Crew misreads altimeter resulting in an altitude undershoot south of dca.

Attributes
ACN	465970
Time
Date	200003
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dca.airport
State Reference	DC
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : iad.tracon tower : ewr.tower
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : irons.4
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 225 flight time total : 6900 flight time type : 5100
ASRS Report	465970
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : undershoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Assigned 10000 ft at 12 mi south of ojaay on the irons 4 arrival dca. Descended to 11000 ft, misread the altimeter (10000 ft), leveled at 11000 ft (10995 ft) and noticed the deviation as we checked in with approach (frequency change given as we descended through about 11800 ft). This could've been avoided by 1) checking center altimeter, 2) mentally checking the 1000 ft above call, and 3) increasing intensity on integral lights on my instrument panel. Once we discovered the error, we notified ATC, who then cleared us below 10000 ft. This event did not precipitate a conflict, but on arrival into dca a 1000 ft deviation is potentially devastating!

Original NASA ASRS Text

Title: CREW MISREADS ALTIMETER RESULTING IN AN ALT UNDERSHOOT S OF DCA.

Narrative: ASSIGNED 10000 FT AT 12 MI S OF OJAAY ON THE IRONS 4 ARR DCA. DSNDED TO 11000 FT, MISREAD THE ALTIMETER (10000 FT), LEVELED AT 11000 FT (10995 FT) AND NOTICED THE DEV AS WE CHKED IN WITH APCH (FREQ CHANGE GIVEN AS WE DSNDED THROUGH ABOUT 11800 FT). THIS COULD'VE BEEN AVOIDED BY 1) CHKING CTR ALTIMETER, 2) MENTALLY CHKING THE 1000 FT ABOVE CALL, AND 3) INCREASING INTENSITY ON INTEGRAL LIGHTS ON MY INST PANEL. ONCE WE DISCOVERED THE ERROR, WE NOTIFIED ATC, WHO THEN CLRED US BELOW 10000 FT. THIS EVENT DID NOT PRECIPITATE A CONFLICT, BUT ON ARR INTO DCA A 1000 FT DEV IS POTENTIALLY DEVASTATING!

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.