A controller had two aircraft from the same company with similar sounding call signs. The controller...

Narrative:

I was working final and aircraft X checked in on the RNAV arrival from the west and I acknowledged with what runway to expect and to use caution for a similar sounding call sign on the frequency. I then told aircraft Y to turn left heading 070 degrees for a base turn and also cautioned that pilot of a similar sounding callsign of aircraft X on the frequency. By that time aircraft Y was in the turn and I could descend to the lower minimum vectoring altitude (MVA); so I transmitted to what I thought was 'aircraft Y descend and maintain 6;500' I heard the readback and went on with other aircraft instructions. It turns out that I used aircraft X callsign when I descended aircraft Y. [Aircraft] descended just below the 8;500 MVA and close to the 8;000 MVA so I turned their base which is away from the higher terrain and then I observed them about a mile from the 7;000 foot MVA and descending through 8;000. So I told them to maintain 7;000 feet and they read back the instruction. I am not sure why the event happened; I must have jumbled the similar callsigns in my head.unfortunately; I don't have a recommendation on how to prevent this; other than exercising extreme caution; which I 'thought' I already did; but apparently the law of averages got me on this one. I will hopefully double my efforts now that this has happened and when I give the similar sounding callsign transmission... I need to slow down and really pay attention to my callsigns. We as controllers seem to think that the similar sounding callsign warning is just for the pilots... But I have learned that it is for me also!

Original NASA ASRS Text

Title: A Controller had two aircraft from the same company with similar sounding call signs. The Controller used the appropriate warning phraseology but then descended the wrong aircraft. The descent placed the aircraft below the Minimum Vectoring Altitude.

Narrative: I was working Final and Aircraft X checked in on the RNAV arrival from the west and I acknowledged with what runway to expect and to use caution for a similar sounding call sign on the frequency. I then told Aircraft Y to turn left heading 070 degrees for a base turn and also cautioned that pilot of a similar sounding callsign of Aircraft X on the frequency. By that time Aircraft Y was in the turn and I could descend to the lower Minimum Vectoring Altitude (MVA); so I transmitted to what I thought was 'Aircraft Y descend and maintain 6;500' I heard the readback and went on with other aircraft instructions. It turns out that I used Aircraft X callsign when I descended Aircraft Y. [Aircraft] descended just below the 8;500 MVA and close to the 8;000 MVA so I turned their base which is away from the higher terrain and then I observed them about a mile from the 7;000 foot MVA and descending through 8;000. So I told them to maintain 7;000 feet and they read back the instruction. I am not sure why the event happened; I must have jumbled the similar callsigns in my head.Unfortunately; I don't have a recommendation on how to prevent this; other than exercising extreme caution; which I 'thought' I already did; but apparently the law of averages got me on this one. I will hopefully double my efforts now that this has happened and when I give the similar sounding callsign transmission... I need to slow down and really pay attention to my callsigns. We as controllers seem to think that the similar sounding callsign warning is just for the pilots... but I have learned that it is for me also!

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	1308781
Time
Date	201511
Local Time Of Day	1801-2400
Place
Locale Reference	S56.TRACON
State Reference	UT
Environment
Light	Night
Aircraft 1
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR WAATS3
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 20.0
Events
Anomaly	ATC Issue All Types Airspace Violation All Types Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

A controller had two aircraft from the same company with similar sounding call signs. The controller used the appropriate warning phraseology but then descended the wrong aircraft. The descent placed the aircraft below the minimum vectoring altitude.