Charlotte approach controller reported stopping an aircraft's descent to prevent a loss of separatio...

Narrative:

Aircraft X was descending via the stocr arrival; south transition; near poore intersection when I noticed him leave 9000 feet. I immediately took action as he went through 8800 feet; issuing a climb back to 9000. The pilot seemed surprised and said something to the effect of 'yes; we will have to climb back up to 9000'. At which point I issued an immediate westbound turn to avoid a clt departure climbing to the southeast. Once I was west of the clt departure; which I believe was an [airliner]; I cannot recall; I put aircraft X back on course to the downwind leg. This was a close call; had I not noticed this pilot deviation as it was happening; it could have been a far worse outcome. The pilot stated on the phone he accidentally deleted the 9000 box from the FMS.I will also add that on initial check-on; aircraft X stated they were on the STOCR1 descending to 7000. This is not an uncommon check on. The STAR's bottom altitude is 7000 and that is; in fact; where they are descending to. I should have pried the whole and correct phraseology from him; but at the time I was busy. The fact that the bottom altitude on these arrivals is below the altitude at which clt departures are climbing is wildly dangerous. This isn't the first instance this has happened. After the first one it should have been changed but it wasn't; so here we go again. Long side arrivals bottom altitude should be 9000. This way; if the FMS drops an altitude; or fix; the clearance limit is at least 9000; not 7000; which is 1000 feet below the altitude of clt departures!

Original NASA ASRS Text

Title: Charlotte Approach Controller reported stopping an aircraft's descent to prevent a loss of separation with another aircraft. Controller stated pilot accidentally deleted altitude from the FMS.

Narrative: Aircraft X was descending via the STOCR arrival; south transition; near POORE intersection when I noticed him leave 9000 feet. I immediately took action as he went through 8800 feet; issuing a climb back to 9000. The pilot seemed surprised and said something to the effect of 'Yes; we will have to climb back up to 9000'. At which point I issued an immediate westbound turn to avoid a CLT departure climbing to the southeast. Once I was west of the CLT departure; which I believe was an [airliner]; I cannot recall; I put Aircraft X back on course to the downwind leg. This was a close call; had I not noticed this pilot deviation as it was happening; it could have been a far worse outcome. The pilot stated on the phone he accidentally deleted the 9000 box from the FMS.I will also add that on initial check-on; Aircraft X stated they were on the STOCR1 descending to 7000. This is not an uncommon check on. The STAR's bottom altitude is 7000 and that is; in fact; where they are descending to. I should have pried the whole and correct phraseology from him; but at the time I was busy. The fact that the bottom altitude on these arrivals is below the altitude at which CLT departures are climbing is wildly dangerous. This isn't the first instance this has happened. After the first one it should have been changed but it wasn't; so here we go again. Long side arrivals bottom altitude should be 9000. This way; if the FMS drops an altitude; or fix; the clearance limit is at least 9000; not 7000; which is 1000 feet below the altitude of CLT departures!

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	1462487
Time
Date	201707
Local Time Of Day	1801-2400
Place
Locale Reference	CLT.TRACON
State Reference	NC
Aircraft 1
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR STOCR2
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Flight Phase	Climb
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 3
Events
Anomaly	ATC Issue All Types Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

Charlotte approach controller reported stopping an aircraft's descent to prevent a loss of separation with another aircraft. Controller stated pilot accidentally deleted altitude from the FMS.