Flight crew descended 300 ft through their assigned altitude.

Attributes
ACN	315400
Time
Date	199509
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : cgt airport : ord
State Reference	IL
Altitude	msl bound lower : 5700 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : ord
Operator	general aviation : corporate
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument
Experience	flight time last 90 days : 100 flight time total : 10300 flight time type : 880
ASRS Report	315400
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : regained aircraft control flight crew : returned to intended course or assigned course
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were in our descent from altitude on our trip from cgf to mdw. Ord approach had cleared us to descend to 7000 ft. The aircraft was on autoplt in the descent. The PNF was off the frequency obtaining the current ATIS information. Upon approach in 7000 ft, approach cleared us to 6000 ft. I acknowledged the clearance to 6000 ft and set the new altitude in the altitude alerter. After setting in the new altitude and continuing the descent, I took a moment to study the approach chart. As I was doing that, the pilot who had been getting the ATIS said, hey, aren't we cleared to 6000 ft. I looked up, and we were passing 5700 ft. The copilot had grabbed the controls to stop the descent. I took the controls and assured that the autoplt was off, and initiated a climb back up to 6000 ft. As we were climbing back to 6000 ft, approach told us that our assigned altitude was 6000 ft and asked us what our altitude was. By that time we were leveling at 6000 ft so we replied that we were level at 6000 ft. I believe that the problem occurred because both pilots were distracted from flying the aircraft during the descent. I should have been monitoring the instruments even though the aircraft was on autoplt. I don't know why the autoplt and flight director didn't capture the altitude, but the incident would have been prevented if one pilot was monitoring the instruments at all times.

Original NASA ASRS Text

Title: FLC DSNDED 300 FT THROUGH THEIR ASSIGNED ALT.

Narrative: WE WERE IN OUR DSCNT FROM ALT ON OUR TRIP FROM CGF TO MDW. ORD APCH HAD CLRED US TO DSND TO 7000 FT. THE ACFT WAS ON AUTOPLT IN THE DSCNT. THE PNF WAS OFF THE FREQ OBTAINING THE CURRENT ATIS INFO. UPON APCH IN 7000 FT, APCH CLRED US TO 6000 FT. I ACKNOWLEDGED THE CLRNC TO 6000 FT AND SET THE NEW ALT IN THE ALT ALERTER. AFTER SETTING IN THE NEW ALT AND CONTINUING THE DSCNT, I TOOK A MOMENT TO STUDY THE APCH CHART. AS I WAS DOING THAT, THE PLT WHO HAD BEEN GETTING THE ATIS SAID, HEY, AREN'T WE CLRED TO 6000 FT. I LOOKED UP, AND WE WERE PASSING 5700 FT. THE COPLT HAD GRABBED THE CTLS TO STOP THE DSCNT. I TOOK THE CTLS AND ASSURED THAT THE AUTOPLT WAS OFF, AND INITIATED A CLB BACK UP TO 6000 FT. AS WE WERE CLBING BACK TO 6000 FT, APCH TOLD US THAT OUR ASSIGNED ALT WAS 6000 FT AND ASKED US WHAT OUR ALT WAS. BY THAT TIME WE WERE LEVELING AT 6000 FT SO WE REPLIED THAT WE WERE LEVEL AT 6000 FT. I BELIEVE THAT THE PROB OCCURRED BECAUSE BOTH PLTS WERE DISTRACTED FROM FLYING THE ACFT DURING THE DSCNT. I SHOULD HAVE BEEN MONITORING THE INSTS EVEN THOUGH THE ACFT WAS ON AUTOPLT. I DON'T KNOW WHY THE AUTOPLT AND FLT DIRECTOR DIDN'T CAPTURE THE ALT, BUT THE INCIDENT WOULD HAVE BEEN PREVENTED IF ONE PLT WAS MONITORING THE INSTS AT ALL TIMES.

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.