Narrative:

On initial contact; air carrier X was given this clearance: 'air carrier X descend via the erlin 5 arrival runway 26R.' approximately 4 mi southeast of stutz; I observed the altitude of air carrier X to be 11400 ft. I told air carrier X it appeared he had descended early on the arrival and to maintain 11000 ft. Air carrier X should have maintained 12000 ft until nofiv; but when the aircraft descended early I assigned the lowest altitude that I owned in that area. I asked the pilot what altitude he was descending to and he said he was 'looking at the next stepdown fix.' that meant he was descending to 7000 ft. If this anomaly had gone unnoticed; aircraft would have been descending through the altitudes of the departure traffic climbing to 10000 ft. I am not sure if this anomaly was caused by pilot error or equipment malfunction. There are several ways to prevent a recurrence of this situation. First; cancel descend via clrncs into atl. Second; if the agency insists on continuing descend via clrncs; then the actual clearance should be withheld until the aircraft is already turning downwind and clear of all conflicts. This will prevent the aircraft from descending into a departure. Third; change the phraseology and give the aircraft a hard altitude to maintain until clear of conflicts; ie; 'cross nofiv at 12000 ft; descend via the erlin 5 arrival; runway 26R.' finally; flight crews need to be more educated on the airspace that they are flying into. No arriving aircraft will ever be issued nor should they be descending to an altitude that is lower than 11000 ft on the departure side of the airport. All turbojet aircraft departing atl are issued an initial altitude of 10000 ft.

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Original NASA ASRS Text

Title: A80 CTLR DESCRIBED ACR EARLY DESCEND ALLEGING 'DESCEND VIA' PHRASEOLOGY AS CONTRIBUTORY.

Narrative: ON INITIAL CONTACT; ACR X WAS GIVEN THIS CLRNC: 'ACR X DSND VIA THE ERLIN 5 ARR RWY 26R.' APPROX 4 MI SE OF STUTZ; I OBSERVED THE ALT OF ACR X TO BE 11400 FT. I TOLD ACR X IT APPEARED HE HAD DSNDED EARLY ON THE ARR AND TO MAINTAIN 11000 FT. ACR X SHOULD HAVE MAINTAINED 12000 FT UNTIL NOFIV; BUT WHEN THE ACFT DSNDED EARLY I ASSIGNED THE LOWEST ALT THAT I OWNED IN THAT AREA. I ASKED THE PLT WHAT ALT HE WAS DSNDING TO AND HE SAID HE WAS 'LOOKING AT THE NEXT STEPDOWN FIX.' THAT MEANT HE WAS DSNDING TO 7000 FT. IF THIS ANOMALY HAD GONE UNNOTICED; ACFT WOULD HAVE BEEN DSNDING THROUGH THE ALTS OF THE DEP TFC CLBING TO 10000 FT. I AM NOT SURE IF THIS ANOMALY WAS CAUSED BY PLT ERROR OR EQUIP MALFUNCTION. THERE ARE SEVERAL WAYS TO PREVENT A RECURRENCE OF THIS SITUATION. FIRST; CANCEL DSND VIA CLRNCS INTO ATL. SECOND; IF THE AGENCY INSISTS ON CONTINUING DSND VIA CLRNCS; THEN THE ACTUAL CLRNC SHOULD BE WITHHELD UNTIL THE ACFT IS ALREADY TURNING DOWNWIND AND CLR OF ALL CONFLICTS. THIS WILL PREVENT THE ACFT FROM DSNDING INTO A DEP. THIRD; CHANGE THE PHRASEOLOGY AND GIVE THE ACFT A HARD ALT TO MAINTAIN UNTIL CLR OF CONFLICTS; IE; 'CROSS NOFIV AT 12000 FT; DSND VIA THE ERLIN 5 ARR; RWY 26R.' FINALLY; FLT CREWS NEED TO BE MORE EDUCATED ON THE AIRSPACE THAT THEY ARE FLYING INTO. NO ARRIVING ACFT WILL EVER BE ISSUED NOR SHOULD THEY BE DSNDING TO AN ALT THAT IS LOWER THAN 11000 FT ON THE DEP SIDE OF THE ARPT. ALL TURBOJET ACFT DEPARTING ATL ARE ISSUED AN INITIAL ALT OF 10000 FT.

Data retrieved from NASA's ASRS site as of May 2009 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.