Narrative:

I was training on local with my trainer closely monitoring me when aircraft X calls. 'Aircraft X just over the marina to the south requesting north shoreline transition to the 10 fwy east/getty.' this is where the miscommunication occurred I heard 'to the getty; east.' I responded 'aircraft X transition approved; cross midfield at or above 900ft.' aircraft Y calls in on the VOR/GPS-a approach; was cleared for the visual and cleared to land on runway 21.at this time aircraft X crosses mid field and proceeds to cross my final along the 10 fwy east; with aircraft Y on a 2.5 mile final. This was observed and action was immediately taken to de-conflict the traffic. 'Aircraft X you are crossing my final; remain north of my final.' at this point my trainer chimes in to ensure the situation would remain safe. Aircraft X turn left immediately; you're flying up my final.' I key up and say 'aircraft Y traffic ahead and to your right; a helicopter turning northbound for you.' aircraft Y replies; 'we got an RA on that guy we have him in sight; we're going to have to go around.'possibly establish VFR helicopter routes that prohibit helicopters from transitioning in an unsafe manner through the class delta. For example: aircraft transitioning out of the lax shoreline route must continue low level along the shore until reaching the pier.

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Original NASA ASRS Text

Title: SMO Developmental Tower Controller reported of issuing instructions to a helicopter. The aircraft did not fly as instructed and became a conflict for arrival traffic. Instructing Controller turned the helicopter to avoid the arrival. Arrival aircraft reported an RA and advised Tower they had the aircraft in sight.

Narrative: I was training on local with my trainer closely monitoring me when Aircraft X calls. 'Aircraft X just over the Marina to the south requesting north shoreline transition to the 10 FWY East/Getty.' This is where the miscommunication occurred I heard 'To the Getty; east.' I responded 'Aircraft X transition approved; cross midfield at or above 900ft.' Aircraft Y calls in on the VOR/GPS-A approach; was cleared for the visual and cleared to land on RWY 21.At this time Aircraft X crosses mid field and proceeds to cross my final along the 10 FWY east; with Aircraft Y on a 2.5 mile final. This was observed and action was immediately taken to de-conflict the traffic. 'Aircraft X you are crossing my final; remain north of my final.' At this point my trainer chimes in to ensure the situation would remain safe. Aircraft X turn left immediately; you're flying up my final.' I key up and say 'Aircraft Y traffic ahead and to your right; a helicopter turning northbound for you.' Aircraft Y replies; 'We got an RA on that guy we have him in sight; we're going to have to go around.'Possibly establish VFR helicopter routes that prohibit helicopters from transitioning in an unsafe manner through the Class Delta. For example: Aircraft transitioning out of the LAX shoreline route must continue low level along the shore until reaching the Pier.

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.