Large transport crew misinterped clearance and departed assigned altitude early.

Attributes
ACN	497144
Time
Date	200012
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : esl.vortac
State Reference	VA
Altitude	msl bound lower : 30500 msl bound upper : 31000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid.artcc tower : mem.tower
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 7500 flight time type : 950
ASRS Report	497144
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On flight from ord to dca, controller (ZID) gave instructions to cross 25 NM west of esl at FL290 at pilot's discretion. Later, controller gave instructions to descend to FL310 (did not cancel crossing instructions). In order to comply with the previous instruction to cross 25 NM west of esl at FL290, we continued to FL290. Passing FL305, the controller asked 'where are you going?' we stated that we were continuing to FL290 as previously instructed to do a pilot's discretion to meet the crossing restr. At that time we were given a vector right of course 240 degrees. We asked if he wanted us to level off or climb back to FL310. The controller stated that it was not necessary, and to continue to FL290. 30 seconds or so later, we were cleared to proceed direct to esl. The confusion may have been eliminated if: 1) the controller had canceled previous instruction with restr to cross 25 NM west of esl at FL290, and 2) had we prompted/asked if we still had restr to cross at FL290.

Original NASA ASRS Text

Title: LGT CREW MISINTERPED CLRNC AND DEPARTED ASSIGNED ALT EARLY.

Narrative: ON FLT FROM ORD TO DCA, CTLR (ZID) GAVE INSTRUCTIONS TO CROSS 25 NM W OF ESL AT FL290 AT PLT'S DISCRETION. LATER, CTLR GAVE INSTRUCTIONS TO DSND TO FL310 (DID NOT CANCEL XING INSTRUCTIONS). IN ORDER TO COMPLY WITH THE PREVIOUS INSTRUCTION TO CROSS 25 NM W OF ESL AT FL290, WE CONTINUED TO FL290. PASSING FL305, THE CTLR ASKED 'WHERE ARE YOU GOING?' WE STATED THAT WE WERE CONTINUING TO FL290 AS PREVIOUSLY INSTRUCTED TO DO A PLT'S DISCRETION TO MEET THE XING RESTR. AT THAT TIME WE WERE GIVEN A VECTOR R OF COURSE 240 DEGS. WE ASKED IF HE WANTED US TO LEVEL OFF OR CLB BACK TO FL310. THE CTLR STATED THAT IT WAS NOT NECESSARY, AND TO CONTINUE TO FL290. 30 SECONDS OR SO LATER, WE WERE CLRED TO PROCEED DIRECT TO ESL. THE CONFUSION MAY HAVE BEEN ELIMINATED IF: 1) THE CTLR HAD CANCELED PREVIOUS INSTRUCTION WITH RESTR TO CROSS 25 NM W OF ESL AT FL290, AND 2) HAD WE PROMPTED/ASKED IF WE STILL HAD RESTR TO CROSS AT FL290.

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.