MD88 crew was cleared to descend through an occupied altitude from controller getting training.

Attributes
ACN	463780
Time
Date	200002
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atl.airport
State Reference	GA
Altitude	msl bound lower : 8000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl.tracon tower : las.tower
Operator	common carrier : air carrier
Make Model Name	MD-88
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Route In Use	arrival star : lagrange
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 27000 flight time type : 900
ASRS Report	463780
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	conflict : airborne less severe non adherence : published procedure
Independent Detector	other controllera other controllerb other flight crewa other flight crewb other other : 3
Resolutory Action	controller : issued new clearance flight crew : took precautionary avoidance action other
Supplementary
Problem Areas	FAA ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

After holding at lgc on arrival to atl, we were given step-down altitudes to 12000 ft. Controller then gave us a descent to 8000 ft. We had him repeat it, set the altitude, both pilots confirmed it and pointed to the set altitude. As we approached 10000 ft and began the approach checklist, the controller told us to climb now to 11000 ft, that he had a B727 climbing to 10000 ft. We immediately climbed with no TCASII indications. Level at 11000 ft we questioned him and he said we might have taken someone else's descent. We told him we had 3 pilots (jump seat seater) that confirmed the 8000 ft. We were given another descent and the supervisor (different voice) came on saying it was just a mix up but there was never any real problem and that it was ok. It could have been a problem especially if not under VFR conditions. I believe it was human error. I do not believe it was our mistake. It was a reminder to be extremely vigilant.

Original NASA ASRS Text

Title: MD88 CREW WAS CLRED TO DSND THROUGH AN OCCUPIED ALT FROM CTLR GETTING TRAINING.

Narrative: AFTER HOLDING AT LGC ON ARR TO ATL, WE WERE GIVEN STEP-DOWN ALTS TO 12000 FT. CTLR THEN GAVE US A DSCNT TO 8000 FT. WE HAD HIM REPEAT IT, SET THE ALT, BOTH PLTS CONFIRMED IT AND POINTED TO THE SET ALT. AS WE APCHED 10000 FT AND BEGAN THE APCH CHKLIST, THE CTLR TOLD US TO CLB NOW TO 11000 FT, THAT HE HAD A B727 CLBING TO 10000 FT. WE IMMEDIATELY CLBED WITH NO TCASII INDICATIONS. LEVEL AT 11000 FT WE QUESTIONED HIM AND HE SAID WE MIGHT HAVE TAKEN SOMEONE ELSE'S DSCNT. WE TOLD HIM WE HAD 3 PLTS (JUMP SEAT SEATER) THAT CONFIRMED THE 8000 FT. WE WERE GIVEN ANOTHER DSCNT AND THE SUPVR (DIFFERENT VOICE) CAME ON SAYING IT WAS JUST A MIX UP BUT THERE WAS NEVER ANY REAL PROB AND THAT IT WAS OK. IT COULD HAVE BEEN A PROB ESPECIALLY IF NOT UNDER VFR CONDITIONS. I BELIEVE IT WAS HUMAN ERROR. I DO NOT BELIEVE IT WAS OUR MISTAKE. IT WAS A REMINDER TO BE EXTREMELY VIGILANT.

Data retrieved from NASA's ASRS site as of July 2007 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.