Aircraft Hand-offs Between Controllers

Introduction

Aircraft are handed off from one ATC unit to the next as a flight progresses. In the real world, many ATC positions have two controllers, and three for busy positions. One to talk to aircraft, one to plan procedurally in the event of a surveillance outage, and one to effect the coordination as described here. We don't have that luxury on the VATNZ network; "transferring the tag" is usually sufficient. However, controllers should first contact adjacent controllers for their agreement to forego formal handoffs.

That said, there are two instances where communication, as described here, must take place.

Handoffs to or from a procedural TWR must be properly coordinated, as tag transfers do not occur in this circumstance.
For departing aircraft, a DEPARTURE notification message must always be sent from a TWR to the next accepting controller (either TMA if a radar/surveillance TWR, or ENR if a procedural TWR).

Method

Handoffs are conducted via ground-to-ground (G2G) communications. The preferred method is voice via the ATC client; however, the EuroScope controller client lacks this functionality. The vatSys client includes an integrated G2G setup called VSCS (Voice Switching and Communication System); however, both controllers must use vatSys to enable this functionality. If one controller is not using vatSys, then acceptable alternatives include, in this order of preference:

text through the ATC clients
Discord coordination channel: the disadvantage here is that it is uncontrolled. Therefore, anyone can join it, disrupting coordination.

Voice coordination between two ATS units relies on the same two-way principle as communicating with aircraft using prescribed phraseology and readbacks.

There are four distinct phases to the handoff process: notification, coordination, release, and transfer.

Notification is usually automatic and can be as simple as a flight strip appearing in the accepting controller's strip bay. For handoffs from a procedural TWR to ENR, or a radar/surveillance tower to TMA, a departure notification message must also be sent (see below).

Coordination is the exchange of pertinent information from the transferring controller to the accepting controller.

Release is the authorisation from a radar/surveillance TWR to a TWR controller to clear an aircraft for take-off into a TMA, except where "auto-release" applies (see below).

Transfer occurs after the accepting controller accepts the aircraft, followed by an instruction for the aircraft to contact the accepting controller.

Auto-release allows an aerodrome controller to depart aircraft assigned a default SID (refer SOP) into a TMA without first obtaining a release from the approach controller. The VATNZ Standard Operating Procedures provide detailed information regarding the airports at which this applies (NZAA, NZWN, NZCH, NZQN).

Auto-releases do not apply:

where the aircraft is cleared on a departure other than the default SID
when the approach controller has temporarily restricted or suspended auto-releases due to traffic congestion or any other reason
for any form of training flight departing into the TMA
for VFR departures into terminal airspace (controlled VFR, covered in the practical training)
where the aircraft requires unusual handling
where the location is not NZAA, NZWN, NZCH, or NZQN.

There are four message categories with specific formatting: ESTIMATE, DEPARTURE, REVISION, and REQUEST.

ESTIMATE message

An ESTIMATE message is a coordination message used between:

TMA or Procedural TWR to ENR,
ENR to ENR, (NZZO is an ENR) and
ENR to TMA or Procedural TWR.

Format:

ESTIMATE [aircraft callsign]
(if departing into NZZO) DEPARTURE [departure time]
[REP] [ETO]
[level] or CLIMBING TO [level] or [level] DESCENDING TO [level]
(if handing over to a procedural TWR) [type of approach] [route]
other information

Example 1: ANZ101 is an NZAA-YSSY flight that departed NZAA at 1823z and is entering NZZO at MADEP REP, with MADEP estimated at 1908z, climbing to RFL FL360. OCR is required to coordinate with ARO at least 10 minutes before ETO MADEP. ANZ101 has advised OCR that it will not reach its RFL (FL360) by MADEP per the SID transition requirement and has requested to cross MADEP at FL330 or higher. OCR must obtain ARO approval for the lower crossing level, since ARO expects ANZ101 to cross MADEP at its RFL.

(OCR to ARO): ESTIMATE ANZ101 DEPARTURE 1823 MADEP 1908 CLIMBING TO FLIGHT LEVEL 360 REQUEST CROSS MADEP FLIGHT LEVEL 330 OR ABOVE

(ARO to OCR): ANZ101 ACCEPTED CLIMBING TO FLIGHT LEVEL 360 CROSS MADEP FLIGHT LEVEL 330 OR ABOVE

(OCR to ARO): CROSS MADEP FLIGHT LEVEL 300 OR ABOVE ANZ101

(ARO to OCR): NEGATIVE ANZ101 CROSS MADEP FLIGHT LEVEL 330 OR ABOVE

(OCR to ARO): CROSS MADEP FLIGHT LEVEL 330 OR ABOVE ANZ101

Example 2: ANZ549 is an NZAA-NZCH flight estimating NP at 0441 at FL360. Coordination is required 10 minutes before NP.

(OCR to NAK): ESTIMATE ANZ549 NP 0441 FLIGHT LEVEL 360 CAUTION SIMILAR CALLSIGN ANZ449 12 MINUTES BEHIND

(NAK to OCR): ANZ549 ACCEPTED FLIGHT LEVEL 360 AND ANZ449 ROGER

Example 3: ANZ699 is an NZAA-NZNV flight estimating OGAVO at 0528, descending through FL210 to FL150 requesting the VOR/DME RWY04 approach for training. Coordination should be effected 10 minutes before OGAVO, the transfer point. As this requires the NV2A arrival rather than the default RNP arrival, STH must obtain TNV approval beforehand.

(STH to TNV): ESTIMATE ANZ699 OGAVO 0528 FLIGHT LEVEL 210 DESCENDING TO FLIGHT LEVEL 150 REQUEST VORDME RWY04 VIA NV2A ARRIVAL

(TNV to STH): ANZ699 ACCEPTED DESCENDING TO FLIGHT LEVEL150 CLEARED NV2A ARRIVAL EXPECT VORDME RWY04 VIA DME ARC

(STH TO TNV): CLEARED NV2A ARRIVAL ANZ699 AND ROGER

DEPARTURE message

A DEPARTURE message is a notification message used for aircraft just departing and originates from a TWR.

Surveillance TWRs (NZWP, NZAA, NZHN, NZRO, NZTG, NZOH, NZPM, NZWN, NZWB, NZCH, NZQN)

Format: DEPARTURE [aircraft callsign] ROLLING RUNWAY [number]

Example: ANZ101 is taking off from RWY23L at NZAA.

(TAA to ATMA): DEPARTURE ANZ101 ROLLING RWY23L

(ATMA to TAA): ANZ101

Procedural TWRs (NZNP, NZGS, NZNR, NZNS, NZDN, NZNV)

Format: DEPARTURE [aircraft callsign] [departure time]

Example: ANZ029M is a flight from NZNR to NZAA, taking off at 0214z.

(TNR to OHA): DEPARTURE ANZ029M 0214

(OHA to TNR): ANZ029M

After the aircraft makes a position report, an ESTIMATE message follows.

(TNR to OHA): ESTIMATE ANZ029M MOOSE 0259 CLIMBING TO FLIGHT LEVEL 190

(OHA to TNR): ANZ029 ACCEPTED FLIGHT LEVEL 190

REVISION message

A REVISION message is a coordination message required when a change to previously coordinated information with the accepting controller is requested or has occurred. Changes to ETO/ETA, route, or level are examples.

Revision to ETO/ETA

If the ETO/ETA varies by 3 minutes or more from what has been coordinated:

Format: REVISION [aircraft callsign] [REP] [new ETO/ETA]

Example: REVISION ANZ029M MOOSE 0255

Revision to level

Format: REVISION [aircraft callsign] CLIMBING TO AMENDED [amended level]

Example: REVISION ANZ029M CLIMBING TO AMENDED FLIGHT LEVEL 170

REQUEST message

A REQUEST message is a coordination message that does not fit into any other category. It may be appended to one of the other categories (as we saw above with ANZ101) or stand alone.

Example 1: JST244 is taxiing southbound on TWY A for RWY02 at NZCH and is under the control of GCH. It is approaching RWY29. GCH requires a clearance from TCH for JST244 to cross RWY29.

(GCH to TCH): REQUEST JST244 SOUTHBOUND ON A TO CROSS RWY29

(TCH TO GCH): JST244 CROSS RWY29

(GCH to TCH): CROSS RWY29 JST244

Example 2: HER11 is at the holding point RW03 at NZWP. TWP is about to call ATMA for a release.

(TWP to ATMA): REQUEST RELEASE HER11

(ATMA to TWP): HER11 HOLD (ATMA is not ready to accept HER11 due to overflying traffic)

(TWP to ATMA): HOLD HER11

A few minutes later:

(ATMA to TWP): HER11 RELEASED

(TWP to ATMA): RELEASED HER11

These examples are not exhaustive; many situations can arise that are different. As long as this basic formatting is followed, the accepting controller should understand.