Controlling on Multiple Frequencies only Permitted for Enroute Controllers Extending Coverage
Controllers in VATNZ Airspace must only control aircraft on their position's primary frequency, unless they are controlling an Enroute position and are extending coverage into another Enroute sector.
The only controllers who should be controlling aircraft on multiple frequencies are Enroute controllers who are extending coverage. In this situation the controller should be cross-coupling the primary frequency for each of the other enroute sectors that they are extending into. The reason for allowing multiple frequency use in this situation is that the enroute frequencies do not cover the entire country and pilots will lose contact with the enroute controller once they move too far beyond the controller's primary airspace boundary.
No-one should be broadcasting on multiple frequencies in any other situation.
If you are connected as an Approach/Departure/Tower controller, the transceiver(s) for your station already have full sea-level coverage throughout your airspace, including any positions that are below you. There is no need for the pilot to change frequencies in order to retain contact, and so you should always keep all aircraft you are controlling on your primary frequency.
If you are an enroute controller, the set of transceivers associated with each enroute sector has full coverage at all of the airports within that sector, and you should not be transferring pilots to the approach/tower/whatever frequency unless you are transferring control to another controller or sending the controller to the UNICOM frequency (122.8).
Example 1
You are controlling NZWN_APP (119.3) and there are no controllers online at NZWN.
Any aircraft arriving at Wellington will stay with you on 119.3 until they are at the gate. Similarly any aircraft departing Wellington will call you for clearance on 119.3.
At no point will either aircraft be on the Wellington Tower, Ground, or Delivery frequency unless there is someone controlling those positions.
Example 2
You are controlling NZAA_CTR (123.9) and extending to cover all of NZZC as there are no other controllers online.
An aircraft flying from Auckland to Christchurch will call you for clearance on 123.9, remain on 123.9 until the Taranaki border then switch to the Taranaki Sector primary (123.7) until the Kaikoura border, then switch to the Kaikoura Sector primary (129.4) and remain on that frequency until they are at the gate.
You will be on the Auckland Sector primary (123.9) and be cross-coupled to the Taranaki Sector (123.7) and Kaikoura Sector (129.4) primaries. You would not be cross-coupled or broadcasting on Auckland APP/TWR/GND/DEL.
Example 3
The same controlling situation as Example 2.
An aircraft flying from Wellington to Christchurch will call you for clearance on the Taranaki Sector primary (123.7), then switch to the Kaikoura Sector primary (129.4) at the Kaikoura boundary and remain on that frequency until they are at the gate.
There are several factors motivating this policy.
Firstly, all of the current ATC or Pilot clients only display the controller's primary frequency (the one they're logged into the fsd network on). This makes it difficult for pilots (especially new or returning pilots) to know which frequency to contact the controller on.
In addition, controllers operating on multiple frequencies can significantly increase the number of transceivers active in the airspace which has a load impact on the voice platform servers.
As the technology on both the client and server-side of the Audio for VATSIM platform matures and the various issues and limitations are worked through, this policy will likely be reviewed.