4.1 ICAO PANS-OPS Volume I - Flight Procedures states that in the event of an ACAS Resolution Advisory (RA) pilots shall respond immediately by following the RA as indicated, unless doing so would jeopardise the safety of the aircraft.
4.2 This does not diminish the authority and responsibility of the pilot-in-command to ensure safe flight.
4.3 ACAS RAs may, in some cases, conflict with flight path requirements due to terrain, such as an obstacle-limited climb segment or an approach to rising terrain. Since many approved instrument procedures and IFR clearances are predicated on avoiding high terrain or obstacles, it is particularly important that pilots maintain situational awareness and continue to use accepted operating practices and judgement when following ACAS RAs.
4.4 Since ACAS does not respond to aircraft unless they are equipped with a functioning transponder, ACAS does not ensure safe separation in every case. It is important, wherever possible, to maintain frequent outside visual scan, use see-and-avoid vigilance and to continue to communicate with ATC as appropriate.