Air carrier X unauthorized descent below assigned altitude because of copying wrong altitude setting...

Attributes
ACN	287167
Time
Date	199411
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : pvd
State Reference	RI
Altitude	msl bound lower : 11000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : zbw
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 120 flight time total : 10000
ASRS Report	287167
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	287473
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

As first officer, I handled communications with ATC on air carrier X. West of providence, ATC instructed us to descend to 11000 ft, and stated the local altimeter. I read back the clearance, understanding the altimeter to be 30.37. At this time, I attempted to listen to bos ATIS on the second radio. No transmission was received which I attributed to the ATIS being in the process of being changed. The preliminary checklist was accomplished, using 30.37 as the altimeter setting. About 5 mins later, the new ATIS was being broadcast. As I copied it, we were descending through 12000 ft. Almost simultaneously, I finished copying the ATIS, we leveled at 11000 ft, and ATC called telling us to check our altitude and altimeter at 29.37. We corrected our altimeters, and climbed back to 11000 ft. There was no other traffic in the area. Factors in this incident include my hearing '.37' and assuming it was the more normal 30.37 rather than the low reading of 29.37, the delay in receiving ATIS information that would have corrected the error, and the transmission by ATC in 1 call of a series of multi-digit numbers.

Original NASA ASRS Text

Title: ACR X UNAUTH DSCNT BELOW ASSIGNED ALT BECAUSE OF COPYING WRONG ALT SETTING.

Narrative: AS FO, I HANDLED COMS WITH ATC ON ACR X. W OF PROVIDENCE, ATC INSTRUCTED US TO DSND TO 11000 FT, AND STATED THE LCL ALTIMETER. I READ BACK THE CLRNC, UNDERSTANDING THE ALTIMETER TO BE 30.37. AT THIS TIME, I ATTEMPTED TO LISTEN TO BOS ATIS ON THE SECOND RADIO. NO XMISSION WAS RECEIVED WHICH I ATTRIBUTED TO THE ATIS BEING IN THE PROCESS OF BEING CHANGED. THE PRELIMINARY CHKLIST WAS ACCOMPLISHED, USING 30.37 AS THE ALTIMETER SETTING. ABOUT 5 MINS LATER, THE NEW ATIS WAS BEING BROADCAST. AS I COPIED IT, WE WERE DSNDING THROUGH 12000 FT. ALMOST SIMULTANEOUSLY, I FINISHED COPYING THE ATIS, WE LEVELED AT 11000 FT, AND ATC CALLED TELLING US TO CHK OUR ALT AND ALTIMETER AT 29.37. WE CORRECTED OUR ALTIMETERS, AND CLBED BACK TO 11000 FT. THERE WAS NO OTHER TFC IN THE AREA. FACTORS IN THIS INCIDENT INCLUDE MY HEARING '.37' AND ASSUMING IT WAS THE MORE NORMAL 30.37 RATHER THAN THE LOW READING OF 29.37, THE DELAY IN RECEIVING ATIS INFO THAT WOULD HAVE CORRECTED THE ERROR, AND THE XMISSION BY ATC IN 1 CALL OF A SERIES OF MULTI-DIGIT NUMBERS.

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.