Narrative:

Aircraft X was inbound to myf from the east. I instructed aircraft X to remain north of final and fly north of lake murray inbound for traffic and expect to pass behind them and make a straight in for runway 28L. Aircraft Y was inbound on the ILS for runway 28R and had not checked in yet. I instructed aircraft X to make a right 360 and remain north of lake murray for traffic. An aircraft responded; whom I believed to be aircraft X saying they would make a 360. Aircraft X then asked if I wanted them to make a left 360; which I responded negative; make a right 360; and now plan to follow an aircraft which was less than 3 miles in trail of the C550. I then noticed aircraft Y turning from about a 5 mile final to the south toward sans class B airspace; and I reached out to aircraft Y asking if they were on frequency. Aircraft Y responded affirmative; and that I had instructed him to make a left 360; which I responded that he took the instructions for another aircraft. I immediately asked my controller in charge (controller in charge)/ front line manager (flm) to call sct and request coordination/instructions. During the coordination I advised aircraft Y to fly eastbound for the [other] traffic he was turning into. My primary response was to separate traffic. My controller in charge/flm advised me that sct told us that we needed to have aircraft Y cancel IFR. At this point I was trying to separate the jet from both traffic inbound to myf of final and sct/san traffic. Aircraft Y advised canceling IFR and maintaining VFR; per the request of sct; and was instructed to make a straight in for runway 28R. During this time I also had to spin aircraft X north of final to avoid traffic as well as 2 aircraft in my right downwind that were in the pattern. I also had 2 aircraft inbound from the west entering the left downwind at the time this happened and departures waiting. Aircraft Y was very confrontational during this whole process and insisted that I instruct him to make a left 360 or remain north of lake murray and said to check the tapes. The traffic was moderate to busy at the time and complexity high which greatly increased when aircraft Y deviated from final. I was unaware/too busy with coordinating and separating aircraft to realize that aircraft Y went below the MVA and did not issue a low altitude alert; which I later learned needed to be issued. The low altitude alarm did not sound during this entire event. I had not established positive two-way communication before or when aircraft Y deviated from final and did not know he was on frequency until he told me I instructed him to make a left 360.I recommend that our air traffic managers (atm) or flms brief the entire facility that in the event of an aircraft deviating from final that a low altitude alert must be issued. I also recommend that the controller in charge/flms providing local assistance be made aware of this; so in the future they can provide an on the spot correction and prevent another controller from missing the opportunity to issue a low altitude alert. I also recommend that the software tracking IFR aircraft should be fixed/modify to alert the controller to issue a low altitude alert as a reminder in event that this situation should occur again. My last recommendation is that the controller at sct that advised my flm/controller in charge to have aircraft Y cancel IFR instead of providing a positive control instruction be explained that this practice is unsafe/not allowed; and advise other sct controllers of the event to prevent this from happening again; and either implement a new procedure for either sct or both sct and myf to ensure low altitude alerts are issued in these cases.

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Original NASA ASRS Text

Title: MYF Tower Controller reported an aircraft took the clearance for another plane inbound; causing an MVA violation and the MSAW alert failed.

Narrative: Aircraft X was inbound to MYF from the east. I instructed Aircraft X to remain north of final and fly north of Lake Murray inbound for traffic and expect to pass behind them and make a straight in for runway 28L. Aircraft Y was inbound on the ILS for runway 28R and had not checked in yet. I instructed Aircraft X to make a right 360 and remain north of Lake Murray for traffic. An aircraft responded; whom I believed to be Aircraft X saying they would make a 360. Aircraft X then asked if I wanted them to make a left 360; which I responded negative; make a right 360; and now plan to follow an aircraft which was less than 3 miles in trail of the C550. I then noticed Aircraft Y turning from about a 5 mile final to the south toward SANs class B airspace; and I reached out to Aircraft Y asking if they were on frequency. Aircraft Y responded affirmative; and that I had instructed him to make a left 360; which I responded that he took the instructions for another aircraft. I immediately asked my Controller in Charge (CIC)/ Front Line Manager (FLM) to call SCT and request coordination/instructions. During the coordination I advised Aircraft Y to fly eastbound for the [other] traffic he was turning into. My primary response was to separate traffic. My CIC/FLM advised me that SCT told us that we needed to have Aircraft Y cancel IFR. At this point I was trying to separate the jet from both traffic inbound to MYF of final and SCT/SAN traffic. Aircraft Y advised canceling IFR and maintaining VFR; per the request of SCT; and was instructed to make a straight in for runway 28R. During this time I also had to spin Aircraft X north of final to avoid traffic as well as 2 aircraft in my right downwind that were in the pattern. I also had 2 aircraft inbound from the west entering the left downwind at the time this happened and departures waiting. Aircraft Y was very confrontational during this whole process and insisted that I instruct him to make a left 360 or remain north of Lake Murray and said to check the tapes. The traffic was moderate to busy at the time and complexity high which greatly increased when Aircraft Y deviated from final. I was unaware/too busy with coordinating and separating aircraft to realize that Aircraft Y went below the MVA and did not issue a low altitude alert; which I later learned needed to be issued. The low altitude alarm did not sound during this entire event. I had not established positive two-way communication before or when Aircraft Y deviated from final and did not know he was on frequency until he told me I instructed him to make a left 360.I recommend that our Air Traffic Managers (ATM) or FLMs brief the entire facility that in the event of an aircraft deviating from final that a low altitude alert must be issued. I also recommend that the CIC/FLMs providing local assistance be made aware of this; so in the future they can provide an on the spot correction and prevent another controller from missing the opportunity to issue a low altitude alert. I also recommend that the software tracking IFR aircraft should be fixed/modify to alert the controller to issue a low altitude alert as a reminder in event that this situation should occur again. My last recommendation is that the controller at SCT that advised my FLM/CIC to have Aircraft Y cancel IFR instead of providing a positive control instruction be explained that this practice is unsafe/not allowed; and advise other SCT controllers of the event to prevent this from happening again; and either implement a new procedure for either SCT or both SCT and MYF to ensure low altitude alerts are issued in these cases.

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.