Narrative:

Air carrier X was on very short final when asde-X gave a go around instruction and highlighted the aircraft on final and maintenance equipment on a closed taxiway (taxiway Q) as the conflict. I was just finishing my scan of the runway (runway 34R) when the alert went off. I noticed the highlighted items on asde-X and could clearly see that this was not an actual conflict and nothing was approaching the runway. I however; have been instructed that we are to issue go around instructions when prompted by the asde-X. I have been instructed that I am not allowed to ignore or use judgment in dis-regarding this type of alert. However; I do feel that this was an unsafe go-around. It would have been much safer to allow the aircraft to land. The aircraft was very low just prior to the approach end of the runway and appeared to struggle to gain enough power to climb out. The aircraft did not verbally respond to the go-around instruction. However; I did visually observe the go-around being executed by the aircraft. In my opinion it would have been detrimental to continue to ask the aircraft to read back the go-around instruction as it was in a critical stage of flight and appeared to be having a hard time gaining power. I have been told we need a read back that includes the words go around. I am not sure the aircraft ever said the phrase go around but I did receive acknowledgement of the altitude and heading assignments issued in conjunction with the go-around after the aircraft was under control. Under the unsafe circumstances caused by this go-around I did not feel it was safe to continue to ask for a read back while the aircraft was trying to get control in the climb out near the approach end. I do believe I got verbal acknowledgement just not sure if it included the phrase go around or something similar. I then did not think to get a read back of a cancel landing clearance after the aircraft read back the climb and heading instructions. The asde-X at salt lake has been very inconsistent and many reports have been given to the supervisory staff. It does not always accurately depict targets in the actual relation to the airport map. It also shows movement that isn't consistent with reality. I am reporting this instance as an example of a false alarm causing an unsafe action that I was required to issue even against my judgment. I am also not sure how this will be interpreted in the qar (quality assurance review) phase if the aircraft didn't say the phrase go-around or landing clearance canceled (referencing punitive reports from other locations). There were several wind shear alerts during the evening along with storms which I believe could have contributed to this being unsafe. I again am not certain the aircraft ever said the phrase go around or cancel landing clearance and I don't believe the pilots were in a position to respond verbally until the climb out was in full progress and then they were able to read back the altitude and heading instructions issued. The read back of the instructions made me think that they were aware of the fact they were going to be re sequenced for another approach and were no longer cleared to land on runway 34R. The supervisor on duty agreed that I did what I was supposed to do even though it appeared to be unsafe. The pilot later relayed to the supervisor on duty that he had never been issued a go-around when that close to the ground prior to this event. Asde-X needs to be correctly adjusted to be accurate; and until that point; if the controller can note the highlighted reasons for the alert and determine it is a false alarm then discretion should be able to be used.

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Original NASA ASRS Text

Title: SLC controller issued go around instructions to an air carrier on short final because of an ASDE-X alarm; the reporter noting the runway was clear/safe and the go around was problematic given the aircraft altitude/speed.

Narrative: Air Carrier X was on very short final when ASDE-X gave a go around instruction and highlighted the aircraft on final and maintenance equipment on a closed taxiway (Taxiway Q) as the conflict. I was just finishing my scan of the runway (Runway 34R) when the alert went off. I noticed the highlighted items on ASDE-X and could clearly see that this was not an actual conflict and nothing was approaching the runway. I however; have been instructed that we are to issue go around instructions when prompted by the ASDE-X. I have been instructed that I am not allowed to ignore or use judgment in dis-regarding this type of alert. However; I do feel that this was an unsafe go-around. It would have been much safer to allow the aircraft to land. The aircraft was very low just prior to the approach end of the runway and appeared to struggle to gain enough power to climb out. The aircraft did not verbally respond to the go-around instruction. However; I did visually observe the go-around being executed by the aircraft. In my opinion it would have been detrimental to continue to ask the aircraft to read back the go-around instruction as it was in a critical stage of flight and appeared to be having a hard time gaining power. I have been told we need a read back that includes the words go around. I am not sure the aircraft ever said the phrase go around but I did receive acknowledgement of the altitude and heading assignments issued in conjunction with the go-around after the aircraft was under control. Under the unsafe circumstances caused by this go-around I did not feel it was safe to continue to ask for a read back while the aircraft was trying to get control in the climb out near the approach end. I do believe I got verbal acknowledgement just not sure if it included the phrase go around or something similar. I then did not think to get a read back of a cancel landing clearance after the aircraft read back the climb and heading instructions. The ASDE-X at Salt Lake has been very inconsistent and many reports have been given to the supervisory staff. It does not always accurately depict targets in the actual relation to the airport map. It also shows movement that isn't consistent with reality. I am reporting this instance as an example of a false alarm causing an unsafe action that I was required to issue even against my judgment. I am also not sure how this will be interpreted in the QAR (Quality Assurance Review) phase if the aircraft didn't say the phrase go-around or landing clearance canceled (referencing punitive reports from other locations). There were several wind shear alerts during the evening along with storms which I believe could have contributed to this being unsafe. I again am not certain the aircraft ever said the phrase go around or cancel landing clearance and I don't believe the pilots were in a position to respond verbally until the climb out was in full progress and then they were able to read back the altitude and heading instructions issued. The read back of the instructions made me think that they were aware of the fact they were going to be re sequenced for another approach and were no longer cleared to land on Runway 34R. The Supervisor on duty agreed that I did what I was supposed to do even though it appeared to be unsafe. The pilot later relayed to the Supervisor on duty that he had never been issued a go-around when that close to the ground prior to this event. ASDE-X needs to be correctly adjusted to be accurate; and until that point; if the controller can note the highlighted reasons for the alert and determine it is a false alarm then discretion should be able to be used.

Data retrieved from NASA's ASRS site as of April 2012 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.