A B727-200 descends 1000 ft below assigned altitude during descent in ZDC, dc, airspace.

Attributes
ACN	382390
Time
Date	199710
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ard
State Reference	PA
Altitude	msl bound lower : 12000 msl bound upper : 13000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	B727-200
Flight Phase	descent other
Route In Use	arrival other arrival star : star enroute other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 70 flight time total : 6000 flight time type : 700
ASRS Report	382390
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 25 flight time total : 1900 flight time type : 25
ASRS Report	382329
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Descending on arrival, ATC cleared us to 13000 ft. I was flying and for some unknown reason I believed the clearance was to 12000 ft. The altitude was set correctly, I descended through 13000 ft, and was in the transition to level off at 12000 ft when my engineer inquired as to what our clearance was. Upon realizing my mistake, I immediately initiated a climb to our cleared altitude of 13000 ft. The controller then cleared us to descend to 11000 ft with no comment about our descent. 2 contributing factors: this airplane's autoplt doesn't have altitude capture and would have leveled off at the set altitude if it were installed. Secondly, I'm a new captain and was unfamiliar with the 'normal' leveloff altitude at somto. A different altitude such as 12000 ft would have keyed me to check the clearance had I known it was an unusual altitude to descend to at that point of the descent profile.

Original NASA ASRS Text

Title: A B727-200 DSNDS 1000 FT BELOW ASSIGNED ALT DURING DSCNT IN ZDC, DC, AIRSPACE.

Narrative: DSNDING ON ARR, ATC CLRED US TO 13000 FT. I WAS FLYING AND FOR SOME UNKNOWN REASON I BELIEVED THE CLRNC WAS TO 12000 FT. THE ALT WAS SET CORRECTLY, I DSNDED THROUGH 13000 FT, AND WAS IN THE TRANSITION TO LEVEL OFF AT 12000 FT WHEN MY ENGINEER INQUIRED AS TO WHAT OUR CLRNC WAS. UPON REALIZING MY MISTAKE, I IMMEDIATELY INITIATED A CLB TO OUR CLRED ALT OF 13000 FT. THE CTLR THEN CLRED US TO DSND TO 11000 FT WITH NO COMMENT ABOUT OUR DSCNT. 2 CONTRIBUTING FACTORS: THIS AIRPLANE'S AUTOPLT DOESN'T HAVE ALT CAPTURE AND WOULD HAVE LEVELED OFF AT THE SET ALT IF IT WERE INSTALLED. SECONDLY, I'M A NEW CAPT AND WAS UNFAMILIAR WITH THE 'NORMAL' LEVELOFF ALT AT SOMTO. A DIFFERENT ALT SUCH AS 12000 FT WOULD HAVE KEYED ME TO CHK THE CLRNC HAD I KNOWN IT WAS AN UNUSUAL ALT TO DSND TO AT THAT POINT OF THE DSCNT PROFILE.

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.