Air carrier large transport altitude deviation overshot during descent.

Attributes
ACN	89239
Time
Date	198806
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 10000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other descent other
Route In Use	enroute airway : zau
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : commercial pilot : instrument
Experience	flight time last 90 days : 180 flight time total : 3200 flight time type : 400
ASRS Report	89239
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 75 flight time total : 4500 flight time type : 250
ASRS Report	89130
Events
Anomaly	altitude deviation : overshoot
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

Being level at FL200, chi center cleared us for descent to 10000'. We acknowledged descent clearance to 10000'. Descending through 11000', chi center advised we were cleared to 12000'. We told the controller we heard 10000' as being the clearance, which we read back with no objection from the controller. Center then gave us descent clearance to 10000'. I think we all have to be more careful checking each other's (pilots/controllers) readback. Way too often, we are given a clearance, read it back wrong to ATC and did not get a corrective response. Another call to ATC confirms our readback was wrong. Too often, ATC does not pay close attention to our readbacks. This problem is the reason for this incident. Whether chi center cleared us to 10000 or 12000', when we read back 10000', ATC should have caught the mistake immediately. The only think we can do, as the airspace gets more and more crowded, is to pay close attention to the clrncs, readbacks, instructions, etc, that are being exchanged between aircraft and ATC.

Original NASA ASRS Text

Title: ACR LGT ALT DEVIATION OVERSHOT DURING DESCENT.

Narrative: BEING LEVEL AT FL200, CHI CENTER CLRED US FOR DSCNT TO 10000'. WE ACKNOWLEDGED DSCNT CLRNC TO 10000'. DSNDING THROUGH 11000', CHI CENTER ADVISED WE WERE CLRED TO 12000'. WE TOLD THE CTLR WE HEARD 10000' AS BEING THE CLRNC, WHICH WE READ BACK WITH NO OBJECTION FROM THE CTLR. CENTER THEN GAVE US DSCNT CLRNC TO 10000'. I THINK WE ALL HAVE TO BE MORE CAREFUL CHKING EACH OTHER'S (PLTS/CTLRS) READBACK. WAY TOO OFTEN, WE ARE GIVEN A CLRNC, READ IT BACK WRONG TO ATC AND DID NOT GET A CORRECTIVE RESPONSE. ANOTHER CALL TO ATC CONFIRMS OUR READBACK WAS WRONG. TOO OFTEN, ATC DOES NOT PAY CLOSE ATTN TO OUR READBACKS. THIS PROB IS THE REASON FOR THIS INCIDENT. WHETHER CHI CENTER CLRED US TO 10000 OR 12000', WHEN WE READ BACK 10000', ATC SHOULD HAVE CAUGHT THE MISTAKE IMMEDIATELY. THE ONLY THINK WE CAN DO, AS THE AIRSPACE GETS MORE AND MORE CROWDED, IS TO PAY CLOSE ATTN TO THE CLRNCS, READBACKS, INSTRUCTIONS, ETC, THAT ARE BEING EXCHANGED BTWN ACFT AND ATC.

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.