Large transport cleared to descent to 11000'. Readback and descended to 10000'.

Attributes
ACN	96824
Time
Date	198810
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : rdu
State Reference	NC
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other descent other
Route In Use	arrival star : star
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 117 flight time total : 10000 flight time type : 8000
ASRS Report	96824
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : cfi pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 120 flight time total : 3570 flight time type : 170
ASRS Report	96820
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

First officer flying, captain handling radios. ZDC cleared us to cross buzzy intersection at 10000' and 250 KTS. I read back buzzy at 10000'/250 KTS along with flight identify. 10000' was set in the altitude alert and the required crossing at buzzy intersection was accomplished. After passing buzzy intersection, ZDC handed us off to rdu approach control. I checked in with appropriate call sign and our altitude: 10000'. Approach acknowledged our transmission and asked us to repeat our altitude, which I did. The controller said 'roger,' and a minute or so later came back and said ZDC had only cleared us to 11000', but since we were at 10000' it was ok. The first officer and F/east both commented at this time that they both heard 10000' and the read back of 10000' and noted the 10000' set in the altitude alert. The probable cause was the controller saying 10000' and thinking he said 11000', and/or the pilots hearing (or thinking they heard) 10000' and reading back 10000' and if there was an error it was not detected by ZDC, nor corrected. The corrective solution to this problem is for all parties to speak clearly and listen to each other's transmission and make sure they all agree with what was said.

Original NASA ASRS Text

Title: LGT CLEARED TO DESCENT TO 11000'. READBACK AND DESCENDED TO 10000'.

Narrative: F/O FLYING, CAPT HANDLING RADIOS. ZDC CLRED US TO CROSS BUZZY INTXN AT 10000' AND 250 KTS. I READ BACK BUZZY AT 10000'/250 KTS ALONG WITH FLT IDENT. 10000' WAS SET IN THE ALT ALERT AND THE REQUIRED XING AT BUZZY INTXN WAS ACCOMPLISHED. AFTER PASSING BUZZY INTXN, ZDC HANDED US OFF TO RDU APCH CTL. I CHKED IN WITH APPROPRIATE CALL SIGN AND OUR ALT: 10000'. APCH ACKNOWLEDGED OUR XMISSION AND ASKED US TO REPEAT OUR ALT, WHICH I DID. THE CTLR SAID 'ROGER,' AND A MINUTE OR SO LATER CAME BACK AND SAID ZDC HAD ONLY CLRED US TO 11000', BUT SINCE WE WERE AT 10000' IT WAS OK. THE F/O AND F/E BOTH COMMENTED AT THIS TIME THAT THEY BOTH HEARD 10000' AND THE READ BACK OF 10000' AND NOTED THE 10000' SET IN THE ALT ALERT. THE PROBABLE CAUSE WAS THE CTLR SAYING 10000' AND THINKING HE SAID 11000', AND/OR THE PLTS HEARING (OR THINKING THEY HEARD) 10000' AND READING BACK 10000' AND IF THERE WAS AN ERROR IT WAS NOT DETECTED BY ZDC, NOR CORRECTED. THE CORRECTIVE SOLUTION TO THIS PROB IS FOR ALL PARTIES TO SPEAK CLEARLY AND LISTEN TO EACH OTHER'S XMISSION AND MAKE SURE THEY ALL AGREE WITH WHAT WAS SAID.

Data retrieved from NASA's ASRS site as of August 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.