Pilot deviation caused by misinterp of ATC clearance.

Attributes
ACN	293690
Time
Date	199501
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mcw
State Reference	IA
Altitude	msl bound lower : 28000 msl bound upper : 28500
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau tower : mco
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other descent 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 : 180 flight time total : 15000 flight time type : 2000
ASRS Report	293690
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : clearance non adherence : far
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were cleared to what we heard as 'FL270' while we were in cruise at FL310 by ZAU. I read back, 'air carrier flight XXX cleared to FL270.' ZAU acknowledged and we started our descent for FL270. As we passed through 28500 ft, ZAU called and stated, 'air carrier flight XXX stop descent at FL280 you were not cleared below FL290.' I stated that 'I had read back cleared to FL270 and was acknowledged by ZAU.' then ZAU cleared us to FL270 without incident. I have been noticing increasing incidents of ATC failing to really 'listen back.' our system is full of checks and balances and the communication of clrncs with transmission, readback, and listen back is fundamental to safety.

Original NASA ASRS Text

Title: PLTDEV CAUSED BY MISINTERP OF ATC CLRNC.

Narrative: WE WERE CLRED TO WHAT WE HEARD AS 'FL270' WHILE WE WERE IN CRUISE AT FL310 BY ZAU. I READ BACK, 'ACR FLT XXX CLRED TO FL270.' ZAU ACKNOWLEDGED AND WE STARTED OUR DSCNT FOR FL270. AS WE PASSED THROUGH 28500 FT, ZAU CALLED AND STATED, 'ACR FLT XXX STOP DSCNT AT FL280 YOU WERE NOT CLRED BELOW FL290.' I STATED THAT 'I HAD READ BACK CLRED TO FL270 AND WAS ACKNOWLEDGED BY ZAU.' THEN ZAU CLRED US TO FL270 WITHOUT INCIDENT. I HAVE BEEN NOTICING INCREASING INCIDENTS OF ATC FAILING TO REALLY 'LISTEN BACK.' OUR SYS IS FULL OF CHKS AND BALS AND THE COM OF CLRNCS WITH XMISSION, READBACK, AND LISTEN BACK IS FUNDAMENTAL TO SAFETY.

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.