A tower controller reported allowing an aircraft to land even though the airport surface detection e...

Narrative:

Aircraft X was upwind in the traffic pattern. Aircraft Y was in the pattern following aircraft X. I was working local control. I anticipated aircraft Y was turning in sooner than the typical pattern so I told aircraft X to start his go around for aircraft Y in trail of him. Aircraft X started his go around and was at approximately 80 feet on the upwind offset left of the runway when the airport surface detection equipment (asde-X) alarmed. The asde-X didn't alarm until aircraft Y had already touched down. Also when the asde-X alarmed it said runway occupied instead of runway go around. I did not issue the go around instructions to aircraft Y because he had already landed and was following thru on his touch and go. The asde-X alarmed when aircraft Y was between taxiways which was much too late for reasonable go around instructions to be issued. The asde-X is a constant problem and go around instructions should not be required due the inaccuracy of the system.

Original NASA ASRS Text

Title: A Tower Controller reported allowing an aircraft to land even though the Airport Surface Detection Equipment (ASDE-X) alarmed for preceding go-around traffic.

Narrative: Aircraft X was upwind in the traffic pattern. Aircraft Y was in the pattern following Aircraft X. I was working Local Control. I anticipated Aircraft Y was turning in sooner than the typical pattern so I told Aircraft X to start his go around for Aircraft Y in trail of him. Aircraft X started his go around and was at approximately 80 feet on the upwind offset left of the runway when the Airport Surface Detection Equipment (ASDE-X) alarmed. The ASDE-X didn't alarm until Aircraft Y had already touched down. Also when the ASDE-X alarmed it said runway occupied instead of runway go around. I did not issue the Go around instructions to Aircraft Y because he had already landed and was following thru on his touch and go. The ASDE-X alarmed when Aircraft Y was between taxiways which was much too late for reasonable go around instructions to be issued. The ASDE-X is a constant problem and go around instructions should not be required due the inaccuracy of the system.

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.

Attributes
ACN	1493524
Time
Date	201711
Local Time Of Day	0601-1200
Place
Locale Reference	SNA.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Helicopter
Flight Phase	Initial Climb
Route In Use	None
Flight Plan	VFR
Aircraft 2
Make Model Name	Small Aircraft
Flight Phase	Landing
Route In Use	Visual Approach
Flight Plan	VFR
Person 1
Function	Local
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

A tower controller reported allowing an aircraft to land even though the airport surface detection equipment (asde-X) alarmed for preceding go-around traffic.