MD88 crew had an altitude deviation in ZTL class a.

Attributes
ACN	572126
Time
Date	200301
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : lgc.vortac
State Reference	GA
Altitude	msl bound lower : 22500 msl bound upper : 23000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Controlling Facilities	artcc : ztl.artcc
Operator	common carrier : air carrier
Make Model Name	MD-88
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : la grange 1
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : ztl.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : atp pilot : multi engine
Experience	flight time last 90 days : 200 flight time total : 8000 flight time type : 1600
ASRS Report	572126
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : overshoot altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : far non adherence : company policies non adherence : clearance non adherence : published procedure
Independent Detector	aircraft equipment : tcas other controllera
Resolutory Action	controller : separated traffic controller : issued new clearance controller : issued alert flight crew : returned to assigned altitude
Miss Distance	vertical : 1500
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were flying the la grange 1 arrival to atl. ZTL cleared us to descend to FL290 with pilot discretion to FL240. Checked in with next atl sector and got clearance for 'cross tiroe intersection at 14000 ft.' I started descent from FL290 and was handed off to next sector. We checked in with 'descending to 14000 ft at tiroe.' controller then stated 'amendy our clearance to level at FL230.' I stopped at FL230. Approximately 2-3 min later, I descended from FL230 for 14000 ft at tiroe, and first officer called the descent. ZTL responded 'go back to FL230.' the lowest altitude I saw was FL225. We did get a TCASII TA on another aircraft at 1500 ft below us. I reversed the pitch and was level at FL230 in approximately 10 seconds. No heading changes or other calls were given by ZTL for any further separation. The remainder of flight was routine. Recommendation: when ATC amends an altitude descent restr (ie, tiroe at 14000 ft) with an intermediate level off (ie, FL230), then the controller should state 'amend your descent to level at FL230 and maintain FL230.' this will clearly delete any doubt about the previous instructions to cross tiroe at 14000 ft.

Original NASA ASRS Text

Title: MD88 CREW HAD AN ALTDEV IN ZTL CLASS A.

Narrative: WE WERE FLYING THE LA GRANGE 1 ARR TO ATL. ZTL CLRED US TO DSND TO FL290 WITH PLT DISCRETION TO FL240. CHKED IN WITH NEXT ATL SECTOR AND GOT CLRNC FOR 'CROSS TIROE INTXN AT 14000 FT.' I STARTED DSCNT FROM FL290 AND WAS HANDED OFF TO NEXT SECTOR. WE CHKED IN WITH 'DSNDING TO 14000 FT AT TIROE.' CTLR THEN STATED 'AMENDY OUR CLRNC TO LEVEL AT FL230.' I STOPPED AT FL230. APPROX 2-3 MIN LATER, I DSNDED FROM FL230 FOR 14000 FT AT TIROE, AND FO CALLED THE DSCNT. ZTL RESPONDED 'GO BACK TO FL230.' THE LOWEST ALT I SAW WAS FL225. WE DID GET A TCASII TA ON ANOTHER ACFT AT 1500 FT BELOW US. I REVERSED THE PITCH AND WAS LEVEL AT FL230 IN APPROX 10 SECONDS. NO HDG CHANGES OR OTHER CALLS WERE GIVEN BY ZTL FOR ANY FURTHER SEPARATION. THE REMAINDER OF FLT WAS ROUTINE. RECOMMENDATION: WHEN ATC AMENDS AN ALT DSCNT RESTR (IE, TIROE AT 14000 FT) WITH AN INTERMEDIATE LEVEL OFF (IE, FL230), THEN THE CTLR SHOULD STATE 'AMEND YOUR DSCNT TO LEVEL AT FL230 AND MAINTAIN FL230.' THIS WILL CLRLY DELETE ANY DOUBT ABOUT THE PREVIOUS INSTRUCTIONS TO CROSS TIROE AT 14000 FT.

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.