mode C readout differs by less than 300ft from the pilot reported altitude of 6,000.
ACT_APP: "N123AB radar contact, two zero miles south of Glen Rose. Expect the visual approach runway 19, Waco altimeter 29.92"
Scenario #2 - Aircraft has already been assigned a squawk code, with no position report
N123AB: "Waco Approach, N123AB with you"
Type F6 N123AB <Enter> and see that a squawk code has already been assigned. Assume the aircraft is still on this assigned code.
ACT_APP: "N123AB, Waco approach, Ident"
N123AB: "Ident, N123AB"
Observe the flash on the radar scope and track the aircraft. Since no pilot reported altitude was given to validate the Mode C readout, ask for the pilot to say their altitude.
ACT_APP: "N123AB radar contact, two zero miles south of Glen Rose. Say Altitude"
N123AB: "6,000 N123AB"
Ensure the mode C readout differs by less than 300ft from the pilot reported altitude of 6,000.
ACT_APP: "N123AB roger, expect the visual approach runway 19, Waco altimeter 29.92"
Scenario #3 - Aircraft has already been assigned a squawk code, with a position report
N123AB: "Waco Approach, N123AB is two zero miles south of Glen Rose at 6,000 with information Alpha"
Type F6 N123AB <Enter> and see that a squawk code has already been assigned. Assume the aircraft is still on this assigned code. Use position correlation as the radar identification method, observe that the mode C readout differs by less than 300ft from the pilot reported altitude, and give no approach information, as all required information was contained in the ATIS.
ACT_APP: "N123AB, Waco approach, radar contact"
5−1−13. RADAR SERVICE TERMINATION
a. Inform aircraft when radar service is terminated.
PHRASEOLOGY− RADAR SERVICE TERMINATED (nonradar routing if required).
b. Radar service is automatically terminated and the aircraft needs not be advised of termination when:
1. An aircraft cancels its IFR flight plan, except within Class B airspace, Class C airspace, TRSA, or where basic radar service is provided.
2. An aircraft conducting an instrument, visual, or contact approach has landed or has been instructed to change to advisory frequency.
3. At tower-controlled airports where radar coverage does not exist to within 1/2 mile of the end of the runway, arriving aircraft must be informed when radar service is terminated.
4. TERMINAL. An arriving VFR aircraft receiving radar service to a tower-controlled airport within Class B airspace, Class C airspace, TRSA, or where basic radar service is provided has landed, or to all other airports, is instructed to change to tower or advisory frequency.