Air carrier captain reported they were unclear on the correct communication procedures for an approa...

Narrative:

On ILS prm (precision runway monitoring) approach; the tower controller was transmitting on both the monitor frequency and tower frequency. When queried; controller suggested we call for clarification after landing.at the gate; I called the tower supervisor to ask about the dual transmissions by tower. Our conversation was friendly and professional. When I mentioned the prm monitor frequency was also being used by the tower controller; supervisor answered that the controllers were complying with the guidance they have from the FAA. When I asked about the separation between the tower and the radar monitor; supervisor stated that the pilots; 'upon reaching the marker; should deselect the monitor frequency as only the tower controller would direct a breakout from that point on.' after reviewing our flight manual and fom guidance; I could not find clear guidance on this issue. We both agreed that there may be room for procedural clarification and standardization of training between ATC and our crews.

Original NASA ASRS Text

Title: Air carrier Captain reported they were unclear on the correct communication procedures for an approach to ORD airport. Tower was reportedly transmitting on both tower and monitor frequencies.

Narrative: On ILS PRM (Precision Runway Monitoring) approach; the tower controller was transmitting on both the monitor frequency and tower frequency. When queried; controller suggested we call for clarification after landing.At the gate; I called the Tower Supervisor to ask about the dual transmissions by tower. Our conversation was friendly and professional. When I mentioned the PRM monitor frequency was also being used by the tower controller; Supervisor answered that the controllers were complying with the guidance they have from the FAA. When I asked about the separation between the Tower and the Radar monitor; Supervisor stated that the pilots; 'upon reaching the marker; should DESELECT the monitor frequency as only the Tower controller would direct a breakout from that point on.' After reviewing our Flight Manual and FOM guidance; I could not find clear guidance on this issue. We both agreed that there may be room for procedural clarification and standardization of training between ATC and our crews.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1547381
Time
Date	201806
Local Time Of Day	1801-2400
Place
Locale Reference	ORD.Airport
State Reference	IL
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 8687 Flight Crew Type 5193
Events
Anomaly	Deviation - Procedural Published Material / Policy

Air carrier captain reported they were unclear on the correct communication procedures for an approach to ord airport. Tower was reportedly transmitting on both tower and monitor frequencies.