Precision Runway Monitor

Changes to TCAS with ILS PRM

When PRM approaches were first employed, requirements were specified by both the FAA and CASA that TCAS mode selectors were to be selected to the ‘TA Only' position during these approaches, due to concerns that the close proximity of aircraft would generate ‘nuisance' Resolution Advisories' (RA). The FAA had not, at that time, included TCAS in PRM risk modelling. Subsequently, a simulation and analysis was undertaken to establish the `likely effect of using TCAS in TA/RA Mode during PRM approaches, resulting in a decision by the FAA to allow flight crews to use TA/RA Mode if desired.

The ICAO Operations Panel have also agreed that there now seems to be evidence supporting the withdrawal of the instruction that TCAS/ACAS mode selectors should be placed in the ‘TA Only' position whilst an aeroplane is making a PRM approach and have concluded that States need not inhibit pilots from operating ACAS in the mode they wish to use. Recommendations made by OPSP/6 for amendments to the guidance material in PANS-OPS Vol 1 Part VII reflect this position and emphasise the need for pilots to always follow the RA (even if it differs from the monitor controller's climb/descent instructions) while complying with the turn portion of the breakout instruction.

AIP amendment 2 September 2004 reflects this change to PRM procedures. A NOTAM has been published amending the TCAS operation notified on the ILS PRM User Instructions page of AIP DAP.

The PRM video, the viewing of which is required prior to conducting a PRM approach, has been amended to reflect the change to TCAS selection.

To order this video on CD, contact community.relations@airservicesaustralia.com

For further information, contact CASA on 131 757