Narrative:

This event happened some time ago. After discussing with other pilots and training staff I decided it warrants a report. Descending into mwcr area. Flying directly to mobix intersection from the north-northwest. We were following an aircraft Y who was nearing mobix also from the north-northwest and was cleared for approach in front of us. Upon aircraft Y reporting mobix; ATC determined that there was sufficient distance in trail and cleared us for the RNAV 08 approach via mobix. TCAS observation led us to believe that aircraft Y did not turn inbound at mobix but had turned outbound to do a course reversal procedure at mobix. After discussion with ATC it was confirmed that aircraft Y had made a course reversal (not what ATC was expecting). Our clearance was then modified to avoid conflict with aircraft Y. After my partner and I discussed what was the correct procedure for entry at zzzzz. We are familiar with the 30 degree ICAO direct approach entry authorization for conventional approaches. We did not know if or how this applied to RNAV procedures. After digging in the jeppesen manuals on way home we discovered that RNAV approaches permit up to a 110 degree turn to join the approach at an IAF or if. This was news to us. Since that time I have met no one else who knew of this. When I show the mobix example to other pilots; check airmen and instructors I have yet to find anyone that really knows. The aircraft Y crew that day thought they had to do a course reversal. Had we not noticed their actions; a conflict might have occurred. Sure seems to be something we are missing in training. Please see my attachments and feel free to call to discuss more if desired.

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Original NASA ASRS Text

Title: A321 Captain reported unfamiliarity with RNAV entry procedures into MWCR caused an airborne conflict.

Narrative: This event happened some time ago. After discussing with other pilots and training staff I decided it warrants a report. Descending into MWCR area. Flying directly to MOBIX Intersection from the north-northwest. We were following an Aircraft Y who was nearing MOBIX also from the north-northwest and was cleared for approach in front of us. Upon Aircraft Y reporting MOBIX; ATC determined that there was sufficient distance in trail and cleared us for the RNAV 08 approach via MOBIX. TCAS observation led us to believe that Aircraft Y did not turn inbound at MOBIX but had turned outbound to do a course reversal procedure at MOBIX. After discussion with ATC it was confirmed that Aircraft Y had made a course reversal (not what ATC was expecting). Our clearance was then modified to avoid conflict with Aircraft Y. After my partner and I discussed what was the correct procedure for entry at ZZZZZ. We are familiar with the 30 degree ICAO direct approach entry authorization for conventional approaches. We did not know if or how this applied to RNAV procedures. After digging in the Jeppesen manuals on way home we discovered that RNAV approaches permit up to a 110 degree turn to join the approach at an IAF or IF. This was news to us. Since that time I have met no one else who knew of this. When I show the MOBIX example to other pilots; check airmen and instructors I have yet to find anyone that really knows. The Aircraft Y crew that day thought they had to do a course reversal. Had we not noticed their actions; a conflict might have occurred. Sure seems to be something we are missing in training. Please see my attachments and feel free to call to discuss more if desired.

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.