An air carrier large transport flight crew descends too low when they, apparently, misinterpret an ARTCC controller's altitude assignment. Approach control questioned the leveloff altitude. No conflict.

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Attributes
ACN	367600
Time
Date	199704
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : aml
State Reference	VA
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc tracon : dca tower : bwi
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 150 flight time total : 20000 flight time type : 700
ASRS Report	367600
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : overshoot non adherence : published procedure non adherence : far non adherence : clearance
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other

Narrative:

ZDC cleared our flight to descend to cross the doccs intersection (jasen 1 arrival) at 10000 ft. This clearance was read back to center and a descent to 10000 ft MSL was initiated. Center switched us to dulles approach and we checked in informing approach of our descent to 10000 ft. As we leveled off at 10000 ft approach asked us if we had been cleared to 11000 ft or 10000 ft. We stated that center had cleared us to 10000 ft and we then asked approach if there was any conflict and the answer was no. The flight continued uneventfully to a landing at dulles. In retrospect, all 3 pilots understood a clearance to 10000 ft and also noted that the published crossing altitude at doccs was 11000 ft MSL. It would have been prudent to have queried the center at that point to determine whether they really meant to descend us to 10000 ft at doccs. Also, neither center nor approach responded to our readback of a clearance to 10000 ft until we leveled off at that altitude. Either controller could have caught the error, but did not.

Original NASA ASRS Text

Title: AN ACR LGT FLC DSNDS TOO LOW WHEN THEY, APPARENTLY, MISINTERPRET AN ARTCC CTLR'S ALT ASSIGNMENT. APCH CTL QUESTIONED THE LEVELOFF ALT. NO CONFLICT.

Narrative: ZDC CLRED OUR FLT TO DSND TO CROSS THE DOCCS INTXN (JASEN 1 ARR) AT 10000 FT. THIS CLRNC WAS READ BACK TO CTR AND A DSCNT TO 10000 FT MSL WAS INITIATED. CTR SWITCHED US TO DULLES APCH AND WE CHKED IN INFORMING APCH OF OUR DSCNT TO 10000 FT. AS WE LEVELED OFF AT 10000 FT APCH ASKED US IF WE HAD BEEN CLRED TO 11000 FT OR 10000 FT. WE STATED THAT CTR HAD CLRED US TO 10000 FT AND WE THEN ASKED APCH IF THERE WAS ANY CONFLICT AND THE ANSWER WAS NO. THE FLT CONTINUED UNEVENTFULLY TO A LNDG AT DULLES. IN RETROSPECT, ALL 3 PLTS UNDERSTOOD A CLRNC TO 10000 FT AND ALSO NOTED THAT THE PUBLISHED XING ALT AT DOCCS WAS 11000 FT MSL. IT WOULD HAVE BEEN PRUDENT TO HAVE QUERIED THE CTR AT THAT POINT TO DETERMINE WHETHER THEY REALLY MEANT TO DSND US TO 10000 FT AT DOCCS. ALSO, NEITHER CTR NOR APCH RESPONDED TO OUR READBACK OF A CLRNC TO 10000 FT UNTIL WE LEVELED OFF AT THAT ALT. EITHER CTLR COULD HAVE CAUGHT THE ERROR, BUT DID NOT.

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.